research article possibilities for advanced encoding techniques at signal...
TRANSCRIPT
Research ArticlePossibilities for Advanced Encoding Techniques at SignalTransmission in the Optical Transmission Medium
Filip Hertiacutek and Rastislav Roacuteka
Institute of Telecommunications Slovak University of Technology in Bratislava Ilkovicova 3 812 19 Bratislava Slovakia
Correspondence should be addressed to Rastislav Roka rastislavrokastubask
Received 25 November 2015 Accepted 13 March 2016
Academic Editor A S Madhukumar
Copyright copy 2016 F Certık and R Roka This is an open access article distributed under the Creative Commons AttributionLicense which permits unrestricted use distribution and reproduction in any medium provided the original work is properlycited
This paper presents a possible simulation of negative effects in the optical transmission medium and an analysis for the utilizationof different signal processing techniques at the optical signal transmission An attention is focused on the high data rate signaltransmission in the optical fiber influenced by linear and nonlinear environmental effects presented by the prepared simulationmodel The analysis includes possible utilization of OOK BPSK DBPSK BFSK QPSK DQPSK 8PSK and 16QAM modulationtechniques together with RS BCH and LDPC encoding techniques for the signal transmission in the optical fiber Moreover theprepared simulation model is compared with real optical transmission systems In the final part a comparison of the selectedmodulation techniques with different encoding techniques and their implementation in real transmission systems is shown
1 Introduction
Nowadays an interest in the signal transmission throughoptical fibers is rapidly increasing due to the transmissionbandwidth Creating new optical transmission paths can betime consuming and expensive [1ndash4] Therefore more effec-tive approaches are appearing to satisfy increased customerrequests In both electric and optical domains utilizing newadvanced signal processing techniques can lead to increasingof the transmission capacity Such solutions can be easilyintegrated With increasing of modulation rates negativeinfluences on the transmitted optical signals are growing andso additional bit errors in information flows are emergentTherefore it is important to design and analyze a perfor-mance of advanced signal processing techniques utilized inthe optical transmission medium with respect to its envi-ronmental influences The simulation can determine trans-mission boundaries of each advanced signal processing tech-nique for the designed optical system and allow comparingall possible solutions before their practical deployment Thesimulation allows evaluating possible increasing of data ratesand transmission ranges in deployed optical transmissionsystems using advanced signal processing techniques and
designing new optical transmission systems with advancedoptical components and fibers
First basic parameters of the optical fiber and principlesof selected encoding techniques are introduced In this paperthe simulation studies are restricted to the block codes Con-volutional codes with different rates and constraint lengthscan later be considered along with the assumed modulationtechniques Then a comparison of the prepared simulationmodelwith real optical transmission systemsmeasured by theCiena system is presented Moreover a specific application ofthe optical transmission system with advanced optical signalprocessing techniques can also be represented in this case Amain attention of the contribution is focused on the analysisof differentmodulation and encoding techniques at the signaltransmission in the optical transmission medium and theirpossible implementation in real transmission systems Fromproposed realized and presented signal modulations onlysome of them are considered for enhanced analysis evalua-tion and comparison purposes In the final part selectedmodulation and encoding techniques implemented on realtransmission systems are analyzed for the high data ratesignal transmissions
Hindawi Publishing CorporationJournal of EngineeringVolume 2016 Article ID 2385372 10 pageshttpdxdoiorg10115520162385372
2 Journal of Engineering
11 Characteristics of the Optical Fiber Each optical fiber rep-resents a transmission system which is frequency dependentA pulse propagation inside this transmission system can bedescribed by the nonlinear Schrodinger equation (NLSE)which is derivate from Maxwellrsquos equations From the NLSEequation we can express effects in optical fibers that are clas-sified as [5 6]
(a) linear effects which are wavelength dependent(b) nonlinear effects which are intensity (power) depen-
dent
Linear Effects Major impairments of optical signals trans-mitted via the optical fiber environment are mainly causedby linear effects the dispersion and the attenuation Theattenuation limits a power of optical signals and representstransmission losses Nowadays optical transmission systemsare able to minimize impact of the attenuation by deployingall-optical amplifiers Another source of the linear effect rep-resents the dispersion causing broadening of optical pulses intime and signal phase shifting at the fiber endThere are threemain dispersion types [5ndash8]
(i) The modal dispersion caused by the different propa-gation velocity of optical modes propagating in mul-timode fibers
(ii) The chromatic dispersion caused by the differentpropagation velocity ofwavelengths generated in lasersources propagating in the optical fiber It consists ofmaterial profile and waveguide dispersions
(iii) The polarization mode dispersion caused by the bire-fringence effect due to a nonsymmetry and imperfec-tions of optical fibers
Nonlinear Effects These effects play an important role at thelong haul optical signal transmission Nonlinear effects canbe classified as follows
(i) Kerr nonlinearities are self-induced effects where thephase velocity of the pulse depends on the pulsersquos ownintensity The Kerr effect describes a change in thefiber refractive index due to electrical perturbationsDue to the Kerr effect following effects are possible todescribe
(a) Self-phase modulation (SPM) is an effect thatchanges the refractive index of the transmissionmedium caused by the pulse intensity [9 10]
(b) Four-wavemixing (FWM) is an effect where thefourth wave can be arisen by mixing of threeoptical waves and this one can appear in thesame wavelength as one of mixed waves [9]
(c) Cross-phase effect (XPM) is an effect that causesa spectral broadening where the optical pulsecan change the phase of another pulse with dif-ferent wavelengths [9ndash11]
(ii) Scattering nonlinearities occur due to a photon inelas-tic scattering to lower energy photons The pulse
energy is transferred to another wave with a differentwavelength Two such effects appear in the opticalfiber
(a) Stimulated Brillouin scattering (SBS) and stim-ulated Raman scattering (SRS) are effects thatchange a variance of light wave into differentwaves when the intensity reaches a certainthreshold [9ndash11]
12 Principles of Selected Encoding Techniques Forward errorcorrection (FEC) techniques represent a system where addi-tional data are inserted into a data message so that it can berecovered by a receiver even when a number of errors due totransmission is emergent These FEC codes are widely usedin systems where a data retransmission is not an option suchas broadcasting and high haul optical transmission systems[12 13] FEC codes are usually divided into convolutional andblock codes
(i) Convolutional codes are processed on a bit-by-bitbasis
(ii) Block codes are processed on a block-by-block basis
Convolutional codes are based on the encoding signalwith a final impulse response This type of coding does notrequire division of bits into the blocksThe convolution codesmay be decoded using the Viterbi algorithm which is amethod of decoding with maximum reliability This methodis based onfinding themost appropriateway forward throughthe possible states of transitionThe complexity of the Viterbialgorithm increases with the number of states in decodingTherefore it is advisable to use codes that use a small amountof redundancy Convolutional codes have lower resistanceagainst noise than the linear block codes and not using theminimal trellis like linear blocks [13 14]
For analysis block codes especially cyclic block codesare considered Cyclic block codes are widely used in datacommunication because their structure makes encoder anddecoder circuitry simple Cyclic block codes are defined asthe cyclic (119899 119896) code if 119862 is a linear code of the length 119899 overa finite field and if any cyclic shift of a codeword is also acodeword as shown in
1198880 1198881 119888
119899minus1isin 119862 997904rArr 119888
119899minus1 1198880 1198881 119888
119899minus2isin 119862 (1)
The information data with the length 119896 are coded with thepolynomial 119892(119909) using (1) Consider
119888 (119909) = 119894 (119909) 119892 (119909) (2)
where 119888(119909) represents the polynomial of degree (119899 minus 1) 119894(119909)is the information polynomial of degree (119896 minus 1) and thegenerator polynomial 119892(119909)must be of degree (119899 minus 119896)
The Reed-Solomon (RS) codes that belong to cyclic blockcodes are widely used in many communication fields [13 14]The RS codes are related to BCH codes and can be defined asa primitive BCH code of the length 119899 where
119899 = 119902 minus 1 = 2119904minus 1 over GF (119902) = GF (2119904) (3)
Journal of Engineering 3
RS codes are specified as RS(119899 119896) or RS(119899 119896 119889) where119899 represent the code length 119896 represents the informationlength and 119889 is the Hamming distance Let 119905 be a number oferrors that can be corrected then correction (119905) or detection(2119905) abilities are specified for the code There exist twoencoding types for RS codes
(i) Nonsystematic(ii) Systematic
The decoding for RS codes is based on syndrome equa-tions
119904119896=
119905
sum119894=1
119884119894119883119896
119894 119896 = 0 1 2119905 minus 1 (4)
where 119883119894is the locator 119894th error and 119884
119894represents its value
(detection of location and value) More information about RSencoding techniques can be found in [13]
The Bose Chaudhuri Hocquenghem (BCH) code is acyclic polynomial code over a finite field with chosen poly-nomial generator BCH codes are 119905-error correcting codesdefined over finite fields GF(119902) where 2119905 + 1 lt 119902 The advan-tage of BCH codes is using syndrome to decode errors inwhich there exist good decoding algorithms that correctmultiple errors [14]
The generating of a binary BCH code over an extensionfield GF(119902119898) is easy to construct The polynomial generator119892(119909) is needed to obtain a cyclic code [12ndash16] For any integer119898 ge 3 and 119905 lt 2119898 minus 1 there exists a primitive BCH code withparameters 119899 = 2119898 minus 1 119899 minus 119896 le 119898 sdot 119905 and 119889min le 2119905 + 1The generator polynomial119892(119909) of 119905-error correcting primitiveBCH codes of the length 2119898 minus 1 is given by
119892 (119909) = LCM 1198981(119909) 119898
2(119909) 119898
2119905minus1(119909) 119898
2119905(119909) (5)
where LCM represents the Least CommonMultipleThen thecode is generated using (2)
BCH codes are decoded with various algorithm based oncalculation of syndromes values for the received codeword
Low Density Parity Check (LDPC) codes belong to linearencoding techniques that can transmit data close to the Shan-non theorem (the channel capacity) The main disadvantageof the LDPC code is the time consumption of the codealgorithm which often limits its utilization in high datarate optical transmission systems However it is possible toencode more low data rate signals and then merge them intoone high data rate signal The high data rate signal can betransmitted via the optical transmission system
The LDPC coding is defined by the LDPC 119867 matrixAssuming the length of information bits K the length ofencoded bits119873 and the average weigh column119908 gt 2 (weightvectors represent the sum of nonzero components of thevector) then119872 = (119873 minus 119870) is the sum of the parity check incodeThe LDPCmatrix119867 is composed of119872 rows and119873 col-umnsThe generationmatrix119866 is necessary to encode codingsequence [14 15]
Prepared block schemes of mentioned encoding tech-niques in the simulation model are shown in Figures 1 and 2Figure 3 shows the schematic block diagram of LDPC source
Bernoullibinary
Bernoulli binary generator
Multiple
Sample_time
Binary inputRS encoderBinary inputRS encoder
1OutGaussian
Gaussian filter
[Orig]
Goto
times
Figure 1 The block scheme for the signal generation with RS andBCH encoding techniques
signal Blocks are initiated using a Bernoulli generator thatgenerates random binary bits representation of the infor-mation signal The signal is then coded with an adequateencoding technique The output signal is filtered with aGaussian filter for representation of the real signal TheLDPC block is created by using 10 Bernoulli generators eachencoded with the LDPC code and merged into the high datarate signal [16 17]
2 The Simulation of the OpticalTransmission System
The prepared simulation model comes out from the simula-tion model for optical communications introduced in [18ndash20] A modeling is performed in the Matlab Simulink 2014programming environment The simulation model presentsan influence of linear and nonlinear effects present in theoptical transmission medium at the signal transmission Thegeneral schematic block diagram is shown in Figure 4 To ver-ify a reliability and exactness of the simulationmodel authorsrealized a comparison of two optical transmission pathsmea-sured in cooperation with the Orange Slovakia companyTheoptical path 1 consists of the 592 km standard SM (ITU-TG652) fiber with the 10Gbits noncoherent OOKmodulatedsignal using 80WDMchannelsThe optical path 2 consists of1707 km standard SM (ITU-T G652) fiber with the 10Gbitsnoncoherent OOK modulated signal using 80 WDM chan-nels Transmitted signals are examined with the 1934 THzfrequency Both paths are utilizing EDFA amplifiers at theoptical fiber end while the optical path 2 is furthermoreusing additional 3 EDFA amplifiers every 40 km Simulationmodels for the optical path 1 and optical path 2 are shownin Figures 5 and 6 respectively For describing informationsignal transmission a bit error rate (BER) parameter can becalculated The BER calculation for each simulation model isdone by comparing input and output bits For both opticalpaths simulation results show theBERparameter higher than10minus12 satisfying common transmission conditions For bothsimulation models the Reed-Solomon code RS(255 239) isutilized to enhance the system BER parameter
For both optical paths presented simulated andmeasuredtransmission parameters (Tables 1 and 2) include besidesother received optical power level values for calculationsrelated to the attenuation As can be seen parameters arevery similar at which the simulation is characterized byworseones Therefore if the optical simulation is passed then thereal system would be properly and correctly operating
4 Journal of Engineering
Bernoullibinary
Bernoulli binarygenerator Multiple
Sample_time
1OutGaussian
Gaussian filter
LDPC encoder
LDPC encoder
In1 In2 In3
In4 In5
Out In6 MergeIn7In8In9
In10
Bernoullibinary
Bernoulli binarygenerator 1
Multiple 1Sample_time 1
LDPC encoder
LDPC encoder 1
Bernoullibinary
Bernoulli binarygenerator 2
Multiple 2Sample_time 2
LDPC encoder
LDPC encoder 2
Bernoullibinary
Bernoulli binarygenerator 3
Multiple 3Sample_time 3
LDPC encoder
LDPC encoder 3
Bernoullibinary
Bernoulli binarygenerator 4
Multiple 4Sample_time 4
LDPC encoder
LDPC encoder 4
Bernoullibinary
Bernoulli binarygenerator 5
Multiple 5Sample_time 5
LDPC encoder
LDPC encoder 5
Bernoullibinary
Bernoulli binarygenerator 6
Multiple 6Sample_time 6 LDPC encoder
LDPC encoder 6
Bernoullibinary
Bernoulli binarygenerator 7
Multiple 7Sample_time 7
LDPC encoder
LDPC encoder 7
Bernoullibinary
Bernoulli binarygenerator 8
Multiple 8Sample_time 8LDPC encoder
LDPC encoder 8
Bernoullibinary
Bernoulli binarygenerator 9
Multiple 9Sample_time 9LDPC encoder
LDPC encoder 9
timestimes
times
times
times
times
times
times
times
times
10 lowast 1Gbits to 10Gbits
Figure 2 The block scheme for the signal generation with the LDPC encoding technique
Table 1 The optical path 1 transmission parameters
Parameters Measured SimulatedRx power (dBm) minus132 minus134OSNR (dB) 259 243PMD (ps) 106 125SPM (dB) 087 122XPM (dB) minus5759 minus605FWM (dB) NA minus1243119876 799 81BER gt10minus15 gt10minus12
3 The Analysis of Selected Modulation andEncoding Techniques
The first modulation technique used for real optical trans-mission systems was the two-level amplitude modulationOOK with the direct detection This system is characterizedby transmission rates from 1Gbits and its limitation isrepresented by the 10Gbits rate over optical single modefibers with the 50 km line length Nowadays OOK systems
Table 2 The optical path 2 transmission parameters
Parameters Measured SimulatedRx power (dBm) minus1369 minus123OSNR (dB) 2107 209PMD (ps) 174 183SPM (dB) 103 11XPM (dB) minus4202 minus405FWM (dB) NA minus112119876 627 62BER gt10minus15 gt10minus12
are deployed with coherent receivers that can increase thesystem range depending on the receiver sensitivity andthe transmittersrsquo generated noise Coherent systems highlyimprove transmission characteristics but their implemen-tation is expensive due to security mechanisms for phaseand polarization detecting Another possible improvementfor coherent systems is represented by using the Duobinarymodulation This leads to a modification in the electricaldomain that is less costly than in case of exchange optical
Journal of Engineering 5
Merge block
1 0 0 1 1 1 1 10 0
1
111
1
1
00
0
0
Gauss filter 10Gbits
10Gbits
110
1Gbits
1Gbits
1Gbits
1Gbits
1Gbits
1Gbits
1Gbits
1Gbits
1Gbits
1Gbits
1Gbits
1Gbits
LDPC codingn = i + k
1Gbits
LDPC codingn = i + k
1Gbits
LDPC codingn = i + k
1Gbits
LDPC codingn = i + k
1Gbits
LDPC codingn = i + k
1Gbits
LDPC codingn = i + k
1Gbits
LDPC codingn = i + k
1Gbits
LDPC codingn = i + k
1Gbits
LDPC codingn = i + k
1Gbits
LDPC codingn = i + k
Bernoulli generatorrectangular impulse
Bernoulli generatorrectangular impulse
Bernoulli generatorrectangular impulse
Bernoulli generatorrectangular impulse
Bernoulli generatorrectangular impulse
Bernoulli generatorrectangular impulse
Bernoulli generatorrectangular impulse
Bernoulli generatorrectangular impulse
Bernoulli generatorrectangular impulse
Bernoulli generatorrectangular impulse
generatorSample
Figure 3 The schematic block diagram for the signal generation with the LDPC encoding technique
System signal source
System signal source
System signal source
1
2
N
Optical fiber
Circ
ulat
or
Localoscillator
Signal with different wavelength
Signal with different wavelength
Laser source
Electric datasignal
Electric datasignal
Mach-Zehndermodulator
Continuousoptical wave
Wavelengthdivision
multiplex
Erbium dopedfiber
Phase andamplitudedetection
Chromatic andpolarization modedispersion [time
broadening signalphase shift]
Four-wave mixing[intensity noise from
neighbour channels ondifferent wavelength]
[phase noise andsignal frequency shiftdue to signal intensity]
Self-phase andcross-phase modulation
[intensity noise fromneighbour channels
and decreasing signalintensity]
Stimulated Brillouinand Raman scattering
attenuation
Figure 4 The schematic block diagram for the optical transmission system
components For given modulation the Monte Carlo algo-rithm can be used because it allows a measuring of theBER parameter The simulation model uses the standard SM(ITU-T G656) optical fiber The comparison of transmissioncharacteristics for coherent OOK and Duobinary systems isshown in Figure 7
Possible solution can be represented by coherent systemswith phase and frequency modulation techniques which are
represented by BPSK DBPSK and BFSK These modula-tion techniques achieve similar transmission characteristics(shown in Figure 8) where the BPSK achieves better resultsabout 01 dB compared to the DBPSK and about 3 dB com-pared to the FSK
Higher modulation formats can be further used toincrease signal transmission rates in the optical system [21ndash25] Such modulation techniques have a lower tolerance to
6 Journal of Engineering
Out1
Data signal In1 Out1 In2
Demodulator
In1
In2Out1
MZM
Out1
CW
Out1
Cooperating channels
In1
In2
In3
Out1
WDM
Out1
EDFA
SMFmdash592km
Figure 5 The simulation model for the optical path 1
Out1
Data signal In1 Out1 In2 Out1
Erbium doped fiber
In1
In2Out1
MZM
Out1
CW
Out1
Cooperating channels
In1
In2
In3
Out1
WDM
Out1
EDFA
In2
Demodulator
In1 Out1 In2 Out1
Erbium doped fiber 1
In1 Out1 In2 Out1
Erbium doped fiber 2
In1 Out1 In2 Out1
Erbium doped fiber 3
SMFmdash442 km
SMFmdash425 km
SMFmdash433km
SMFmdash407 km
Figure 6 The simulation model for the optical path 2
the optical signal-to-noise ratio (OSNR) and therefore it isnecessary to analyze the BER parameter depending on theOSNR Figure 9 shows transmission characteristics for high-level modulation formats QPSK and DQPSK keying exhibitsimilar resistance to noise as BPSK andDBPSK keying In thiscase the transmission ratewould be increased twice and if thepolarization modulation (PDM) is used then the 40Gbitstransmission rate can be reached This solution requires thedeployment of MZM modulators and the PDM modulatorFor 8PSK and 16QAM modulations the noise resistance isdecreasing around 2 dB that in some systems will lead to
higher bit error rates caused by laser noise amplifier noiseandor nonlinear effects of the optical transmission medium
For improving transmission rates of modulation formatsdifferent encoding techniques can be used [26 27] A com-plete scheme of the prepared optical transmission system isshown in Figure 10 where the total optical fiber length isextended to 320 km
After theoretical analysis the following codes RS(255239) BCH(255 231) and LDPC(960 480)were selectedTheRS and BCH codes are capable of encoding data quicklyup to 10Gbits however the LDPC codes require more
Journal of Engineering 7
0 2 4 6 8 10 12 14 16 18
BER
OOK NRZDuobinary
100
10minus1
10minus2
10minus3
10minus4
10minus5
10minus6
10minus7
10minus8
EbN0 (dB)
Figure 7 BER transmission characteristics for OOK keying andDuobinary modulation
0 2 4 6 8 10 12 14 16 18
BER
DBPSKBPSKBFSK
EbN0 (dB)
100
10minus1
10minus2
10minus3
10minus4
10minus5
10minus6
10minus7
10minus8
Figure 8 BER transmission characteristics for BPSK DBPSK andBFSK keying
0 2 4 6 8 10 12 14 16 18
BER
DQPSK8PSK
QPSK16QAM
100
10minus1
10minus2
10minus3
10minus4
10minus5
10minus6
10minus7
10minus8
EbN0 (dB)
Figure 9 BER transmission characteristics for QPSK DQPSK8PSK and 16QAM keying
time to encode data Therefore 10 data streams are encodedseparately and afterwards multiplexed into one data stream(shown in Figure 2) For analyzing and simulating onlybinary modulation formats are used
A comparison of binary modulation techniques (nonco-herent OOK BPSK and DBPSK) combined with encodingtechniques (RS BCH and LDPC) is shown in Figure 11Encoding techniques can increase the system range from50 km up to 160 km depending on appropriate code Bettertransmission characteristics are achievable through coherentphase modulations BPSK and DBPSK where limitations arebetween 80 and 100 km The BCH and RS codes increasethe range of these systems up to 160 km and this systemrange can be increased up to 230 km by using the LDPCcodeThe LDPC code is more than 50 efficient compared toBCH and RS codes however such a system needs encodingindividual data signals with lower transmission rates than thetotal system transmission rate Therefore it is more effectiveto use the LDPC code inmetropolitan networks where a timemultiplexing is used
4 The Implementation of Modulation andEncoding Techniques
Selected modulation and encoding techniques are imple-mented on the optical transmission system with the standardSM fiber (ITU-TG652) where a data signal with the 10Gbitstransmission rate and 80WDMchannels is transmitted Indi-vidual transmitters are designed using the MZM modulatorwhere a continuous wave generated in the CW-DFB laseris modulated with a data signal generated by the Bernoulligenerator The CW-DFB laser generates a continuous wavewith 1mW power and embeds the 4 dB amplitude noise Itis considered that a phase noise is suppressed The analyzedsignal is transmitted with the 1934 THz optical frequencyand the resulting OSNR is 30 dB For increasing the opticaltransmission path range EDFA amplifiers are used every40 km for amplifying the transmitted signal where a noisefigureNF is equal to 4 dBTheoptical fiberwith a negativeCDis placed before a receiver to compensate the CD effect in thesystemThe received signal is detected by a coherent detectorwhose sensitivity is around minus17 dBm Based on the previousanalysis a hard decision scheme with the LDPC(960 480)code is selected for implementation
First binary modulation techniques can be consideredwhere the OOK has the worst transmission characteristicsand therefore the transmission system range is limited to230 km The analyzed BPSK and BFSK modulations achievesimilar transmission characteristics where both systems arecapable of having a signal transmission over the 300 km linelength with the 10Gbits transmission rate It is optional touse these modulations to achieve the longest transmissionsystem range For increasing transmission rates of thesemodulations it is possible to use a combination with thePDM (PDM-BPSK and PDM-BFSK) where the transmissionrate of these systems will be higher twice (20Gbits) Forachieving higher transmission rates it is necessary to usemultilevel modulation formats The QPSK signal range isaround 300 km where a transmission rate compared with
8 Journal of Engineering
Out1
Data signal In2 Out1
Erbium doped fiber
In1
In2Out1
MZMOut1
CW
Out1
Cooperating channels
In1In2In3
Out1
WDM
Out1
EDFA
In2
Demodulator
In2 Out1
Erbium doped fiber 1
In2 Out1
Erbium doped fiber 2
In2 Out1
Erbium doped fiber 3
In Out
PMD
In Out
CHD
In Out
FWM
In2 Out1
SPM amp XPM
In1 Out1
SRS amp SBS amp attenuation
In Out
PMD1
In Out
CHD1
In Out
FWM1
In2 Out1
SPM amp XPM1
In1 Out1
SRS amp SBS amp attenuation 1
In Out
PMD2
In Out
CHD2
In Out
FWM2
In2 Out1
SPM amp XPM2
In1 Out1
SRS amp SBS amp attenuation 2
In Out
PMD3
In Out
CHD3
In Out
FWM3
In2 Out1
SPM amp XPM3
In1 Out1
SRS amp SBS amp attenuation 3
Samsung SM NZD-SF 80km length
Samsung SM NZD-SF 80km length
Samsung SM NZD-SF 80km length
Samsung SM NZD-SF 80km length
Figure 10 The block scheme for analysis of the selected modulation and encoding techniques
Table 3 Comparison of selected modulation techniques implemented for the optical transmission system
Modulation techniques Parameters Fiber length [km]40 80 120 160 200 240 280 320
OOK BER [ ] 10minus12 10minus12 10minus12 10minus9 10minus2 10minus1 10minus1 10minus1
OSNR [dB] 25 19 14 7 2 1 1 1
BPSK BER [ ] 10minus12 10minus12 10minus12 10minus12 10minus12 10minus12 10minus11 10minus9
OSNR [dB] 27 24 20 17 15 11 8 5
DBPSK BER [ ] 10minus12 10minus12 10minus12 10minus12 10minus12 10minus12 10minus10 10minus8
OSNR [dB] 27 24 20 17 15 11 8 5
BFSK BER [ ] 10minus12 10minus12 10minus12 10minus12 10minus12 10minus12 10minus11 10minus9
OSNR [dB] 28 26 24 21 18 16 13 10
QPSK BER [ ] 10minus12 10minus12 10minus12 10minus12 10minus12 10minus12 10minus11 10minus9
OSNR [dB] 27 24 20 17 15 11 8 5
8PSK BER [ ] 10minus12 10minus12 10minus12 10minus12 10minus10 10minus6 10minus3 10minus2
OSNR [dB] 27 23 19 14 9 6 2 1
16QAM BER [ ] 10minus12 10minus12 10minus12 10minus12 10minus9 10minus3 10minus1 10minus1
OSNR [dB] 27 22 17 12 7 2 2 1
Calculated BER
BER
0
1
2
3
4
5
6
7
8
9
10
Length (km)0 50 100 150 200 250 300 350
OOKBPSKDBPSK
times10minus3
OOK-RS (255 239)
DBPSK-RS (255 239)
OOK-BCH (255 231)BPSK-BCH (255 231)DBPSK-BCH (255 231)OOK-LDPC (960 480)BPSK-LDPC (960 480)DBPSK-LDPC (960 480)
BPSK-RS (255 239)
Figure 11 Comparison of binary modulation techniques combinedwith encoding techniques
binarymodulations is twice higher Using a combinationwiththe PDM the result transmission rate achieves 40GbitsThe maximum range of 8PSK and 16QAM systems is around200 kmThe decreased range of these systems is due to ampli-fier noises and nonlinear effects in the optical environmentHowever these systems using the PDM have transmissionrates 60Gbits (PDM-8PSK) and 80Gbits (PDM-16QAM)per channel The analysis shows that the range limitationis mainly caused by amplifier noises and nonlinear effectsthat are accumulating For increasing the system range ofmultilevel modulation formats the use of encoding tech-niques such as the LDPC(960 480) code is optional Forfurther improvement of transmission characteristics opticalamplifiers with a low noise figure advanced detectors andsoft encoding schemes can be used However these compo-nents rapidly increase the system cost and particular financialanalysis for the system effectiveness is necessary Outputtransmission characteristics for each modulation techniqueare shown in Table 3
Journal of Engineering 9
5 Conclusion
This contribution analyzes a possible utilization of selectedmodulation and advanced encoding techniques at high datarate signal transmission in optical transmission medium Atfirst the prepared simulation model for optical transmissionsystems with real transmission systems is compared Next aperformance analysis of different binary andmultilevel mod-ulation techniques in combination with RS BCH and LDPCcodes utilized in optical transmission systems is presentedThe simulation results show the limitation of binary modu-lation techniques and their possible improvement using FECcodes The LDPC code can improve a systemrsquos performancefor all modulation schemes Finally a prepared optical systemwith real parameters is enhanced using the LDPC code andselected modulation and encoding techniques are analyzedfor their practical implementation
In future analyses convolutional or turbo codes with dif-ferent rates and constraint length can be considered More-over other recent modulation techniques in possible com-binations with encoding techniques are analyzed Besides autilization of solitons with available optical signal processingtechniques is a very interesting area
Disclosure
This work is a part of research activities conducted atSlovak University of Technology Bratislava Faculty of Elec-trical Engineering and Information Technology Institute ofTelecommunications within the scope of Projects VEGA no1017416 ldquoAdvanced Algorithms and Methods for New Gen-eration Optical Networks for the IMS and NGN ConvergedInfrastructurerdquo and KEGA no 007STU-42016 ldquoProgressiveEducational Methods in the Field of TelecommunicationsMultiservice Networksrdquo
Competing Interests
The authors declare that they have no competing interests
References
[1] K Fukuchi T KasamatsuMMorie et al ldquo1092-Tbs (273times40-Gbs) triple-bandultra-dense WDM optical-repeatered trans-mission experimentrdquo in Proceedings of the Optical Fiber Com-munication Conference (OFC rsquo01) Paper PD24 2001
[2] Z Jia J Yu H-C Chien Z Dong and D Di Huo ldquoField trans-mission of 100G and beyond multiple baud rates and mixedline rates using nyquist-WDM technologyrdquo Journal of LightwaveTechnology vol 30 no 24 Article ID 6235964 pp 3793ndash38042012
[3] H Rohde E Gottwald A Teixeira et al ldquoCoherent ultra denseWDM technology for next generation optical metro and accessnetworksrdquo Journal of Lightwave Technology vol 32 no 10 pp2041ndash2052 2014
[4] H Taga ldquoLong distance transmission experiments using theWDM technologyrdquo Journal of Lightwave Technology vol 14 no6 pp 1287ndash1298 1996
[5] B E A Saleh and M C Teich Fundamentals of PhotonicsWiley-Interscience 1991
[6] L N Binh Optical Fiber Communication Systems CRC PressNew York NY USA 2010
[7] G Keiser Optical Fiber Communications John Wiley amp SonsNew York NY USA 2003
[8] Z Jamaludin A F Abas A S M Noor and M K AbfullahldquoIssues on polarization mode dispersion (PMD) for high speedfiber optics transmissionrdquo Suranaree Journal of Science andTechnology vol 12 no 2 pp 98ndash106 2005
[9] S P Singh andN Singh ldquoNonlinear effects in optical fibers ori-ginmanagement and applicationsrdquoProgress in ElectromagneticsResearch vol 73 pp 249ndash275 2007
[10] E Iannone F Matera A Mecozzi andM SettembreNonlinearOptical Communication Networks TK510359N66 John Wileyamp Sons New York NY USA 1998
[11] D Cotter ldquoNonlinearity in optical fibre communicationsrdquo inNonlinear Optics in Signal Processing RW Eason andAMillerEds vol 49 of Engineering Aspects of Lasers Series SpringerAmsterdam Netherlands 1993
[12] R Hill A First Course in Coding Theory Clarendon PressOxford UK 1980
[13] W Trappe and L C Washington Introduction to CryptographywithCodingTheory PearsonPrenticeHall New JerseyNJUSA2006
[14] J H van Lint Introduction to Coding Theory Springer BerlinGermany 1999
[15] M BossertChannel Coding for Telecommunications JohnWileyamp Sons New York NY USA 1999
[16] F Certık ldquoUtilization of encoding techniques at the signal trans-mission in the optical fiberrdquo in Advances in Signal Processingvol 3 no 2 pp 17ndash24 2015
[17] F Certık ldquoThe analysis of different encoding and modulationtechniques at the signal transmission in the optical mediumrdquo inProceedings of the 37th International Symposium on the Appli-cation of Computers and Operations Research in the MineralIndustry (APCOM rsquo15) pp 978ndash80 STU Publishing HouseBratislava Slovakia
[18] R Roka ldquoFixed transmission mediardquo in Technology and Engi-neering Applications of Simulink S Chakravarty Ed pp 41ndash68InTech Rijeka Croatia 2012
[19] R Roka and F Certık ldquoSimulation tools for broadband passiveoptical networksrdquo in Simulation Technologies in Networking andCommunications Selecting the Best Tool for the Test CRC PressBoca Raton Fla USA 2014
[20] R Roka ldquoThe environment of fixed transmission media andtheir negative influences in the simulationrdquo International Jour-nal ofMathematics and Computers in Simulation vol 9 pp 190ndash205 2015
[21] R Essiambre G Kramer P J Winzer G J Foschini and BGoebel ldquoCapacity limits of optical fiber networksrdquo Journal ofLightwave Technology vol 28 no 4 pp 662ndash701 2010
[22] P J Winzer and R J Essiambre ldquoAdvanced optical modulationformatsrdquo Proceedings of the IEEE vol 94 no 5 pp 952ndash9852006
[23] M I Olmedo T Zuo J B Jensen et al ldquoMultiband carrierlessamplitude phase modulation for high capacity optical datalinksrdquo Journal of Lightwave Technology vol 32 no 4 pp 798ndash804 2014
[24] T Rahman D Rafigue A Napoli et al ldquoUltralong haul 128-Tbs PM-16QAMWDM transmission employing hybrid amplifica-tionrdquo Journal of Lightwave Technology vol 33 no 9 pp 1794ndash1804 2015
10 Journal of Engineering
[25] S Chandrasekhar and X Liu ldquoExperimental investigation onthe performance of closely spaced multi-carrier PDM-QPSKwith digital coherent detectionrdquo Optics Express vol 17 no 24pp 21350ndash21361 2009
[26] I B Djordjevic ldquoGeneralized LDPC codes and turbo-productcodes with reed-muller component codesrdquo in Proceedings of the8th International Conference on Telecommunications in ModernSatellite Cable and Broadcasting Services (TELSIKS rsquo07) pp127ndash134 Nis Serbia September 2007
[27] D Ouchi K Kubo T Mizuochi et al ldquoA fully integrated blockturbo code FEC for 10Gbs optical communication systemsrdquoin Proceedings of the Optical Fiber Communication (OFC rsquo06)Anaheim Calif USA March 2006
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2 Journal of Engineering
11 Characteristics of the Optical Fiber Each optical fiber rep-resents a transmission system which is frequency dependentA pulse propagation inside this transmission system can bedescribed by the nonlinear Schrodinger equation (NLSE)which is derivate from Maxwellrsquos equations From the NLSEequation we can express effects in optical fibers that are clas-sified as [5 6]
(a) linear effects which are wavelength dependent(b) nonlinear effects which are intensity (power) depen-
dent
Linear Effects Major impairments of optical signals trans-mitted via the optical fiber environment are mainly causedby linear effects the dispersion and the attenuation Theattenuation limits a power of optical signals and representstransmission losses Nowadays optical transmission systemsare able to minimize impact of the attenuation by deployingall-optical amplifiers Another source of the linear effect rep-resents the dispersion causing broadening of optical pulses intime and signal phase shifting at the fiber endThere are threemain dispersion types [5ndash8]
(i) The modal dispersion caused by the different propa-gation velocity of optical modes propagating in mul-timode fibers
(ii) The chromatic dispersion caused by the differentpropagation velocity ofwavelengths generated in lasersources propagating in the optical fiber It consists ofmaterial profile and waveguide dispersions
(iii) The polarization mode dispersion caused by the bire-fringence effect due to a nonsymmetry and imperfec-tions of optical fibers
Nonlinear Effects These effects play an important role at thelong haul optical signal transmission Nonlinear effects canbe classified as follows
(i) Kerr nonlinearities are self-induced effects where thephase velocity of the pulse depends on the pulsersquos ownintensity The Kerr effect describes a change in thefiber refractive index due to electrical perturbationsDue to the Kerr effect following effects are possible todescribe
(a) Self-phase modulation (SPM) is an effect thatchanges the refractive index of the transmissionmedium caused by the pulse intensity [9 10]
(b) Four-wavemixing (FWM) is an effect where thefourth wave can be arisen by mixing of threeoptical waves and this one can appear in thesame wavelength as one of mixed waves [9]
(c) Cross-phase effect (XPM) is an effect that causesa spectral broadening where the optical pulsecan change the phase of another pulse with dif-ferent wavelengths [9ndash11]
(ii) Scattering nonlinearities occur due to a photon inelas-tic scattering to lower energy photons The pulse
energy is transferred to another wave with a differentwavelength Two such effects appear in the opticalfiber
(a) Stimulated Brillouin scattering (SBS) and stim-ulated Raman scattering (SRS) are effects thatchange a variance of light wave into differentwaves when the intensity reaches a certainthreshold [9ndash11]
12 Principles of Selected Encoding Techniques Forward errorcorrection (FEC) techniques represent a system where addi-tional data are inserted into a data message so that it can berecovered by a receiver even when a number of errors due totransmission is emergent These FEC codes are widely usedin systems where a data retransmission is not an option suchas broadcasting and high haul optical transmission systems[12 13] FEC codes are usually divided into convolutional andblock codes
(i) Convolutional codes are processed on a bit-by-bitbasis
(ii) Block codes are processed on a block-by-block basis
Convolutional codes are based on the encoding signalwith a final impulse response This type of coding does notrequire division of bits into the blocksThe convolution codesmay be decoded using the Viterbi algorithm which is amethod of decoding with maximum reliability This methodis based onfinding themost appropriateway forward throughthe possible states of transitionThe complexity of the Viterbialgorithm increases with the number of states in decodingTherefore it is advisable to use codes that use a small amountof redundancy Convolutional codes have lower resistanceagainst noise than the linear block codes and not using theminimal trellis like linear blocks [13 14]
For analysis block codes especially cyclic block codesare considered Cyclic block codes are widely used in datacommunication because their structure makes encoder anddecoder circuitry simple Cyclic block codes are defined asthe cyclic (119899 119896) code if 119862 is a linear code of the length 119899 overa finite field and if any cyclic shift of a codeword is also acodeword as shown in
1198880 1198881 119888
119899minus1isin 119862 997904rArr 119888
119899minus1 1198880 1198881 119888
119899minus2isin 119862 (1)
The information data with the length 119896 are coded with thepolynomial 119892(119909) using (1) Consider
119888 (119909) = 119894 (119909) 119892 (119909) (2)
where 119888(119909) represents the polynomial of degree (119899 minus 1) 119894(119909)is the information polynomial of degree (119896 minus 1) and thegenerator polynomial 119892(119909)must be of degree (119899 minus 119896)
The Reed-Solomon (RS) codes that belong to cyclic blockcodes are widely used in many communication fields [13 14]The RS codes are related to BCH codes and can be defined asa primitive BCH code of the length 119899 where
119899 = 119902 minus 1 = 2119904minus 1 over GF (119902) = GF (2119904) (3)
Journal of Engineering 3
RS codes are specified as RS(119899 119896) or RS(119899 119896 119889) where119899 represent the code length 119896 represents the informationlength and 119889 is the Hamming distance Let 119905 be a number oferrors that can be corrected then correction (119905) or detection(2119905) abilities are specified for the code There exist twoencoding types for RS codes
(i) Nonsystematic(ii) Systematic
The decoding for RS codes is based on syndrome equa-tions
119904119896=
119905
sum119894=1
119884119894119883119896
119894 119896 = 0 1 2119905 minus 1 (4)
where 119883119894is the locator 119894th error and 119884
119894represents its value
(detection of location and value) More information about RSencoding techniques can be found in [13]
The Bose Chaudhuri Hocquenghem (BCH) code is acyclic polynomial code over a finite field with chosen poly-nomial generator BCH codes are 119905-error correcting codesdefined over finite fields GF(119902) where 2119905 + 1 lt 119902 The advan-tage of BCH codes is using syndrome to decode errors inwhich there exist good decoding algorithms that correctmultiple errors [14]
The generating of a binary BCH code over an extensionfield GF(119902119898) is easy to construct The polynomial generator119892(119909) is needed to obtain a cyclic code [12ndash16] For any integer119898 ge 3 and 119905 lt 2119898 minus 1 there exists a primitive BCH code withparameters 119899 = 2119898 minus 1 119899 minus 119896 le 119898 sdot 119905 and 119889min le 2119905 + 1The generator polynomial119892(119909) of 119905-error correcting primitiveBCH codes of the length 2119898 minus 1 is given by
119892 (119909) = LCM 1198981(119909) 119898
2(119909) 119898
2119905minus1(119909) 119898
2119905(119909) (5)
where LCM represents the Least CommonMultipleThen thecode is generated using (2)
BCH codes are decoded with various algorithm based oncalculation of syndromes values for the received codeword
Low Density Parity Check (LDPC) codes belong to linearencoding techniques that can transmit data close to the Shan-non theorem (the channel capacity) The main disadvantageof the LDPC code is the time consumption of the codealgorithm which often limits its utilization in high datarate optical transmission systems However it is possible toencode more low data rate signals and then merge them intoone high data rate signal The high data rate signal can betransmitted via the optical transmission system
The LDPC coding is defined by the LDPC 119867 matrixAssuming the length of information bits K the length ofencoded bits119873 and the average weigh column119908 gt 2 (weightvectors represent the sum of nonzero components of thevector) then119872 = (119873 minus 119870) is the sum of the parity check incodeThe LDPCmatrix119867 is composed of119872 rows and119873 col-umnsThe generationmatrix119866 is necessary to encode codingsequence [14 15]
Prepared block schemes of mentioned encoding tech-niques in the simulation model are shown in Figures 1 and 2Figure 3 shows the schematic block diagram of LDPC source
Bernoullibinary
Bernoulli binary generator
Multiple
Sample_time
Binary inputRS encoderBinary inputRS encoder
1OutGaussian
Gaussian filter
[Orig]
Goto
times
Figure 1 The block scheme for the signal generation with RS andBCH encoding techniques
signal Blocks are initiated using a Bernoulli generator thatgenerates random binary bits representation of the infor-mation signal The signal is then coded with an adequateencoding technique The output signal is filtered with aGaussian filter for representation of the real signal TheLDPC block is created by using 10 Bernoulli generators eachencoded with the LDPC code and merged into the high datarate signal [16 17]
2 The Simulation of the OpticalTransmission System
The prepared simulation model comes out from the simula-tion model for optical communications introduced in [18ndash20] A modeling is performed in the Matlab Simulink 2014programming environment The simulation model presentsan influence of linear and nonlinear effects present in theoptical transmission medium at the signal transmission Thegeneral schematic block diagram is shown in Figure 4 To ver-ify a reliability and exactness of the simulationmodel authorsrealized a comparison of two optical transmission pathsmea-sured in cooperation with the Orange Slovakia companyTheoptical path 1 consists of the 592 km standard SM (ITU-TG652) fiber with the 10Gbits noncoherent OOKmodulatedsignal using 80WDMchannelsThe optical path 2 consists of1707 km standard SM (ITU-T G652) fiber with the 10Gbitsnoncoherent OOK modulated signal using 80 WDM chan-nels Transmitted signals are examined with the 1934 THzfrequency Both paths are utilizing EDFA amplifiers at theoptical fiber end while the optical path 2 is furthermoreusing additional 3 EDFA amplifiers every 40 km Simulationmodels for the optical path 1 and optical path 2 are shownin Figures 5 and 6 respectively For describing informationsignal transmission a bit error rate (BER) parameter can becalculated The BER calculation for each simulation model isdone by comparing input and output bits For both opticalpaths simulation results show theBERparameter higher than10minus12 satisfying common transmission conditions For bothsimulation models the Reed-Solomon code RS(255 239) isutilized to enhance the system BER parameter
For both optical paths presented simulated andmeasuredtransmission parameters (Tables 1 and 2) include besidesother received optical power level values for calculationsrelated to the attenuation As can be seen parameters arevery similar at which the simulation is characterized byworseones Therefore if the optical simulation is passed then thereal system would be properly and correctly operating
4 Journal of Engineering
Bernoullibinary
Bernoulli binarygenerator Multiple
Sample_time
1OutGaussian
Gaussian filter
LDPC encoder
LDPC encoder
In1 In2 In3
In4 In5
Out In6 MergeIn7In8In9
In10
Bernoullibinary
Bernoulli binarygenerator 1
Multiple 1Sample_time 1
LDPC encoder
LDPC encoder 1
Bernoullibinary
Bernoulli binarygenerator 2
Multiple 2Sample_time 2
LDPC encoder
LDPC encoder 2
Bernoullibinary
Bernoulli binarygenerator 3
Multiple 3Sample_time 3
LDPC encoder
LDPC encoder 3
Bernoullibinary
Bernoulli binarygenerator 4
Multiple 4Sample_time 4
LDPC encoder
LDPC encoder 4
Bernoullibinary
Bernoulli binarygenerator 5
Multiple 5Sample_time 5
LDPC encoder
LDPC encoder 5
Bernoullibinary
Bernoulli binarygenerator 6
Multiple 6Sample_time 6 LDPC encoder
LDPC encoder 6
Bernoullibinary
Bernoulli binarygenerator 7
Multiple 7Sample_time 7
LDPC encoder
LDPC encoder 7
Bernoullibinary
Bernoulli binarygenerator 8
Multiple 8Sample_time 8LDPC encoder
LDPC encoder 8
Bernoullibinary
Bernoulli binarygenerator 9
Multiple 9Sample_time 9LDPC encoder
LDPC encoder 9
timestimes
times
times
times
times
times
times
times
times
10 lowast 1Gbits to 10Gbits
Figure 2 The block scheme for the signal generation with the LDPC encoding technique
Table 1 The optical path 1 transmission parameters
Parameters Measured SimulatedRx power (dBm) minus132 minus134OSNR (dB) 259 243PMD (ps) 106 125SPM (dB) 087 122XPM (dB) minus5759 minus605FWM (dB) NA minus1243119876 799 81BER gt10minus15 gt10minus12
3 The Analysis of Selected Modulation andEncoding Techniques
The first modulation technique used for real optical trans-mission systems was the two-level amplitude modulationOOK with the direct detection This system is characterizedby transmission rates from 1Gbits and its limitation isrepresented by the 10Gbits rate over optical single modefibers with the 50 km line length Nowadays OOK systems
Table 2 The optical path 2 transmission parameters
Parameters Measured SimulatedRx power (dBm) minus1369 minus123OSNR (dB) 2107 209PMD (ps) 174 183SPM (dB) 103 11XPM (dB) minus4202 minus405FWM (dB) NA minus112119876 627 62BER gt10minus15 gt10minus12
are deployed with coherent receivers that can increase thesystem range depending on the receiver sensitivity andthe transmittersrsquo generated noise Coherent systems highlyimprove transmission characteristics but their implemen-tation is expensive due to security mechanisms for phaseand polarization detecting Another possible improvementfor coherent systems is represented by using the Duobinarymodulation This leads to a modification in the electricaldomain that is less costly than in case of exchange optical
Journal of Engineering 5
Merge block
1 0 0 1 1 1 1 10 0
1
111
1
1
00
0
0
Gauss filter 10Gbits
10Gbits
110
1Gbits
1Gbits
1Gbits
1Gbits
1Gbits
1Gbits
1Gbits
1Gbits
1Gbits
1Gbits
1Gbits
1Gbits
LDPC codingn = i + k
1Gbits
LDPC codingn = i + k
1Gbits
LDPC codingn = i + k
1Gbits
LDPC codingn = i + k
1Gbits
LDPC codingn = i + k
1Gbits
LDPC codingn = i + k
1Gbits
LDPC codingn = i + k
1Gbits
LDPC codingn = i + k
1Gbits
LDPC codingn = i + k
1Gbits
LDPC codingn = i + k
Bernoulli generatorrectangular impulse
Bernoulli generatorrectangular impulse
Bernoulli generatorrectangular impulse
Bernoulli generatorrectangular impulse
Bernoulli generatorrectangular impulse
Bernoulli generatorrectangular impulse
Bernoulli generatorrectangular impulse
Bernoulli generatorrectangular impulse
Bernoulli generatorrectangular impulse
Bernoulli generatorrectangular impulse
generatorSample
Figure 3 The schematic block diagram for the signal generation with the LDPC encoding technique
System signal source
System signal source
System signal source
1
2
N
Optical fiber
Circ
ulat
or
Localoscillator
Signal with different wavelength
Signal with different wavelength
Laser source
Electric datasignal
Electric datasignal
Mach-Zehndermodulator
Continuousoptical wave
Wavelengthdivision
multiplex
Erbium dopedfiber
Phase andamplitudedetection
Chromatic andpolarization modedispersion [time
broadening signalphase shift]
Four-wave mixing[intensity noise from
neighbour channels ondifferent wavelength]
[phase noise andsignal frequency shiftdue to signal intensity]
Self-phase andcross-phase modulation
[intensity noise fromneighbour channels
and decreasing signalintensity]
Stimulated Brillouinand Raman scattering
attenuation
Figure 4 The schematic block diagram for the optical transmission system
components For given modulation the Monte Carlo algo-rithm can be used because it allows a measuring of theBER parameter The simulation model uses the standard SM(ITU-T G656) optical fiber The comparison of transmissioncharacteristics for coherent OOK and Duobinary systems isshown in Figure 7
Possible solution can be represented by coherent systemswith phase and frequency modulation techniques which are
represented by BPSK DBPSK and BFSK These modula-tion techniques achieve similar transmission characteristics(shown in Figure 8) where the BPSK achieves better resultsabout 01 dB compared to the DBPSK and about 3 dB com-pared to the FSK
Higher modulation formats can be further used toincrease signal transmission rates in the optical system [21ndash25] Such modulation techniques have a lower tolerance to
6 Journal of Engineering
Out1
Data signal In1 Out1 In2
Demodulator
In1
In2Out1
MZM
Out1
CW
Out1
Cooperating channels
In1
In2
In3
Out1
WDM
Out1
EDFA
SMFmdash592km
Figure 5 The simulation model for the optical path 1
Out1
Data signal In1 Out1 In2 Out1
Erbium doped fiber
In1
In2Out1
MZM
Out1
CW
Out1
Cooperating channels
In1
In2
In3
Out1
WDM
Out1
EDFA
In2
Demodulator
In1 Out1 In2 Out1
Erbium doped fiber 1
In1 Out1 In2 Out1
Erbium doped fiber 2
In1 Out1 In2 Out1
Erbium doped fiber 3
SMFmdash442 km
SMFmdash425 km
SMFmdash433km
SMFmdash407 km
Figure 6 The simulation model for the optical path 2
the optical signal-to-noise ratio (OSNR) and therefore it isnecessary to analyze the BER parameter depending on theOSNR Figure 9 shows transmission characteristics for high-level modulation formats QPSK and DQPSK keying exhibitsimilar resistance to noise as BPSK andDBPSK keying In thiscase the transmission ratewould be increased twice and if thepolarization modulation (PDM) is used then the 40Gbitstransmission rate can be reached This solution requires thedeployment of MZM modulators and the PDM modulatorFor 8PSK and 16QAM modulations the noise resistance isdecreasing around 2 dB that in some systems will lead to
higher bit error rates caused by laser noise amplifier noiseandor nonlinear effects of the optical transmission medium
For improving transmission rates of modulation formatsdifferent encoding techniques can be used [26 27] A com-plete scheme of the prepared optical transmission system isshown in Figure 10 where the total optical fiber length isextended to 320 km
After theoretical analysis the following codes RS(255239) BCH(255 231) and LDPC(960 480)were selectedTheRS and BCH codes are capable of encoding data quicklyup to 10Gbits however the LDPC codes require more
Journal of Engineering 7
0 2 4 6 8 10 12 14 16 18
BER
OOK NRZDuobinary
100
10minus1
10minus2
10minus3
10minus4
10minus5
10minus6
10minus7
10minus8
EbN0 (dB)
Figure 7 BER transmission characteristics for OOK keying andDuobinary modulation
0 2 4 6 8 10 12 14 16 18
BER
DBPSKBPSKBFSK
EbN0 (dB)
100
10minus1
10minus2
10minus3
10minus4
10minus5
10minus6
10minus7
10minus8
Figure 8 BER transmission characteristics for BPSK DBPSK andBFSK keying
0 2 4 6 8 10 12 14 16 18
BER
DQPSK8PSK
QPSK16QAM
100
10minus1
10minus2
10minus3
10minus4
10minus5
10minus6
10minus7
10minus8
EbN0 (dB)
Figure 9 BER transmission characteristics for QPSK DQPSK8PSK and 16QAM keying
time to encode data Therefore 10 data streams are encodedseparately and afterwards multiplexed into one data stream(shown in Figure 2) For analyzing and simulating onlybinary modulation formats are used
A comparison of binary modulation techniques (nonco-herent OOK BPSK and DBPSK) combined with encodingtechniques (RS BCH and LDPC) is shown in Figure 11Encoding techniques can increase the system range from50 km up to 160 km depending on appropriate code Bettertransmission characteristics are achievable through coherentphase modulations BPSK and DBPSK where limitations arebetween 80 and 100 km The BCH and RS codes increasethe range of these systems up to 160 km and this systemrange can be increased up to 230 km by using the LDPCcodeThe LDPC code is more than 50 efficient compared toBCH and RS codes however such a system needs encodingindividual data signals with lower transmission rates than thetotal system transmission rate Therefore it is more effectiveto use the LDPC code inmetropolitan networks where a timemultiplexing is used
4 The Implementation of Modulation andEncoding Techniques
Selected modulation and encoding techniques are imple-mented on the optical transmission system with the standardSM fiber (ITU-TG652) where a data signal with the 10Gbitstransmission rate and 80WDMchannels is transmitted Indi-vidual transmitters are designed using the MZM modulatorwhere a continuous wave generated in the CW-DFB laseris modulated with a data signal generated by the Bernoulligenerator The CW-DFB laser generates a continuous wavewith 1mW power and embeds the 4 dB amplitude noise Itis considered that a phase noise is suppressed The analyzedsignal is transmitted with the 1934 THz optical frequencyand the resulting OSNR is 30 dB For increasing the opticaltransmission path range EDFA amplifiers are used every40 km for amplifying the transmitted signal where a noisefigureNF is equal to 4 dBTheoptical fiberwith a negativeCDis placed before a receiver to compensate the CD effect in thesystemThe received signal is detected by a coherent detectorwhose sensitivity is around minus17 dBm Based on the previousanalysis a hard decision scheme with the LDPC(960 480)code is selected for implementation
First binary modulation techniques can be consideredwhere the OOK has the worst transmission characteristicsand therefore the transmission system range is limited to230 km The analyzed BPSK and BFSK modulations achievesimilar transmission characteristics where both systems arecapable of having a signal transmission over the 300 km linelength with the 10Gbits transmission rate It is optional touse these modulations to achieve the longest transmissionsystem range For increasing transmission rates of thesemodulations it is possible to use a combination with thePDM (PDM-BPSK and PDM-BFSK) where the transmissionrate of these systems will be higher twice (20Gbits) Forachieving higher transmission rates it is necessary to usemultilevel modulation formats The QPSK signal range isaround 300 km where a transmission rate compared with
8 Journal of Engineering
Out1
Data signal In2 Out1
Erbium doped fiber
In1
In2Out1
MZMOut1
CW
Out1
Cooperating channels
In1In2In3
Out1
WDM
Out1
EDFA
In2
Demodulator
In2 Out1
Erbium doped fiber 1
In2 Out1
Erbium doped fiber 2
In2 Out1
Erbium doped fiber 3
In Out
PMD
In Out
CHD
In Out
FWM
In2 Out1
SPM amp XPM
In1 Out1
SRS amp SBS amp attenuation
In Out
PMD1
In Out
CHD1
In Out
FWM1
In2 Out1
SPM amp XPM1
In1 Out1
SRS amp SBS amp attenuation 1
In Out
PMD2
In Out
CHD2
In Out
FWM2
In2 Out1
SPM amp XPM2
In1 Out1
SRS amp SBS amp attenuation 2
In Out
PMD3
In Out
CHD3
In Out
FWM3
In2 Out1
SPM amp XPM3
In1 Out1
SRS amp SBS amp attenuation 3
Samsung SM NZD-SF 80km length
Samsung SM NZD-SF 80km length
Samsung SM NZD-SF 80km length
Samsung SM NZD-SF 80km length
Figure 10 The block scheme for analysis of the selected modulation and encoding techniques
Table 3 Comparison of selected modulation techniques implemented for the optical transmission system
Modulation techniques Parameters Fiber length [km]40 80 120 160 200 240 280 320
OOK BER [ ] 10minus12 10minus12 10minus12 10minus9 10minus2 10minus1 10minus1 10minus1
OSNR [dB] 25 19 14 7 2 1 1 1
BPSK BER [ ] 10minus12 10minus12 10minus12 10minus12 10minus12 10minus12 10minus11 10minus9
OSNR [dB] 27 24 20 17 15 11 8 5
DBPSK BER [ ] 10minus12 10minus12 10minus12 10minus12 10minus12 10minus12 10minus10 10minus8
OSNR [dB] 27 24 20 17 15 11 8 5
BFSK BER [ ] 10minus12 10minus12 10minus12 10minus12 10minus12 10minus12 10minus11 10minus9
OSNR [dB] 28 26 24 21 18 16 13 10
QPSK BER [ ] 10minus12 10minus12 10minus12 10minus12 10minus12 10minus12 10minus11 10minus9
OSNR [dB] 27 24 20 17 15 11 8 5
8PSK BER [ ] 10minus12 10minus12 10minus12 10minus12 10minus10 10minus6 10minus3 10minus2
OSNR [dB] 27 23 19 14 9 6 2 1
16QAM BER [ ] 10minus12 10minus12 10minus12 10minus12 10minus9 10minus3 10minus1 10minus1
OSNR [dB] 27 22 17 12 7 2 2 1
Calculated BER
BER
0
1
2
3
4
5
6
7
8
9
10
Length (km)0 50 100 150 200 250 300 350
OOKBPSKDBPSK
times10minus3
OOK-RS (255 239)
DBPSK-RS (255 239)
OOK-BCH (255 231)BPSK-BCH (255 231)DBPSK-BCH (255 231)OOK-LDPC (960 480)BPSK-LDPC (960 480)DBPSK-LDPC (960 480)
BPSK-RS (255 239)
Figure 11 Comparison of binary modulation techniques combinedwith encoding techniques
binarymodulations is twice higher Using a combinationwiththe PDM the result transmission rate achieves 40GbitsThe maximum range of 8PSK and 16QAM systems is around200 kmThe decreased range of these systems is due to ampli-fier noises and nonlinear effects in the optical environmentHowever these systems using the PDM have transmissionrates 60Gbits (PDM-8PSK) and 80Gbits (PDM-16QAM)per channel The analysis shows that the range limitationis mainly caused by amplifier noises and nonlinear effectsthat are accumulating For increasing the system range ofmultilevel modulation formats the use of encoding tech-niques such as the LDPC(960 480) code is optional Forfurther improvement of transmission characteristics opticalamplifiers with a low noise figure advanced detectors andsoft encoding schemes can be used However these compo-nents rapidly increase the system cost and particular financialanalysis for the system effectiveness is necessary Outputtransmission characteristics for each modulation techniqueare shown in Table 3
Journal of Engineering 9
5 Conclusion
This contribution analyzes a possible utilization of selectedmodulation and advanced encoding techniques at high datarate signal transmission in optical transmission medium Atfirst the prepared simulation model for optical transmissionsystems with real transmission systems is compared Next aperformance analysis of different binary andmultilevel mod-ulation techniques in combination with RS BCH and LDPCcodes utilized in optical transmission systems is presentedThe simulation results show the limitation of binary modu-lation techniques and their possible improvement using FECcodes The LDPC code can improve a systemrsquos performancefor all modulation schemes Finally a prepared optical systemwith real parameters is enhanced using the LDPC code andselected modulation and encoding techniques are analyzedfor their practical implementation
In future analyses convolutional or turbo codes with dif-ferent rates and constraint length can be considered More-over other recent modulation techniques in possible com-binations with encoding techniques are analyzed Besides autilization of solitons with available optical signal processingtechniques is a very interesting area
Disclosure
This work is a part of research activities conducted atSlovak University of Technology Bratislava Faculty of Elec-trical Engineering and Information Technology Institute ofTelecommunications within the scope of Projects VEGA no1017416 ldquoAdvanced Algorithms and Methods for New Gen-eration Optical Networks for the IMS and NGN ConvergedInfrastructurerdquo and KEGA no 007STU-42016 ldquoProgressiveEducational Methods in the Field of TelecommunicationsMultiservice Networksrdquo
Competing Interests
The authors declare that they have no competing interests
References
[1] K Fukuchi T KasamatsuMMorie et al ldquo1092-Tbs (273times40-Gbs) triple-bandultra-dense WDM optical-repeatered trans-mission experimentrdquo in Proceedings of the Optical Fiber Com-munication Conference (OFC rsquo01) Paper PD24 2001
[2] Z Jia J Yu H-C Chien Z Dong and D Di Huo ldquoField trans-mission of 100G and beyond multiple baud rates and mixedline rates using nyquist-WDM technologyrdquo Journal of LightwaveTechnology vol 30 no 24 Article ID 6235964 pp 3793ndash38042012
[3] H Rohde E Gottwald A Teixeira et al ldquoCoherent ultra denseWDM technology for next generation optical metro and accessnetworksrdquo Journal of Lightwave Technology vol 32 no 10 pp2041ndash2052 2014
[4] H Taga ldquoLong distance transmission experiments using theWDM technologyrdquo Journal of Lightwave Technology vol 14 no6 pp 1287ndash1298 1996
[5] B E A Saleh and M C Teich Fundamentals of PhotonicsWiley-Interscience 1991
[6] L N Binh Optical Fiber Communication Systems CRC PressNew York NY USA 2010
[7] G Keiser Optical Fiber Communications John Wiley amp SonsNew York NY USA 2003
[8] Z Jamaludin A F Abas A S M Noor and M K AbfullahldquoIssues on polarization mode dispersion (PMD) for high speedfiber optics transmissionrdquo Suranaree Journal of Science andTechnology vol 12 no 2 pp 98ndash106 2005
[9] S P Singh andN Singh ldquoNonlinear effects in optical fibers ori-ginmanagement and applicationsrdquoProgress in ElectromagneticsResearch vol 73 pp 249ndash275 2007
[10] E Iannone F Matera A Mecozzi andM SettembreNonlinearOptical Communication Networks TK510359N66 John Wileyamp Sons New York NY USA 1998
[11] D Cotter ldquoNonlinearity in optical fibre communicationsrdquo inNonlinear Optics in Signal Processing RW Eason andAMillerEds vol 49 of Engineering Aspects of Lasers Series SpringerAmsterdam Netherlands 1993
[12] R Hill A First Course in Coding Theory Clarendon PressOxford UK 1980
[13] W Trappe and L C Washington Introduction to CryptographywithCodingTheory PearsonPrenticeHall New JerseyNJUSA2006
[14] J H van Lint Introduction to Coding Theory Springer BerlinGermany 1999
[15] M BossertChannel Coding for Telecommunications JohnWileyamp Sons New York NY USA 1999
[16] F Certık ldquoUtilization of encoding techniques at the signal trans-mission in the optical fiberrdquo in Advances in Signal Processingvol 3 no 2 pp 17ndash24 2015
[17] F Certık ldquoThe analysis of different encoding and modulationtechniques at the signal transmission in the optical mediumrdquo inProceedings of the 37th International Symposium on the Appli-cation of Computers and Operations Research in the MineralIndustry (APCOM rsquo15) pp 978ndash80 STU Publishing HouseBratislava Slovakia
[18] R Roka ldquoFixed transmission mediardquo in Technology and Engi-neering Applications of Simulink S Chakravarty Ed pp 41ndash68InTech Rijeka Croatia 2012
[19] R Roka and F Certık ldquoSimulation tools for broadband passiveoptical networksrdquo in Simulation Technologies in Networking andCommunications Selecting the Best Tool for the Test CRC PressBoca Raton Fla USA 2014
[20] R Roka ldquoThe environment of fixed transmission media andtheir negative influences in the simulationrdquo International Jour-nal ofMathematics and Computers in Simulation vol 9 pp 190ndash205 2015
[21] R Essiambre G Kramer P J Winzer G J Foschini and BGoebel ldquoCapacity limits of optical fiber networksrdquo Journal ofLightwave Technology vol 28 no 4 pp 662ndash701 2010
[22] P J Winzer and R J Essiambre ldquoAdvanced optical modulationformatsrdquo Proceedings of the IEEE vol 94 no 5 pp 952ndash9852006
[23] M I Olmedo T Zuo J B Jensen et al ldquoMultiband carrierlessamplitude phase modulation for high capacity optical datalinksrdquo Journal of Lightwave Technology vol 32 no 4 pp 798ndash804 2014
[24] T Rahman D Rafigue A Napoli et al ldquoUltralong haul 128-Tbs PM-16QAMWDM transmission employing hybrid amplifica-tionrdquo Journal of Lightwave Technology vol 33 no 9 pp 1794ndash1804 2015
10 Journal of Engineering
[25] S Chandrasekhar and X Liu ldquoExperimental investigation onthe performance of closely spaced multi-carrier PDM-QPSKwith digital coherent detectionrdquo Optics Express vol 17 no 24pp 21350ndash21361 2009
[26] I B Djordjevic ldquoGeneralized LDPC codes and turbo-productcodes with reed-muller component codesrdquo in Proceedings of the8th International Conference on Telecommunications in ModernSatellite Cable and Broadcasting Services (TELSIKS rsquo07) pp127ndash134 Nis Serbia September 2007
[27] D Ouchi K Kubo T Mizuochi et al ldquoA fully integrated blockturbo code FEC for 10Gbs optical communication systemsrdquoin Proceedings of the Optical Fiber Communication (OFC rsquo06)Anaheim Calif USA March 2006
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International Journal of
Journal of Engineering 3
RS codes are specified as RS(119899 119896) or RS(119899 119896 119889) where119899 represent the code length 119896 represents the informationlength and 119889 is the Hamming distance Let 119905 be a number oferrors that can be corrected then correction (119905) or detection(2119905) abilities are specified for the code There exist twoencoding types for RS codes
(i) Nonsystematic(ii) Systematic
The decoding for RS codes is based on syndrome equa-tions
119904119896=
119905
sum119894=1
119884119894119883119896
119894 119896 = 0 1 2119905 minus 1 (4)
where 119883119894is the locator 119894th error and 119884
119894represents its value
(detection of location and value) More information about RSencoding techniques can be found in [13]
The Bose Chaudhuri Hocquenghem (BCH) code is acyclic polynomial code over a finite field with chosen poly-nomial generator BCH codes are 119905-error correcting codesdefined over finite fields GF(119902) where 2119905 + 1 lt 119902 The advan-tage of BCH codes is using syndrome to decode errors inwhich there exist good decoding algorithms that correctmultiple errors [14]
The generating of a binary BCH code over an extensionfield GF(119902119898) is easy to construct The polynomial generator119892(119909) is needed to obtain a cyclic code [12ndash16] For any integer119898 ge 3 and 119905 lt 2119898 minus 1 there exists a primitive BCH code withparameters 119899 = 2119898 minus 1 119899 minus 119896 le 119898 sdot 119905 and 119889min le 2119905 + 1The generator polynomial119892(119909) of 119905-error correcting primitiveBCH codes of the length 2119898 minus 1 is given by
119892 (119909) = LCM 1198981(119909) 119898
2(119909) 119898
2119905minus1(119909) 119898
2119905(119909) (5)
where LCM represents the Least CommonMultipleThen thecode is generated using (2)
BCH codes are decoded with various algorithm based oncalculation of syndromes values for the received codeword
Low Density Parity Check (LDPC) codes belong to linearencoding techniques that can transmit data close to the Shan-non theorem (the channel capacity) The main disadvantageof the LDPC code is the time consumption of the codealgorithm which often limits its utilization in high datarate optical transmission systems However it is possible toencode more low data rate signals and then merge them intoone high data rate signal The high data rate signal can betransmitted via the optical transmission system
The LDPC coding is defined by the LDPC 119867 matrixAssuming the length of information bits K the length ofencoded bits119873 and the average weigh column119908 gt 2 (weightvectors represent the sum of nonzero components of thevector) then119872 = (119873 minus 119870) is the sum of the parity check incodeThe LDPCmatrix119867 is composed of119872 rows and119873 col-umnsThe generationmatrix119866 is necessary to encode codingsequence [14 15]
Prepared block schemes of mentioned encoding tech-niques in the simulation model are shown in Figures 1 and 2Figure 3 shows the schematic block diagram of LDPC source
Bernoullibinary
Bernoulli binary generator
Multiple
Sample_time
Binary inputRS encoderBinary inputRS encoder
1OutGaussian
Gaussian filter
[Orig]
Goto
times
Figure 1 The block scheme for the signal generation with RS andBCH encoding techniques
signal Blocks are initiated using a Bernoulli generator thatgenerates random binary bits representation of the infor-mation signal The signal is then coded with an adequateencoding technique The output signal is filtered with aGaussian filter for representation of the real signal TheLDPC block is created by using 10 Bernoulli generators eachencoded with the LDPC code and merged into the high datarate signal [16 17]
2 The Simulation of the OpticalTransmission System
The prepared simulation model comes out from the simula-tion model for optical communications introduced in [18ndash20] A modeling is performed in the Matlab Simulink 2014programming environment The simulation model presentsan influence of linear and nonlinear effects present in theoptical transmission medium at the signal transmission Thegeneral schematic block diagram is shown in Figure 4 To ver-ify a reliability and exactness of the simulationmodel authorsrealized a comparison of two optical transmission pathsmea-sured in cooperation with the Orange Slovakia companyTheoptical path 1 consists of the 592 km standard SM (ITU-TG652) fiber with the 10Gbits noncoherent OOKmodulatedsignal using 80WDMchannelsThe optical path 2 consists of1707 km standard SM (ITU-T G652) fiber with the 10Gbitsnoncoherent OOK modulated signal using 80 WDM chan-nels Transmitted signals are examined with the 1934 THzfrequency Both paths are utilizing EDFA amplifiers at theoptical fiber end while the optical path 2 is furthermoreusing additional 3 EDFA amplifiers every 40 km Simulationmodels for the optical path 1 and optical path 2 are shownin Figures 5 and 6 respectively For describing informationsignal transmission a bit error rate (BER) parameter can becalculated The BER calculation for each simulation model isdone by comparing input and output bits For both opticalpaths simulation results show theBERparameter higher than10minus12 satisfying common transmission conditions For bothsimulation models the Reed-Solomon code RS(255 239) isutilized to enhance the system BER parameter
For both optical paths presented simulated andmeasuredtransmission parameters (Tables 1 and 2) include besidesother received optical power level values for calculationsrelated to the attenuation As can be seen parameters arevery similar at which the simulation is characterized byworseones Therefore if the optical simulation is passed then thereal system would be properly and correctly operating
4 Journal of Engineering
Bernoullibinary
Bernoulli binarygenerator Multiple
Sample_time
1OutGaussian
Gaussian filter
LDPC encoder
LDPC encoder
In1 In2 In3
In4 In5
Out In6 MergeIn7In8In9
In10
Bernoullibinary
Bernoulli binarygenerator 1
Multiple 1Sample_time 1
LDPC encoder
LDPC encoder 1
Bernoullibinary
Bernoulli binarygenerator 2
Multiple 2Sample_time 2
LDPC encoder
LDPC encoder 2
Bernoullibinary
Bernoulli binarygenerator 3
Multiple 3Sample_time 3
LDPC encoder
LDPC encoder 3
Bernoullibinary
Bernoulli binarygenerator 4
Multiple 4Sample_time 4
LDPC encoder
LDPC encoder 4
Bernoullibinary
Bernoulli binarygenerator 5
Multiple 5Sample_time 5
LDPC encoder
LDPC encoder 5
Bernoullibinary
Bernoulli binarygenerator 6
Multiple 6Sample_time 6 LDPC encoder
LDPC encoder 6
Bernoullibinary
Bernoulli binarygenerator 7
Multiple 7Sample_time 7
LDPC encoder
LDPC encoder 7
Bernoullibinary
Bernoulli binarygenerator 8
Multiple 8Sample_time 8LDPC encoder
LDPC encoder 8
Bernoullibinary
Bernoulli binarygenerator 9
Multiple 9Sample_time 9LDPC encoder
LDPC encoder 9
timestimes
times
times
times
times
times
times
times
times
10 lowast 1Gbits to 10Gbits
Figure 2 The block scheme for the signal generation with the LDPC encoding technique
Table 1 The optical path 1 transmission parameters
Parameters Measured SimulatedRx power (dBm) minus132 minus134OSNR (dB) 259 243PMD (ps) 106 125SPM (dB) 087 122XPM (dB) minus5759 minus605FWM (dB) NA minus1243119876 799 81BER gt10minus15 gt10minus12
3 The Analysis of Selected Modulation andEncoding Techniques
The first modulation technique used for real optical trans-mission systems was the two-level amplitude modulationOOK with the direct detection This system is characterizedby transmission rates from 1Gbits and its limitation isrepresented by the 10Gbits rate over optical single modefibers with the 50 km line length Nowadays OOK systems
Table 2 The optical path 2 transmission parameters
Parameters Measured SimulatedRx power (dBm) minus1369 minus123OSNR (dB) 2107 209PMD (ps) 174 183SPM (dB) 103 11XPM (dB) minus4202 minus405FWM (dB) NA minus112119876 627 62BER gt10minus15 gt10minus12
are deployed with coherent receivers that can increase thesystem range depending on the receiver sensitivity andthe transmittersrsquo generated noise Coherent systems highlyimprove transmission characteristics but their implemen-tation is expensive due to security mechanisms for phaseand polarization detecting Another possible improvementfor coherent systems is represented by using the Duobinarymodulation This leads to a modification in the electricaldomain that is less costly than in case of exchange optical
Journal of Engineering 5
Merge block
1 0 0 1 1 1 1 10 0
1
111
1
1
00
0
0
Gauss filter 10Gbits
10Gbits
110
1Gbits
1Gbits
1Gbits
1Gbits
1Gbits
1Gbits
1Gbits
1Gbits
1Gbits
1Gbits
1Gbits
1Gbits
LDPC codingn = i + k
1Gbits
LDPC codingn = i + k
1Gbits
LDPC codingn = i + k
1Gbits
LDPC codingn = i + k
1Gbits
LDPC codingn = i + k
1Gbits
LDPC codingn = i + k
1Gbits
LDPC codingn = i + k
1Gbits
LDPC codingn = i + k
1Gbits
LDPC codingn = i + k
1Gbits
LDPC codingn = i + k
Bernoulli generatorrectangular impulse
Bernoulli generatorrectangular impulse
Bernoulli generatorrectangular impulse
Bernoulli generatorrectangular impulse
Bernoulli generatorrectangular impulse
Bernoulli generatorrectangular impulse
Bernoulli generatorrectangular impulse
Bernoulli generatorrectangular impulse
Bernoulli generatorrectangular impulse
Bernoulli generatorrectangular impulse
generatorSample
Figure 3 The schematic block diagram for the signal generation with the LDPC encoding technique
System signal source
System signal source
System signal source
1
2
N
Optical fiber
Circ
ulat
or
Localoscillator
Signal with different wavelength
Signal with different wavelength
Laser source
Electric datasignal
Electric datasignal
Mach-Zehndermodulator
Continuousoptical wave
Wavelengthdivision
multiplex
Erbium dopedfiber
Phase andamplitudedetection
Chromatic andpolarization modedispersion [time
broadening signalphase shift]
Four-wave mixing[intensity noise from
neighbour channels ondifferent wavelength]
[phase noise andsignal frequency shiftdue to signal intensity]
Self-phase andcross-phase modulation
[intensity noise fromneighbour channels
and decreasing signalintensity]
Stimulated Brillouinand Raman scattering
attenuation
Figure 4 The schematic block diagram for the optical transmission system
components For given modulation the Monte Carlo algo-rithm can be used because it allows a measuring of theBER parameter The simulation model uses the standard SM(ITU-T G656) optical fiber The comparison of transmissioncharacteristics for coherent OOK and Duobinary systems isshown in Figure 7
Possible solution can be represented by coherent systemswith phase and frequency modulation techniques which are
represented by BPSK DBPSK and BFSK These modula-tion techniques achieve similar transmission characteristics(shown in Figure 8) where the BPSK achieves better resultsabout 01 dB compared to the DBPSK and about 3 dB com-pared to the FSK
Higher modulation formats can be further used toincrease signal transmission rates in the optical system [21ndash25] Such modulation techniques have a lower tolerance to
6 Journal of Engineering
Out1
Data signal In1 Out1 In2
Demodulator
In1
In2Out1
MZM
Out1
CW
Out1
Cooperating channels
In1
In2
In3
Out1
WDM
Out1
EDFA
SMFmdash592km
Figure 5 The simulation model for the optical path 1
Out1
Data signal In1 Out1 In2 Out1
Erbium doped fiber
In1
In2Out1
MZM
Out1
CW
Out1
Cooperating channels
In1
In2
In3
Out1
WDM
Out1
EDFA
In2
Demodulator
In1 Out1 In2 Out1
Erbium doped fiber 1
In1 Out1 In2 Out1
Erbium doped fiber 2
In1 Out1 In2 Out1
Erbium doped fiber 3
SMFmdash442 km
SMFmdash425 km
SMFmdash433km
SMFmdash407 km
Figure 6 The simulation model for the optical path 2
the optical signal-to-noise ratio (OSNR) and therefore it isnecessary to analyze the BER parameter depending on theOSNR Figure 9 shows transmission characteristics for high-level modulation formats QPSK and DQPSK keying exhibitsimilar resistance to noise as BPSK andDBPSK keying In thiscase the transmission ratewould be increased twice and if thepolarization modulation (PDM) is used then the 40Gbitstransmission rate can be reached This solution requires thedeployment of MZM modulators and the PDM modulatorFor 8PSK and 16QAM modulations the noise resistance isdecreasing around 2 dB that in some systems will lead to
higher bit error rates caused by laser noise amplifier noiseandor nonlinear effects of the optical transmission medium
For improving transmission rates of modulation formatsdifferent encoding techniques can be used [26 27] A com-plete scheme of the prepared optical transmission system isshown in Figure 10 where the total optical fiber length isextended to 320 km
After theoretical analysis the following codes RS(255239) BCH(255 231) and LDPC(960 480)were selectedTheRS and BCH codes are capable of encoding data quicklyup to 10Gbits however the LDPC codes require more
Journal of Engineering 7
0 2 4 6 8 10 12 14 16 18
BER
OOK NRZDuobinary
100
10minus1
10minus2
10minus3
10minus4
10minus5
10minus6
10minus7
10minus8
EbN0 (dB)
Figure 7 BER transmission characteristics for OOK keying andDuobinary modulation
0 2 4 6 8 10 12 14 16 18
BER
DBPSKBPSKBFSK
EbN0 (dB)
100
10minus1
10minus2
10minus3
10minus4
10minus5
10minus6
10minus7
10minus8
Figure 8 BER transmission characteristics for BPSK DBPSK andBFSK keying
0 2 4 6 8 10 12 14 16 18
BER
DQPSK8PSK
QPSK16QAM
100
10minus1
10minus2
10minus3
10minus4
10minus5
10minus6
10minus7
10minus8
EbN0 (dB)
Figure 9 BER transmission characteristics for QPSK DQPSK8PSK and 16QAM keying
time to encode data Therefore 10 data streams are encodedseparately and afterwards multiplexed into one data stream(shown in Figure 2) For analyzing and simulating onlybinary modulation formats are used
A comparison of binary modulation techniques (nonco-herent OOK BPSK and DBPSK) combined with encodingtechniques (RS BCH and LDPC) is shown in Figure 11Encoding techniques can increase the system range from50 km up to 160 km depending on appropriate code Bettertransmission characteristics are achievable through coherentphase modulations BPSK and DBPSK where limitations arebetween 80 and 100 km The BCH and RS codes increasethe range of these systems up to 160 km and this systemrange can be increased up to 230 km by using the LDPCcodeThe LDPC code is more than 50 efficient compared toBCH and RS codes however such a system needs encodingindividual data signals with lower transmission rates than thetotal system transmission rate Therefore it is more effectiveto use the LDPC code inmetropolitan networks where a timemultiplexing is used
4 The Implementation of Modulation andEncoding Techniques
Selected modulation and encoding techniques are imple-mented on the optical transmission system with the standardSM fiber (ITU-TG652) where a data signal with the 10Gbitstransmission rate and 80WDMchannels is transmitted Indi-vidual transmitters are designed using the MZM modulatorwhere a continuous wave generated in the CW-DFB laseris modulated with a data signal generated by the Bernoulligenerator The CW-DFB laser generates a continuous wavewith 1mW power and embeds the 4 dB amplitude noise Itis considered that a phase noise is suppressed The analyzedsignal is transmitted with the 1934 THz optical frequencyand the resulting OSNR is 30 dB For increasing the opticaltransmission path range EDFA amplifiers are used every40 km for amplifying the transmitted signal where a noisefigureNF is equal to 4 dBTheoptical fiberwith a negativeCDis placed before a receiver to compensate the CD effect in thesystemThe received signal is detected by a coherent detectorwhose sensitivity is around minus17 dBm Based on the previousanalysis a hard decision scheme with the LDPC(960 480)code is selected for implementation
First binary modulation techniques can be consideredwhere the OOK has the worst transmission characteristicsand therefore the transmission system range is limited to230 km The analyzed BPSK and BFSK modulations achievesimilar transmission characteristics where both systems arecapable of having a signal transmission over the 300 km linelength with the 10Gbits transmission rate It is optional touse these modulations to achieve the longest transmissionsystem range For increasing transmission rates of thesemodulations it is possible to use a combination with thePDM (PDM-BPSK and PDM-BFSK) where the transmissionrate of these systems will be higher twice (20Gbits) Forachieving higher transmission rates it is necessary to usemultilevel modulation formats The QPSK signal range isaround 300 km where a transmission rate compared with
8 Journal of Engineering
Out1
Data signal In2 Out1
Erbium doped fiber
In1
In2Out1
MZMOut1
CW
Out1
Cooperating channels
In1In2In3
Out1
WDM
Out1
EDFA
In2
Demodulator
In2 Out1
Erbium doped fiber 1
In2 Out1
Erbium doped fiber 2
In2 Out1
Erbium doped fiber 3
In Out
PMD
In Out
CHD
In Out
FWM
In2 Out1
SPM amp XPM
In1 Out1
SRS amp SBS amp attenuation
In Out
PMD1
In Out
CHD1
In Out
FWM1
In2 Out1
SPM amp XPM1
In1 Out1
SRS amp SBS amp attenuation 1
In Out
PMD2
In Out
CHD2
In Out
FWM2
In2 Out1
SPM amp XPM2
In1 Out1
SRS amp SBS amp attenuation 2
In Out
PMD3
In Out
CHD3
In Out
FWM3
In2 Out1
SPM amp XPM3
In1 Out1
SRS amp SBS amp attenuation 3
Samsung SM NZD-SF 80km length
Samsung SM NZD-SF 80km length
Samsung SM NZD-SF 80km length
Samsung SM NZD-SF 80km length
Figure 10 The block scheme for analysis of the selected modulation and encoding techniques
Table 3 Comparison of selected modulation techniques implemented for the optical transmission system
Modulation techniques Parameters Fiber length [km]40 80 120 160 200 240 280 320
OOK BER [ ] 10minus12 10minus12 10minus12 10minus9 10minus2 10minus1 10minus1 10minus1
OSNR [dB] 25 19 14 7 2 1 1 1
BPSK BER [ ] 10minus12 10minus12 10minus12 10minus12 10minus12 10minus12 10minus11 10minus9
OSNR [dB] 27 24 20 17 15 11 8 5
DBPSK BER [ ] 10minus12 10minus12 10minus12 10minus12 10minus12 10minus12 10minus10 10minus8
OSNR [dB] 27 24 20 17 15 11 8 5
BFSK BER [ ] 10minus12 10minus12 10minus12 10minus12 10minus12 10minus12 10minus11 10minus9
OSNR [dB] 28 26 24 21 18 16 13 10
QPSK BER [ ] 10minus12 10minus12 10minus12 10minus12 10minus12 10minus12 10minus11 10minus9
OSNR [dB] 27 24 20 17 15 11 8 5
8PSK BER [ ] 10minus12 10minus12 10minus12 10minus12 10minus10 10minus6 10minus3 10minus2
OSNR [dB] 27 23 19 14 9 6 2 1
16QAM BER [ ] 10minus12 10minus12 10minus12 10minus12 10minus9 10minus3 10minus1 10minus1
OSNR [dB] 27 22 17 12 7 2 2 1
Calculated BER
BER
0
1
2
3
4
5
6
7
8
9
10
Length (km)0 50 100 150 200 250 300 350
OOKBPSKDBPSK
times10minus3
OOK-RS (255 239)
DBPSK-RS (255 239)
OOK-BCH (255 231)BPSK-BCH (255 231)DBPSK-BCH (255 231)OOK-LDPC (960 480)BPSK-LDPC (960 480)DBPSK-LDPC (960 480)
BPSK-RS (255 239)
Figure 11 Comparison of binary modulation techniques combinedwith encoding techniques
binarymodulations is twice higher Using a combinationwiththe PDM the result transmission rate achieves 40GbitsThe maximum range of 8PSK and 16QAM systems is around200 kmThe decreased range of these systems is due to ampli-fier noises and nonlinear effects in the optical environmentHowever these systems using the PDM have transmissionrates 60Gbits (PDM-8PSK) and 80Gbits (PDM-16QAM)per channel The analysis shows that the range limitationis mainly caused by amplifier noises and nonlinear effectsthat are accumulating For increasing the system range ofmultilevel modulation formats the use of encoding tech-niques such as the LDPC(960 480) code is optional Forfurther improvement of transmission characteristics opticalamplifiers with a low noise figure advanced detectors andsoft encoding schemes can be used However these compo-nents rapidly increase the system cost and particular financialanalysis for the system effectiveness is necessary Outputtransmission characteristics for each modulation techniqueare shown in Table 3
Journal of Engineering 9
5 Conclusion
This contribution analyzes a possible utilization of selectedmodulation and advanced encoding techniques at high datarate signal transmission in optical transmission medium Atfirst the prepared simulation model for optical transmissionsystems with real transmission systems is compared Next aperformance analysis of different binary andmultilevel mod-ulation techniques in combination with RS BCH and LDPCcodes utilized in optical transmission systems is presentedThe simulation results show the limitation of binary modu-lation techniques and their possible improvement using FECcodes The LDPC code can improve a systemrsquos performancefor all modulation schemes Finally a prepared optical systemwith real parameters is enhanced using the LDPC code andselected modulation and encoding techniques are analyzedfor their practical implementation
In future analyses convolutional or turbo codes with dif-ferent rates and constraint length can be considered More-over other recent modulation techniques in possible com-binations with encoding techniques are analyzed Besides autilization of solitons with available optical signal processingtechniques is a very interesting area
Disclosure
This work is a part of research activities conducted atSlovak University of Technology Bratislava Faculty of Elec-trical Engineering and Information Technology Institute ofTelecommunications within the scope of Projects VEGA no1017416 ldquoAdvanced Algorithms and Methods for New Gen-eration Optical Networks for the IMS and NGN ConvergedInfrastructurerdquo and KEGA no 007STU-42016 ldquoProgressiveEducational Methods in the Field of TelecommunicationsMultiservice Networksrdquo
Competing Interests
The authors declare that they have no competing interests
References
[1] K Fukuchi T KasamatsuMMorie et al ldquo1092-Tbs (273times40-Gbs) triple-bandultra-dense WDM optical-repeatered trans-mission experimentrdquo in Proceedings of the Optical Fiber Com-munication Conference (OFC rsquo01) Paper PD24 2001
[2] Z Jia J Yu H-C Chien Z Dong and D Di Huo ldquoField trans-mission of 100G and beyond multiple baud rates and mixedline rates using nyquist-WDM technologyrdquo Journal of LightwaveTechnology vol 30 no 24 Article ID 6235964 pp 3793ndash38042012
[3] H Rohde E Gottwald A Teixeira et al ldquoCoherent ultra denseWDM technology for next generation optical metro and accessnetworksrdquo Journal of Lightwave Technology vol 32 no 10 pp2041ndash2052 2014
[4] H Taga ldquoLong distance transmission experiments using theWDM technologyrdquo Journal of Lightwave Technology vol 14 no6 pp 1287ndash1298 1996
[5] B E A Saleh and M C Teich Fundamentals of PhotonicsWiley-Interscience 1991
[6] L N Binh Optical Fiber Communication Systems CRC PressNew York NY USA 2010
[7] G Keiser Optical Fiber Communications John Wiley amp SonsNew York NY USA 2003
[8] Z Jamaludin A F Abas A S M Noor and M K AbfullahldquoIssues on polarization mode dispersion (PMD) for high speedfiber optics transmissionrdquo Suranaree Journal of Science andTechnology vol 12 no 2 pp 98ndash106 2005
[9] S P Singh andN Singh ldquoNonlinear effects in optical fibers ori-ginmanagement and applicationsrdquoProgress in ElectromagneticsResearch vol 73 pp 249ndash275 2007
[10] E Iannone F Matera A Mecozzi andM SettembreNonlinearOptical Communication Networks TK510359N66 John Wileyamp Sons New York NY USA 1998
[11] D Cotter ldquoNonlinearity in optical fibre communicationsrdquo inNonlinear Optics in Signal Processing RW Eason andAMillerEds vol 49 of Engineering Aspects of Lasers Series SpringerAmsterdam Netherlands 1993
[12] R Hill A First Course in Coding Theory Clarendon PressOxford UK 1980
[13] W Trappe and L C Washington Introduction to CryptographywithCodingTheory PearsonPrenticeHall New JerseyNJUSA2006
[14] J H van Lint Introduction to Coding Theory Springer BerlinGermany 1999
[15] M BossertChannel Coding for Telecommunications JohnWileyamp Sons New York NY USA 1999
[16] F Certık ldquoUtilization of encoding techniques at the signal trans-mission in the optical fiberrdquo in Advances in Signal Processingvol 3 no 2 pp 17ndash24 2015
[17] F Certık ldquoThe analysis of different encoding and modulationtechniques at the signal transmission in the optical mediumrdquo inProceedings of the 37th International Symposium on the Appli-cation of Computers and Operations Research in the MineralIndustry (APCOM rsquo15) pp 978ndash80 STU Publishing HouseBratislava Slovakia
[18] R Roka ldquoFixed transmission mediardquo in Technology and Engi-neering Applications of Simulink S Chakravarty Ed pp 41ndash68InTech Rijeka Croatia 2012
[19] R Roka and F Certık ldquoSimulation tools for broadband passiveoptical networksrdquo in Simulation Technologies in Networking andCommunications Selecting the Best Tool for the Test CRC PressBoca Raton Fla USA 2014
[20] R Roka ldquoThe environment of fixed transmission media andtheir negative influences in the simulationrdquo International Jour-nal ofMathematics and Computers in Simulation vol 9 pp 190ndash205 2015
[21] R Essiambre G Kramer P J Winzer G J Foschini and BGoebel ldquoCapacity limits of optical fiber networksrdquo Journal ofLightwave Technology vol 28 no 4 pp 662ndash701 2010
[22] P J Winzer and R J Essiambre ldquoAdvanced optical modulationformatsrdquo Proceedings of the IEEE vol 94 no 5 pp 952ndash9852006
[23] M I Olmedo T Zuo J B Jensen et al ldquoMultiband carrierlessamplitude phase modulation for high capacity optical datalinksrdquo Journal of Lightwave Technology vol 32 no 4 pp 798ndash804 2014
[24] T Rahman D Rafigue A Napoli et al ldquoUltralong haul 128-Tbs PM-16QAMWDM transmission employing hybrid amplifica-tionrdquo Journal of Lightwave Technology vol 33 no 9 pp 1794ndash1804 2015
10 Journal of Engineering
[25] S Chandrasekhar and X Liu ldquoExperimental investigation onthe performance of closely spaced multi-carrier PDM-QPSKwith digital coherent detectionrdquo Optics Express vol 17 no 24pp 21350ndash21361 2009
[26] I B Djordjevic ldquoGeneralized LDPC codes and turbo-productcodes with reed-muller component codesrdquo in Proceedings of the8th International Conference on Telecommunications in ModernSatellite Cable and Broadcasting Services (TELSIKS rsquo07) pp127ndash134 Nis Serbia September 2007
[27] D Ouchi K Kubo T Mizuochi et al ldquoA fully integrated blockturbo code FEC for 10Gbs optical communication systemsrdquoin Proceedings of the Optical Fiber Communication (OFC rsquo06)Anaheim Calif USA March 2006
International Journal of
AerospaceEngineeringHindawi Publishing Corporationhttpwwwhindawicom Volume 2014
RoboticsJournal of
Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014
Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014
Active and Passive Electronic Components
Control Scienceand Engineering
Journal of
Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014
International Journal of
RotatingMachinery
Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014
Hindawi Publishing Corporation httpwwwhindawicom
Journal ofEngineeringVolume 2014
Submit your manuscripts athttpwwwhindawicom
VLSI Design
Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014
Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014
Shock and Vibration
Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014
Civil EngineeringAdvances in
Acoustics and VibrationAdvances in
Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014
Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014
Electrical and Computer Engineering
Journal of
Advances inOptoElectronics
Hindawi Publishing Corporation httpwwwhindawicom
Volume 2014
The Scientific World JournalHindawi Publishing Corporation httpwwwhindawicom Volume 2014
SensorsJournal of
Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014
Modelling amp Simulation in EngineeringHindawi Publishing Corporation httpwwwhindawicom Volume 2014
Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014
Chemical EngineeringInternational Journal of Antennas and
Propagation
International Journal of
Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014
Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014
Navigation and Observation
International Journal of
Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014
DistributedSensor Networks
International Journal of
4 Journal of Engineering
Bernoullibinary
Bernoulli binarygenerator Multiple
Sample_time
1OutGaussian
Gaussian filter
LDPC encoder
LDPC encoder
In1 In2 In3
In4 In5
Out In6 MergeIn7In8In9
In10
Bernoullibinary
Bernoulli binarygenerator 1
Multiple 1Sample_time 1
LDPC encoder
LDPC encoder 1
Bernoullibinary
Bernoulli binarygenerator 2
Multiple 2Sample_time 2
LDPC encoder
LDPC encoder 2
Bernoullibinary
Bernoulli binarygenerator 3
Multiple 3Sample_time 3
LDPC encoder
LDPC encoder 3
Bernoullibinary
Bernoulli binarygenerator 4
Multiple 4Sample_time 4
LDPC encoder
LDPC encoder 4
Bernoullibinary
Bernoulli binarygenerator 5
Multiple 5Sample_time 5
LDPC encoder
LDPC encoder 5
Bernoullibinary
Bernoulli binarygenerator 6
Multiple 6Sample_time 6 LDPC encoder
LDPC encoder 6
Bernoullibinary
Bernoulli binarygenerator 7
Multiple 7Sample_time 7
LDPC encoder
LDPC encoder 7
Bernoullibinary
Bernoulli binarygenerator 8
Multiple 8Sample_time 8LDPC encoder
LDPC encoder 8
Bernoullibinary
Bernoulli binarygenerator 9
Multiple 9Sample_time 9LDPC encoder
LDPC encoder 9
timestimes
times
times
times
times
times
times
times
times
10 lowast 1Gbits to 10Gbits
Figure 2 The block scheme for the signal generation with the LDPC encoding technique
Table 1 The optical path 1 transmission parameters
Parameters Measured SimulatedRx power (dBm) minus132 minus134OSNR (dB) 259 243PMD (ps) 106 125SPM (dB) 087 122XPM (dB) minus5759 minus605FWM (dB) NA minus1243119876 799 81BER gt10minus15 gt10minus12
3 The Analysis of Selected Modulation andEncoding Techniques
The first modulation technique used for real optical trans-mission systems was the two-level amplitude modulationOOK with the direct detection This system is characterizedby transmission rates from 1Gbits and its limitation isrepresented by the 10Gbits rate over optical single modefibers with the 50 km line length Nowadays OOK systems
Table 2 The optical path 2 transmission parameters
Parameters Measured SimulatedRx power (dBm) minus1369 minus123OSNR (dB) 2107 209PMD (ps) 174 183SPM (dB) 103 11XPM (dB) minus4202 minus405FWM (dB) NA minus112119876 627 62BER gt10minus15 gt10minus12
are deployed with coherent receivers that can increase thesystem range depending on the receiver sensitivity andthe transmittersrsquo generated noise Coherent systems highlyimprove transmission characteristics but their implemen-tation is expensive due to security mechanisms for phaseand polarization detecting Another possible improvementfor coherent systems is represented by using the Duobinarymodulation This leads to a modification in the electricaldomain that is less costly than in case of exchange optical
Journal of Engineering 5
Merge block
1 0 0 1 1 1 1 10 0
1
111
1
1
00
0
0
Gauss filter 10Gbits
10Gbits
110
1Gbits
1Gbits
1Gbits
1Gbits
1Gbits
1Gbits
1Gbits
1Gbits
1Gbits
1Gbits
1Gbits
1Gbits
LDPC codingn = i + k
1Gbits
LDPC codingn = i + k
1Gbits
LDPC codingn = i + k
1Gbits
LDPC codingn = i + k
1Gbits
LDPC codingn = i + k
1Gbits
LDPC codingn = i + k
1Gbits
LDPC codingn = i + k
1Gbits
LDPC codingn = i + k
1Gbits
LDPC codingn = i + k
1Gbits
LDPC codingn = i + k
Bernoulli generatorrectangular impulse
Bernoulli generatorrectangular impulse
Bernoulli generatorrectangular impulse
Bernoulli generatorrectangular impulse
Bernoulli generatorrectangular impulse
Bernoulli generatorrectangular impulse
Bernoulli generatorrectangular impulse
Bernoulli generatorrectangular impulse
Bernoulli generatorrectangular impulse
Bernoulli generatorrectangular impulse
generatorSample
Figure 3 The schematic block diagram for the signal generation with the LDPC encoding technique
System signal source
System signal source
System signal source
1
2
N
Optical fiber
Circ
ulat
or
Localoscillator
Signal with different wavelength
Signal with different wavelength
Laser source
Electric datasignal
Electric datasignal
Mach-Zehndermodulator
Continuousoptical wave
Wavelengthdivision
multiplex
Erbium dopedfiber
Phase andamplitudedetection
Chromatic andpolarization modedispersion [time
broadening signalphase shift]
Four-wave mixing[intensity noise from
neighbour channels ondifferent wavelength]
[phase noise andsignal frequency shiftdue to signal intensity]
Self-phase andcross-phase modulation
[intensity noise fromneighbour channels
and decreasing signalintensity]
Stimulated Brillouinand Raman scattering
attenuation
Figure 4 The schematic block diagram for the optical transmission system
components For given modulation the Monte Carlo algo-rithm can be used because it allows a measuring of theBER parameter The simulation model uses the standard SM(ITU-T G656) optical fiber The comparison of transmissioncharacteristics for coherent OOK and Duobinary systems isshown in Figure 7
Possible solution can be represented by coherent systemswith phase and frequency modulation techniques which are
represented by BPSK DBPSK and BFSK These modula-tion techniques achieve similar transmission characteristics(shown in Figure 8) where the BPSK achieves better resultsabout 01 dB compared to the DBPSK and about 3 dB com-pared to the FSK
Higher modulation formats can be further used toincrease signal transmission rates in the optical system [21ndash25] Such modulation techniques have a lower tolerance to
6 Journal of Engineering
Out1
Data signal In1 Out1 In2
Demodulator
In1
In2Out1
MZM
Out1
CW
Out1
Cooperating channels
In1
In2
In3
Out1
WDM
Out1
EDFA
SMFmdash592km
Figure 5 The simulation model for the optical path 1
Out1
Data signal In1 Out1 In2 Out1
Erbium doped fiber
In1
In2Out1
MZM
Out1
CW
Out1
Cooperating channels
In1
In2
In3
Out1
WDM
Out1
EDFA
In2
Demodulator
In1 Out1 In2 Out1
Erbium doped fiber 1
In1 Out1 In2 Out1
Erbium doped fiber 2
In1 Out1 In2 Out1
Erbium doped fiber 3
SMFmdash442 km
SMFmdash425 km
SMFmdash433km
SMFmdash407 km
Figure 6 The simulation model for the optical path 2
the optical signal-to-noise ratio (OSNR) and therefore it isnecessary to analyze the BER parameter depending on theOSNR Figure 9 shows transmission characteristics for high-level modulation formats QPSK and DQPSK keying exhibitsimilar resistance to noise as BPSK andDBPSK keying In thiscase the transmission ratewould be increased twice and if thepolarization modulation (PDM) is used then the 40Gbitstransmission rate can be reached This solution requires thedeployment of MZM modulators and the PDM modulatorFor 8PSK and 16QAM modulations the noise resistance isdecreasing around 2 dB that in some systems will lead to
higher bit error rates caused by laser noise amplifier noiseandor nonlinear effects of the optical transmission medium
For improving transmission rates of modulation formatsdifferent encoding techniques can be used [26 27] A com-plete scheme of the prepared optical transmission system isshown in Figure 10 where the total optical fiber length isextended to 320 km
After theoretical analysis the following codes RS(255239) BCH(255 231) and LDPC(960 480)were selectedTheRS and BCH codes are capable of encoding data quicklyup to 10Gbits however the LDPC codes require more
Journal of Engineering 7
0 2 4 6 8 10 12 14 16 18
BER
OOK NRZDuobinary
100
10minus1
10minus2
10minus3
10minus4
10minus5
10minus6
10minus7
10minus8
EbN0 (dB)
Figure 7 BER transmission characteristics for OOK keying andDuobinary modulation
0 2 4 6 8 10 12 14 16 18
BER
DBPSKBPSKBFSK
EbN0 (dB)
100
10minus1
10minus2
10minus3
10minus4
10minus5
10minus6
10minus7
10minus8
Figure 8 BER transmission characteristics for BPSK DBPSK andBFSK keying
0 2 4 6 8 10 12 14 16 18
BER
DQPSK8PSK
QPSK16QAM
100
10minus1
10minus2
10minus3
10minus4
10minus5
10minus6
10minus7
10minus8
EbN0 (dB)
Figure 9 BER transmission characteristics for QPSK DQPSK8PSK and 16QAM keying
time to encode data Therefore 10 data streams are encodedseparately and afterwards multiplexed into one data stream(shown in Figure 2) For analyzing and simulating onlybinary modulation formats are used
A comparison of binary modulation techniques (nonco-herent OOK BPSK and DBPSK) combined with encodingtechniques (RS BCH and LDPC) is shown in Figure 11Encoding techniques can increase the system range from50 km up to 160 km depending on appropriate code Bettertransmission characteristics are achievable through coherentphase modulations BPSK and DBPSK where limitations arebetween 80 and 100 km The BCH and RS codes increasethe range of these systems up to 160 km and this systemrange can be increased up to 230 km by using the LDPCcodeThe LDPC code is more than 50 efficient compared toBCH and RS codes however such a system needs encodingindividual data signals with lower transmission rates than thetotal system transmission rate Therefore it is more effectiveto use the LDPC code inmetropolitan networks where a timemultiplexing is used
4 The Implementation of Modulation andEncoding Techniques
Selected modulation and encoding techniques are imple-mented on the optical transmission system with the standardSM fiber (ITU-TG652) where a data signal with the 10Gbitstransmission rate and 80WDMchannels is transmitted Indi-vidual transmitters are designed using the MZM modulatorwhere a continuous wave generated in the CW-DFB laseris modulated with a data signal generated by the Bernoulligenerator The CW-DFB laser generates a continuous wavewith 1mW power and embeds the 4 dB amplitude noise Itis considered that a phase noise is suppressed The analyzedsignal is transmitted with the 1934 THz optical frequencyand the resulting OSNR is 30 dB For increasing the opticaltransmission path range EDFA amplifiers are used every40 km for amplifying the transmitted signal where a noisefigureNF is equal to 4 dBTheoptical fiberwith a negativeCDis placed before a receiver to compensate the CD effect in thesystemThe received signal is detected by a coherent detectorwhose sensitivity is around minus17 dBm Based on the previousanalysis a hard decision scheme with the LDPC(960 480)code is selected for implementation
First binary modulation techniques can be consideredwhere the OOK has the worst transmission characteristicsand therefore the transmission system range is limited to230 km The analyzed BPSK and BFSK modulations achievesimilar transmission characteristics where both systems arecapable of having a signal transmission over the 300 km linelength with the 10Gbits transmission rate It is optional touse these modulations to achieve the longest transmissionsystem range For increasing transmission rates of thesemodulations it is possible to use a combination with thePDM (PDM-BPSK and PDM-BFSK) where the transmissionrate of these systems will be higher twice (20Gbits) Forachieving higher transmission rates it is necessary to usemultilevel modulation formats The QPSK signal range isaround 300 km where a transmission rate compared with
8 Journal of Engineering
Out1
Data signal In2 Out1
Erbium doped fiber
In1
In2Out1
MZMOut1
CW
Out1
Cooperating channels
In1In2In3
Out1
WDM
Out1
EDFA
In2
Demodulator
In2 Out1
Erbium doped fiber 1
In2 Out1
Erbium doped fiber 2
In2 Out1
Erbium doped fiber 3
In Out
PMD
In Out
CHD
In Out
FWM
In2 Out1
SPM amp XPM
In1 Out1
SRS amp SBS amp attenuation
In Out
PMD1
In Out
CHD1
In Out
FWM1
In2 Out1
SPM amp XPM1
In1 Out1
SRS amp SBS amp attenuation 1
In Out
PMD2
In Out
CHD2
In Out
FWM2
In2 Out1
SPM amp XPM2
In1 Out1
SRS amp SBS amp attenuation 2
In Out
PMD3
In Out
CHD3
In Out
FWM3
In2 Out1
SPM amp XPM3
In1 Out1
SRS amp SBS amp attenuation 3
Samsung SM NZD-SF 80km length
Samsung SM NZD-SF 80km length
Samsung SM NZD-SF 80km length
Samsung SM NZD-SF 80km length
Figure 10 The block scheme for analysis of the selected modulation and encoding techniques
Table 3 Comparison of selected modulation techniques implemented for the optical transmission system
Modulation techniques Parameters Fiber length [km]40 80 120 160 200 240 280 320
OOK BER [ ] 10minus12 10minus12 10minus12 10minus9 10minus2 10minus1 10minus1 10minus1
OSNR [dB] 25 19 14 7 2 1 1 1
BPSK BER [ ] 10minus12 10minus12 10minus12 10minus12 10minus12 10minus12 10minus11 10minus9
OSNR [dB] 27 24 20 17 15 11 8 5
DBPSK BER [ ] 10minus12 10minus12 10minus12 10minus12 10minus12 10minus12 10minus10 10minus8
OSNR [dB] 27 24 20 17 15 11 8 5
BFSK BER [ ] 10minus12 10minus12 10minus12 10minus12 10minus12 10minus12 10minus11 10minus9
OSNR [dB] 28 26 24 21 18 16 13 10
QPSK BER [ ] 10minus12 10minus12 10minus12 10minus12 10minus12 10minus12 10minus11 10minus9
OSNR [dB] 27 24 20 17 15 11 8 5
8PSK BER [ ] 10minus12 10minus12 10minus12 10minus12 10minus10 10minus6 10minus3 10minus2
OSNR [dB] 27 23 19 14 9 6 2 1
16QAM BER [ ] 10minus12 10minus12 10minus12 10minus12 10minus9 10minus3 10minus1 10minus1
OSNR [dB] 27 22 17 12 7 2 2 1
Calculated BER
BER
0
1
2
3
4
5
6
7
8
9
10
Length (km)0 50 100 150 200 250 300 350
OOKBPSKDBPSK
times10minus3
OOK-RS (255 239)
DBPSK-RS (255 239)
OOK-BCH (255 231)BPSK-BCH (255 231)DBPSK-BCH (255 231)OOK-LDPC (960 480)BPSK-LDPC (960 480)DBPSK-LDPC (960 480)
BPSK-RS (255 239)
Figure 11 Comparison of binary modulation techniques combinedwith encoding techniques
binarymodulations is twice higher Using a combinationwiththe PDM the result transmission rate achieves 40GbitsThe maximum range of 8PSK and 16QAM systems is around200 kmThe decreased range of these systems is due to ampli-fier noises and nonlinear effects in the optical environmentHowever these systems using the PDM have transmissionrates 60Gbits (PDM-8PSK) and 80Gbits (PDM-16QAM)per channel The analysis shows that the range limitationis mainly caused by amplifier noises and nonlinear effectsthat are accumulating For increasing the system range ofmultilevel modulation formats the use of encoding tech-niques such as the LDPC(960 480) code is optional Forfurther improvement of transmission characteristics opticalamplifiers with a low noise figure advanced detectors andsoft encoding schemes can be used However these compo-nents rapidly increase the system cost and particular financialanalysis for the system effectiveness is necessary Outputtransmission characteristics for each modulation techniqueare shown in Table 3
Journal of Engineering 9
5 Conclusion
This contribution analyzes a possible utilization of selectedmodulation and advanced encoding techniques at high datarate signal transmission in optical transmission medium Atfirst the prepared simulation model for optical transmissionsystems with real transmission systems is compared Next aperformance analysis of different binary andmultilevel mod-ulation techniques in combination with RS BCH and LDPCcodes utilized in optical transmission systems is presentedThe simulation results show the limitation of binary modu-lation techniques and their possible improvement using FECcodes The LDPC code can improve a systemrsquos performancefor all modulation schemes Finally a prepared optical systemwith real parameters is enhanced using the LDPC code andselected modulation and encoding techniques are analyzedfor their practical implementation
In future analyses convolutional or turbo codes with dif-ferent rates and constraint length can be considered More-over other recent modulation techniques in possible com-binations with encoding techniques are analyzed Besides autilization of solitons with available optical signal processingtechniques is a very interesting area
Disclosure
This work is a part of research activities conducted atSlovak University of Technology Bratislava Faculty of Elec-trical Engineering and Information Technology Institute ofTelecommunications within the scope of Projects VEGA no1017416 ldquoAdvanced Algorithms and Methods for New Gen-eration Optical Networks for the IMS and NGN ConvergedInfrastructurerdquo and KEGA no 007STU-42016 ldquoProgressiveEducational Methods in the Field of TelecommunicationsMultiservice Networksrdquo
Competing Interests
The authors declare that they have no competing interests
References
[1] K Fukuchi T KasamatsuMMorie et al ldquo1092-Tbs (273times40-Gbs) triple-bandultra-dense WDM optical-repeatered trans-mission experimentrdquo in Proceedings of the Optical Fiber Com-munication Conference (OFC rsquo01) Paper PD24 2001
[2] Z Jia J Yu H-C Chien Z Dong and D Di Huo ldquoField trans-mission of 100G and beyond multiple baud rates and mixedline rates using nyquist-WDM technologyrdquo Journal of LightwaveTechnology vol 30 no 24 Article ID 6235964 pp 3793ndash38042012
[3] H Rohde E Gottwald A Teixeira et al ldquoCoherent ultra denseWDM technology for next generation optical metro and accessnetworksrdquo Journal of Lightwave Technology vol 32 no 10 pp2041ndash2052 2014
[4] H Taga ldquoLong distance transmission experiments using theWDM technologyrdquo Journal of Lightwave Technology vol 14 no6 pp 1287ndash1298 1996
[5] B E A Saleh and M C Teich Fundamentals of PhotonicsWiley-Interscience 1991
[6] L N Binh Optical Fiber Communication Systems CRC PressNew York NY USA 2010
[7] G Keiser Optical Fiber Communications John Wiley amp SonsNew York NY USA 2003
[8] Z Jamaludin A F Abas A S M Noor and M K AbfullahldquoIssues on polarization mode dispersion (PMD) for high speedfiber optics transmissionrdquo Suranaree Journal of Science andTechnology vol 12 no 2 pp 98ndash106 2005
[9] S P Singh andN Singh ldquoNonlinear effects in optical fibers ori-ginmanagement and applicationsrdquoProgress in ElectromagneticsResearch vol 73 pp 249ndash275 2007
[10] E Iannone F Matera A Mecozzi andM SettembreNonlinearOptical Communication Networks TK510359N66 John Wileyamp Sons New York NY USA 1998
[11] D Cotter ldquoNonlinearity in optical fibre communicationsrdquo inNonlinear Optics in Signal Processing RW Eason andAMillerEds vol 49 of Engineering Aspects of Lasers Series SpringerAmsterdam Netherlands 1993
[12] R Hill A First Course in Coding Theory Clarendon PressOxford UK 1980
[13] W Trappe and L C Washington Introduction to CryptographywithCodingTheory PearsonPrenticeHall New JerseyNJUSA2006
[14] J H van Lint Introduction to Coding Theory Springer BerlinGermany 1999
[15] M BossertChannel Coding for Telecommunications JohnWileyamp Sons New York NY USA 1999
[16] F Certık ldquoUtilization of encoding techniques at the signal trans-mission in the optical fiberrdquo in Advances in Signal Processingvol 3 no 2 pp 17ndash24 2015
[17] F Certık ldquoThe analysis of different encoding and modulationtechniques at the signal transmission in the optical mediumrdquo inProceedings of the 37th International Symposium on the Appli-cation of Computers and Operations Research in the MineralIndustry (APCOM rsquo15) pp 978ndash80 STU Publishing HouseBratislava Slovakia
[18] R Roka ldquoFixed transmission mediardquo in Technology and Engi-neering Applications of Simulink S Chakravarty Ed pp 41ndash68InTech Rijeka Croatia 2012
[19] R Roka and F Certık ldquoSimulation tools for broadband passiveoptical networksrdquo in Simulation Technologies in Networking andCommunications Selecting the Best Tool for the Test CRC PressBoca Raton Fla USA 2014
[20] R Roka ldquoThe environment of fixed transmission media andtheir negative influences in the simulationrdquo International Jour-nal ofMathematics and Computers in Simulation vol 9 pp 190ndash205 2015
[21] R Essiambre G Kramer P J Winzer G J Foschini and BGoebel ldquoCapacity limits of optical fiber networksrdquo Journal ofLightwave Technology vol 28 no 4 pp 662ndash701 2010
[22] P J Winzer and R J Essiambre ldquoAdvanced optical modulationformatsrdquo Proceedings of the IEEE vol 94 no 5 pp 952ndash9852006
[23] M I Olmedo T Zuo J B Jensen et al ldquoMultiband carrierlessamplitude phase modulation for high capacity optical datalinksrdquo Journal of Lightwave Technology vol 32 no 4 pp 798ndash804 2014
[24] T Rahman D Rafigue A Napoli et al ldquoUltralong haul 128-Tbs PM-16QAMWDM transmission employing hybrid amplifica-tionrdquo Journal of Lightwave Technology vol 33 no 9 pp 1794ndash1804 2015
10 Journal of Engineering
[25] S Chandrasekhar and X Liu ldquoExperimental investigation onthe performance of closely spaced multi-carrier PDM-QPSKwith digital coherent detectionrdquo Optics Express vol 17 no 24pp 21350ndash21361 2009
[26] I B Djordjevic ldquoGeneralized LDPC codes and turbo-productcodes with reed-muller component codesrdquo in Proceedings of the8th International Conference on Telecommunications in ModernSatellite Cable and Broadcasting Services (TELSIKS rsquo07) pp127ndash134 Nis Serbia September 2007
[27] D Ouchi K Kubo T Mizuochi et al ldquoA fully integrated blockturbo code FEC for 10Gbs optical communication systemsrdquoin Proceedings of the Optical Fiber Communication (OFC rsquo06)Anaheim Calif USA March 2006
International Journal of
AerospaceEngineeringHindawi Publishing Corporationhttpwwwhindawicom Volume 2014
RoboticsJournal of
Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014
Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014
Active and Passive Electronic Components
Control Scienceand Engineering
Journal of
Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014
International Journal of
RotatingMachinery
Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014
Hindawi Publishing Corporation httpwwwhindawicom
Journal ofEngineeringVolume 2014
Submit your manuscripts athttpwwwhindawicom
VLSI Design
Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014
Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014
Shock and Vibration
Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014
Civil EngineeringAdvances in
Acoustics and VibrationAdvances in
Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014
Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014
Electrical and Computer Engineering
Journal of
Advances inOptoElectronics
Hindawi Publishing Corporation httpwwwhindawicom
Volume 2014
The Scientific World JournalHindawi Publishing Corporation httpwwwhindawicom Volume 2014
SensorsJournal of
Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014
Modelling amp Simulation in EngineeringHindawi Publishing Corporation httpwwwhindawicom Volume 2014
Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014
Chemical EngineeringInternational Journal of Antennas and
Propagation
International Journal of
Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014
Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014
Navigation and Observation
International Journal of
Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014
DistributedSensor Networks
International Journal of
Journal of Engineering 5
Merge block
1 0 0 1 1 1 1 10 0
1
111
1
1
00
0
0
Gauss filter 10Gbits
10Gbits
110
1Gbits
1Gbits
1Gbits
1Gbits
1Gbits
1Gbits
1Gbits
1Gbits
1Gbits
1Gbits
1Gbits
1Gbits
LDPC codingn = i + k
1Gbits
LDPC codingn = i + k
1Gbits
LDPC codingn = i + k
1Gbits
LDPC codingn = i + k
1Gbits
LDPC codingn = i + k
1Gbits
LDPC codingn = i + k
1Gbits
LDPC codingn = i + k
1Gbits
LDPC codingn = i + k
1Gbits
LDPC codingn = i + k
1Gbits
LDPC codingn = i + k
Bernoulli generatorrectangular impulse
Bernoulli generatorrectangular impulse
Bernoulli generatorrectangular impulse
Bernoulli generatorrectangular impulse
Bernoulli generatorrectangular impulse
Bernoulli generatorrectangular impulse
Bernoulli generatorrectangular impulse
Bernoulli generatorrectangular impulse
Bernoulli generatorrectangular impulse
Bernoulli generatorrectangular impulse
generatorSample
Figure 3 The schematic block diagram for the signal generation with the LDPC encoding technique
System signal source
System signal source
System signal source
1
2
N
Optical fiber
Circ
ulat
or
Localoscillator
Signal with different wavelength
Signal with different wavelength
Laser source
Electric datasignal
Electric datasignal
Mach-Zehndermodulator
Continuousoptical wave
Wavelengthdivision
multiplex
Erbium dopedfiber
Phase andamplitudedetection
Chromatic andpolarization modedispersion [time
broadening signalphase shift]
Four-wave mixing[intensity noise from
neighbour channels ondifferent wavelength]
[phase noise andsignal frequency shiftdue to signal intensity]
Self-phase andcross-phase modulation
[intensity noise fromneighbour channels
and decreasing signalintensity]
Stimulated Brillouinand Raman scattering
attenuation
Figure 4 The schematic block diagram for the optical transmission system
components For given modulation the Monte Carlo algo-rithm can be used because it allows a measuring of theBER parameter The simulation model uses the standard SM(ITU-T G656) optical fiber The comparison of transmissioncharacteristics for coherent OOK and Duobinary systems isshown in Figure 7
Possible solution can be represented by coherent systemswith phase and frequency modulation techniques which are
represented by BPSK DBPSK and BFSK These modula-tion techniques achieve similar transmission characteristics(shown in Figure 8) where the BPSK achieves better resultsabout 01 dB compared to the DBPSK and about 3 dB com-pared to the FSK
Higher modulation formats can be further used toincrease signal transmission rates in the optical system [21ndash25] Such modulation techniques have a lower tolerance to
6 Journal of Engineering
Out1
Data signal In1 Out1 In2
Demodulator
In1
In2Out1
MZM
Out1
CW
Out1
Cooperating channels
In1
In2
In3
Out1
WDM
Out1
EDFA
SMFmdash592km
Figure 5 The simulation model for the optical path 1
Out1
Data signal In1 Out1 In2 Out1
Erbium doped fiber
In1
In2Out1
MZM
Out1
CW
Out1
Cooperating channels
In1
In2
In3
Out1
WDM
Out1
EDFA
In2
Demodulator
In1 Out1 In2 Out1
Erbium doped fiber 1
In1 Out1 In2 Out1
Erbium doped fiber 2
In1 Out1 In2 Out1
Erbium doped fiber 3
SMFmdash442 km
SMFmdash425 km
SMFmdash433km
SMFmdash407 km
Figure 6 The simulation model for the optical path 2
the optical signal-to-noise ratio (OSNR) and therefore it isnecessary to analyze the BER parameter depending on theOSNR Figure 9 shows transmission characteristics for high-level modulation formats QPSK and DQPSK keying exhibitsimilar resistance to noise as BPSK andDBPSK keying In thiscase the transmission ratewould be increased twice and if thepolarization modulation (PDM) is used then the 40Gbitstransmission rate can be reached This solution requires thedeployment of MZM modulators and the PDM modulatorFor 8PSK and 16QAM modulations the noise resistance isdecreasing around 2 dB that in some systems will lead to
higher bit error rates caused by laser noise amplifier noiseandor nonlinear effects of the optical transmission medium
For improving transmission rates of modulation formatsdifferent encoding techniques can be used [26 27] A com-plete scheme of the prepared optical transmission system isshown in Figure 10 where the total optical fiber length isextended to 320 km
After theoretical analysis the following codes RS(255239) BCH(255 231) and LDPC(960 480)were selectedTheRS and BCH codes are capable of encoding data quicklyup to 10Gbits however the LDPC codes require more
Journal of Engineering 7
0 2 4 6 8 10 12 14 16 18
BER
OOK NRZDuobinary
100
10minus1
10minus2
10minus3
10minus4
10minus5
10minus6
10minus7
10minus8
EbN0 (dB)
Figure 7 BER transmission characteristics for OOK keying andDuobinary modulation
0 2 4 6 8 10 12 14 16 18
BER
DBPSKBPSKBFSK
EbN0 (dB)
100
10minus1
10minus2
10minus3
10minus4
10minus5
10minus6
10minus7
10minus8
Figure 8 BER transmission characteristics for BPSK DBPSK andBFSK keying
0 2 4 6 8 10 12 14 16 18
BER
DQPSK8PSK
QPSK16QAM
100
10minus1
10minus2
10minus3
10minus4
10minus5
10minus6
10minus7
10minus8
EbN0 (dB)
Figure 9 BER transmission characteristics for QPSK DQPSK8PSK and 16QAM keying
time to encode data Therefore 10 data streams are encodedseparately and afterwards multiplexed into one data stream(shown in Figure 2) For analyzing and simulating onlybinary modulation formats are used
A comparison of binary modulation techniques (nonco-herent OOK BPSK and DBPSK) combined with encodingtechniques (RS BCH and LDPC) is shown in Figure 11Encoding techniques can increase the system range from50 km up to 160 km depending on appropriate code Bettertransmission characteristics are achievable through coherentphase modulations BPSK and DBPSK where limitations arebetween 80 and 100 km The BCH and RS codes increasethe range of these systems up to 160 km and this systemrange can be increased up to 230 km by using the LDPCcodeThe LDPC code is more than 50 efficient compared toBCH and RS codes however such a system needs encodingindividual data signals with lower transmission rates than thetotal system transmission rate Therefore it is more effectiveto use the LDPC code inmetropolitan networks where a timemultiplexing is used
4 The Implementation of Modulation andEncoding Techniques
Selected modulation and encoding techniques are imple-mented on the optical transmission system with the standardSM fiber (ITU-TG652) where a data signal with the 10Gbitstransmission rate and 80WDMchannels is transmitted Indi-vidual transmitters are designed using the MZM modulatorwhere a continuous wave generated in the CW-DFB laseris modulated with a data signal generated by the Bernoulligenerator The CW-DFB laser generates a continuous wavewith 1mW power and embeds the 4 dB amplitude noise Itis considered that a phase noise is suppressed The analyzedsignal is transmitted with the 1934 THz optical frequencyand the resulting OSNR is 30 dB For increasing the opticaltransmission path range EDFA amplifiers are used every40 km for amplifying the transmitted signal where a noisefigureNF is equal to 4 dBTheoptical fiberwith a negativeCDis placed before a receiver to compensate the CD effect in thesystemThe received signal is detected by a coherent detectorwhose sensitivity is around minus17 dBm Based on the previousanalysis a hard decision scheme with the LDPC(960 480)code is selected for implementation
First binary modulation techniques can be consideredwhere the OOK has the worst transmission characteristicsand therefore the transmission system range is limited to230 km The analyzed BPSK and BFSK modulations achievesimilar transmission characteristics where both systems arecapable of having a signal transmission over the 300 km linelength with the 10Gbits transmission rate It is optional touse these modulations to achieve the longest transmissionsystem range For increasing transmission rates of thesemodulations it is possible to use a combination with thePDM (PDM-BPSK and PDM-BFSK) where the transmissionrate of these systems will be higher twice (20Gbits) Forachieving higher transmission rates it is necessary to usemultilevel modulation formats The QPSK signal range isaround 300 km where a transmission rate compared with
8 Journal of Engineering
Out1
Data signal In2 Out1
Erbium doped fiber
In1
In2Out1
MZMOut1
CW
Out1
Cooperating channels
In1In2In3
Out1
WDM
Out1
EDFA
In2
Demodulator
In2 Out1
Erbium doped fiber 1
In2 Out1
Erbium doped fiber 2
In2 Out1
Erbium doped fiber 3
In Out
PMD
In Out
CHD
In Out
FWM
In2 Out1
SPM amp XPM
In1 Out1
SRS amp SBS amp attenuation
In Out
PMD1
In Out
CHD1
In Out
FWM1
In2 Out1
SPM amp XPM1
In1 Out1
SRS amp SBS amp attenuation 1
In Out
PMD2
In Out
CHD2
In Out
FWM2
In2 Out1
SPM amp XPM2
In1 Out1
SRS amp SBS amp attenuation 2
In Out
PMD3
In Out
CHD3
In Out
FWM3
In2 Out1
SPM amp XPM3
In1 Out1
SRS amp SBS amp attenuation 3
Samsung SM NZD-SF 80km length
Samsung SM NZD-SF 80km length
Samsung SM NZD-SF 80km length
Samsung SM NZD-SF 80km length
Figure 10 The block scheme for analysis of the selected modulation and encoding techniques
Table 3 Comparison of selected modulation techniques implemented for the optical transmission system
Modulation techniques Parameters Fiber length [km]40 80 120 160 200 240 280 320
OOK BER [ ] 10minus12 10minus12 10minus12 10minus9 10minus2 10minus1 10minus1 10minus1
OSNR [dB] 25 19 14 7 2 1 1 1
BPSK BER [ ] 10minus12 10minus12 10minus12 10minus12 10minus12 10minus12 10minus11 10minus9
OSNR [dB] 27 24 20 17 15 11 8 5
DBPSK BER [ ] 10minus12 10minus12 10minus12 10minus12 10minus12 10minus12 10minus10 10minus8
OSNR [dB] 27 24 20 17 15 11 8 5
BFSK BER [ ] 10minus12 10minus12 10minus12 10minus12 10minus12 10minus12 10minus11 10minus9
OSNR [dB] 28 26 24 21 18 16 13 10
QPSK BER [ ] 10minus12 10minus12 10minus12 10minus12 10minus12 10minus12 10minus11 10minus9
OSNR [dB] 27 24 20 17 15 11 8 5
8PSK BER [ ] 10minus12 10minus12 10minus12 10minus12 10minus10 10minus6 10minus3 10minus2
OSNR [dB] 27 23 19 14 9 6 2 1
16QAM BER [ ] 10minus12 10minus12 10minus12 10minus12 10minus9 10minus3 10minus1 10minus1
OSNR [dB] 27 22 17 12 7 2 2 1
Calculated BER
BER
0
1
2
3
4
5
6
7
8
9
10
Length (km)0 50 100 150 200 250 300 350
OOKBPSKDBPSK
times10minus3
OOK-RS (255 239)
DBPSK-RS (255 239)
OOK-BCH (255 231)BPSK-BCH (255 231)DBPSK-BCH (255 231)OOK-LDPC (960 480)BPSK-LDPC (960 480)DBPSK-LDPC (960 480)
BPSK-RS (255 239)
Figure 11 Comparison of binary modulation techniques combinedwith encoding techniques
binarymodulations is twice higher Using a combinationwiththe PDM the result transmission rate achieves 40GbitsThe maximum range of 8PSK and 16QAM systems is around200 kmThe decreased range of these systems is due to ampli-fier noises and nonlinear effects in the optical environmentHowever these systems using the PDM have transmissionrates 60Gbits (PDM-8PSK) and 80Gbits (PDM-16QAM)per channel The analysis shows that the range limitationis mainly caused by amplifier noises and nonlinear effectsthat are accumulating For increasing the system range ofmultilevel modulation formats the use of encoding tech-niques such as the LDPC(960 480) code is optional Forfurther improvement of transmission characteristics opticalamplifiers with a low noise figure advanced detectors andsoft encoding schemes can be used However these compo-nents rapidly increase the system cost and particular financialanalysis for the system effectiveness is necessary Outputtransmission characteristics for each modulation techniqueare shown in Table 3
Journal of Engineering 9
5 Conclusion
This contribution analyzes a possible utilization of selectedmodulation and advanced encoding techniques at high datarate signal transmission in optical transmission medium Atfirst the prepared simulation model for optical transmissionsystems with real transmission systems is compared Next aperformance analysis of different binary andmultilevel mod-ulation techniques in combination with RS BCH and LDPCcodes utilized in optical transmission systems is presentedThe simulation results show the limitation of binary modu-lation techniques and their possible improvement using FECcodes The LDPC code can improve a systemrsquos performancefor all modulation schemes Finally a prepared optical systemwith real parameters is enhanced using the LDPC code andselected modulation and encoding techniques are analyzedfor their practical implementation
In future analyses convolutional or turbo codes with dif-ferent rates and constraint length can be considered More-over other recent modulation techniques in possible com-binations with encoding techniques are analyzed Besides autilization of solitons with available optical signal processingtechniques is a very interesting area
Disclosure
This work is a part of research activities conducted atSlovak University of Technology Bratislava Faculty of Elec-trical Engineering and Information Technology Institute ofTelecommunications within the scope of Projects VEGA no1017416 ldquoAdvanced Algorithms and Methods for New Gen-eration Optical Networks for the IMS and NGN ConvergedInfrastructurerdquo and KEGA no 007STU-42016 ldquoProgressiveEducational Methods in the Field of TelecommunicationsMultiservice Networksrdquo
Competing Interests
The authors declare that they have no competing interests
References
[1] K Fukuchi T KasamatsuMMorie et al ldquo1092-Tbs (273times40-Gbs) triple-bandultra-dense WDM optical-repeatered trans-mission experimentrdquo in Proceedings of the Optical Fiber Com-munication Conference (OFC rsquo01) Paper PD24 2001
[2] Z Jia J Yu H-C Chien Z Dong and D Di Huo ldquoField trans-mission of 100G and beyond multiple baud rates and mixedline rates using nyquist-WDM technologyrdquo Journal of LightwaveTechnology vol 30 no 24 Article ID 6235964 pp 3793ndash38042012
[3] H Rohde E Gottwald A Teixeira et al ldquoCoherent ultra denseWDM technology for next generation optical metro and accessnetworksrdquo Journal of Lightwave Technology vol 32 no 10 pp2041ndash2052 2014
[4] H Taga ldquoLong distance transmission experiments using theWDM technologyrdquo Journal of Lightwave Technology vol 14 no6 pp 1287ndash1298 1996
[5] B E A Saleh and M C Teich Fundamentals of PhotonicsWiley-Interscience 1991
[6] L N Binh Optical Fiber Communication Systems CRC PressNew York NY USA 2010
[7] G Keiser Optical Fiber Communications John Wiley amp SonsNew York NY USA 2003
[8] Z Jamaludin A F Abas A S M Noor and M K AbfullahldquoIssues on polarization mode dispersion (PMD) for high speedfiber optics transmissionrdquo Suranaree Journal of Science andTechnology vol 12 no 2 pp 98ndash106 2005
[9] S P Singh andN Singh ldquoNonlinear effects in optical fibers ori-ginmanagement and applicationsrdquoProgress in ElectromagneticsResearch vol 73 pp 249ndash275 2007
[10] E Iannone F Matera A Mecozzi andM SettembreNonlinearOptical Communication Networks TK510359N66 John Wileyamp Sons New York NY USA 1998
[11] D Cotter ldquoNonlinearity in optical fibre communicationsrdquo inNonlinear Optics in Signal Processing RW Eason andAMillerEds vol 49 of Engineering Aspects of Lasers Series SpringerAmsterdam Netherlands 1993
[12] R Hill A First Course in Coding Theory Clarendon PressOxford UK 1980
[13] W Trappe and L C Washington Introduction to CryptographywithCodingTheory PearsonPrenticeHall New JerseyNJUSA2006
[14] J H van Lint Introduction to Coding Theory Springer BerlinGermany 1999
[15] M BossertChannel Coding for Telecommunications JohnWileyamp Sons New York NY USA 1999
[16] F Certık ldquoUtilization of encoding techniques at the signal trans-mission in the optical fiberrdquo in Advances in Signal Processingvol 3 no 2 pp 17ndash24 2015
[17] F Certık ldquoThe analysis of different encoding and modulationtechniques at the signal transmission in the optical mediumrdquo inProceedings of the 37th International Symposium on the Appli-cation of Computers and Operations Research in the MineralIndustry (APCOM rsquo15) pp 978ndash80 STU Publishing HouseBratislava Slovakia
[18] R Roka ldquoFixed transmission mediardquo in Technology and Engi-neering Applications of Simulink S Chakravarty Ed pp 41ndash68InTech Rijeka Croatia 2012
[19] R Roka and F Certık ldquoSimulation tools for broadband passiveoptical networksrdquo in Simulation Technologies in Networking andCommunications Selecting the Best Tool for the Test CRC PressBoca Raton Fla USA 2014
[20] R Roka ldquoThe environment of fixed transmission media andtheir negative influences in the simulationrdquo International Jour-nal ofMathematics and Computers in Simulation vol 9 pp 190ndash205 2015
[21] R Essiambre G Kramer P J Winzer G J Foschini and BGoebel ldquoCapacity limits of optical fiber networksrdquo Journal ofLightwave Technology vol 28 no 4 pp 662ndash701 2010
[22] P J Winzer and R J Essiambre ldquoAdvanced optical modulationformatsrdquo Proceedings of the IEEE vol 94 no 5 pp 952ndash9852006
[23] M I Olmedo T Zuo J B Jensen et al ldquoMultiband carrierlessamplitude phase modulation for high capacity optical datalinksrdquo Journal of Lightwave Technology vol 32 no 4 pp 798ndash804 2014
[24] T Rahman D Rafigue A Napoli et al ldquoUltralong haul 128-Tbs PM-16QAMWDM transmission employing hybrid amplifica-tionrdquo Journal of Lightwave Technology vol 33 no 9 pp 1794ndash1804 2015
10 Journal of Engineering
[25] S Chandrasekhar and X Liu ldquoExperimental investigation onthe performance of closely spaced multi-carrier PDM-QPSKwith digital coherent detectionrdquo Optics Express vol 17 no 24pp 21350ndash21361 2009
[26] I B Djordjevic ldquoGeneralized LDPC codes and turbo-productcodes with reed-muller component codesrdquo in Proceedings of the8th International Conference on Telecommunications in ModernSatellite Cable and Broadcasting Services (TELSIKS rsquo07) pp127ndash134 Nis Serbia September 2007
[27] D Ouchi K Kubo T Mizuochi et al ldquoA fully integrated blockturbo code FEC for 10Gbs optical communication systemsrdquoin Proceedings of the Optical Fiber Communication (OFC rsquo06)Anaheim Calif USA March 2006
International Journal of
AerospaceEngineeringHindawi Publishing Corporationhttpwwwhindawicom Volume 2014
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Active and Passive Electronic Components
Control Scienceand Engineering
Journal of
Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014
International Journal of
RotatingMachinery
Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014
Hindawi Publishing Corporation httpwwwhindawicom
Journal ofEngineeringVolume 2014
Submit your manuscripts athttpwwwhindawicom
VLSI Design
Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014
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Shock and Vibration
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Civil EngineeringAdvances in
Acoustics and VibrationAdvances in
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Electrical and Computer Engineering
Journal of
Advances inOptoElectronics
Hindawi Publishing Corporation httpwwwhindawicom
Volume 2014
The Scientific World JournalHindawi Publishing Corporation httpwwwhindawicom Volume 2014
SensorsJournal of
Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014
Modelling amp Simulation in EngineeringHindawi Publishing Corporation httpwwwhindawicom Volume 2014
Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014
Chemical EngineeringInternational Journal of Antennas and
Propagation
International Journal of
Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014
Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014
Navigation and Observation
International Journal of
Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014
DistributedSensor Networks
International Journal of
6 Journal of Engineering
Out1
Data signal In1 Out1 In2
Demodulator
In1
In2Out1
MZM
Out1
CW
Out1
Cooperating channels
In1
In2
In3
Out1
WDM
Out1
EDFA
SMFmdash592km
Figure 5 The simulation model for the optical path 1
Out1
Data signal In1 Out1 In2 Out1
Erbium doped fiber
In1
In2Out1
MZM
Out1
CW
Out1
Cooperating channels
In1
In2
In3
Out1
WDM
Out1
EDFA
In2
Demodulator
In1 Out1 In2 Out1
Erbium doped fiber 1
In1 Out1 In2 Out1
Erbium doped fiber 2
In1 Out1 In2 Out1
Erbium doped fiber 3
SMFmdash442 km
SMFmdash425 km
SMFmdash433km
SMFmdash407 km
Figure 6 The simulation model for the optical path 2
the optical signal-to-noise ratio (OSNR) and therefore it isnecessary to analyze the BER parameter depending on theOSNR Figure 9 shows transmission characteristics for high-level modulation formats QPSK and DQPSK keying exhibitsimilar resistance to noise as BPSK andDBPSK keying In thiscase the transmission ratewould be increased twice and if thepolarization modulation (PDM) is used then the 40Gbitstransmission rate can be reached This solution requires thedeployment of MZM modulators and the PDM modulatorFor 8PSK and 16QAM modulations the noise resistance isdecreasing around 2 dB that in some systems will lead to
higher bit error rates caused by laser noise amplifier noiseandor nonlinear effects of the optical transmission medium
For improving transmission rates of modulation formatsdifferent encoding techniques can be used [26 27] A com-plete scheme of the prepared optical transmission system isshown in Figure 10 where the total optical fiber length isextended to 320 km
After theoretical analysis the following codes RS(255239) BCH(255 231) and LDPC(960 480)were selectedTheRS and BCH codes are capable of encoding data quicklyup to 10Gbits however the LDPC codes require more
Journal of Engineering 7
0 2 4 6 8 10 12 14 16 18
BER
OOK NRZDuobinary
100
10minus1
10minus2
10minus3
10minus4
10minus5
10minus6
10minus7
10minus8
EbN0 (dB)
Figure 7 BER transmission characteristics for OOK keying andDuobinary modulation
0 2 4 6 8 10 12 14 16 18
BER
DBPSKBPSKBFSK
EbN0 (dB)
100
10minus1
10minus2
10minus3
10minus4
10minus5
10minus6
10minus7
10minus8
Figure 8 BER transmission characteristics for BPSK DBPSK andBFSK keying
0 2 4 6 8 10 12 14 16 18
BER
DQPSK8PSK
QPSK16QAM
100
10minus1
10minus2
10minus3
10minus4
10minus5
10minus6
10minus7
10minus8
EbN0 (dB)
Figure 9 BER transmission characteristics for QPSK DQPSK8PSK and 16QAM keying
time to encode data Therefore 10 data streams are encodedseparately and afterwards multiplexed into one data stream(shown in Figure 2) For analyzing and simulating onlybinary modulation formats are used
A comparison of binary modulation techniques (nonco-herent OOK BPSK and DBPSK) combined with encodingtechniques (RS BCH and LDPC) is shown in Figure 11Encoding techniques can increase the system range from50 km up to 160 km depending on appropriate code Bettertransmission characteristics are achievable through coherentphase modulations BPSK and DBPSK where limitations arebetween 80 and 100 km The BCH and RS codes increasethe range of these systems up to 160 km and this systemrange can be increased up to 230 km by using the LDPCcodeThe LDPC code is more than 50 efficient compared toBCH and RS codes however such a system needs encodingindividual data signals with lower transmission rates than thetotal system transmission rate Therefore it is more effectiveto use the LDPC code inmetropolitan networks where a timemultiplexing is used
4 The Implementation of Modulation andEncoding Techniques
Selected modulation and encoding techniques are imple-mented on the optical transmission system with the standardSM fiber (ITU-TG652) where a data signal with the 10Gbitstransmission rate and 80WDMchannels is transmitted Indi-vidual transmitters are designed using the MZM modulatorwhere a continuous wave generated in the CW-DFB laseris modulated with a data signal generated by the Bernoulligenerator The CW-DFB laser generates a continuous wavewith 1mW power and embeds the 4 dB amplitude noise Itis considered that a phase noise is suppressed The analyzedsignal is transmitted with the 1934 THz optical frequencyand the resulting OSNR is 30 dB For increasing the opticaltransmission path range EDFA amplifiers are used every40 km for amplifying the transmitted signal where a noisefigureNF is equal to 4 dBTheoptical fiberwith a negativeCDis placed before a receiver to compensate the CD effect in thesystemThe received signal is detected by a coherent detectorwhose sensitivity is around minus17 dBm Based on the previousanalysis a hard decision scheme with the LDPC(960 480)code is selected for implementation
First binary modulation techniques can be consideredwhere the OOK has the worst transmission characteristicsand therefore the transmission system range is limited to230 km The analyzed BPSK and BFSK modulations achievesimilar transmission characteristics where both systems arecapable of having a signal transmission over the 300 km linelength with the 10Gbits transmission rate It is optional touse these modulations to achieve the longest transmissionsystem range For increasing transmission rates of thesemodulations it is possible to use a combination with thePDM (PDM-BPSK and PDM-BFSK) where the transmissionrate of these systems will be higher twice (20Gbits) Forachieving higher transmission rates it is necessary to usemultilevel modulation formats The QPSK signal range isaround 300 km where a transmission rate compared with
8 Journal of Engineering
Out1
Data signal In2 Out1
Erbium doped fiber
In1
In2Out1
MZMOut1
CW
Out1
Cooperating channels
In1In2In3
Out1
WDM
Out1
EDFA
In2
Demodulator
In2 Out1
Erbium doped fiber 1
In2 Out1
Erbium doped fiber 2
In2 Out1
Erbium doped fiber 3
In Out
PMD
In Out
CHD
In Out
FWM
In2 Out1
SPM amp XPM
In1 Out1
SRS amp SBS amp attenuation
In Out
PMD1
In Out
CHD1
In Out
FWM1
In2 Out1
SPM amp XPM1
In1 Out1
SRS amp SBS amp attenuation 1
In Out
PMD2
In Out
CHD2
In Out
FWM2
In2 Out1
SPM amp XPM2
In1 Out1
SRS amp SBS amp attenuation 2
In Out
PMD3
In Out
CHD3
In Out
FWM3
In2 Out1
SPM amp XPM3
In1 Out1
SRS amp SBS amp attenuation 3
Samsung SM NZD-SF 80km length
Samsung SM NZD-SF 80km length
Samsung SM NZD-SF 80km length
Samsung SM NZD-SF 80km length
Figure 10 The block scheme for analysis of the selected modulation and encoding techniques
Table 3 Comparison of selected modulation techniques implemented for the optical transmission system
Modulation techniques Parameters Fiber length [km]40 80 120 160 200 240 280 320
OOK BER [ ] 10minus12 10minus12 10minus12 10minus9 10minus2 10minus1 10minus1 10minus1
OSNR [dB] 25 19 14 7 2 1 1 1
BPSK BER [ ] 10minus12 10minus12 10minus12 10minus12 10minus12 10minus12 10minus11 10minus9
OSNR [dB] 27 24 20 17 15 11 8 5
DBPSK BER [ ] 10minus12 10minus12 10minus12 10minus12 10minus12 10minus12 10minus10 10minus8
OSNR [dB] 27 24 20 17 15 11 8 5
BFSK BER [ ] 10minus12 10minus12 10minus12 10minus12 10minus12 10minus12 10minus11 10minus9
OSNR [dB] 28 26 24 21 18 16 13 10
QPSK BER [ ] 10minus12 10minus12 10minus12 10minus12 10minus12 10minus12 10minus11 10minus9
OSNR [dB] 27 24 20 17 15 11 8 5
8PSK BER [ ] 10minus12 10minus12 10minus12 10minus12 10minus10 10minus6 10minus3 10minus2
OSNR [dB] 27 23 19 14 9 6 2 1
16QAM BER [ ] 10minus12 10minus12 10minus12 10minus12 10minus9 10minus3 10minus1 10minus1
OSNR [dB] 27 22 17 12 7 2 2 1
Calculated BER
BER
0
1
2
3
4
5
6
7
8
9
10
Length (km)0 50 100 150 200 250 300 350
OOKBPSKDBPSK
times10minus3
OOK-RS (255 239)
DBPSK-RS (255 239)
OOK-BCH (255 231)BPSK-BCH (255 231)DBPSK-BCH (255 231)OOK-LDPC (960 480)BPSK-LDPC (960 480)DBPSK-LDPC (960 480)
BPSK-RS (255 239)
Figure 11 Comparison of binary modulation techniques combinedwith encoding techniques
binarymodulations is twice higher Using a combinationwiththe PDM the result transmission rate achieves 40GbitsThe maximum range of 8PSK and 16QAM systems is around200 kmThe decreased range of these systems is due to ampli-fier noises and nonlinear effects in the optical environmentHowever these systems using the PDM have transmissionrates 60Gbits (PDM-8PSK) and 80Gbits (PDM-16QAM)per channel The analysis shows that the range limitationis mainly caused by amplifier noises and nonlinear effectsthat are accumulating For increasing the system range ofmultilevel modulation formats the use of encoding tech-niques such as the LDPC(960 480) code is optional Forfurther improvement of transmission characteristics opticalamplifiers with a low noise figure advanced detectors andsoft encoding schemes can be used However these compo-nents rapidly increase the system cost and particular financialanalysis for the system effectiveness is necessary Outputtransmission characteristics for each modulation techniqueare shown in Table 3
Journal of Engineering 9
5 Conclusion
This contribution analyzes a possible utilization of selectedmodulation and advanced encoding techniques at high datarate signal transmission in optical transmission medium Atfirst the prepared simulation model for optical transmissionsystems with real transmission systems is compared Next aperformance analysis of different binary andmultilevel mod-ulation techniques in combination with RS BCH and LDPCcodes utilized in optical transmission systems is presentedThe simulation results show the limitation of binary modu-lation techniques and their possible improvement using FECcodes The LDPC code can improve a systemrsquos performancefor all modulation schemes Finally a prepared optical systemwith real parameters is enhanced using the LDPC code andselected modulation and encoding techniques are analyzedfor their practical implementation
In future analyses convolutional or turbo codes with dif-ferent rates and constraint length can be considered More-over other recent modulation techniques in possible com-binations with encoding techniques are analyzed Besides autilization of solitons with available optical signal processingtechniques is a very interesting area
Disclosure
This work is a part of research activities conducted atSlovak University of Technology Bratislava Faculty of Elec-trical Engineering and Information Technology Institute ofTelecommunications within the scope of Projects VEGA no1017416 ldquoAdvanced Algorithms and Methods for New Gen-eration Optical Networks for the IMS and NGN ConvergedInfrastructurerdquo and KEGA no 007STU-42016 ldquoProgressiveEducational Methods in the Field of TelecommunicationsMultiservice Networksrdquo
Competing Interests
The authors declare that they have no competing interests
References
[1] K Fukuchi T KasamatsuMMorie et al ldquo1092-Tbs (273times40-Gbs) triple-bandultra-dense WDM optical-repeatered trans-mission experimentrdquo in Proceedings of the Optical Fiber Com-munication Conference (OFC rsquo01) Paper PD24 2001
[2] Z Jia J Yu H-C Chien Z Dong and D Di Huo ldquoField trans-mission of 100G and beyond multiple baud rates and mixedline rates using nyquist-WDM technologyrdquo Journal of LightwaveTechnology vol 30 no 24 Article ID 6235964 pp 3793ndash38042012
[3] H Rohde E Gottwald A Teixeira et al ldquoCoherent ultra denseWDM technology for next generation optical metro and accessnetworksrdquo Journal of Lightwave Technology vol 32 no 10 pp2041ndash2052 2014
[4] H Taga ldquoLong distance transmission experiments using theWDM technologyrdquo Journal of Lightwave Technology vol 14 no6 pp 1287ndash1298 1996
[5] B E A Saleh and M C Teich Fundamentals of PhotonicsWiley-Interscience 1991
[6] L N Binh Optical Fiber Communication Systems CRC PressNew York NY USA 2010
[7] G Keiser Optical Fiber Communications John Wiley amp SonsNew York NY USA 2003
[8] Z Jamaludin A F Abas A S M Noor and M K AbfullahldquoIssues on polarization mode dispersion (PMD) for high speedfiber optics transmissionrdquo Suranaree Journal of Science andTechnology vol 12 no 2 pp 98ndash106 2005
[9] S P Singh andN Singh ldquoNonlinear effects in optical fibers ori-ginmanagement and applicationsrdquoProgress in ElectromagneticsResearch vol 73 pp 249ndash275 2007
[10] E Iannone F Matera A Mecozzi andM SettembreNonlinearOptical Communication Networks TK510359N66 John Wileyamp Sons New York NY USA 1998
[11] D Cotter ldquoNonlinearity in optical fibre communicationsrdquo inNonlinear Optics in Signal Processing RW Eason andAMillerEds vol 49 of Engineering Aspects of Lasers Series SpringerAmsterdam Netherlands 1993
[12] R Hill A First Course in Coding Theory Clarendon PressOxford UK 1980
[13] W Trappe and L C Washington Introduction to CryptographywithCodingTheory PearsonPrenticeHall New JerseyNJUSA2006
[14] J H van Lint Introduction to Coding Theory Springer BerlinGermany 1999
[15] M BossertChannel Coding for Telecommunications JohnWileyamp Sons New York NY USA 1999
[16] F Certık ldquoUtilization of encoding techniques at the signal trans-mission in the optical fiberrdquo in Advances in Signal Processingvol 3 no 2 pp 17ndash24 2015
[17] F Certık ldquoThe analysis of different encoding and modulationtechniques at the signal transmission in the optical mediumrdquo inProceedings of the 37th International Symposium on the Appli-cation of Computers and Operations Research in the MineralIndustry (APCOM rsquo15) pp 978ndash80 STU Publishing HouseBratislava Slovakia
[18] R Roka ldquoFixed transmission mediardquo in Technology and Engi-neering Applications of Simulink S Chakravarty Ed pp 41ndash68InTech Rijeka Croatia 2012
[19] R Roka and F Certık ldquoSimulation tools for broadband passiveoptical networksrdquo in Simulation Technologies in Networking andCommunications Selecting the Best Tool for the Test CRC PressBoca Raton Fla USA 2014
[20] R Roka ldquoThe environment of fixed transmission media andtheir negative influences in the simulationrdquo International Jour-nal ofMathematics and Computers in Simulation vol 9 pp 190ndash205 2015
[21] R Essiambre G Kramer P J Winzer G J Foschini and BGoebel ldquoCapacity limits of optical fiber networksrdquo Journal ofLightwave Technology vol 28 no 4 pp 662ndash701 2010
[22] P J Winzer and R J Essiambre ldquoAdvanced optical modulationformatsrdquo Proceedings of the IEEE vol 94 no 5 pp 952ndash9852006
[23] M I Olmedo T Zuo J B Jensen et al ldquoMultiband carrierlessamplitude phase modulation for high capacity optical datalinksrdquo Journal of Lightwave Technology vol 32 no 4 pp 798ndash804 2014
[24] T Rahman D Rafigue A Napoli et al ldquoUltralong haul 128-Tbs PM-16QAMWDM transmission employing hybrid amplifica-tionrdquo Journal of Lightwave Technology vol 33 no 9 pp 1794ndash1804 2015
10 Journal of Engineering
[25] S Chandrasekhar and X Liu ldquoExperimental investigation onthe performance of closely spaced multi-carrier PDM-QPSKwith digital coherent detectionrdquo Optics Express vol 17 no 24pp 21350ndash21361 2009
[26] I B Djordjevic ldquoGeneralized LDPC codes and turbo-productcodes with reed-muller component codesrdquo in Proceedings of the8th International Conference on Telecommunications in ModernSatellite Cable and Broadcasting Services (TELSIKS rsquo07) pp127ndash134 Nis Serbia September 2007
[27] D Ouchi K Kubo T Mizuochi et al ldquoA fully integrated blockturbo code FEC for 10Gbs optical communication systemsrdquoin Proceedings of the Optical Fiber Communication (OFC rsquo06)Anaheim Calif USA March 2006
International Journal of
AerospaceEngineeringHindawi Publishing Corporationhttpwwwhindawicom Volume 2014
RoboticsJournal of
Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014
Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014
Active and Passive Electronic Components
Control Scienceand Engineering
Journal of
Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014
International Journal of
RotatingMachinery
Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014
Hindawi Publishing Corporation httpwwwhindawicom
Journal ofEngineeringVolume 2014
Submit your manuscripts athttpwwwhindawicom
VLSI Design
Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014
Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014
Shock and Vibration
Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014
Civil EngineeringAdvances in
Acoustics and VibrationAdvances in
Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014
Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014
Electrical and Computer Engineering
Journal of
Advances inOptoElectronics
Hindawi Publishing Corporation httpwwwhindawicom
Volume 2014
The Scientific World JournalHindawi Publishing Corporation httpwwwhindawicom Volume 2014
SensorsJournal of
Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014
Modelling amp Simulation in EngineeringHindawi Publishing Corporation httpwwwhindawicom Volume 2014
Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014
Chemical EngineeringInternational Journal of Antennas and
Propagation
International Journal of
Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014
Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014
Navigation and Observation
International Journal of
Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014
DistributedSensor Networks
International Journal of
Journal of Engineering 7
0 2 4 6 8 10 12 14 16 18
BER
OOK NRZDuobinary
100
10minus1
10minus2
10minus3
10minus4
10minus5
10minus6
10minus7
10minus8
EbN0 (dB)
Figure 7 BER transmission characteristics for OOK keying andDuobinary modulation
0 2 4 6 8 10 12 14 16 18
BER
DBPSKBPSKBFSK
EbN0 (dB)
100
10minus1
10minus2
10minus3
10minus4
10minus5
10minus6
10minus7
10minus8
Figure 8 BER transmission characteristics for BPSK DBPSK andBFSK keying
0 2 4 6 8 10 12 14 16 18
BER
DQPSK8PSK
QPSK16QAM
100
10minus1
10minus2
10minus3
10minus4
10minus5
10minus6
10minus7
10minus8
EbN0 (dB)
Figure 9 BER transmission characteristics for QPSK DQPSK8PSK and 16QAM keying
time to encode data Therefore 10 data streams are encodedseparately and afterwards multiplexed into one data stream(shown in Figure 2) For analyzing and simulating onlybinary modulation formats are used
A comparison of binary modulation techniques (nonco-herent OOK BPSK and DBPSK) combined with encodingtechniques (RS BCH and LDPC) is shown in Figure 11Encoding techniques can increase the system range from50 km up to 160 km depending on appropriate code Bettertransmission characteristics are achievable through coherentphase modulations BPSK and DBPSK where limitations arebetween 80 and 100 km The BCH and RS codes increasethe range of these systems up to 160 km and this systemrange can be increased up to 230 km by using the LDPCcodeThe LDPC code is more than 50 efficient compared toBCH and RS codes however such a system needs encodingindividual data signals with lower transmission rates than thetotal system transmission rate Therefore it is more effectiveto use the LDPC code inmetropolitan networks where a timemultiplexing is used
4 The Implementation of Modulation andEncoding Techniques
Selected modulation and encoding techniques are imple-mented on the optical transmission system with the standardSM fiber (ITU-TG652) where a data signal with the 10Gbitstransmission rate and 80WDMchannels is transmitted Indi-vidual transmitters are designed using the MZM modulatorwhere a continuous wave generated in the CW-DFB laseris modulated with a data signal generated by the Bernoulligenerator The CW-DFB laser generates a continuous wavewith 1mW power and embeds the 4 dB amplitude noise Itis considered that a phase noise is suppressed The analyzedsignal is transmitted with the 1934 THz optical frequencyand the resulting OSNR is 30 dB For increasing the opticaltransmission path range EDFA amplifiers are used every40 km for amplifying the transmitted signal where a noisefigureNF is equal to 4 dBTheoptical fiberwith a negativeCDis placed before a receiver to compensate the CD effect in thesystemThe received signal is detected by a coherent detectorwhose sensitivity is around minus17 dBm Based on the previousanalysis a hard decision scheme with the LDPC(960 480)code is selected for implementation
First binary modulation techniques can be consideredwhere the OOK has the worst transmission characteristicsand therefore the transmission system range is limited to230 km The analyzed BPSK and BFSK modulations achievesimilar transmission characteristics where both systems arecapable of having a signal transmission over the 300 km linelength with the 10Gbits transmission rate It is optional touse these modulations to achieve the longest transmissionsystem range For increasing transmission rates of thesemodulations it is possible to use a combination with thePDM (PDM-BPSK and PDM-BFSK) where the transmissionrate of these systems will be higher twice (20Gbits) Forachieving higher transmission rates it is necessary to usemultilevel modulation formats The QPSK signal range isaround 300 km where a transmission rate compared with
8 Journal of Engineering
Out1
Data signal In2 Out1
Erbium doped fiber
In1
In2Out1
MZMOut1
CW
Out1
Cooperating channels
In1In2In3
Out1
WDM
Out1
EDFA
In2
Demodulator
In2 Out1
Erbium doped fiber 1
In2 Out1
Erbium doped fiber 2
In2 Out1
Erbium doped fiber 3
In Out
PMD
In Out
CHD
In Out
FWM
In2 Out1
SPM amp XPM
In1 Out1
SRS amp SBS amp attenuation
In Out
PMD1
In Out
CHD1
In Out
FWM1
In2 Out1
SPM amp XPM1
In1 Out1
SRS amp SBS amp attenuation 1
In Out
PMD2
In Out
CHD2
In Out
FWM2
In2 Out1
SPM amp XPM2
In1 Out1
SRS amp SBS amp attenuation 2
In Out
PMD3
In Out
CHD3
In Out
FWM3
In2 Out1
SPM amp XPM3
In1 Out1
SRS amp SBS amp attenuation 3
Samsung SM NZD-SF 80km length
Samsung SM NZD-SF 80km length
Samsung SM NZD-SF 80km length
Samsung SM NZD-SF 80km length
Figure 10 The block scheme for analysis of the selected modulation and encoding techniques
Table 3 Comparison of selected modulation techniques implemented for the optical transmission system
Modulation techniques Parameters Fiber length [km]40 80 120 160 200 240 280 320
OOK BER [ ] 10minus12 10minus12 10minus12 10minus9 10minus2 10minus1 10minus1 10minus1
OSNR [dB] 25 19 14 7 2 1 1 1
BPSK BER [ ] 10minus12 10minus12 10minus12 10minus12 10minus12 10minus12 10minus11 10minus9
OSNR [dB] 27 24 20 17 15 11 8 5
DBPSK BER [ ] 10minus12 10minus12 10minus12 10minus12 10minus12 10minus12 10minus10 10minus8
OSNR [dB] 27 24 20 17 15 11 8 5
BFSK BER [ ] 10minus12 10minus12 10minus12 10minus12 10minus12 10minus12 10minus11 10minus9
OSNR [dB] 28 26 24 21 18 16 13 10
QPSK BER [ ] 10minus12 10minus12 10minus12 10minus12 10minus12 10minus12 10minus11 10minus9
OSNR [dB] 27 24 20 17 15 11 8 5
8PSK BER [ ] 10minus12 10minus12 10minus12 10minus12 10minus10 10minus6 10minus3 10minus2
OSNR [dB] 27 23 19 14 9 6 2 1
16QAM BER [ ] 10minus12 10minus12 10minus12 10minus12 10minus9 10minus3 10minus1 10minus1
OSNR [dB] 27 22 17 12 7 2 2 1
Calculated BER
BER
0
1
2
3
4
5
6
7
8
9
10
Length (km)0 50 100 150 200 250 300 350
OOKBPSKDBPSK
times10minus3
OOK-RS (255 239)
DBPSK-RS (255 239)
OOK-BCH (255 231)BPSK-BCH (255 231)DBPSK-BCH (255 231)OOK-LDPC (960 480)BPSK-LDPC (960 480)DBPSK-LDPC (960 480)
BPSK-RS (255 239)
Figure 11 Comparison of binary modulation techniques combinedwith encoding techniques
binarymodulations is twice higher Using a combinationwiththe PDM the result transmission rate achieves 40GbitsThe maximum range of 8PSK and 16QAM systems is around200 kmThe decreased range of these systems is due to ampli-fier noises and nonlinear effects in the optical environmentHowever these systems using the PDM have transmissionrates 60Gbits (PDM-8PSK) and 80Gbits (PDM-16QAM)per channel The analysis shows that the range limitationis mainly caused by amplifier noises and nonlinear effectsthat are accumulating For increasing the system range ofmultilevel modulation formats the use of encoding tech-niques such as the LDPC(960 480) code is optional Forfurther improvement of transmission characteristics opticalamplifiers with a low noise figure advanced detectors andsoft encoding schemes can be used However these compo-nents rapidly increase the system cost and particular financialanalysis for the system effectiveness is necessary Outputtransmission characteristics for each modulation techniqueare shown in Table 3
Journal of Engineering 9
5 Conclusion
This contribution analyzes a possible utilization of selectedmodulation and advanced encoding techniques at high datarate signal transmission in optical transmission medium Atfirst the prepared simulation model for optical transmissionsystems with real transmission systems is compared Next aperformance analysis of different binary andmultilevel mod-ulation techniques in combination with RS BCH and LDPCcodes utilized in optical transmission systems is presentedThe simulation results show the limitation of binary modu-lation techniques and their possible improvement using FECcodes The LDPC code can improve a systemrsquos performancefor all modulation schemes Finally a prepared optical systemwith real parameters is enhanced using the LDPC code andselected modulation and encoding techniques are analyzedfor their practical implementation
In future analyses convolutional or turbo codes with dif-ferent rates and constraint length can be considered More-over other recent modulation techniques in possible com-binations with encoding techniques are analyzed Besides autilization of solitons with available optical signal processingtechniques is a very interesting area
Disclosure
This work is a part of research activities conducted atSlovak University of Technology Bratislava Faculty of Elec-trical Engineering and Information Technology Institute ofTelecommunications within the scope of Projects VEGA no1017416 ldquoAdvanced Algorithms and Methods for New Gen-eration Optical Networks for the IMS and NGN ConvergedInfrastructurerdquo and KEGA no 007STU-42016 ldquoProgressiveEducational Methods in the Field of TelecommunicationsMultiservice Networksrdquo
Competing Interests
The authors declare that they have no competing interests
References
[1] K Fukuchi T KasamatsuMMorie et al ldquo1092-Tbs (273times40-Gbs) triple-bandultra-dense WDM optical-repeatered trans-mission experimentrdquo in Proceedings of the Optical Fiber Com-munication Conference (OFC rsquo01) Paper PD24 2001
[2] Z Jia J Yu H-C Chien Z Dong and D Di Huo ldquoField trans-mission of 100G and beyond multiple baud rates and mixedline rates using nyquist-WDM technologyrdquo Journal of LightwaveTechnology vol 30 no 24 Article ID 6235964 pp 3793ndash38042012
[3] H Rohde E Gottwald A Teixeira et al ldquoCoherent ultra denseWDM technology for next generation optical metro and accessnetworksrdquo Journal of Lightwave Technology vol 32 no 10 pp2041ndash2052 2014
[4] H Taga ldquoLong distance transmission experiments using theWDM technologyrdquo Journal of Lightwave Technology vol 14 no6 pp 1287ndash1298 1996
[5] B E A Saleh and M C Teich Fundamentals of PhotonicsWiley-Interscience 1991
[6] L N Binh Optical Fiber Communication Systems CRC PressNew York NY USA 2010
[7] G Keiser Optical Fiber Communications John Wiley amp SonsNew York NY USA 2003
[8] Z Jamaludin A F Abas A S M Noor and M K AbfullahldquoIssues on polarization mode dispersion (PMD) for high speedfiber optics transmissionrdquo Suranaree Journal of Science andTechnology vol 12 no 2 pp 98ndash106 2005
[9] S P Singh andN Singh ldquoNonlinear effects in optical fibers ori-ginmanagement and applicationsrdquoProgress in ElectromagneticsResearch vol 73 pp 249ndash275 2007
[10] E Iannone F Matera A Mecozzi andM SettembreNonlinearOptical Communication Networks TK510359N66 John Wileyamp Sons New York NY USA 1998
[11] D Cotter ldquoNonlinearity in optical fibre communicationsrdquo inNonlinear Optics in Signal Processing RW Eason andAMillerEds vol 49 of Engineering Aspects of Lasers Series SpringerAmsterdam Netherlands 1993
[12] R Hill A First Course in Coding Theory Clarendon PressOxford UK 1980
[13] W Trappe and L C Washington Introduction to CryptographywithCodingTheory PearsonPrenticeHall New JerseyNJUSA2006
[14] J H van Lint Introduction to Coding Theory Springer BerlinGermany 1999
[15] M BossertChannel Coding for Telecommunications JohnWileyamp Sons New York NY USA 1999
[16] F Certık ldquoUtilization of encoding techniques at the signal trans-mission in the optical fiberrdquo in Advances in Signal Processingvol 3 no 2 pp 17ndash24 2015
[17] F Certık ldquoThe analysis of different encoding and modulationtechniques at the signal transmission in the optical mediumrdquo inProceedings of the 37th International Symposium on the Appli-cation of Computers and Operations Research in the MineralIndustry (APCOM rsquo15) pp 978ndash80 STU Publishing HouseBratislava Slovakia
[18] R Roka ldquoFixed transmission mediardquo in Technology and Engi-neering Applications of Simulink S Chakravarty Ed pp 41ndash68InTech Rijeka Croatia 2012
[19] R Roka and F Certık ldquoSimulation tools for broadband passiveoptical networksrdquo in Simulation Technologies in Networking andCommunications Selecting the Best Tool for the Test CRC PressBoca Raton Fla USA 2014
[20] R Roka ldquoThe environment of fixed transmission media andtheir negative influences in the simulationrdquo International Jour-nal ofMathematics and Computers in Simulation vol 9 pp 190ndash205 2015
[21] R Essiambre G Kramer P J Winzer G J Foschini and BGoebel ldquoCapacity limits of optical fiber networksrdquo Journal ofLightwave Technology vol 28 no 4 pp 662ndash701 2010
[22] P J Winzer and R J Essiambre ldquoAdvanced optical modulationformatsrdquo Proceedings of the IEEE vol 94 no 5 pp 952ndash9852006
[23] M I Olmedo T Zuo J B Jensen et al ldquoMultiband carrierlessamplitude phase modulation for high capacity optical datalinksrdquo Journal of Lightwave Technology vol 32 no 4 pp 798ndash804 2014
[24] T Rahman D Rafigue A Napoli et al ldquoUltralong haul 128-Tbs PM-16QAMWDM transmission employing hybrid amplifica-tionrdquo Journal of Lightwave Technology vol 33 no 9 pp 1794ndash1804 2015
10 Journal of Engineering
[25] S Chandrasekhar and X Liu ldquoExperimental investigation onthe performance of closely spaced multi-carrier PDM-QPSKwith digital coherent detectionrdquo Optics Express vol 17 no 24pp 21350ndash21361 2009
[26] I B Djordjevic ldquoGeneralized LDPC codes and turbo-productcodes with reed-muller component codesrdquo in Proceedings of the8th International Conference on Telecommunications in ModernSatellite Cable and Broadcasting Services (TELSIKS rsquo07) pp127ndash134 Nis Serbia September 2007
[27] D Ouchi K Kubo T Mizuochi et al ldquoA fully integrated blockturbo code FEC for 10Gbs optical communication systemsrdquoin Proceedings of the Optical Fiber Communication (OFC rsquo06)Anaheim Calif USA March 2006
International Journal of
AerospaceEngineeringHindawi Publishing Corporationhttpwwwhindawicom Volume 2014
RoboticsJournal of
Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014
Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014
Active and Passive Electronic Components
Control Scienceand Engineering
Journal of
Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014
International Journal of
RotatingMachinery
Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014
Hindawi Publishing Corporation httpwwwhindawicom
Journal ofEngineeringVolume 2014
Submit your manuscripts athttpwwwhindawicom
VLSI Design
Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014
Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014
Shock and Vibration
Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014
Civil EngineeringAdvances in
Acoustics and VibrationAdvances in
Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014
Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014
Electrical and Computer Engineering
Journal of
Advances inOptoElectronics
Hindawi Publishing Corporation httpwwwhindawicom
Volume 2014
The Scientific World JournalHindawi Publishing Corporation httpwwwhindawicom Volume 2014
SensorsJournal of
Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014
Modelling amp Simulation in EngineeringHindawi Publishing Corporation httpwwwhindawicom Volume 2014
Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014
Chemical EngineeringInternational Journal of Antennas and
Propagation
International Journal of
Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014
Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014
Navigation and Observation
International Journal of
Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014
DistributedSensor Networks
International Journal of
8 Journal of Engineering
Out1
Data signal In2 Out1
Erbium doped fiber
In1
In2Out1
MZMOut1
CW
Out1
Cooperating channels
In1In2In3
Out1
WDM
Out1
EDFA
In2
Demodulator
In2 Out1
Erbium doped fiber 1
In2 Out1
Erbium doped fiber 2
In2 Out1
Erbium doped fiber 3
In Out
PMD
In Out
CHD
In Out
FWM
In2 Out1
SPM amp XPM
In1 Out1
SRS amp SBS amp attenuation
In Out
PMD1
In Out
CHD1
In Out
FWM1
In2 Out1
SPM amp XPM1
In1 Out1
SRS amp SBS amp attenuation 1
In Out
PMD2
In Out
CHD2
In Out
FWM2
In2 Out1
SPM amp XPM2
In1 Out1
SRS amp SBS amp attenuation 2
In Out
PMD3
In Out
CHD3
In Out
FWM3
In2 Out1
SPM amp XPM3
In1 Out1
SRS amp SBS amp attenuation 3
Samsung SM NZD-SF 80km length
Samsung SM NZD-SF 80km length
Samsung SM NZD-SF 80km length
Samsung SM NZD-SF 80km length
Figure 10 The block scheme for analysis of the selected modulation and encoding techniques
Table 3 Comparison of selected modulation techniques implemented for the optical transmission system
Modulation techniques Parameters Fiber length [km]40 80 120 160 200 240 280 320
OOK BER [ ] 10minus12 10minus12 10minus12 10minus9 10minus2 10minus1 10minus1 10minus1
OSNR [dB] 25 19 14 7 2 1 1 1
BPSK BER [ ] 10minus12 10minus12 10minus12 10minus12 10minus12 10minus12 10minus11 10minus9
OSNR [dB] 27 24 20 17 15 11 8 5
DBPSK BER [ ] 10minus12 10minus12 10minus12 10minus12 10minus12 10minus12 10minus10 10minus8
OSNR [dB] 27 24 20 17 15 11 8 5
BFSK BER [ ] 10minus12 10minus12 10minus12 10minus12 10minus12 10minus12 10minus11 10minus9
OSNR [dB] 28 26 24 21 18 16 13 10
QPSK BER [ ] 10minus12 10minus12 10minus12 10minus12 10minus12 10minus12 10minus11 10minus9
OSNR [dB] 27 24 20 17 15 11 8 5
8PSK BER [ ] 10minus12 10minus12 10minus12 10minus12 10minus10 10minus6 10minus3 10minus2
OSNR [dB] 27 23 19 14 9 6 2 1
16QAM BER [ ] 10minus12 10minus12 10minus12 10minus12 10minus9 10minus3 10minus1 10minus1
OSNR [dB] 27 22 17 12 7 2 2 1
Calculated BER
BER
0
1
2
3
4
5
6
7
8
9
10
Length (km)0 50 100 150 200 250 300 350
OOKBPSKDBPSK
times10minus3
OOK-RS (255 239)
DBPSK-RS (255 239)
OOK-BCH (255 231)BPSK-BCH (255 231)DBPSK-BCH (255 231)OOK-LDPC (960 480)BPSK-LDPC (960 480)DBPSK-LDPC (960 480)
BPSK-RS (255 239)
Figure 11 Comparison of binary modulation techniques combinedwith encoding techniques
binarymodulations is twice higher Using a combinationwiththe PDM the result transmission rate achieves 40GbitsThe maximum range of 8PSK and 16QAM systems is around200 kmThe decreased range of these systems is due to ampli-fier noises and nonlinear effects in the optical environmentHowever these systems using the PDM have transmissionrates 60Gbits (PDM-8PSK) and 80Gbits (PDM-16QAM)per channel The analysis shows that the range limitationis mainly caused by amplifier noises and nonlinear effectsthat are accumulating For increasing the system range ofmultilevel modulation formats the use of encoding tech-niques such as the LDPC(960 480) code is optional Forfurther improvement of transmission characteristics opticalamplifiers with a low noise figure advanced detectors andsoft encoding schemes can be used However these compo-nents rapidly increase the system cost and particular financialanalysis for the system effectiveness is necessary Outputtransmission characteristics for each modulation techniqueare shown in Table 3
Journal of Engineering 9
5 Conclusion
This contribution analyzes a possible utilization of selectedmodulation and advanced encoding techniques at high datarate signal transmission in optical transmission medium Atfirst the prepared simulation model for optical transmissionsystems with real transmission systems is compared Next aperformance analysis of different binary andmultilevel mod-ulation techniques in combination with RS BCH and LDPCcodes utilized in optical transmission systems is presentedThe simulation results show the limitation of binary modu-lation techniques and their possible improvement using FECcodes The LDPC code can improve a systemrsquos performancefor all modulation schemes Finally a prepared optical systemwith real parameters is enhanced using the LDPC code andselected modulation and encoding techniques are analyzedfor their practical implementation
In future analyses convolutional or turbo codes with dif-ferent rates and constraint length can be considered More-over other recent modulation techniques in possible com-binations with encoding techniques are analyzed Besides autilization of solitons with available optical signal processingtechniques is a very interesting area
Disclosure
This work is a part of research activities conducted atSlovak University of Technology Bratislava Faculty of Elec-trical Engineering and Information Technology Institute ofTelecommunications within the scope of Projects VEGA no1017416 ldquoAdvanced Algorithms and Methods for New Gen-eration Optical Networks for the IMS and NGN ConvergedInfrastructurerdquo and KEGA no 007STU-42016 ldquoProgressiveEducational Methods in the Field of TelecommunicationsMultiservice Networksrdquo
Competing Interests
The authors declare that they have no competing interests
References
[1] K Fukuchi T KasamatsuMMorie et al ldquo1092-Tbs (273times40-Gbs) triple-bandultra-dense WDM optical-repeatered trans-mission experimentrdquo in Proceedings of the Optical Fiber Com-munication Conference (OFC rsquo01) Paper PD24 2001
[2] Z Jia J Yu H-C Chien Z Dong and D Di Huo ldquoField trans-mission of 100G and beyond multiple baud rates and mixedline rates using nyquist-WDM technologyrdquo Journal of LightwaveTechnology vol 30 no 24 Article ID 6235964 pp 3793ndash38042012
[3] H Rohde E Gottwald A Teixeira et al ldquoCoherent ultra denseWDM technology for next generation optical metro and accessnetworksrdquo Journal of Lightwave Technology vol 32 no 10 pp2041ndash2052 2014
[4] H Taga ldquoLong distance transmission experiments using theWDM technologyrdquo Journal of Lightwave Technology vol 14 no6 pp 1287ndash1298 1996
[5] B E A Saleh and M C Teich Fundamentals of PhotonicsWiley-Interscience 1991
[6] L N Binh Optical Fiber Communication Systems CRC PressNew York NY USA 2010
[7] G Keiser Optical Fiber Communications John Wiley amp SonsNew York NY USA 2003
[8] Z Jamaludin A F Abas A S M Noor and M K AbfullahldquoIssues on polarization mode dispersion (PMD) for high speedfiber optics transmissionrdquo Suranaree Journal of Science andTechnology vol 12 no 2 pp 98ndash106 2005
[9] S P Singh andN Singh ldquoNonlinear effects in optical fibers ori-ginmanagement and applicationsrdquoProgress in ElectromagneticsResearch vol 73 pp 249ndash275 2007
[10] E Iannone F Matera A Mecozzi andM SettembreNonlinearOptical Communication Networks TK510359N66 John Wileyamp Sons New York NY USA 1998
[11] D Cotter ldquoNonlinearity in optical fibre communicationsrdquo inNonlinear Optics in Signal Processing RW Eason andAMillerEds vol 49 of Engineering Aspects of Lasers Series SpringerAmsterdam Netherlands 1993
[12] R Hill A First Course in Coding Theory Clarendon PressOxford UK 1980
[13] W Trappe and L C Washington Introduction to CryptographywithCodingTheory PearsonPrenticeHall New JerseyNJUSA2006
[14] J H van Lint Introduction to Coding Theory Springer BerlinGermany 1999
[15] M BossertChannel Coding for Telecommunications JohnWileyamp Sons New York NY USA 1999
[16] F Certık ldquoUtilization of encoding techniques at the signal trans-mission in the optical fiberrdquo in Advances in Signal Processingvol 3 no 2 pp 17ndash24 2015
[17] F Certık ldquoThe analysis of different encoding and modulationtechniques at the signal transmission in the optical mediumrdquo inProceedings of the 37th International Symposium on the Appli-cation of Computers and Operations Research in the MineralIndustry (APCOM rsquo15) pp 978ndash80 STU Publishing HouseBratislava Slovakia
[18] R Roka ldquoFixed transmission mediardquo in Technology and Engi-neering Applications of Simulink S Chakravarty Ed pp 41ndash68InTech Rijeka Croatia 2012
[19] R Roka and F Certık ldquoSimulation tools for broadband passiveoptical networksrdquo in Simulation Technologies in Networking andCommunications Selecting the Best Tool for the Test CRC PressBoca Raton Fla USA 2014
[20] R Roka ldquoThe environment of fixed transmission media andtheir negative influences in the simulationrdquo International Jour-nal ofMathematics and Computers in Simulation vol 9 pp 190ndash205 2015
[21] R Essiambre G Kramer P J Winzer G J Foschini and BGoebel ldquoCapacity limits of optical fiber networksrdquo Journal ofLightwave Technology vol 28 no 4 pp 662ndash701 2010
[22] P J Winzer and R J Essiambre ldquoAdvanced optical modulationformatsrdquo Proceedings of the IEEE vol 94 no 5 pp 952ndash9852006
[23] M I Olmedo T Zuo J B Jensen et al ldquoMultiband carrierlessamplitude phase modulation for high capacity optical datalinksrdquo Journal of Lightwave Technology vol 32 no 4 pp 798ndash804 2014
[24] T Rahman D Rafigue A Napoli et al ldquoUltralong haul 128-Tbs PM-16QAMWDM transmission employing hybrid amplifica-tionrdquo Journal of Lightwave Technology vol 33 no 9 pp 1794ndash1804 2015
10 Journal of Engineering
[25] S Chandrasekhar and X Liu ldquoExperimental investigation onthe performance of closely spaced multi-carrier PDM-QPSKwith digital coherent detectionrdquo Optics Express vol 17 no 24pp 21350ndash21361 2009
[26] I B Djordjevic ldquoGeneralized LDPC codes and turbo-productcodes with reed-muller component codesrdquo in Proceedings of the8th International Conference on Telecommunications in ModernSatellite Cable and Broadcasting Services (TELSIKS rsquo07) pp127ndash134 Nis Serbia September 2007
[27] D Ouchi K Kubo T Mizuochi et al ldquoA fully integrated blockturbo code FEC for 10Gbs optical communication systemsrdquoin Proceedings of the Optical Fiber Communication (OFC rsquo06)Anaheim Calif USA March 2006
International Journal of
AerospaceEngineeringHindawi Publishing Corporationhttpwwwhindawicom Volume 2014
RoboticsJournal of
Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014
Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014
Active and Passive Electronic Components
Control Scienceand Engineering
Journal of
Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014
International Journal of
RotatingMachinery
Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014
Hindawi Publishing Corporation httpwwwhindawicom
Journal ofEngineeringVolume 2014
Submit your manuscripts athttpwwwhindawicom
VLSI Design
Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014
Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014
Shock and Vibration
Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014
Civil EngineeringAdvances in
Acoustics and VibrationAdvances in
Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014
Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014
Electrical and Computer Engineering
Journal of
Advances inOptoElectronics
Hindawi Publishing Corporation httpwwwhindawicom
Volume 2014
The Scientific World JournalHindawi Publishing Corporation httpwwwhindawicom Volume 2014
SensorsJournal of
Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014
Modelling amp Simulation in EngineeringHindawi Publishing Corporation httpwwwhindawicom Volume 2014
Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014
Chemical EngineeringInternational Journal of Antennas and
Propagation
International Journal of
Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014
Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014
Navigation and Observation
International Journal of
Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014
DistributedSensor Networks
International Journal of
Journal of Engineering 9
5 Conclusion
This contribution analyzes a possible utilization of selectedmodulation and advanced encoding techniques at high datarate signal transmission in optical transmission medium Atfirst the prepared simulation model for optical transmissionsystems with real transmission systems is compared Next aperformance analysis of different binary andmultilevel mod-ulation techniques in combination with RS BCH and LDPCcodes utilized in optical transmission systems is presentedThe simulation results show the limitation of binary modu-lation techniques and their possible improvement using FECcodes The LDPC code can improve a systemrsquos performancefor all modulation schemes Finally a prepared optical systemwith real parameters is enhanced using the LDPC code andselected modulation and encoding techniques are analyzedfor their practical implementation
In future analyses convolutional or turbo codes with dif-ferent rates and constraint length can be considered More-over other recent modulation techniques in possible com-binations with encoding techniques are analyzed Besides autilization of solitons with available optical signal processingtechniques is a very interesting area
Disclosure
This work is a part of research activities conducted atSlovak University of Technology Bratislava Faculty of Elec-trical Engineering and Information Technology Institute ofTelecommunications within the scope of Projects VEGA no1017416 ldquoAdvanced Algorithms and Methods for New Gen-eration Optical Networks for the IMS and NGN ConvergedInfrastructurerdquo and KEGA no 007STU-42016 ldquoProgressiveEducational Methods in the Field of TelecommunicationsMultiservice Networksrdquo
Competing Interests
The authors declare that they have no competing interests
References
[1] K Fukuchi T KasamatsuMMorie et al ldquo1092-Tbs (273times40-Gbs) triple-bandultra-dense WDM optical-repeatered trans-mission experimentrdquo in Proceedings of the Optical Fiber Com-munication Conference (OFC rsquo01) Paper PD24 2001
[2] Z Jia J Yu H-C Chien Z Dong and D Di Huo ldquoField trans-mission of 100G and beyond multiple baud rates and mixedline rates using nyquist-WDM technologyrdquo Journal of LightwaveTechnology vol 30 no 24 Article ID 6235964 pp 3793ndash38042012
[3] H Rohde E Gottwald A Teixeira et al ldquoCoherent ultra denseWDM technology for next generation optical metro and accessnetworksrdquo Journal of Lightwave Technology vol 32 no 10 pp2041ndash2052 2014
[4] H Taga ldquoLong distance transmission experiments using theWDM technologyrdquo Journal of Lightwave Technology vol 14 no6 pp 1287ndash1298 1996
[5] B E A Saleh and M C Teich Fundamentals of PhotonicsWiley-Interscience 1991
[6] L N Binh Optical Fiber Communication Systems CRC PressNew York NY USA 2010
[7] G Keiser Optical Fiber Communications John Wiley amp SonsNew York NY USA 2003
[8] Z Jamaludin A F Abas A S M Noor and M K AbfullahldquoIssues on polarization mode dispersion (PMD) for high speedfiber optics transmissionrdquo Suranaree Journal of Science andTechnology vol 12 no 2 pp 98ndash106 2005
[9] S P Singh andN Singh ldquoNonlinear effects in optical fibers ori-ginmanagement and applicationsrdquoProgress in ElectromagneticsResearch vol 73 pp 249ndash275 2007
[10] E Iannone F Matera A Mecozzi andM SettembreNonlinearOptical Communication Networks TK510359N66 John Wileyamp Sons New York NY USA 1998
[11] D Cotter ldquoNonlinearity in optical fibre communicationsrdquo inNonlinear Optics in Signal Processing RW Eason andAMillerEds vol 49 of Engineering Aspects of Lasers Series SpringerAmsterdam Netherlands 1993
[12] R Hill A First Course in Coding Theory Clarendon PressOxford UK 1980
[13] W Trappe and L C Washington Introduction to CryptographywithCodingTheory PearsonPrenticeHall New JerseyNJUSA2006
[14] J H van Lint Introduction to Coding Theory Springer BerlinGermany 1999
[15] M BossertChannel Coding for Telecommunications JohnWileyamp Sons New York NY USA 1999
[16] F Certık ldquoUtilization of encoding techniques at the signal trans-mission in the optical fiberrdquo in Advances in Signal Processingvol 3 no 2 pp 17ndash24 2015
[17] F Certık ldquoThe analysis of different encoding and modulationtechniques at the signal transmission in the optical mediumrdquo inProceedings of the 37th International Symposium on the Appli-cation of Computers and Operations Research in the MineralIndustry (APCOM rsquo15) pp 978ndash80 STU Publishing HouseBratislava Slovakia
[18] R Roka ldquoFixed transmission mediardquo in Technology and Engi-neering Applications of Simulink S Chakravarty Ed pp 41ndash68InTech Rijeka Croatia 2012
[19] R Roka and F Certık ldquoSimulation tools for broadband passiveoptical networksrdquo in Simulation Technologies in Networking andCommunications Selecting the Best Tool for the Test CRC PressBoca Raton Fla USA 2014
[20] R Roka ldquoThe environment of fixed transmission media andtheir negative influences in the simulationrdquo International Jour-nal ofMathematics and Computers in Simulation vol 9 pp 190ndash205 2015
[21] R Essiambre G Kramer P J Winzer G J Foschini and BGoebel ldquoCapacity limits of optical fiber networksrdquo Journal ofLightwave Technology vol 28 no 4 pp 662ndash701 2010
[22] P J Winzer and R J Essiambre ldquoAdvanced optical modulationformatsrdquo Proceedings of the IEEE vol 94 no 5 pp 952ndash9852006
[23] M I Olmedo T Zuo J B Jensen et al ldquoMultiband carrierlessamplitude phase modulation for high capacity optical datalinksrdquo Journal of Lightwave Technology vol 32 no 4 pp 798ndash804 2014
[24] T Rahman D Rafigue A Napoli et al ldquoUltralong haul 128-Tbs PM-16QAMWDM transmission employing hybrid amplifica-tionrdquo Journal of Lightwave Technology vol 33 no 9 pp 1794ndash1804 2015
10 Journal of Engineering
[25] S Chandrasekhar and X Liu ldquoExperimental investigation onthe performance of closely spaced multi-carrier PDM-QPSKwith digital coherent detectionrdquo Optics Express vol 17 no 24pp 21350ndash21361 2009
[26] I B Djordjevic ldquoGeneralized LDPC codes and turbo-productcodes with reed-muller component codesrdquo in Proceedings of the8th International Conference on Telecommunications in ModernSatellite Cable and Broadcasting Services (TELSIKS rsquo07) pp127ndash134 Nis Serbia September 2007
[27] D Ouchi K Kubo T Mizuochi et al ldquoA fully integrated blockturbo code FEC for 10Gbs optical communication systemsrdquoin Proceedings of the Optical Fiber Communication (OFC rsquo06)Anaheim Calif USA March 2006
International Journal of
AerospaceEngineeringHindawi Publishing Corporationhttpwwwhindawicom Volume 2014
RoboticsJournal of
Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014
Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014
Active and Passive Electronic Components
Control Scienceand Engineering
Journal of
Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014
International Journal of
RotatingMachinery
Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014
Hindawi Publishing Corporation httpwwwhindawicom
Journal ofEngineeringVolume 2014
Submit your manuscripts athttpwwwhindawicom
VLSI Design
Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014
Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014
Shock and Vibration
Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014
Civil EngineeringAdvances in
Acoustics and VibrationAdvances in
Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014
Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014
Electrical and Computer Engineering
Journal of
Advances inOptoElectronics
Hindawi Publishing Corporation httpwwwhindawicom
Volume 2014
The Scientific World JournalHindawi Publishing Corporation httpwwwhindawicom Volume 2014
SensorsJournal of
Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014
Modelling amp Simulation in EngineeringHindawi Publishing Corporation httpwwwhindawicom Volume 2014
Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014
Chemical EngineeringInternational Journal of Antennas and
Propagation
International Journal of
Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014
Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014
Navigation and Observation
International Journal of
Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014
DistributedSensor Networks
International Journal of
10 Journal of Engineering
[25] S Chandrasekhar and X Liu ldquoExperimental investigation onthe performance of closely spaced multi-carrier PDM-QPSKwith digital coherent detectionrdquo Optics Express vol 17 no 24pp 21350ndash21361 2009
[26] I B Djordjevic ldquoGeneralized LDPC codes and turbo-productcodes with reed-muller component codesrdquo in Proceedings of the8th International Conference on Telecommunications in ModernSatellite Cable and Broadcasting Services (TELSIKS rsquo07) pp127ndash134 Nis Serbia September 2007
[27] D Ouchi K Kubo T Mizuochi et al ldquoA fully integrated blockturbo code FEC for 10Gbs optical communication systemsrdquoin Proceedings of the Optical Fiber Communication (OFC rsquo06)Anaheim Calif USA March 2006
International Journal of
AerospaceEngineeringHindawi Publishing Corporationhttpwwwhindawicom Volume 2014
RoboticsJournal of
Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014
Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014
Active and Passive Electronic Components
Control Scienceand Engineering
Journal of
Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014
International Journal of
RotatingMachinery
Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014
Hindawi Publishing Corporation httpwwwhindawicom
Journal ofEngineeringVolume 2014
Submit your manuscripts athttpwwwhindawicom
VLSI Design
Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014
Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014
Shock and Vibration
Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014
Civil EngineeringAdvances in
Acoustics and VibrationAdvances in
Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014
Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014
Electrical and Computer Engineering
Journal of
Advances inOptoElectronics
Hindawi Publishing Corporation httpwwwhindawicom
Volume 2014
The Scientific World JournalHindawi Publishing Corporation httpwwwhindawicom Volume 2014
SensorsJournal of
Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014
Modelling amp Simulation in EngineeringHindawi Publishing Corporation httpwwwhindawicom Volume 2014
Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014
Chemical EngineeringInternational Journal of Antennas and
Propagation
International Journal of
Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014
Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014
Navigation and Observation
International Journal of
Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014
DistributedSensor Networks
International Journal of
International Journal of
AerospaceEngineeringHindawi Publishing Corporationhttpwwwhindawicom Volume 2014
RoboticsJournal of
Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014
Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014
Active and Passive Electronic Components
Control Scienceand Engineering
Journal of
Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014
International Journal of
RotatingMachinery
Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014
Hindawi Publishing Corporation httpwwwhindawicom
Journal ofEngineeringVolume 2014
Submit your manuscripts athttpwwwhindawicom
VLSI Design
Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014
Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014
Shock and Vibration
Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014
Civil EngineeringAdvances in
Acoustics and VibrationAdvances in
Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014
Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014
Electrical and Computer Engineering
Journal of
Advances inOptoElectronics
Hindawi Publishing Corporation httpwwwhindawicom
Volume 2014
The Scientific World JournalHindawi Publishing Corporation httpwwwhindawicom Volume 2014
SensorsJournal of
Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014
Modelling amp Simulation in EngineeringHindawi Publishing Corporation httpwwwhindawicom Volume 2014
Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014
Chemical EngineeringInternational Journal of Antennas and
Propagation
International Journal of
Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014
Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014
Navigation and Observation
International Journal of
Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014
DistributedSensor Networks
International Journal of