EECS891EECS891
Anthony LeungAnthony LeungApril 23, 2004
Performance Analysis of SCM Optical Performance Analysis of SCM Optical Transmission Link for FiberTransmission Link for Fiber--toto--thethe--HomeHome
Department of Electrical Engineering & Computer Science, University of Kansas
Department of Electrical Engineering & Computer Science, University of Kansas 2
OutlineIntroduction
• Fiber-to-the-home & WDM-PON Approach• SCM Approach & Project Goal
SCM Network• SCM Network Architecture• Optical Modulator & Optical Signal Side Band Modulation• Noises Contribution in SCM Externally Modulated Optical Link
Transmission Link Performance Analysis• System Standard Requirements• CATV CNR Analysis & SCM Network Scalability Using Conventional MZ Modulator• Dual Parallel MZ Modulators• CATV CNR Analysis & SCM Network Scalability Using DPMZ Modulators• Digital Q-Value Analysis Uisng DPMZ Modulators
Fiber Nonlinearities• Stimulated Raman Scattering (SRS) Frequency Response• Cross Phase Modulation (XPM) Frequency Response• SRS+XPM Crosstalk analysis in SCM Network• Four-wave Mixing
Overall Transmission Performance Analysis Includes Signal-Crosstalk Noise
Conclusion & Future Work
Department of Electrical Engineering & Computer Science, University of Kansas 3
Introduction: FTTH & WDM-PON
Technology Improvements
• Future Access Network “One for All” Architecture
Increasing Data Services Requirements
• Continued increasing data bandwidth demand• DSL & Cable Modem unlikely to meet longer
term needs
Competition • Entertainment Video Overlay
Cost Improvements • Cost of optoelectronic equipment continues to decline
• Reduced maintenance costs
Department of Electrical Engineering & Computer Science, University of Kansas 4
ITU-T G.983.3 Wavelength Allocation Standard1.3 µm wavelength band (Upstream)
1260 13601340132013001280
G983.1 Upstream Band(unchanged at 100 nm bandpass)
Upstream Window (no change)Basic Band (constrained APON band)Enhancement Band (other uses)For future use
1360 14601440142014001380
Reserved for allocation by ITU-T Guard band
1480
Guard band
Intermediate wavelength band (Upstream and/or Downstream)
1.5 µm wavelength band (Upstream and/or Downstream)Enhancement BandBasic Band
ATM-PON
DownstreamGuard band Guard band
Future L Band
Reserved forallocation by ITU-T
λ 1λ
2λ
4λ
3λ
5λ
6
1.3 µm wavelength band (Upstream)
1260 13601340132013001280
G983.1 Upstream Band(unchanged at 100 nm bandpass)
Upstream Window (no change)Basic Band (constrained APON band)Enhancement Band (other uses)For future use
1360 14601440142014001380
Reserved for allocation by ITU-T Guard band
1480
Guard band
Intermediate wavelength band (Upstream and/or Downstream)
1360 14601440142014001380
Reserved for allocation by ITU-T Guard band
1480
Guard band
Intermediate wavelength band (Upstream and/or Downstream)
1.5 µm wavelength band (Upstream and/or Downstream)Enhancement BandBasic Band
ATM-PON
DownstreamGuard band Guard band
Future L Band
Reserved forallocation by ITU-T
λ 1λ
2λ
4λ
3λ
5λ
6
Enhancement BandBasic Band
ATM-PON
DownstreamGuard band Guard band
Future L Band
Reserved forallocation by ITU-T
1λ
2λ
4λ
3λ
5λ
6
ITU-T G.983.3 standard for Enhancement Band1.5µm wavelength Enhancement band (Upstream and /or Downstream)Application options at Enhancement Band (1539nm to 1560nm) are:1) Additional Digital Service Uses2) Video Distribution Service
Department of Electrical Engineering & Computer Science, University of Kansas 5
WDM-PON Network Architecture
Video(RF)
Data Data
OLT(Optical Line Terminal)
Downstream1490 nm
Data Upstream1310 nm
1490nm/1310nm, 1550nm
DataData & Video
OpticalSplitter
EDFA(Erbium Doped Fiber Amplifier)
1310 nm 1490 nmDownstreamUpstream
DownstreamDigital Data
1550 nm
Video
Analog TV
550 MHz42 MHz
Upstream Digital Data
Bandwidths & Services
OpticalCouplers(WDM)
Video1550 nm
Central Office
Customer Premises
ONT(Optical Network Terminal)
E/O
Requires 3 Wavelengths Bandwidth to support Broadband ServicesRequires light source at customer home
Department of Electrical Engineering & Computer Science, University of Kansas 6
SCM Approach
10 Km
1550 nm
FTTX ONT
Central Office/Hub Site
ONT
ONT
Power Splitter
1550 nm
1550 nm
DownstreamData at lower sideband of optical carrier (1550nm)Video at lower sideband of optical carrier (1550nm) Optical subcarrier at upper sideband of optical carrier (1550nm)UpstreamData at upper sideband of optical carrier (1550nm)
Use Microwave double side band technologyOptical modulated 78 CATV channel & 1 Gb/s digital data at the lower side band of optical carrier.At the same time, Optical modulated a sinusoidal RF signal at the upper side band of optical carrier and deliver from CO to Customer, this optical RF signal is used as optical light source for upstream data transmission. Therefore, no laser source requires at customer side.
78 CATV 1Gb/s dataSinusoidal Signal
Upstream digital data
Department of Electrical Engineering & Computer Science, University of Kansas 7
Project GoalExamine Physical Transmission Performance Using SCM Approach transmitting 78 CATV channel and 1Gb/s digital channel from CO to Customer Premises
• Analyze 78 Analog CATV Carrier-to-Noise Ratio (CNR) Performance
• Analyze 1Gb/s Digital Channel Q-Value Performance
• Analyze the fiber crosstalk in SCM Network• Stimulated Raman Scattering (SRS)• Cross Phase Modulation (XPM)• Four wave Mixing (FWM)
• Evaluated the Overall Transmission Performance due to fiber crosstalk
This project is the first time to demonstrate for this comprehensive analysisusing microwave double side band technology for FTTH application
Department of Electrical Engineering & Computer Science, University of Kansas 8
SCM Network Architecture
CA
TVC
hann
el 2
CA
TVC
hann
el 7
8
1Gb/
s da
tado
wns
tream
CCATV
Channel 2
CATVChannel 78
f1
f78
1Gb/s datadownstream
fd
2π
Σ o90
o0
Laser
FPI
O/E
f78 fd
Σ
f1
UpstreamData
O/EUpstream
Data
C
Splitter
OptFilter
Central Office (CO)
10 Km
FPIReflection
FPITransmission
G
CCCirculator Circulator
Hyb
rid
Customer Premise
Sinusoidal RF signal
Department of Electrical Engineering & Computer Science, University of Kansas 9
Optical Modulation & MZ Modulator
RF ∆θ =
RF ∆θ =
RF ∆θ =
Optical ∆ψ =Optical ∆ψ =Optical ∆ψ =
)cos( θω +ts
Optical Input Optical OutputDC
AC
AC
Bias
+++
++= )cos(coscoscos
2)( θωπωωππω
πππ
tVVtt
VV
VVtAtE i
acci
acdcco
Optical Output
2π
−
ω0-ωS ω0 ω0+ωS
ω0 ω0+ωS ω0-ωS ω0
ω0-ωS ω0 ω0+ωS ω0-ωS ω0 ω0+ωS
ω0-ωS ω0 ω0 ω0+ωS
π
2π
2π
− π2π
)cos( tsω
Optical Phase Difference between Upper and Lower arms of MZ Modulator
RF Phase Difference between Upper and Lower arms of MZ Modulator
[1]
Department of Electrical Engineering & Computer Science, University of Kansas 10
Optical Single Side Band Modulation
Optical Input Optical OutputDC
AC
AC
Optical Output
90º
0º
CATVChannel 2
CATVChannel 78
f1
f78
1Gb/s datadownstream
fd
S
78 RF Modulated Video streams: tcAts miciii
i )cos()(78
1ωω −⋅= ∑
=Downstream digital RF Channel: )cos()()( ttxts dd ω⋅=
Upstream RF Channel: )cos()( tts uu ω=
Analog TV Digital Ch.Optical RFSubcarrier
2πV
Vdc =
44MHz to 550MHz
[ ]
−−
+−
−+−
−=
∑=
tV
AJE
ttxV
AJE
tV
AJE
ttV
AJEtE
uci
dci
imici
cci
)cos()(
)cos()()(
))(cos()(
)sin()cos()(2
)(
1
1
78
11
0
ωωπ
ωωπ
ωωωπ
ωωπ
π
π
π
π
Hyb
rid
Department of Electrical Engineering & Computer Science, University of Kansas 11
Noise Contributions in Optical Transmission
Thermal Noise: Noise is generated in resistive elements (Photo-detector)Shot Noise: Noise is generated when an optical signal is incident on the photo-detectorRIN Noise: Noise is generated by spontaneous emission with the laser sourceBooster Amplifier Noise: Noise generated by AmplifierClipping: It set the fundamental limitation on how much the laser can be clipped for composite input signalIntermodulation Distortion: Composite second order (CSO) & Composite Triple Beat (CTB) generated by Conventional MZ Modulator
Thermal Noise Limited Shot Noise Limited RIN Noise Limited ASE Noise Limited
Optical Receiver Power Increase
G
ASE Noise
Analog orDigital Data
RF Carrier
Χ
Thermal NoiseShot Noise
Laser MZ Modulator
Analog orDigital Data
RF Carrier
Χ
RIN Noise &Clipping CSO/CTB
Ps Pase , GPs
LPase ,GLPs
Department of Electrical Engineering & Computer Science, University of Kansas 12
Nonlinear Distortions (CSO, CTB) of Convention MZ ModulatorTransfer function of MZ modulator is a sine wave-like function of input voltage
Composite Second Order (CSO) : Max 79 CSO Distortion terms fall at RF channel 1 Composite Triple Beat (CTB) : Max 2185 CTB distortion terms fall at RF channel 38
))(cos(222
)(
cos 2 θπθπ
π
π −+=
−⋅=
VtVPPV
tV
PP ooos
0 10 20 30 40 50 60 70 80-20
0
20
40
60
80Second Order product count vs. RF Channel Index
Num
ber o
f Ter
ms
fa-fbfa+fb
0 10 20 30 40 50 60 70 801400
1600
1800
2000
2200Third Order product count vs. RF Channel Index
RF Channel Index
Num
ber o
f Ter
ms
Department of Electrical Engineering & Computer Science, University of Kansas 13
Nonlinear Distortions (CSO, CTB) of Convention MZ ModulatorPower ratio of CSO/C
2
2
101
20
21
})sin(
)cos({
)]()[(2
)]([)]([2
dc
dc
CSON
N
VV
VV
N
VAJ
VAJ
VAJ
VAJ
CCSO
π
π
ππ
ππ
π
π
ππ
ππ
⋅
=−
−
Power ratio of CTB/C
2
2
101
30
31
})sin(
)sin({
)]()[(2
)]([)]([2
dc
dc
CTBN
N
VV
VV
N
VAJ
VAJ
VAJ
VAJ
CCTB
π
π
ππ
ππ
π
π
ππ
ππ
⋅
=−
−
• CSO Cancelled when Applied DC Voltage bias at ±0.5Vπ ,±1.5Vπ,…(Q-point)
• CTB independent of Applied DC Voltage
• CSO is negligible
-1 -0.8 -0.6 -0.4 -0.2 0 0.2 0.4 0.6 0.8 1
-80
-60
-40
-20
0
20
CTB/C, CSO/C vs. Applied DC bias voltage (OMI=5%)
Applied Bias DC Voltage normalized to Vpi
CTB
/C, C
SO/C
(-dB
c)
CSO/CCTB/C
Department of Electrical Engineering & Computer Science, University of Kansas 14
Transmission Standard & Device Parameter Values
666Digital Q-Value
-60dBc-53dBc +/- 2dB> 51dBc [Section 76.605 (a) (8)]CATV CTB
-60dBc-53dBc +/- 2dB> 51dBc [Section 76.605 (a) (8)]CATV CSO
50dB48dB +/- 2dB > 43dB [Section 76.605 (a) (7)] CATV Carrier/Noise
Project TargetTypical ValueFCC RequirementParameter
Laser MZ Modulator Booster Amplifier Photodiode Power = 6, 8 &10dBm Loss=5dB Input Power -1, 1 & 3dBm Responsivity = 0.8, 0.9A/W
Wavelength = 1550nm Bandwidth = 20GHz Output Power = 17dBm BW = 6MHz (CATV)
RIN=-155, -160dB/Hz Noise Figure = 5dB BW = 0.75GHz (Digital)
nsp = 1.5849 T=300K, Kb=1.38e-23
Coupling and Isolator loss = 2dB Resistance = 1000 ohms
Department of Electrical Engineering & Computer Science, University of Kansas 15
CATV CNR Analysis using Conventional MZ Modulator
Parameter Values Optical Power budget : 1 end UsersRIN=-155dB/Hz-1dBm input at Booster AmplifierR=0.8 A/W
• CNR=43.1dB (Maximum)C/CTB = 47dB OMI = 1.84%
• Disregarding CTB term for the moment:1) CNR increases to 50dB, as OMI increases to 3.4% OMI.
2) As OMI continues to increase, Clipping becomes dominant
3) Optimized OMI from 3% to 5% range
( ) 14
13
21
21
21
221
221
2
221
1111111
]16[]612[]8
[]4
[]8
[]2
[2
−−−−−−−
−−−−−−−
⋅+
+++++
⋅=
+++++=
ctbsp
s
p
pp
p
ptotal
CTBClippingASEshotThermalRINtotal
Nme
RBhfnIm
BqIIm
RKTB
Im
BIRIN
ImCNR
CNRCNRCNRCNRCNRCNRCNR
µµπ µ
10-4
10-3
10-2
10-1
100
101
0
10
20
30
40
50
60
70
80CNR vs OMI with one Remote Unit
OMI
CN
R
ASE Noise Shot Noise RIN Noise Thermal Noise Laser ClippingCTB CNR
Department of Electrical Engineering & Computer Science, University of Kansas 16
Scalability of SCM network using Conventional MZ ModulatorParameters Line 1 Line 2 Line 3 Line 4
Input power at Booster Amplifier -1dBm 1dBm 1dBm 3dBm
Laser RIN -155dB/Hz -155dB/Hz -160dB/Hz -160dB/Hz
Photodiode Responsivity 0.8 A/W 0.8 A/W 0.9A/W 0.9 A/W
Fiber distance 10km 10km 10km 10km
The “SCM/WDM-PON” network scalability can not be improved further as the third order nonlinear distortion (CTB) severe limit overall CNR performance It cannot implement in practical CATV network without reduced CTB noise
Increase SCM Network Scalability
Improved ASE NoiseImproved Laser RIN NoiseImproved Receiver Noise
0 10 20 30 40 50 6039
40
41
42
43
44
45
46CNR vs Number End-Users
Number of End-users
CN
R (d
B)
Line1Line2Line3Line4
Department of Electrical Engineering & Computer Science, University of Kansas 17
Dual Parallel Linearized External Modulators
Primary Modulator bias at Q-point (Vdc = 0.5Vπ)Secondary Modulator bias at Q-point 180º from the point chosen for the primary modulator (Vdc = 1.5Vπ)Apply higher RF driver power and less Optical power to secondary modulator. This result higher OMI and higher distortion. CTB created in secondary modulator can be made to cancel the distortion products from the primary modulator [2]
Transfer Function of DPMZ
A = Optical Power Ratio B = RF Power Ratio
−−+=
−−+
−=
ππ
ππ ππππππ
VtVBA
VtVA
VtVB
AV
tV
APP
in
out )(sin)1()(sin121
22
3)(
cos)1(2
2)(
cos 22
Primary ModulatorTransfer Function
Secondary ModulatorTransfer Function
Laser 1
Laser 2
V(t) + Vbias 1
BV(t) + Vbias 2
)))(sin(1(21 tV
VP
p
p+
)))(sin(1(22 tBV
VP
p
p-
Laser
V(t) + Vbias 1
)))(sin(1(2
tVV
PAp
p+
)))(sin(1(2
)1( tBVV
PA
p
p--
Approach # 1BV(t) + Vbias 2
A
1-A
Powerdivider
PrimaryModulator
SecondaryModulator Secondary
Modulator
PrimaryModulator
PhaseModulator
Approach # 2
)))(sin()1())(sin(1(2
tBVV
AtVV
AP
pp
pp --+
Department of Electrical Engineering & Computer Science, University of Kansas 18
0.01 0.02 0.03 0.04 0.05 0.06 0.07 0.08 0.09 0.10.8
0.82
0.84
0.86
0.88
0.9
0.92
0.94
0.96
0.98
1DPMZ Power Divider Ratio vs. OMI
Optical Modulation Index m
Pow
er D
ivid
er R
atio
(A)
B=2 B=2.5B=3
Dual Parallel Linearized External Modulators1
011
01 )()()1()()( −− −−= NN
in VABJ
VABJA
VAJ
VAAJ
PP
k
ππππ
ω ππππ
30
31
30
31 )()()1()()( −−++
−−= NN
in VABJ
VABJA
VAJ
VAAJ
P
Pkjk
ππππ
ωωω ππππ
30
31
30
31
30
31
)()()()(
)()(
−−
−
+=
NN
N
VABJ
VABJ
VAJ
VAJ
VABJ
VABJ
A
ππππ
ππ
ππππ
ππ
Amplitude of Fundamental carrier with frequency ωk
Amplitude of third order distortion component of the frequency ωi+ωj+ωk
B = 2, A =0.87 to 0.89
B = 2.5, A =0.92 to 0.94
B = 3, A =0.94 to 0.97
The optimize value of OMI is from 3% to5%, Laser clipping becomes dominant asOMI increases to 5%
Department of Electrical Engineering & Computer Science, University of Kansas 19
DPMZ
Case I: A=0.88, B=2, OMI = (1% - 4.5%), CTB/C > 60 dB
Case II: A=0.93, B=2.5, OMI = (1% - 4.4%), CTB/C > 60 dB
Case III: A=0.96, B=3, OMI = (1% - 3.4%), CTB/C > 60 dB
0.01 0.02 0.03 0.04 0.05 0.06 0.07 0.08 0.09 0.10
20
40
60
80
100
120
C/CTB Performance with B=2.5 and A=0.92, 0.93 & 0.94
OMI
C/C
TB (d
B)
A=0.92 & B=2.5 A=0.93 & B=2.5 A=0.94 & B=2.5 Nonlinearized modulator
0.01 0.02 0.03 0.04 0.05 0.06 0.07 0.08 0.09 0.10
20
40
60
80
100
120
C/CTB Performance with B=2 and A=0.87, 0.88 & 0.89
OMI
C/C
TB (d
B)
A=0.87 & B=2 A=0.88 & B=2 A=0.89 & B=2 Nonlinearized modulator
0.01 0.02 0.03 0.04 0.05 0.06 0.07 0.08 0.09 0.10
20
40
60
80
100
120
C/CTB Performance with B=3 and A=0.94, 0.95, 0.96 & 0.97
OMI
C/C
TB (d
B)
A=0.94 & B=3 A=0.95 & B=3 A=0.96 & B=3 A=0.97 & B=3 Nonlinearized modulator
C/C
TB (d
B)
Best Case when B=2
Best Case when B=3
Best Case when B=2.5
Department of Electrical Engineering & Computer Science, University of Kansas 20
CATV CNR Analysis Using Linearized MZ Modulator
Parameter ValuesLinear Modulator
• A = 2 & B = 0.88
Optical Power budget • 8 Customers• 30 Customers• 60 Customers
RIN=-155dB/Hz-1dBm input at Booster AmplifierR=0.8 A/W
Results• Optical Power Budget = 8
Customers• CNR=50dB • C/CTB = 60.5dBc
OMI = 4.48%10
-410
-310
-210
-110
010
10
10
20
30
40
50
60
70
80CNR vs OMI using Case I linearized Modulator
OMI
CN
R
ASE Noise Shot Noise RIN Noise Thermal Noise Laser Clipping CTB CIR5 CNR 8 end-users CNR 30 end-usersCNR 60 end-users
Department of Electrical Engineering & Computer Science, University of Kansas 21
Scalability of SCM Externally M0odulated Optical Link Using DPZMPARAMETERS Line 1 Line 2 Line 3 Line 4
Case I : MZ Modulator A=0.88 & B=2
A=0.88 & B=2
A=0.88 & B=2
A=0.88 & B=2
Input power at Booster Amplifier -1dBm 1dBm 1dBm 3dBmLaser RIN -155dB/Hz -155dB/Hz -1 60dB/Hz -160dB/Hz
Photodiode Responsivity 0.8 A/W 0.8 A/W 0.9A/W 0.9 A/WFiber distance 10km 10km 10km 10km
RESULTSNo. of End -Users > 50dB CNR 8 15 22 27
CNR per Channel 50 dB 50.1163 dB 50.0553dB 50.0079 dBC/CTB per Channel 60.4695 dB 60.6555 dB 60.65dB 60.655dB
OMI per Channel 4.48 % 4.47 % 4.47 % 4.47%Receiver Optical Power per RF Channel -13.647dBm -16.37dBm -18dBm -18.9dBm
0 10 20 30 40 50 6045
46
47
48
49
50
51
52
53
54
55CNR vs. Number End-Users using Case I Linear Modulator
Number of End-users
CN
R (d
B)
Line1Line2Line3Line4
Department of Electrical Engineering & Computer Science, University of Kansas 22
Scalability of SCM Externally Modulated Optical Link Using DPZMPARAMETERS Line 1 Line 2 Line 3 Line 4
Case II: MZ Modulator A= 0.93 & B=2.5
A=0.93 & B=2.5
A=0.93 & B=2.5
A=0.93 & B=2.5
Input power at Booster Amplifier -1dBm 1dBm 1dBm 3dBmLaser RIN -155dB/Hz -155dB/Hz -160dB/Hz -160dB/Hz
Photodiode Responsivity 0.8 A/W 0.8 A/W 0.9A/W 0.9 A/WFiber distance 10km 10km 10km 10k m
RESULTSNo. of End -Users > 50dB CNR 12 19 26 30
CNR per Channel 50.036 dB 50.085 dB 50.043dB 50.08 dBC/CTB per Channel 61.9 dB 61.89dB 61.89dB 61.89dB
OMI per Channel 4.34 % 4.34 % 4.34 % 4.34%Receiver Optical Power per RF Ch -14.8dBm -16.8dBm -18.1dBm -18.8dBm
0 10 20 30 40 50 6044
46
48
50
52
54
56CNR vs. Number End-Users using Case II Linear Modulator
Number of End-users
CN
R (d
B)
Line1Line2Line3Line4
Department of Electrical Engineering & Computer Science, University of Kansas 23
Scalability of SCM Externally Modulated Optical Link Using DPZMParameters Line 1 Line 2 Line 3 Line 4
Case III: MZ Modulator A=0.96 & B=3
A=0.96 & B=3
A=0.96 & B=3
A=0.96 & B=3
Input power at Booster Amplifier -1dBm 1dBm 1dBm 3dBmLaser RIN -155dB/Hz -155dB/Hz -160dB/Hz -160dB/Hz
Photodiode Responsivity 0.8 A/W 0.8 A/W 0.9A/W 0.9 A/WFiber distance 10km 10km 10km 10km
RESULTSNo. of End -Users > 50dB CNR 0 6 12 18
CNR per Channel 49.47 dB 50.062 dB 50.1182dB 50.05 dBC/CTB per Channel 60.0191 dB 60.0191dB 60.0191dB 60.0191dB
OMI per Channel 3.43 % 3.43 % 3.43 % 3.43%Receiver Optical Power per RF Channel -4.6dBm -12.38dBm -15.9dBm -17.6dBm
0 10 20 30 40 50 6043
44
45
46
47
48
49
50
51
52
53CNR vs. Number End-Users using Case III Linear Modulator
Number of End-users
CN
R (d
B)
Line1Line2Line3Line4
Department of Electrical Engineering & Computer Science, University of Kansas 24
Digital Data Q-Value Analysis})cos()()()()1(2)cos()()()(2{ 1
011
01
⋅⋅−−
⋅⋅⋅= −− ttx
VVBJ
VVBJAttx
VVJ
VVAJII d
Nd
Np ωππωππ
ππππ
)(2
})2
)(1(2)2
(2{2
)1()1()1()1(
4/4/ 222
ASEThermalRINShot
NmBNm
PPBPSK
eBmAemAIIIQ
σσσσσσ +++
−−
⋅⋅
=−+−−
=
−−
)(2
})2
)(1(2)2
(2{
)2
1()2
1(
)2
1()2
1( 4/4/ 222
ASEThermalRINShot
NmBNmPP
QPSK
eBmAemAIIIQ
σσσσσσ +++⋅
−−
⋅
=−+
−−=
−−
)(2
})2
)(1(2)2
(2{
)0()1()0()1(
4/4/ 222
ASEThermalRINShot
NmBNm
PPASK
eBmAemAIIIQ
σσσσσσ +++
−−
⋅
=+−
=
−−
Parameter Set 1 Set 2 Set 3Linear MZ Modulator A=0.88 & B=2 A=0.93 & B=2.5 A=0.96 & B=3
Input power at Booster Amplifier 3dBm 3dBm 3dBmLaser RIN -160dB/Hz -160dB/Hz -160dB/Hz
Photodiode Responsivity 0.9 A/W 0.9 A/W 0.9A/WFiber distance 10km 10km 10km
No. of End-Users 27 30 18OMI / Channel 4.47% 4.34% 3.43%
Receiver Optical Channel Power -18.9dBm -18.8dBm -17.6dBm
Department of Electrical Engineering & Computer Science, University of Kansas 25
Digital Data Q-Value Analysis
0 0.005 0.01 0.015 0.02 0.025 0.03 0.035 0.04 0.045 0.050
5
10
15
20
OMI at 27 End-Users Optical Power Budget
Q
BPSKQPSKASK
-24 -22 -20 -18 -16 -14 -12 -10 -8 -6 -40
10
20
30
40
Receiver Optical Power per Channel at 4.47% OMI
Q
BPSKQPSKASK
0 0.005 0.01 0.015 0.02 0.025 0.03 0.035 0.04 0.045 0.050
5
10
15
20Set 3
OMI at 18 End-Users Optical Power Budget
Q
BPSKQPSKASK
-24 -22 -20 -18 -16 -14 -12 -10 -8 -6 -40
10
20
30
40
Receiver Optical Power per Channel at 3.43% OMI
Q
BPSKQPSKASK
0 0.005 0.01 0.015 0.02 0.025 0.03 0.035 0.04 0.045 0.050
5
10
15
20
Set 1 Set 2 Set 3RESULTSBPSK Q-Value 14.3 15.7 16.9QPSK Q-Value 10.1 11 11.9ASK Q-Value 7.2 7.8 8.4
Set 1 Set 2
OMI at 30 End-Users Optical Power Budget
Q
BPSKQPSKASK
-22 -20 -18 -16 -14 -12 -10 -8 -6 -40
10
20
30
40
Receiver Optical Power per Channel at 4.34% OMI
Q
BPSKQPSKASK
1) The Requirements of Digital is more relax compared to Analog channel.
2) High Optical Power Transmission in SCM Network
3) Q-Value continues to increase as optical power increase
Department of Electrical Engineering & Computer Science, University of Kansas 26
Fiber Nonlinearities (From Linear to Non-linear Propagation)
Types of Fiber NonlinearitiesStimulated Scattering• Raman (SRS)
Nonlinear index (Kerr Effect)• Cross-phase modulation (XPM)• Four-wave mixing (FWM)
λSRS
λFWM
Department of Electrical Engineering & Computer Science, University of Kansas 27
Stimulated Raman Scattering (SRS) Frequency Response Concept in WDM Network [3]
0 0.5 1 1.5 2 2.5 3 3.5 4 4.5 5
x 109
-85
-80
-75
-70
-65
-60
-55
-50
-45SRS Frequency Response
Modulation Freqency (Hz)
SRS
(dB
)
1nm frequency spacing4nm frequency spacing8nm frequency spacing
Parameter ValuesSM fiber, Slope of Raman Gain = 5e-15m/W/THz10dBm optical power entering fiber10km fiber lengthDispersion = 17ps/nm/km
• Transfer Function of SRS has a low pass filter characteristic
• SRS increases, as the Frequency Spacing between two channel increases.
• SRS is dominant at high frequency spacing and at small modulation frequency
121
1
1 )(1 IgItI
zI
αν
−=∂∂
+∂∂
212
2
2 )(1 IgIt
IzI
αν
−−=∂∂
+∂∂
−−=
+−≈
−−−− ∫ α
µµµα
αααz
oeff
zo
z z
eff
z ePAgePdzezdP
AgePP 11),0(1),0(),0(
0
''12212222
'
−+=
++≈
−−−− ∫ α
µµµα
αααz
oeff
zo
z z
eff
z ePAgePdzezdP
AgePP 11),0(1),0(),0(
0
''12121111
'
λ2 λ1
Optical Carrier power after fiber loss
Interaction between the opticalcarriers, results in optical dc power gain or loss
Use coupled propagation equations to solve for SRS Crosstalk level
Department of Electrical Engineering & Computer Science, University of Kansas 28
Cross Phase Modulation (XPM) Frequency Response Concept in WDM Network [4]
PumpChannel K
ProbeChannel J
),()],(2[),(
2),(1),(
2),(
2
22 ztAzzdtPi
tztAi
tztA
ztAz
ztAjjkkj
jj
jj
j −=∂
∂+
∂
∂++
∂
∂γ
βν
α
0 0.5 1 1.5 2 2.5 3 3.5 4 4.5 5
x 109
-120
-110
-100
-90
-80
-70
-60
-50
-40
-30XPM Frequency Response
Modulation Freqency (Hz)
XPM
(dB
)
1nm frequency spacing4nm frequency spacing8nm frequency spacing
Fiber Loss Linear Phase Delay Phase Modulation in the channel J induced by channel k
Fiber Dispersion results in convert Phase Modulation to Intensity Modulation
Parameter Values10dBm optical power entering fiber10km fiber lengthDispersion = 17ps/nm/km
• XPM transfer function has a high pass filter characteristic
• XPM increases, as the Frequency Spacing between two channel decreases.
• XPM is dominant at small frequency spacing and at large modulation frequency
Department of Electrical Engineering & Computer Science, University of Kansas 29
Constructive & Destructive SRS+XPM Frequency Response Concept inWDM Network [3]
Channel 2 CWChannel 1
CWChannel 2 Channel 1
Crosstalk at Channel 1 (Constructive)Power gain through SRS InteractionXPM crosstalk at Channel 1
Crosstalk at Channel 2 (Destructive)Power depletion through SRS InteractionXPM crosstalk at Channel 2
0 0.5 1 1.5 2 2.5 3 3.5 4 4.5 5
x 109
-80
-70
-60
-50
Crosstalk Frequency Response at Channel 1
Xta
lk F
requ
ency
Res
pons
e
Constructive CrosstalkSRS XPM
0 0.5 1 1.5 2 2.5 3 3.5 4 4.5 5
x 109
-80
-70
-60
-50
Crosstalk Frequency Response at Channel 2
Modulation Freqency (Hz)
Xta
lk F
requ
ency
Res
pons
e
Destructive CrosstalkSRS XPM
• SRS dominant for small modulated frequency or large wavelength separation
• XPM is dominant for large modulated frequency or small wavelength separation
• In between we must consider whether the Channel suffered by SRS is going through power gain or depletion
Parameter Values10dBm optical power entering fiber10km fiber length17ps/nm/km Dispersion0.8 nm Frequency spacing
Department of Electrical Engineering & Computer Science, University of Kansas 30
SRS+XPM crosstalk in SCM Externally Modulated Network
CATV Ch.Digital Ch.1 2 78
1GHz to 10GHz frequency spacings6MHz
0 1 2 3 4 5 6
x 106
-280
-260
-240
-220
-200
-180
-160
-140Crosstalk Frequency Response (SRS & XPM)
Modulation Freqency (Hz)
Cro
ssta
lk F
requ
ency
Res
pons
e (d
B)
6MHz Wavelength separation 60MHz Wavelength separation 0.6GHz Wavelength separation6GHz Wavelength separation
Parameter ValuesOptical Power Budget = 30 End-Users-15.6dBm optical channel power entering fiber 10km fiber length, 0.22dB/km5e-15m/W/THz SRS Gain Slope17ps/nm/km Dispersion
Department of Electrical Engineering & Computer Science, University of Kansas 31
SRS+XPM Crosstalk in SCM Externally Modulated Network
0 0.02 0.04 0.06 0.08 0.1 0.12 0.14 0.16 0.18-120
-110
-100
-90
-80Crostalk Optical power(dBm) vs. Wavelength Separation (nm)
Cro
ssta
lk O
ptic
al P
ower
(dB
m)
SRS XPM Crosstalk(SRS+XPM)
Wavelength Separation (nm)0 0.02 0.04 0.06 0.08 0.1 0.12 0.14 0.16 0.18
-110
-100
-90
-80
-70
-60Crosstalk optical power normalized to transmitted ch. power vs. Wavelength Separation (nm)
Cro
ssta
lk le
vel (
dB)
SRS XPM Crosstalk(SRS+XPM)
Wavelength Separation (nm)
SRS is the dominant crosstalk compared to XPM
Overall result, SRS & XPM crosstalk shows very minimal impact between two subcarrier under same wavelength
Department of Electrical Engineering & Computer Science, University of Kansas 32
Four-Wave Mixing
0 0.02 0.04 0.06 0.08 0.1 0.12 0.14 0.16 0.18-86
-84
-82
-80
-78Ratio of FWM power to transmitted ch. power vs. Wavelength Separation(nm)
Wavelength Separation(nm)
FWM
cro
ssta
lk le
vel
0 0.02 0.04 0.06 0.08 0.1 0.12 0.14 0.16 0.18-104
-102
-100
-98
-96FWM optical power (dBm) vs. Wavelength Separation (nm)
FWM
opt
ical
pow
er (d
Bm
)
Wavelength Separation(nm)
ηλπ 2
22
1111224
6
)()(1024)( effeff
kjiijk L
A
PPPDX
cnLP =
Parameter ValuesOptical Power Budget = 30 End Users-15.6dBm optical channel power entering fiber 10km SM standard fiber 17ps/nm/km DispersionD=6 (None of Frequencies are the same)
Department of Electrical Engineering & Computer Science, University of Kansas 33
Total Crosstalk in SCM Externally Modulated Network
0 0.02 0.04 0.06 0.08 0.1 0.12 0.14 0.16-95
-90
-85
-80
-75
-70
-65Crosstalk level vs. Wavelength Separation(nm)
Wavelength Separation(nm)
Cro
ssta
lk le
vel (
dB)
Total CrosstalkFWM SRS+XPM
FWM is the major source of nonlinear crosstalk in SCM optical systems with extremely narrow spacing between RF channels
SRS becomes dominant as channel spacing increases
Department of Electrical Engineering & Computer Science, University of Kansas 34
Total Crosstalk in SCM Externally Modulated Network
CATV Ch.Digital Ch.1 2 78
1GHz to 10GHz frequency spacings6MHz
0 10 20 30 40 50 60 70
-58.9
-58.8
-58.7
-58.6
-58.5
-58.4
-58.3
-58.2
Crosstalk (dB) per Individual CATV Channel
Cro
ssta
lk le
vel (
dB)
78 CATV Channel Index
1 2 3 4 5 6 7 8 9 10-57
-56
-55
-54
-53
-52
-51
-50
-49Crosstalk (dB) at Digital Channel
Frequency Spacing (GHz)
Cro
ssta
lk le
vel (
dB)
Freq. Spacing between Digital Ch. and CATV ch. # 78
Department of Electrical Engineering & Computer Science, University of Kansas 35
Total Crosstalk in SCM Externally Modulated Network
The CATV Crosstalk level remains constant as power increases because FWM is the dominant Crosstalk at narrow channel spacing
It demonstrates that as optical power increases, FWM becomes the dominant crosstalk in SCM externally modulated Network
-20 -18 -16 -14 -12 -10 -8 -6 -4 -2 0-65
-60
-55
-50
-45
-40
-35
-30
-25Crosstalk level at channel power at CATV Channel 1
Input fiber optical channel power (dBm)
Cro
ssta
lk le
vel (
dB)
1GHz spacing from digital ch. 2GHz spacing from digital ch. 3GHz spacing from digital ch 4GHz spacing from digital ch. 5GHz spacing from digital ch. 6GHz spacing from digital ch. 7GHz spacing from digital ch. 8GHz spacing from digital ch. 9GHz spacing from digital ch. 10GHz spacing from digital ch.
-20 -18 -16 -14 -12 -10 -8 -6 -4 -2 0-65
-60
-55
-50
-45
-40
-35
-30
-25Crosstalk level at Digital Channel
Input fiber optical channel power (dBm)
Cro
ssta
lk le
vel (
dB)
1GHz spacing from CATV 2GHz spacing from CATV 3GHz spacing from CATV 4GHz spacing from CATV 5GHz spacing from CATV 6Hz spacing from CATV 7GHz spacing from CATV 8GHz spacng from CATV 9GHz spacing from CATV 10GHz spacing from CATV
Department of Electrical Engineering & Computer Science, University of Kansas 36
Signal-crosstalk Noise in SCM Transmission Performance for CATV PARAMETERS Case 1 Case 2
Linearized MZ Modulator A=0.93 & B=2.5 A=0.93 & B=2.5 Input power at Booster Amplifier -1dBm 3dBm
Laser RIN -155dB/Hz -160dB/Hz Photodiode Responsivity 0.8 A/W 0.9 A/W
Fiber distance 10km 10km OMI 4.343% 4.343%
-22 -20 -18 -16 -14 -12 -10 -8 -6 -425
30
35
40
45
50
55
60CNR vs. Receiver optical power per RF channel
Receiver optical power per channel
CN
R(d
B)
Case 1 CNR (no crosstalk) Case 2, CNR (no crosstalk) Case 1 CNR (with crosstalk)Case 2 CNR (with crosstalk)
Department of Electrical Engineering & Computer Science, University of Kansas 37
Signal-crosstalk Noise in SCM Transmission Performance for Digital DataPARAMETERS
Linearized MZ Modulator A=0.93 & B=2.5 Input power at Booster Amplifier 3dBm
Laser RIN -160dB/Hz Photodiode Responsivity 0.9 A/W
Fiber distance 10km OMI 4.343%
-22 -20 -18 -16 -14 -12 -10 -8 -6 -44
6
8
10
12
14
16
18
20
22BPSK, QPSK & ASK vs. Receiver Optical power at Digital RF Channel
Receiver Optical Power per Channel
Q
BPSK
QPSK
ASK
Department of Electrical Engineering & Computer Science, University of Kansas 38
Conclusion
Transmission Quality• Optimizing the Receiver Optical Power per RF Channel = -17dBm to -20dBm• CATV CNR in the range of 48dB to 48.5dB• Digital BPSK Q = 13 to 17• Digital QPSK Q = 9 to 12• Digital ASK Q = 6 to 8
Network Scalability• Number of Customers premises = 20 to 40
0 10 20 30 40 50 6025
30
35
40
45
50
55
60CATV CNR vs. Customer Premise
Number of Customer Premise
CN
R (d
B)
Case 1 CNR (no crosstalk) Case 2, CNR (no crosstalk) Case 1 CNR (with crosstalk)Case 2 CNR (with crosstalk)
0 10 20 30 40 50 604
6
8
10
12
14
16
18
20
22BPSK, QPSK & ASK Q Value vs. Customer Premise
Number of Customer Premise
Q
BPSK
QPSK
ASK
Department of Electrical Engineering & Computer Science, University of Kansas 39
Future Work
Analyze the uplink transmission performance and the impact of optical crosstalk under bi-directional fiber transmission.
Analyze uplink multiple access method such as Time Division Multiple Access (TDMA), Subcarrier Multiple Access (SCMA) and their efficiencies.
Because Narrow-band optical filter is relative expensive compared to wide-band optical filter, further study in separate upper and lower side-band of optical carrier at end-user is suggested.
The even-order distortion produced by a MZ modulator can be cancelled using OSSB Modulation. CSO is also affected by various phenomena such as chirp, fiber chromatic dispersion and polarization-mod dispersion (PMD), self-phase modulation (SPM) as well as gain-tilt of optical amplifiers. Future study in CSO distortion in SCM externally modulated optical network is suggested.
Department of Electrical Engineering & Computer Science, University of Kansas 40
Acknowledgements & Questions
Many Thanks to:
Dr. Hui for his guidance throughout this project
Dr. Frost and Dr. Saiedian for their service on the project committee
Questions?
Department of Electrical Engineering & Computer Science, University of Kansas 41
References cited in this presentation:
[1] R. Hui, B. Zhu, R. Huang, C. Allen, K. Demarest, D. Richards, “Subcarrier Multiplexing for High-speed Optical Transmission,” Journal of Lightwave Technology, vol. 20, no. 3, March 2002
[2] J. Brooks, G. Maurer, R. Becker, “Implementation and Evaluation of a Dual Parallel Linearization System for AM-SCM Video Transmission,” Journal of Lightwave Technology, vol. 11, no. 1, January 1993.
[3] M Phillips & D. Ott, “Crosstalk Due to Optical Fiber Nonlinearities in WDM CATV Lightwave Systems,” Journal of Lightwave Technology, vol 17, no. 10, Oct. 1999.
[4] R. Hui, Y. Wang, K. Demarest, C. Allen, “Frequency Response of Cross-Phase Modulation in Multispan WDM Optical Fiber Systems,” IEEE Photonics Technology letters, vol 10, no. 9, September, 1998