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BHARAT SANCHAR NIGAM LIMITED

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Introduction of OFC.

OF Cable is a guided medium, in which

information (voice, data or video) is

transmitted through a glass or plastic fibre, in

the form of light from one end to other end.

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Technology in OF cable.

Transmission sequence Principles of operation

TIR

Propagation of light

To Achieve TIR

Value of IOR

Propagation angle

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Optical parameters.

Wavelength

Frequency

Window

Attenuation

Dispersion

Bandwidth or NA

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Type of OF Cable.

Single Mode Fibre

Multi Mode Fibre

Plastic Optic Fibre

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Single Mode Fibre

A much smaller core Diameter

The Core dia is 8 to 10 Micrometer

Cladding Dia is 125 Micrometer

Very large bandwidth

Light can go for very long distances

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Multimode

Has a large Core Diameter

Core Diameter - 50, 62.5, 100 Micro meterCladding dia - 125 Micro meter

Light waves are dispersed into number ofpaths

Multiple path of light cause signal distortion

Suitable for shorter length like LAN

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Graded Index Fibre

Multi Mode Fibre

Step Index Fibre

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Advantages of OF Cable.

Unlimited bandwidth

Low Loss - 0.5db per km

Less number of Repeaters

Electro Magnetic Immunity

Small size & Light Weight - Easy to handle

Greater Safety - No Electric Hazards

Higher Security

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Parameters of Cabling

Tensile Strength ( Pull)

Crushing Resistance

Protection from Excess Bending

Abrasion Protection

Anti-Twist

Chemical protection

OFC Construction

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1. Core

It is made by silica or Glass

More RI and it is 1.48

diameter 8-10 micrometer

Light is transmitted through

the core

2. Cladding

It is made by silica or glass

More RI and it is 1.46

diameter 125 micrometer

OFC Construction

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OFC Sizes

6 Fibre

12 Fibre

24 Fibre

48 Fibre

96 Fibre

Note: Standard drum length is 2000M

+10% 0r 4000 m

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PDH

Plesiochronous Digital Hierarchy.

Support large amount of data to transport .

The term PLESIOCHRONOUS is derived from Greek plesio

which means near, and chronous, time.

It means, networks works in different state but not perfectly

within network.

Transmission and reception are synchronized but timing is not

The channel clocks derived from diff master clock and range is

within limit . It called PLESIOCHRONOUS SIGNAL.

PDH signal are neither SYNCHRONOUS nor ASYNCHRONOUS.

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VERSIONS OF PDH

There are two version in PDH namely

THE EUROPEAN AND

THE AMERICAN.

They are different Bit rates and same

EUROPEAN PCM = 30 CHANNELS

NORTH AMERICAN PCM = 24 CHANNELS

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EUROPEAN PDH HIERARCHYWITH BIT RATES

MUX BIT RATE PARTS PERMILLION

CHANNELS

2 Mbps 2.048 Mbps +/- 50 ppm 30

8 Mbps 8.448 Mbps +/- 30 ppm 120

34 Mbps 34.368Mbps

+/- 20 ppm 480

140 Mbps 139.264Mbps

+/- 15 ppm 1920

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MULTIPLEXING TECHNIQUE

Digital data from multiple streams are combined

called Multiplexing .

Taking one bit from each stream and followed byother one .

Multiplexer also adds some additional bits to

enable the reliable.

The additional bit called JUSTIFICATION OR

STUFFING bits.

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30 Chl Digital Hierarchy

III Order

Mux

480 Chls

IV Order

Mux

1920 Chls

Primary

Mux

30 ChlsII orderMux120 Chls

X 4 X 4

2.048 Mbps 8.448 Mbps 34.368 Mbps 139.264 Mbps

X 4

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DIGITAL MUX CONCEPTS

BIT INTERLEAVING: It means Alternately each channel code can be

scanned one digit at a time.

It is adopted in Higher order Multiplexing.

BYTE/WORD/BLOCK INTERLEAVINGIf TS is long enough to accommodate thegroup of bits, then signal called Byteinterleaving.

A1 A2 A3 A4 B1 B2 B3 B4 C1 C2 C3 C4 D1 D2 D3 D4

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SLIP, JUSTIFICATION AND JITTER

SLIP This occurs when incoming bit rates does

not match with the divided MUX/DEMUX clock

rate .Same bit may be read twice or loss of bit

will occur.

JUSTIFICATION:- It is process of adding

additional bits to solve this SLIP problem.

JITTER:- Displacement of pulse from its normal

significant instant is called Jitter.

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PROBLEMS INVOLVED IN HIGHER ORDERMULTIPLEXING AND SOLUTIONS FOR THEM

MUX CLOCK SPEEDS SHOULD BE SAME AT BOTH THEENDS.

SOLUTION :- It solved by using PLL circuit at receive tmlto recover the clock.

SYNCHRONIZATION:-SOLUTION- It is solved by FRAME ALIGNMENT WORD(FAW).

TRIBUTARY BIT RATE AND MUX CLOCK (DIVIDED)SHOULD BE THE SAME:-

SOLUTION - It is solved by adding additional Stuffing bitor Justification bit during process.

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FOTS

FIBRE OPTIC TRANSMISSION SYSTEM.

It has the following sub system

DIGITAL MULTIPLEX SUB SYSTEM.

OPTICAL LINE TRANSMISSION SUB SYSTEM.

CENTRAL SUPERVISORY SUB SYSTEM

POWER SUB SYSTEM

ALARM SUB SYSTEM

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LIMITATIONS

Lower capacity

Add and drop difficult

MUX/DEMUX process Complex

No Universal standard

Internetworking betn. Hierarchies complex.

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DISADVANTAGES OF PDH SYSTE

Bandwidth is limited

To access LO tributary involves whole process.

No common standard between vendors.

Only Point to Point configuration.

No provision for NMS

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SYNCHRONOUS :ONE MASTER CLOCK & ALL ELEMENTSSYNCHRONISE WITH IT.

DIGITAL:INFORMATION IN BINARY.

HIERARCHY:

SET OF BIT RATES IN A HIERARCHIAL ORDER.

WHAT IS S D H ?

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ADVANTAGES OF SDH

1. SIMPLIFIED MULTIPLEXING/DEMULTIPLEXING TECHNIQUES.

2. DIRECT ACCESS TO LOWER ORDER TRIBUTARIES.

3. ACCOMMODATES EXISTING PDH SIGNALS.

4. CAPABLE OF TRANSPORTING BROADBAND SIGNALS.

5. MULTI-VENDOR, MULTI OPERATOR ENVIRONMENT.

6. PROTECTION SWITCHING TO TRAFFIC IS OFFERED BY RINGS.

7. ENHANCED BANDWIDTH.

8. NMS FACILITY.

9. UNLIMITED BANDWIDTH

10. GROWTH OF THE EXISTING TO THE HIGHER ORDER SYSTEM IS

SIMPLE.

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The Container (C)

Basic packaging unit for tributary signals (PDH)

Synchronous to the STM-1

Bitrate adaptation is done via a positive stuffingprocedure

Adaptation of synchronous tributaries by fixed

stuffing bits

Bit by bit stuffing

The Virtual Container (VC)

Formation of the Container by adding of a POH(Path Overhead)

Transport as a unit through the network (SDH)

A VC containing several VCs has also a pointerarea

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The Tributary Unit (TU)

Is formed via adding a pointer to the VC

The Tributary Unit Group (TUG) Combines several TUs for a new VC

The Administrative Unit (AU)

Is shaped if a pointer is allocated to the

VC formed at last

The Syncronous Transport Module Level 1(STM-1)

Formed by adding a Section Overhead (SOH) toAUs

Clock justification through positive-zero-negativestuffing in the AU pointer area

byte by byte stuffing

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STM1 Frames

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STM-N AUG AU-4 VC-4

TUG-3 TU-3 VC-3

C-4

C-3

TUG-2

TU-1 VC-1 C-1

140Mbps

34Mbps

2Mbps

(REDUCED DIAGRAM FOR SDH-MULTIPLEXING)

REDUCED MUXSTRUCTURE

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Containers: C-3, C-2, C-12 and C-11

Container Carries signals at

C-11 1.544 Mbit/s

C-12 2.048 Mbit/s

C-2 6.312 Mbit/s

C-3 34.368 Mbit/s and 44.736 Mbit/s

C-4 139.264 Mbit/s

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SDH BIT RATES

SDH Levels Bit rates in Kbps

STM-1 155520

STM-4 622080

STM-16

STM-64

2488320

9953.28

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SOH BYTE ALLOCATION

A1A2 Frame alignment

B1B2 Error monitoring

D1..D3 Data comm channel for RSOH

D4..D12 Data comm channel for MSOH

E1-E2 Order wire channel

F1 Maintenance

J0 STM Identifier

K1 K2 Automatic protection switching

S1 SYNCHRONISATION STATUS

M1 Txmn Error acknowledgement

Media dependent bytes

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SDH NETWORK ELEMENTS

The different network elements are

SYNCHRONOUS MULTIPLEXER

SYNCHRONOUS DIGITAL CROSS CONNECT

REGENERATOR

NMS

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SYNCHRONOUS MUX

Types of synchronous multiplexers

TERMINAL MULTIPLEXER(TM)

ADD DROP MULTIPLEXER(ADM)

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TM


TM Accepts a no. Of tributary signals and

multiplex them to appropriate optical/electrical

aggregate signal viz STM1,STM4,STM16 etc.

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Only signals that need to be accessed are

dropped or inserted

Remaining traffic continues thru the NE

without requiring special signal process.

ADD DROP MULTIPLEXER(TM)

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ADM

ADD DROP MULTIPLEXER(TM)

AGGREGATE SIGNAL AGGREGATE SIGNALSDH(E/O) SDH(E/O)

ADM

TRIBUTARY SIGNALS (PDH/SDH)

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It works as semi permanent switch for varying

B/W.

It can pick out one or more lower order channelsfor transmitting signal without trans. Chls.

Chls. can be 64Kbps up to STM1

Under software program the need of

demultiplexing

CROSS CONNECT EQUIPMENT

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TYPES OF NETWORKTOPOLOGY

STRING/BUS/LINEAR Topology

RING Topology

STAR Topology

MESH Topology

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STRING/BUS/LINEARTOPOLOGY

TMADM ADM ADMREG

Aggregate signal

Tributarysignal

(STM1/STM4/STM16)

(2/34/140Mbps/STM1(e)/ STM1(o))

TM

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RING TOPOLOGY

Ring is a linear network looped back to

itself

Network elements are ADMs or

REGENERATORS

Every node on a ring has two

communication paths to each other node

via the two directions around the ring.

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RING TOPOLOGY

Ring network is self healing type

Ring protocol can detect failure of fibre

segment or node

Then rapidly reestablish communications,

Duration is on the order of milliseconds.

It known as protection or protection

switching

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RING TOPOLOGY

Rings gives greater flexibility in the

allocation of band width to thedifferent users.

Normally used in LAN,WAN, Core

Network,Regional Network etc.

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STAR TOPOLOGY

Traffic passes thru a central node called

HUB.

The HUB is a DXC.

If HUB fails ,total traffic fails.

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DWDM BASICS

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DWDM BASICS

SINGLE FIBRE

SDH OPTICAL SIGNALS

NEW REQUIREMENTS:

A hi i hi h b d idth

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Achieving high bandwidth

Three possible solutions.

Install new fiber

Invest in new TDM

technology to achieve

higher bandwidth.

Deploy DWDM

Expensive

Very expensiveRequire new typefibre.

Economical.

DWDM

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DWDM

DWDM IS A TECHNOLOGY THAT USES MULTIPLE LASERS

TO TRANSMIT MANY WAVELENGTHS OF LIGHTSIMULTANEOUSLY OVER A SINGLE OPTICAL FIBRE.

EACH SIGNAL IS MODULATED BY DIFFERENT SOURCE

DATA (TEXT, VIDEO ETC) AND TRAVELS WITHIN ITS OWN

UNIQUE COLOUR BAND WAVELENGTH.

DWDM DRAMATICALLY INCREASES THE FIBRE

INFRASTRUCTURE IN THE OPTICAL TRANSPORT NETWORK.

BIT RATE TRANSPARENCY

QUICK DEPLOYMENT

WAVELENGTH ROUTING

WAVELENGTH SWITCHING.

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COMPONENTS AND OPERATION

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COMPONENTS AND OPERATION

TRANS SIDE:- LASERS WITH PRECISE AND STABLE WAVE

LENGTH.

LINK SIDE:- FIBRE THAT EXHIBITS LOW LOSS AND

TRANSMISSION PERFORMANCE IN THE RELEVANT

WAVELENGTH SPECTRA, IN ADDITION TO FLAT GAIN

AMPLIFIERS TO BOOST THE SIGNALS ON LONGER SPAN.

RECEIVE SIDE:- PHOTO DETECTORS AND OPTICAL

DEMUX USING THIN FILM FILTERS OR DIFFRACTIVEELEMENTS.

OPTICAL ADM.

OPTICAL CROSS CONNECT COMPONENTS.

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DWDM SYSTEM Vs OTHER SYSTEMS

OTHER SYSTEMS

REGENERATORS WEREEMPLOYED TO BOOST ORREGENERATE THESIGNALS.

INDIVIDUAL SYSTEMS,INDIVIDUAL FIBRES.

CONSUMES MOREENERGY.

CAPACITY ENHANCEMENTWAS NOT POSSIBLE..

DWDM SYSTEMS

OPTICAL FIBREAMPLIFIERS ARE USEDCOMMONLY.

ONE COMMON FIBRE ISENOUGH.

OPTICAL COMPONENTSMINIMIZE ENERGY.

POSSIBLE TO ENHANCE

BANDWIDTH.

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MAIN NETWORK ELEMENTS

1.TRANSPONDER

2.OPTICAL MULTIPLEXER

3.OPTICAL DEMULTIPLEXER

4.OPTICAL AMPLIFIERS

5.OPTICAL ADD DROP MULTIPLEXER

6.OPTICAL CROSS CONNECT

7.OPTICAL REPEATER

JUST LIKE WIDENING OF ROAD USING AVAILABLE LAND TO MEET

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JUST LIKE WIDENING OF ROAD USING AVAILABLE LAND TO MEET

INCREASED TRAFFIC.

STM 1

STM 4

STM 16

ATM

IP TFC

OFA

WDMWDM

TRANSPONDERS

TX RX

NEW REQUIREMENT OPTICAL SIGNALS

DWDM BLOCK SCHEMATIC

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EXTRACTING HIGHER CAPACITY BY SENDING

SEVERAL LOW BITRATE SIGNALS ON SAME FIBRE

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STAGES IN EVOLUTION OF

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STAGES IN EVOLUTION OFOPTICAL COMMUNICATION:

Improvised Fiber

Point-to-point transport of medium bit ratesignals over short distance : single opticalchannel, 850 nm; using multimode (MM) fibre

Point-to-point transport of medium/high bitratesignals over medium/long distance : singleoptical channel 1310 nm; (Single Mode fibre)

Point-to-point transport of very high bitratesignals over long distance using two optical

channels (second & third windows) : WDM ; (SMfibre)

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EDFAs Invention of the Optical Amplifier (EDFA):

It amplifies all the DWDM channels in the fibre

The erbium doped fiber amplifier is the most

successful design for 1550 nm. (both L and C

bands)..

STAGES IN EVOLUTION OF

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NEW FIBRES Type of fiber:

DSF. G.653: Shifts dispersion minimum

from 1300 to 1550. Ideal for low loss, lowdispersion use with EDFAs.

DSF , G.654 (

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ACCESS Entry of Fibre into the access network (FTTC,

FTTB, FTTH) :

In order to meet the QoS, and bandwidth

requirements of customers. Also to overcome the limitations of existing

copper based access network.

This is facilitating the convergence of Long

distance with Local and Broadband serivces.

ADVANTAGES OF DWDM

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Why Optical (DWDM)Networking?

Fibre Exhaust : Unlimited bandwidth on a fibrepair

Bit Rate Transparency

Format/Protocol Transparency : IP, ATM etc.

Efficient use and rearrangement of embeddedoptical capacity as per demand.

Minimal Capital Expenditure : CapacityExpansions Demand

Simpler Operations : Embedded DCC --->Limited Nes --> Alarm Storm

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OPTICAL BANDS

EXTENSIVE USE OF WAVELENGTHS

DIFFERENT VENDORS:INTEROPERABILITY ISSUES

NEED FOR STANDARD WAVELENGTH VALUES

ITU Classification of bands

Standard values : ITU Grid

Center frequency: 193.10THz (1552.52 nm)

Standard spacings of 200, 100, 50 GHz for different

applications

ITU-T BAND ALLOCATION

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ITU T BAND ALLOCATION

Optical

Supervisorychannel

1500 1520 1530 1542 1547 1560 1620

RED

BAND

C BAND L BAND

BLUE

BAND

C BAND PRODUCTS ARE COMMERCIALLY AVAILABLE. ERBIUM DOPED FIBRE AMPLIFIERS SUITABLE FOR C BAND.

GAIN IN RED BAND FLATTEST FOR EDFA. SOME MANUFACTURERS PROVIDE 16 CHANNELS IN

RED BAND ONLY. OTHERS USE BOTH RED & BLUE BANDS.

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