Training on Optical Fiber Network

5/26/2018 Training on Optical Fiber Network

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RailTel Corporation of India Ltd.

Training

onOptical Fiber Networks

By: Raj Kumar Vishwakarma

Dy. Manager/ Network Planning & ImplementationE-Mail: [email protected]

Phone #: 09717644139


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How fiber cable look like


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Advantages of Optical Communication

Explosive demand for higher bandwidth

Low bandwidth of copper

Nearly 25THz possible with fiber

Low Loss-Longer distance transmission(Less Repeaters)

No EMI in fiber-based telecom

Less cross-talk, more reliability More secure communications

Lighter than copper

Lower cost per unit bandwidth(made of silica which is very cheap) Safer and more advantages


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What is Optical Communication?

Optical communication is any form of

telecommunication that uses light as thetransmission medium.

transmitter, which encodes an electronic pulse

into an optical signal, which carries the signal to

its destination, and a receiver, which reproducesthe message from the received optical signal.


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Journey through the Optical TunnelJourney through the Optical Tunnel


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Transmit-Receive OverviewTransmit-Receive Overview


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Optical FiberThe most common type ofchannel for optical

communications

Flexible optically transparentfiber made of glass or plastic

through which light can be

transmitted by the process of total

nterna re ect on

Consists of a core , cladding andcoating

Core is the inner glass layer of

high refractive index

Cladding is the outer layerwhich covers the core/ has a lower

refractive index

Coating is the outer most layerwhich provides environmental and

physical protection for the fiber


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Theory of Optical FiberTransmits light along its axis using the process oftotal internal reflection

Based upon the principle of Snells Law

Snells Law Total internal reflection can occur when light attempts to move from amaterial with high index of refraction to one with lower index of refraction

In an optical Fiber, the core has high

re rac ve n ex n w c e g en er ng e

fiber is guided

Cladding has a refractive index slightly less

than that of the core

By principle of total internal reflection the

light entering the fiber (core) at one end travels

along the fiber by bouncing repeatedly of the

inside of the interface of the glass with the

surrounding medium (cladding)


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How Does an Optical Fiber Transmit Light?

The light in a fiber-optic cable travels through the core by constantly

bouncing from the cladding (mirror-lined walls), a principle called total

internal reflection. Because the cladding does not absorb any light from the

core, the light wave can travel great distances.

gna egra es w t n t e er

essentially due to

Impurities in glass

Wavelength of transmitted light

850 nm 60-75% per Km

1300 nm 50-60% per KM


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Types of Optical FiberOptical Fibers are classified as Single Mode or MultiMode fiber

Multi mode fiber has a core diameter around 50um andcladding diameter of 125 um

Single mode fiber core is less than 10um and can support

only one mode of propagationOptical fiber are also grouped as step index and gradedindex fiber

In a step index fiber, the refractive index of the core is

constant throughoutA graded index fiber has core with varying refractiveindex


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125um

125um

Single Mode Fiber Multi Mode Fiber

9.2um 50um


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Fiber Optic Communication

History

Fiber Optic Communication System

Benefits of Optic Communication

Limitation of Optic Communication


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History

Early People used light Signal to communicate

Telegraphs, coaxial cables and micro wave systemsDue to their limitation in communicating between long distances, inthe second half of the 20th century, the idea of optical carrier ofinformation arrived and found that it is better than other existing carrier

Due to lack of suitable coherent light source and better transmissionmedium no remarkable even took place until 1960

In 1960 laser was developed and ten years later optical fiber wasdeveloped

Between 1970 and 1980, the first commercial fiber optic system wasdeveloped with a bit rate of 45Mbps and a repeater spacing of 10 Km


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Fiber Optic communication System

Four major parts in the system

Optical Transmitter Semi conductors like LED or Lasersconvert electrical signals to Optical signals to send it into theoptical fiber

and buildings carry the light signal between transmitters,amplifiers and receivers

Optical Amplifier amplifies the light signals to reduceeffects of distortions and attenuation

Optical Receiver Recovers the light signal back to theelectrical signal


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BenefitsPermits transmission over longer distances and at higherbandwidth (data rates) than other forms ofcommunication.

Signals travel along them with less loss and are alsoimmune to electromagnetic interference

No electromagnetic interference hence better S/N ratioHigh electrical resistance makes it safer to use whereelectrical isolation is required

Light weight and small size makes them ideal for

multiple applicationsHigh on security, difficult to tap in and read data beingtransmitted


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Limitations

Dispersion; spreading of optical pulses as they

travel along fiber

Attenuation; caused by combination of material

Material absorption of silica is 0.3 db/km, but impuritiesincrease this amount to 1000 db/km

Modern fiber has attenuation of 00.3 db/km

Microscopic fluctuation in density and imperfectsplicing increases attenuation


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Contents

Plesiochronous Digital Heirarchy

Synchronous Digital Hierarchy

Wave Division Multiplexing


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Plesiochronous Digital Heirarchy

Plesiochronous is a Greek word meaning

Almost Synchronous , but not fullysynchronous.

In Plesiochronous system every equipment isgenerating its own clock for synchronization.


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Plesiochronous TransmissionPulse Code Modulation

Voice Frequency ranges upto 4 Khz Sampling the Voice Signal @ 8 Khz (Double the Max. Frequency) 8 bits per sample =

Building up the Base Stream (2MB)

30 Voice Channels @ 64 Khz

One channel for Frame (64 K) One channel for Signaling (64 K) Total number of Channels = 32 Bit Rate: 32 X 64 K= 2048 Khz (2Mb)


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PDH Bit RatesE1-2048 Kbps (2Mb) [30 Voice Channel]

E2-8448 Kbps (8Mb) [120 Voice Channel]

E3-34368 Kbps (34Mb) [480 Voice Channel]

-


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Bit-Interleaved Multiplexing It is TDM

One bit will be taken from all Tributaries.


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Stuffing and Justification

In a PDH multiplexer individual bits must be running at the

same speed otherwise the bits cannot be interleaved The possible Plesiochronous difference is catered for by

using a technique known as Justification

Extra bits are added(stuffed)into the digital tributaries whicheffectively increases the speed of the tributary until they are all

identical

The speed of the higher order side is generated by an internal

oscillator in the multiplexer and is not derived from the

primary reference clock


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PDH Multiplexing / Demultiplexing is time consuming

Incompatibility of standard equipment fromdifferent vendors

US and Euro ean s stems have too little in common -

Expensive mediators for transatlantic transmission

No self checking - expensive manual check and repairsystem

No standard for high bandwidth links - proprietary


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1...


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The Main Standards G.707 , G.708 , G709 (G.707/Y SINCE 96/93)

Transmission ratesSignal formatMultiplexing structuresTributary mapping for the network node interface

G782 (Merge with G.783 in 97) , G.783Operation of synchronous multiplexers

G.781SDH synchronization networking

G.784SDH network management


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The SDH Advantages High transmission rates

Lower level signals embedded and can beidentified from the higher level (much simplerAdd & Drop)

Optical standard

Can be introduced into existing networks

Allowance of European and North AmericanPDH systems


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More of the SDH Advantages:

High availability and capacity matching

Reliability

Centralized synchronization

Network management channels (the data usedfor maintenance is embedded in the signal)

Centralized network control enabled through

the management channels


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SDH - Synchronous Digital Hierarchy

An international standard for high-speed

optical /electrical telecommunicationsnetworks

built-in management channel for remote

management of complex topologies


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Synchronous Multiplexer InterfacesTributaries

1.5 Mbps

2 Mbps

6 Mbps

34 Mbps

45 Mbps

140 Mbps

STM-1 Electrical

STM-1 Optical

STM-4 Optical

LAN / MAN

FDDI

ISDN / BISDN

ATM

Video

STM-1 155 Mbps

STM-4 622 Mbps

STM-16 2.4GbpsSTM-64 10 Gbps

STM-256 40 Gbps


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SDH ElementsTERMINAL

MULTIPLEXER

STM-n

STM-m

E1-E4

TM REGENERATOR

ADD-and-DROP

MULTIPLEXER

E1-E4

STM-nSTM-n ADM

REGSTM-n STM-n

-n

ADD-and-DROP MULTIPLEXER with

LOCAL CROSS-CONNECT

CAPABILITY

STM-n

E1-E4

STM-n STM-nLXC

SYNCHRONOUS DIGITAL

CROSS-CONNECT

SDXCSTM-n

STM-n

E1-E4

STM-m

STM-n


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Network Topologies

Point-to-Point

Chain

Mesh

Add-Drop Multiplexer

Digital Cross-Connect

Terminal Multiplexer

Ring

Star (Hub)


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Network Management

SDH

Multiplexer Site 4

Site 3

Site 2

Management

Station

Ethernet

GatewaySite 1


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Management Functions

Alarm / Event Management

Configuration Management

Performance Management

Access and Security Management


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Transport SystemsSTM-n

Video

34

Mbps

2 Mbps2 Mbps

...2 Mbps

Fiber

Highway

Pleisiochronous


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SDH Network Segments

RegeneratorSection

Multiplexer

Section

Multiplexer

Section

RegeneratorSection

s

s

RegeneratorSection

Path

Tributar

i

SDHTerminal

Multiplexer

Traffic Assembly

Tributari

SDHTerminal

Multiplexer

SDHAdd & DropMultiplexer

SDHRegenerator

SDHRegenerator

Traffic Disassembly


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Protection Schemes

PathSection

main:

protection:


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Multiplexing Process Step By Step

E1

StaffingBytes

C-12POHVC-12

TUp.

TU-12x3

TUG-2

Path

RS

x

7TUG-3x 3

O

verhead

VC-4AU-4 P.

MS

Example for multiplexing 2 Mbps tributary into STM-1 level


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Multiplexing Structure 139.264 Mbps

x3

AU-4 C-4

AU-3 VC-3

VC-4STM-nxN

AUGx1

x3

TUG-3x1

44.736 Mbps34.368 Mbps

C-3

TU-3 VC-3

*

*

*

x7 x7 6.312 Mbps

C-2VC-2TU-2

2.048 Mbps

C-12VC-12TU-12

TUG-2x1

x3

x4TU-11 VC-11

1.544 Mbps

C-11

* Pointer ProcessingMultiplexingAligningMapping

AUG Administrative Unit GroupAU Administrative UnitTUG Tributary Unit GroupTU Tributary UnitVC Virtual ContainerC Container *

*

*


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SDH Multiplexing technique

4321 9 rows

4 columnsTU 12

4 X 9

743 6521 743 6521 743 6521

321 TUG-212 X 9

TUG-3

84 X 9

P

O

H

P

O

H

P

O

H

Stuffing and

POH

TUG - 3TUG - 3TUG - 3

Section OverHead

(9 X 9) 261 X 9


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Mapping of 2Mbps into STM N

2.048 Mbps(E1)

1 2 3 32

32 Bytes

1 2 3 32C-12

Stuffing Bytes

34 Bytes

1 2 3 32VC-1235 Bytes

POH (Lower Order)


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TU-1236 Bytes

Pointer

9 Rows

4 Columns

TU 12 is arranged

Into Matrix of 9 X 4


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9 Rows

TU-12 TU-12 TU-12


TUG-2 9 Rows

12 Columns

4 Columns4 Columns4 Columns

Multiplexing


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7 TUG-2s

Stuffin B tesX 7 TUG-2 TUG-3(multiplexing)


86 Columns

84 Columns

TUG 3


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TUG - 3 TUG - 3 TUG - 3

86 Columns

X 3 TUG3


HOPOH

-

258 Columns

Stuffing Bytes

261 Columns


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Pay Load

VC - 4

9 rows


261 Columns

AU 4 (Adding Pointer)

Pay Load

AU Pointer

9 Columns

4 th Row

261 Columns


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The process of matching the signals to the network is called mapping

The container is the basic package unit for tributary channels,a special

container is provided for each PDH tributary signal

Mapping(Stuffing) in SDH

The containers are much larger than the payload to be transported.Theremaining capacity is partly used forjustification(stuffing)in order to

equalize out timing inaccuracies in the PDH signals

A virtual container(VC) is made up from the container thus formed

together with the path overhead(POH)


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The next step towards formation of a complete STM-N signal is theaddition of a pointer indicating start of the POH

The unit formed by the pointer and the virtual container is called anadministrative unit (AU-n) or a tributary unit(TU-n)

Aligning and Multiplexing in SDH

Several TUs (multiplexed) taken together to form a tributary unitgroup(TUG);these are in turn collected together into a VC

One or more AUs form an administrative unit group(AUG)

AUG plus the section overhead(SOH) forms the STM-N

Advantages Of SDH / PDH


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Advantages Of SDH / PDH

PDH SDH

The reference clock is not synchronized

throughout the network

The reference clock is synchronized

throughout the network.

Multiplexing / Demultiplexing operations

have to be performed from one level to the

next level step by step.

The synchronous multiplexing results in

simple access to SDH system has

consistent frame structures throughout the

.

The payload is not transparent. The payload is transparent

PDH system has different frame structures

at different hierarchy levels.

SDH system has consistent frame

structures throughout the hierarchy.

Physical cross-connections on the same

level on DDF are forced if any

Digital cross- connections are provided at

different signal levels and in different

ways on NMS

Advantages Of SDH / PDH(Contd..)


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PDH SDH

G.702 specifies maximum 45Mpbs &

140Mpbs & no higher order (faster) signal

structure is not specified

G.707 specified the first level of

SDH.That is, STM-1, Synchronous

Transport Module 1st Order & higher.

(STM-1,STM-4,STM-16, STM-64)

PDH system does not bear capacity to

SDH network is designed to be a transport

Advantages Of SDH / PDH(Contd..)

- . - ,

structured signal.

Few services are available It will transport variety of services.

Limited amount of extra capacity for user

/ management

It will transport service bandwidths

Sufficient number of OHBs is available

Bit - by - bit stuff multiplexing Byte interleaved synchronous

multiplexing.


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Signal Structure

M Columns

F B B

N x M BytesF F FF

N Rows

B B

N x M Bytes

1

2

Order of

transmission


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STM-1 Frame Structure

AU Pointer

Regenerator

Section

Overhead

(RSOH)

261 Bytes9 Bytes

1

23

4

9 rows x 270 columns x 8 bits / byte x 8000 f/s = 155.52 Mbps

Multiplexer

Section

Overhead

(MSOH)

270 Columns (Bytes)

56

7

8

9

P a y l o a d


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STM-1 - Virtual Container (VC-4)F F FF

Serial Signal Stream

155.52 Mbps

ec on

Overhead

Payload Capacity = 149.76 MbpsDesigned for 140 Mbps transport

Pat

hOverhea

d


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Tributary Unit Frame Structure155.52 Mbps Serial Signal StreamF F FF

ion

ead

ws

ead

Se

c

Over

9R

PathOve

r

261

Columns

TributaryUnit Frame

STM-1Payloadarea


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Tributary Unit Frame Structure

ion

ead

ead

155.52 Mbps Serial Signal StreamF F FF

TU Pointer

Sec

Over

PathOve

r VC Path

Overhead

Low-rateTributary

Signal Container

VirtualContainer

Different Sizes of Tributary Unit Frames


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TU-2TU-12

9

R

o

ws

TU-11 TU-3TU pointers area

Optimized forOptimized for

N. AmericanDS2 signal

(6.312 Mbps)

12

columns6.912 Mbps

Europeansignal

(2.048 Mbps)

4

columns2.304 Mbps


(1.544 Mbps)

3

columns1.728 Mbps


(44.736 Mbps)Will also carry a

Europeansignal

(34.368 Mbps)

86

columns49.54 Mbps


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TU Numbering System: KLM

TU-12

1-4-2

TU-3

3

TU-22-4

S h B I l d M l i l i


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Synchronous Byte-Interleaved Multiplexing

Byte-

STM-1

Signal A

STM-1Signal B

= timing rate

n er eave

Multiplexer

STM-4(4 * STM-1)

Denotes 8-bit Byte

At STM-4 Signal Rate

STM-1Signal C

STM-1

Signal D

Denotes 8-bit Byte

At STM-1 Signal Rate


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STM-4 Frame Structure

Byte-

F F F

125 sec.Serial Signal Stream

STM-1 A

STM-1 B

Multiplexer

9720 (270 * 9 * 4 Bytes / Frame) x 8 (Bits / Byte) x 8000 f/s = 622.08 Mbps

STM-1 C

STM-1 D

261 columnsVC-4

9 columnsSOH

9 Rows36 columns

Interleaved

SectionOverhead

1044 columns

4 Interleaved VC-4s


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Overhead Functions Define and build the SDH frame structure

Provide data transportation monitoringindicators

rov e a arm state n cat ons

Enable maintenance activities

Provide routing functions (protection

switching)


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STM 4 S ti O h d B t St t


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STM-4 Section Overhead Byte Structure

36 columns

B1 E1 F1

D1 D2 D3

A2 A2 A2 A2 A2 A2 A2 A2 A2 A2 Z0 Z0A1 A1 A1 A1 A1 A1 A1 A1 A1 A1 A1A1 A2 A2 J0 Z0

Administrative Unit Pointer(s)

Bytes reserved for national use

B2 B2 B2 B2 B2 B2 B2 B2 B2 B2 B2B2 K1 K2

D4 D5 D6

D7 D8 D9

D10 D11 D12

S1 M1 E2


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DENSE WAVE DIVISION

MULTIPLEXING

Wavelength MultiplexingWavelength Multiplexing


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Wavelength MultiplexingWavelength MultiplexingMULTIPLE FIBER

OPTICAL MULTIPLEXERS

SINGLE FIBER


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Wave Length Multiplexing Multiplexing multiple wavelengths over a

single fiber Two Major Types

oarse ave eng v s on

Multiplexing

Channel Spacing 20 nanometers

DWDM Dense Wave Length Division

Multiplexing

Channel Spacing 8 nanometers


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WDM Categories Wrapperless SystemsProtocol Independent

Wrapper Systems

Framed optical channel

Various low-level transmission functions Error checking

Performance monitoring

Forward Error Correction (FEC)

Management channel to support OAM&P

Optical bitstream interpretable by higher-level

protocols

TDM Vs WDMTDM Vs WDM


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TDM Vs WDMTDM Vs WDM

DWDM EvolutionDWDM Evolution


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DWDM EvolutionDWDM Evolution

WAVELENGTH WINDOWSWAVELENGTH WINDOWS


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ITU-T WAVELENGTH GRIDITU-T WAVELENGTH GRID


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ITU T WAVELENGTH GRIDITU T WAVELENGTH GRID


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Channel

2

Channel 1 1

2

OA OA

FiberOADM

1

2

ChannelN

N

Opt.

MUX

Opt.

De-MUX

1

, 2

,.., N

1, 2,.., N

N

= Laser Diode

= Receiver


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Transmitter Basic SpecificationsTransmitter Basic Specifications


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pp

Laser/ LED DriversLaser/ LED Drivers


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LASER Temperature CompensationLASER Temperature Compensation


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p pp p

Receiver Basic SpecificationsReceiver Basic Specifications


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pp

Receiver Block DiagramReceiver Block Diagram


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1000 , 160

, (), , , ,,

Attenuation

Wavelength 1.3 1.4 1.5 1.6(m)

1.0 dB/KM

0.3


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,

.

Wave 1Wave 1

Wave 2Wave 2

Wave 3Wave 3

Wave 4Wave 4

Wave 1Wave 1

Wave 2Wave 2

Wave 3Wave 3

Wave 4Wave 4


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OCOCOCOC----48484848

STM16STM16STM16STM16

OCOCOCOC----3/STM13/STM13/STM13/STM1

OCOCOCOC----12/STM412/STM412/STM412/STM4

OCOCOCOC----

24/STM824/STM824/STM824/STM8

OCOCOCOC----NNNN

Delhi

Bombay

Cal

Chennai

NagpurX-Connect

Propagation modePropagation mode


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Single Mode FiberSingle Mode Fiber


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Multi Mode FiberMulti Mode Fiber


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Number of Modes:

M = V2/2

Graded Index FiberGraded Index Fiber


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Propagation in Graded Index FiberPropagation in Graded Index Fiber


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Number of Modes, M = (a/(a+2))*(v2/2)

where a is Profile parameter

Energy Distribution in SM FiberEnergy Distribution in SM Fiber


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Attenuation in Optical FiberAttenuation in Optical Fiber


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Power expressed in dbmPower expressed in dbm


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Its simple to relate to attenuation if Power is also expressed in terms of db.

So if mW is the reference: Power in dbm = 10log10(P/mW)

Where W is the reference: Power in dbm = 10log10

(P/W)

Dispersion BW LossesDispersion BW Losses


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Dispersions in MM & SM FiberDispersions in MM & SM Fiber


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Dispersion in Step Indexed FiberDispersion in Step Indexed Fiber


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Graded Index Fiber less dispersionGraded Index Fiber less dispersion


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Chromatic DispersionChromatic Dispersion


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LED: Typical spectral width 75-125 nm LASER: Typical spectral width 2-5 nm

Material DispersionMaterial Dispersion


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Wave guide DispersionWave guide Dispersion


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PolarizationPolarization


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Bending Losses


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Training on Optical Fiber Network

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