training on optical fiber networks by arun rawat [compatibility mode]

7/30/2019 Training on Optical Fiber Networks by Arun Rawat [Compatibility Mode]

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RailTel Corporation of India Ltd.

Training

onOptical Fiber Networks

By: Arun Singh RawatDeputy Manager/Project

E-mail: [email protected] no.:09958018833


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How fiber cable look like


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Advantages of Optical Communication

Explosive demand for higher bandwidthLow bandwidth of copper

Nearly 25THz possible with fiberLow Loss-Longer distance transmission(Less Repeaters)No EMI in fiber-based telecom

Less cross-talk, more reliabilityMore 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 pulseinto 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 of channel for opticalcommunicationsFlexible optically transparentfiber made of glass or plasticthrough which light can betransmitted by the process of totalnterna re ect on

Consists of a core , cladding andcoatingCore is the inner glass layer of high refractive index

Cladding is the outer layerwhich covers the core/ has a lowerrefractive indexCoating is the outer most layerwhich provides environmental andphysical protection for the fiber


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Theory of Optical FiberTransmits light along its axis using the process of total internal reflectionBased 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 highre rac ve n ex n w c e g en er ng efiber is guided

Cladding has a refractive index slightly lessthan that of the core

By principle of total internal reflection thelight entering the fiber (core) at one end travelsalong the fiber by bouncing repeatedly of theinside of the interface of the glass with thesurrounding 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 totalinternal reflection. Because the cladding does not absorb any light from thecore, the light wave can travel great distances.

gna egra es w t n t e eressentially 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 fiberMulti mode fiber has a core diameter around 50um andcladding diameter of 125 umSingle mode fiber core is less than 10um and can support

only one mode of propagationOptical fiber are also grouped as step index and gradedindex fiberIn a step index fiber, the refractive index of the core isconstant throughoutA graded index fiber has core with varying refractiveindex


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Types of Optical Fiber

125um 125um

Single Mode Fiber Multi Mode Fiber

9.2um 50um


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Fiber Optic CommunicationHistoryFiber Optic Communication SystemBenefits of Optic Communication

Limitation of Optic Communication


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HistoryEarly 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 20 th century, the idea of optical carrier of information 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 1960In 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 SystemFour 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 of communication.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 requiredLight weight and small size makes them ideal formultiple applicationsHigh on security, difficult to tap in and read data beingtransmitted


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LimitationsDispersion; spreading of optical pulses as theytravel along fiberAttenuation; 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 imperfect

splicing increases attenuation


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ContentsPlesiochronous Digital HeirarchySynchronous Digital HierarchyWave 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 allidentical

The speed of the higher order side is generated by an internaloscillator in the multiplexer and is not derived from theprimary 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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NOVEMBER 1988...


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

Transmission rates Signal format Multiplexing structures Tributary mapping for the network node interface

G782 (Merge with G.783 in 97) , G.783 Operation of synchronous multiplexers G.781

SDH synchronization networking G.784

SDH 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 throughthe management channels


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SDH - Synchronous Digital Hierarchy An international standard for high-speed

optical /electrical telecommunicationsnetworks

built-in management channel for remotemanagement of complex topologies


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Synchronous Multiplexer InterfacesTributaries1.5 Mbps

2 Mbps6 Mbps

34 Mbps45 Mbps

140 MbpsSTM-1 Electrical

STM-1 OpticalSTM-4 Optical

LAN / MANFDDI

ISDN / BISDNATMVideo

STM-1 155 MbpsSTM-4 622 Mbps

STM-16 2.4GbpsSTM-64 10 GbpsSTM-256 40 Gbps


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SDH ElementsT ERMINAL

M ULTIPLEXER

STM-n

STM-m

E1-E4TM R EGENERATOR

ADD-and- DROPM ULTIPLEXER

E1-E4

STM-nSTM-n ADM

REGSTM-n STM-n

-n

ADD-and-DROP MULTIPLEXER with

L OCAL C ROSS- C ONNECTC APABILITY

STM-n

E1-E4

STM-n STM-nLXC

SYNCHRONOUS D IGITALC ROSS- C ONNECT

SDXCSTM-n

STM-n

E1-E4

STM-m

STM-n


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Network Topologies

Point-to-Point

Chain

Mesh

Add-Drop MultiplexerDigital Cross-Connect

Terminal Multiplexer

Ring

Star (Hub)


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Network Management

SDHMultiplexer 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

Video34

Mbps

2 Mbps2 Mbps

...2 Mbps

Fiber

Highway

Pleisiochronous


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SDH Network Segments

RegeneratorSection

Multiplexer

Section

Multiplexer

SectionRegenerator

Section

s

s

RegeneratorSection

Path

T r

i b u

t a r

i

SDHTerminal

Multiplexer

Traffic Assembly

T r

i b u

t a r

i

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

E 1

S t a f f i n

gB

y t e s

C-12P OHVC-12

T U p .

TU-12x3

TUG-2

P a t h

RS

x7TUG-3x 3

O v e r h e a d

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-384 X 9

POH

POH

POH

Stuffing andPOH

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-12Stuffing 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 arrangedInto 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 specialcontainer 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 for justification(stuffing) in order toequalize out timing inaccuracies in the PDH signals

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

Ad t g Of SDH / PDH


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Advantages Of SDH / PDH

PDH SDH

The reference clock is not synchronizedthroughout the network

The reference clock is synchronizedthroughout the network.

Multiplexing / Demultiplexing operationshave to be performed from one level to thenext level step by step.

The synchronous multiplexing results insimple access to SDH system hasconsistent frame structures throughout the

.

The payload is not transparent. The payload is transparent

PDH system has different frame structuresat different hierarchy levels.

SDH system has consistent framestructures throughout the hierarchy.

Physical cross-connections on the samelevel on DDF are forced if any

Digital cross- connections are provided atdifferent signal levels and in differentways on NMS

Advantages Of SDH / PDH(Contd )


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PDH SDH

G.702 specifies maximum 45Mpbs &140Mpbs & no higher order (faster) signalstructure is not specified

G.707 specified the first level of SDH.That is, STM-1, SynchronousTransport 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 synchronousmultiplexing.


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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

2Order oftransmission


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STM-1 Frame Structure

AU Pointer

RegeneratorSection

Overhead(RSOH)

261 Bytes9 Bytes

1

23

4

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

MultiplexerSection

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

OverheadPayload Capacity = 149.76 MbpsDesigned for 140 Mbps transport

P a t h O v e r

h e a d


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

i o n

e a

d

w s

e a

d

S e

c

O v e r

9 R

P a

t h O v e

r

261Columns

TributaryUnit Frame

STM-1Payloadarea


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Tributary Unit Frame Structure

i o n

e a

d

e a

d

155.52 Mbps Serial Signal StreamF F FF

TU Pointer

S e c

O v e r

P a

t h O v e

r VC PathOverhead

Low-rateTributary

Signal Container

VirtualContainer

Different Sizes of Tributary Unit Frames


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TU-2TU-12

9

R

o w

s

TU-11 TU-3TU pointers area

Optimized for Optimized for

N. AmericanDS2 signal

(6.312 Mbps)

12columns

6.912 Mbps

Europeansignal

(2.048 Mbps)

4columns

2.304 Mbps


(1.544 Mbps)

3columns

1.728 Mbps


(44.736 Mbps)Will also carry a

Europeansignal

(34.368 Mbps)

86columns

49.54 Mbps


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TU Numbering System: KLM

TU-12

1-4-2 TU-33

TU-22-4


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Synchronous Byte-Interleaved Multiplexing

Byte-

STM-1Signal A

STM-1Signal B

= timing rate

n er eaveMultiplexer

STM-4(4 * STM-1)

Denotes 8-bit Byte At STM-4 Signal Rate

STM-1Signal C

STM-1

Signal DDenotes 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 columns VC-4

9 columns SOH

9 Rows 36 columns Interleaved

Section Overhead

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 i O h d B S


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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 onMultiplexing

Channel Spacing 20 nanometers

DWDM Dense Wave Length DivisionMultiplexing

Channel Spacing 8 nanometers


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WDM Categories Wrapperless Systems Protocol 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

A Typical DWDM Link


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A Typical DWDM Link

Channel2

Channel 1 1

2

OA OA

FiberOADM

1

2

ChannelN

N

Opt.MUX

Opt.De-MUX

1,

2,..,

N1, 2,.., N

N

= Laser Diode

= Receiver

Transmitter Simple Block DiagramTransmitter Simple Block Diagram


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Transmitter Simple Block DiagramTransmitter Simple Block Diagram

Transmitter Basic SpecificationsTransmitter Basic Specifications


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Transmitter Basic SpecificationsTransmitter Basic Specifications

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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gg

Dense Wave Division MultiplexingDense Wave Division Multiplexing


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DWDM Standard support 1000 colors of light, only 160 colors supported

today

Key players - Ciena, Cerent (Cisco), Lucent, Marconi, Nortel,Siemens, Sycamore

Supports PoS packet over Sonet to Wavelength Supports LAMBDA routing

Attenuation

Wavelength 1.3 1.4 1.5 1.6(m)

1.0 dB/KM

0.3

What is an Optical Wave?What is an Optical Wave?What is an Optical Wave?What is an Optical Wave?


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An optical wave is a transponder-based service whichprovides unprotected, customized bandwidth primarilyfor data traffic and allows data carriers requiring low

restoration rates to provide protection switching usingtheir own equipment.

Wave 1Wave 1

Wave 2Wave 2

Wave 3Wave 3

Wave 4Wave 4

Wave 1Wave 1

Wave 2Wave 2

Wave 3Wave 3

Wave 4Wave 4

Customized BandwidthCustomized BandwidthCustomized BandwidthCustomized Bandwidth


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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))*(v 2/2)

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 = 10log 10 (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 networks by arun rawat [compatibility mode]

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