S04 TGENFOC110 _ Fibre Optic Communication

7/31/2019 S04 TGENFOC110 _ Fibre Optic Communication

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Fiber Optic Communication

Module Id : TGENFOC110


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Topics Covered

Introduction to Optical Fibre

Classification of Optical Fibre

Application of Fibre Optic Cable

Transmission Systems


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Introduction

Advantages of OF MediaLow Losses in path

Very high information carrying capacity

Very less Transmit power required

No electromagnetic interference

Light weight

Easy fault localization


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Introduction

A Basic Optical fiber consists of twoconcentric layers.

Inner layer called core has a refractive index

slight higher than the outer layer calledcladding.

Light injected into the core.

This light strikes the core-cladding surface at

an angle greater than the critical angle and

gets reflected back into the core


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Introduction

An Optical Fibre System uses light waves as carrierof the information signals.

Transmitted through an Optical Fibre using the

principle of Total Internal reflection.

Main portion of an optical transmitter is light source( LED or LASER diode.)

This changes electrical signals to optical signals.

Receiver contains a photo diode which converts

light back into electrical signals.Detected signal is then amplified and shaped

appropriately.


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Transmission sequences given below:

Information is encoded into electrical

signals.

Electrical signals are converted into

light signals.Light travels down the fiber.

A detector changes the light signals

into electrical signals.

Electrical signals are decoded intoinformation.

Transmission in Optical Fiber


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Fiber Construction

1. Core: 8 m diameterfor SMF & 50 m dia for

MMF

2. Cladding: 125 m dia.

3. Buffer: 250 m dia.4. Jacket: 400 m dia


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Fiber Construction

Optical Fiber

Thin strands of highly transparent glass orsometimes plastic that guide light.

Core

The centre of the fiber where the light is

transmitted Cladding

The outside optical layer of the fiber that traps thelight in the core and guides it along - even throughcurves

Buffer coating or primary coatingA hard plastic coating on the outside of the fiber

that protects the glass from moisture or physical damage.


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Optical Fibre Classification

Based on material

1. Glass Fibres [glass core & glass cladding]2. Plastic-clad Silica Fibres [glass core &

plastic cladding]

3. Plastic Fibres [plastic core & plastic fibres]Based on size

1. Multi-mode fibres

2. Single-mode fibres

Based on refractive index1. Step-Index Fiber

2. Graded-index Fiber


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Single Mode Multi-mode Mode

Modes


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Types of Fiber

Single-mode l fiber (SMF)

designed to carry only asingle ray of light (mode)

Use for long distancecommunication e.g. 50km

Multimode fiber (MMF) hashigher "light-gathering"capacity than SMF, carrymany rays of light

Use for Short distancecommunication e.g. 200mtrs


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Patch Cords & Pigtails

Patch Cords

It has connectors on bothend

Size 5,10,20 mtrs

PigTails

It has connectors on oneend

Size 5,10,20 mtrs


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O F C Joint & Termination Box

Joint Box Require at every 2Km as cable drum length islimited to 2Km

Should be air tight & waterproof with high tensile

strength The splice joint of fiber is placed inside

Different type of joint boxes are used e.g StraightJoint , T-joint etc.

Termination Box Require at both the end of fibre cable for

terminating to FDF in PCM Room One side Fiber Cable & other side Pigtails are

terminated


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Splice

Permanent connection between two fibres Involves cutting of the edges of the two

fibres to be splicedAlignment of the cores of the fibres to be

connected is important to reduce splice loss

Splicing MethodsSingle Fiber Mechanical splicing

Adhesive bonding or Glue splicingTemp. Mechanical splicingFusion Splicing


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Optical Testers

Light SourcePower MeterVariable Attenuator

Variable Attenuator

For artificially introducingThe losses in fiber for

Testing

Power MeterFor Testing the

output power of theOptical system or

Light source

Light Source

For Testing thefiber losses &

Fiber cuts


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Common carrier nationwide networks.

Telephone interoffice trunk lines.Customer premise communication

networks.Undersea cables.

High EMI areas (Power lines, Rails, Roads).Factory communication/Automation.Control systems.Expensive environments.

High lightning areas.Military applications.Classified (secure) communication

Applications of Fibre Optics in

Communications


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Elements of Fiber Optic System

Optical Transmitter (E-O)Optical Receiver (O-E)Fiber OpticsOptical Amplifier (O-O)MultiplexerDemultiplexer


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What is PDH?

The Plesiochronous Digital Hierarchy (PDH)is a technology used in telecommunicationsnetworks to transport large quantities of dataover digital transport equipment such as fibreoptic and microwave radio systems

PDH networks run in a state where different

parts of the network are nearly, but not quite

perfectly, synchronised


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PDH

There are three different standards of PDH

European

American

JapaneseThese versions of the PDH system differ

slightly in the some technical details, but theprinciples are the same


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Limitation of PDH

Existing PDH is point to point system

O F capacity is under utilized

Difficulty in centralized supervision

Restoration of fault is time consuming

Manpower requirement is more


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Synchronous: One master clock and allelements synchronized with itDigital: Information in binary

Hierarchy: Set of bit rates in hierarchicalorderSDH is an ITU-T standard for high capacity

telecom network

SDH is a synchronous digital transportsystem, aim to provide a simple, economical

and flexible telecom infrastructure

What is SDH?


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When do we use SDH ?

When networks need to increase capacity ,SDH simply acts as a means of increasingtransmission capacity

When networks need to improve flexibility , to

provide services quickly or to respond to newchange more rapidly

when networks need to improve survivabilityfor important user services

when networks need to reduce operationcosts , which are becoming a heavy burden


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SDH bit rates

STM-1 ----------------

STM-4 ----------------

STM-16 --------------

STM-64 --------------

155.520 Mb/s

622.080 Mb/s

2488.32 Mb/s

9953.28 Mb/s

Apart from the above, There is STM-0 is of51.84 Mb/s


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SDH Advantages

Up gradation of system is easy

Existing PDH can work on SDH

Network Simplification- A single synchronous

multiplexer can perform the multiplexing

function

Future Proof Networking SDH is able to

handle video on demand and all other new

systems like ATM, Ethernet, FICON,ESCON, DVB, etc.


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SDH Network Elements

Terminal multiplexer

Add Drop Multiplexer

Regenerator

Digital cross connect (DXC)


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Terminal multiplexer

The terminal multiplexer is used to multiplexlocal tributaries (low rate) to the STM-N (highrate) aggregate. The terminal is used in the chaintopology as an end element

E1-E4

STM-M

STM-NTM


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Add Drop MultiplexerThe Add And Drop Multiplexer (ADM) passes the (high rate)

stm-N through from his one side to the other and has theability to drop or add any (low rate) tributary

The ADM used in all topologies

E1-E4STM-M

STM-N

TM

STM-N


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Regenerator

It mainly performs 3R function:

1R Re amplification

2R Retiming

3R Reshaping

STM-N

REG

STM-N


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Digital Cross-Connect (DXC) Form lowest

level to highest level semi-permanent

interconnections between different channels

and routing of them are performed

34 Mb/s

STM-1

STM-16

STM-4

140 Mb/s

2 Mb/s

STM-16

STM-1

140 Mb/s34 Mb/s

2 Mb/s

STM-4

Cross - connect


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SDH Network Topology

Point to Point

STM-NTM TM

PDH

STM-M

PDH

STM-M


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SDH Network Topology

Point to Multipoint or Bus

STM-NTM TM

STM-N

ADM

PDH

STM-M

PDH

STM-M

PDH STM-M


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Application of SDH

SDH Systems are used as a core network ofservice provider

It is also use for access network

It carries most of the Existing PDH Bit rates,ATM etc

New Generation SDH can carry Ethernet ,Fast ethernet, Gigabit Ethernet, etc.


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DWDM System Components


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S04 TGENFOC110 _ Fibre Optic Communication