NAME : S.PRIYADHARSINI

YEAR : III YEAR

SECTION : ECE –A

REG NO : 1090110103283

GAGET : OTDR

DATE : 07-10-2011

OTDR

Optical Time-Domain Reflectometer

Image from exfo.com

WHAT ARE OPTICAL FIBERS ?

Optical Fibers are thins long (km) strands of ultra pure glass (silica) or plastic that can to transmit light from one end to another without much attenuation or loss.

The glass used to make Optical Fibers is so pure that if the Pacific Ocean was filled with this glass then we would be able to see the ocean bottom form the surface….!!!!

This is to be believed as repeater distances on long haul routes for optical fibers vary from 50 to 150 km.

BLOCK DIAGRAM

Working of Optical fibers?

The light source (LAZER) at

the transmitting (Tx) end is

modulated by the electrical

signal and this modulated light

energy is fed into the Optical

Fiber.

At the receiving end (Rx) this

light energy is made incident

on photo-sensors which

convert this light signal back to

electrical signal.

TYPICAL OTDR TRACE

As mans need and hunger for communication increased, the amount of bandwidth required increased exponentially.

Initially we used smoke signals, then horse riders for communicating. But these ways were way to slow and had very little bandwidth or data caring capacity.

Then came the telephone and telegraph that used copper wires for communication. But soon demand out striped the capacity and capability of copper wires and data transport got added to voice communication. Then came Coaxial copper cables, VHF and UHF Radios, Satellite but demand still outstripped the supply.

It was not until Optical Fibers came on the scene that large amount of communication bandwidth became economically and easily available to everyone.

As an example 50,000 voice / data circuit copper cable is massive in size and very expensive, while a single Optical Fiber, the diameter of human hair, can carry 5,00,000 circuits of voice and data. This capacity is increasing day by day as supporting electronics is developing. In itself the capacity of Optical Fibers is limitless.

Why Optical Fibers ?

OTDR Uses Measure loss

Locate breaks, splices, and connectors

Produces graphic display of fiber status

Can be stored for documentation and later reference

Cable can be measured from one end

VARIOUS TYPES OF OPTICAL FIBER CABLES

1. OPGW Cable

2. ADSS type OF Cable

3. Self-Support AERIAL figure 8 type OF Cable

4. LASHED type OF Cable

5. UNDERGROUND / BURRIED type OF Cables

6. DUCT Type OF Cable

1. VERY HIGH INFORMATION CARRING CAPACITY.

2. LESS ATTENUATION (order of 0.2 db/km)

3. SMALL IN DIAMETER AND SIZE & LIGHT WEIGHT

4. LOW COST AS COMPARED TO COPPER (as glass is made from sand..the

raw material used to make OF is free….)

5. GREATER SAFETY AND IMMUNE TO EMI & RFI, MOISTURE &

COROSSION

6. FLEXIBLE AND EASY TO INSTALL IN TIGHT CONDUICTS

7. ZERO RESALE VALUE (so theft is less)

8. IS DILECTRIC IN NATURE SO CAN BE LAID IN ELECTICALLY

SENSITIVE SURROUNDINGS

9. DIFFICULT TO TAP FIBERS, SO SECURE

10. NO CROSS TALK AND DISTURBANCES

ADVANTAGES OF OPTICAL FIBERS

1. The terminating equipment is still costly as compared to copper equipment.

2. Of is delicate so has to be handled carefully.

3. Last mile is still not totally fiberised due to costly subscriber premises equipment.

4. Communication is not totally in optical domain, so repeated electric –optical – electrical conversion is needed.

5. Optical amplifiers, splitters, MUX-DEMUX are still in development stages.

6. Tapping is not possible. Specialized equipment is needed to tap a fiber.

7. Optical fiber splicing is a specialized technique and needs expertly trained manpower.

8. The splicing and testing equipments are very expensive as compared to copper equipments.

DISADVANTAGES OF OPTICAL FIBERS…

APPLICATIONS OF OPTICAL FIBERS…

1. LONG DISTANCE COMMUNICATION BACKBONES

2. INTER-EXCHANGE JUNCTIONS

3. VIDEO TRANSMISSION

4. BROADBAND SERVICES

5. COMPUTER DATA COMMUNICATION (LAN, WAN etc..)

6. HIGHT EMI AREAS

7. MILITARY APPLICATION

8. NON-COMMUNICATION APPLICATIONS (sensors etc…)

THANK YOU