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Introduction

Optical Fiber It is a glass filament or wire which carries light. It is a cylindrical waveguide that operate at optical frequency. It confines electromagnetic energy in the form of light. COMMUNICATION

It may be broadly defined as the transfer of information from one point to another.

HISTORY

Hollow Logs, Drum (different sizes), Wind Instruments (pipes), Smoke Signals,Signal fires and Signaling lamps.

The first optical fiber exhibited very high attenuation i.e. 1000 dB/Km. Whilecoaxial cable losses were 5-10 dB/Km.

Fiber losses were reduced to below 5 dB/Km. Development of fiber waveguides with optical frequencies at small wavelengths

requires the development of all optical components.

Laser Life at the start was 1000 Hrs & now is 100 years. At present two optical windows are in operation i.e. 1310 nm ,1550nm.

Advantages of Optical Fiber

1. Enormous potential bandwidthThe maximum capacity of single mode step index fiber is 1.6 Tb/Sec w.r.t coaxial cable

bandwidth of 500 MHZ.

2. Small size and weight

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Optical fibers have very small diameter i.e. 125um which is just like a human hair

while the dia of one copper is 0.8mm.The ratio of weight as compared to other cables is

25:1.

3. Electrical isolationOptical fibers are fabricated from glass which are electrical insulated hence they

don't exhibit interference problem.

4. Immunity to Interference & Cross talkThe material of optical fiber is dielectric/glass hence there is no possibility of

cross talk or leakage.

5. Signal SecurityThe light from optical fibers doesn't radiate significantly and therefore they

provide a high degree of signal security.

6. Low transmission lossLaser light travels with high speed on pure transparent glass. This development of

optical fiber over the last twenty years has resulted in the production of O/F cables with

very low attenuation i.e. 0.2 dB/Km.

7. Ruggedness & FlexibilityCable structures have been developed which have proved flexible, compact &

extremely high.

8. System Reliability & Ease of MaintenanceDue to low transmission loss, intermediate repeaters & line amplifiers are

reduced. Hence with few repeaters system reliability is generally enhanced. The optical

component life time is 20 to 30 years.

9. Potential Low CostThe glass which generally provides the optical fiber transmission medium is made

from sand which is available in abundance.

10.Long distance transmission

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Because of less attenuation transmission at a longer distance is possible.

Disadvantages of Optical Fiber

1. Very small hole on the surface of fiber may weakens the tensile strength.2. A small bend on optical fiber causes radiation loss.3. Alignment problem, connectors & core misalignment.4. The cost of fusion splicing is high.5. The fault localization is some what difficult.

6. Clean environment is required during splicing. A small dust particle can createhigh attenuation.

7. As the optical fibers are of very small, testing procedures tend to be morecomplex.

8. High investment cost, doubt of reliability in the presence of moisture etc

Applications of optical fiber communications

1. Optical fiber can be used as a medium for telecommunication andnetworkingbecause it is flexible and can be bundled as cables. It is especially advantageous

for long-distance communications.

2. Optical fibers have many uses in remote sensing. In some applications, the sensoris itself an optical fiber. Optical fibers can be used as sensors to measurestrain,

temperature,pressureand other quantities.3. Fibers are widely used in illumination applications. They are used aslight guides

in medical and other applications where bright light needs to be shone on a

target without a clear line-of-sight path.

4. Optical fiber is also used in imaging optics.

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5. Optical fiber is also used for data communications, video control, protectionswitching, power and military applications.