OPTICAL FIBER COMMUNICATIONS

Optical Fibres Sheath 1 Sheath 2 Sheath 3 Aluminum Tape Strength Member Steal Wire Reinforcement

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.

Light is the form of electromagnetic Wave just as radio waves, but with high frequency and shorter wavelength. SpectrumFrequencyWavelength Radio waves100 KHZ to1 THZ3KM to 300 µm Infra Red light1 THZ to 100 THZ300 to 3 µm Optical Communication 176 THz to 375 THZ1.7 to 0.8 µm 1550 nm Window193.5 THz1.550 µm 1310 nm Window230 THz1.310 µm 850 nm Window353 THz0.85 µm Visible Light428 to 750 THZ0.7 TO 0.4 µm UV,X & γ rays750 to 10 7 THZ0.4 to 3x µm

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 dB/Km. While coaxial 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 nm,1550nm.

Advantages of Optical Fiber Enormous potential bandwidth The maximum capacity of single mode step index fiber is 1.6 Tb/Sec w.r.t coaxial cable bandwidth of 500 MHZ. Small size and weight 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. Electrical isolation Optical fibers are fabricated from glass which are electrical insulated hence they don't exhibit interference problem.

Advantages of Optical Fiber Immunity to Interference & Cross talk The material of optical fiber is dielectric/glass hence there is no possibility of cross talk or leakage. Signal Security The light from optical fibers doesn't radiate significantly and therefore they provide a high degree of signal security. Low transmission loss Laser 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.

Advantages of Optical Fiber Ruggedness & Flexibility Cable structures have been developed which have proved flexible, compact & extremely high. System Reliability & Ease of Mtce Due 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. Potential Low Cost The glass which generally provides the optical fiber transmission medium is made from sand which is available in abundance.

Disadvantages of Optical Fiber Very small hole on the surface of fiber may weakens the tensile strength. A small bend on optical fiber causes radiation loss. Alignment problem, connectors & core misalignment. The cost of fusion splicing is high. The fault localization is some what difficult. Clean environment is required during splicing. A small dust particle can create high attenuation.