• Fiber optics deals with study of propagation of light through transparent dielectric wage guides. The fiber optics are used for transmission of data from point to point Fiber optic systems currently used most extensively as the transmission line between terrestrial hardwired systems.
  • The carrier frequencies used in conventional systems had the limitations in handling the volume and rate of the data transmission. The greater the carrier frequency larger the available bandwidth and information carrying

First generation


  • The first generation of light wave systems uses GaAs semiconductor laser and operating region was near 0.8 µm. Other specifications of this generation are as under:


i)                     Bit rate


ii)                   Repeater spacing


Second generation

: 45 Mb/s


: 10 km

i)    Bit rate

: 100 Mb/s to 1.7 Gb/s

ii) Repeater spacing

: 50 km

iii) Operation wavelength

: 1.3 µm

iv) Semiconductor

: In GaAsP

Third generation


i)    Bit rate



: 10 Gb/s

ii) Repeater spacing

: 100 km

iii) Operating wavelength

: 1.55 µm





Fourth generation


Fourth generation uses WDM technique.


Bit rate                                                : 10 Tb/s


Repeater spacing                                 : > 10,000 km


Operating wavelength                         : 1.45 to 1.62 µm


Fifth generation


Fifth generation uses Roman amplification technique and optical solitiors. Bit rate                                                      : 40 - 160 Gb/s

Repeater spacing                                 : 24000 km - 35000 km


Operating wavelength                         : 1.53 to 1.57 µm


Need of fiber optic communication


  • Fiber optic communication system has emerged as most important communication Compared to traditional system because of following requirements :
    1. In long haul transmission system there is need of low loss transmission medium


  1. There is need of compact and least weight transmitters and


  1. There is need of increase dspan of


  1. There is need of increased bit rate-distrance


  • A fiber optic communication system fulfills these requirements, hence most widely