Give some application of optical fibers?

Now a days these fibres are playing a very important role in wire (line) communication systems. Such optical fibers offer some important advantages over wires. Light travels faster in glass than electric signals in the conventional metallic wires. Further on using monochromatic light (lasers) the signal distortion is low. Optical fibres have a high bandwidth (data carrying capacity) of the order of GHz. Consequently, they carry 100 million times more information and 100 times faster than telephone lines.
These optical fibres are very light in weight, easily twistable and have a low attenuation (powerloss and hence information loss) i.e. 0.5 decibels/kilometre (dB/km) which is approximate 10 times less than telephone cables. Since it is made up of cylindrical silica which is non conductive and non radiative, there is no possibilities of cross talk. Fibers are resistive to high temperature as the melting point of silica is very high i.e 1900 degree Celsius. Besides, the transmitted signals are optical and problems associated with sparking at the ends of cable are not encountered in this case.
Single mode fibres have bandwidth of more than 3GHz and mostly are use in submarine cable network. These fibres are less expensive. Graded index fibres have bandwidth of 200 MHz to 3 GHz and are used in telephone trunk. These are most expensive. Step index fibre has a bandwidth of less then 200 MHz and is mostly used in data link for computer network. These fibres are least expensive.

Thanks and Regards
Apoorva Arora
IIT Roorkee
askIITians Faculty