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Unformatted text preview: communication system because a
transmitting station can receive back its own transmission and check whether the
satellite has transmitted the information correctly. If not, it can retransmit the data.
A satellite communication system, however, suffers from the following
1. The initial cost of placing a satellite into its orbit is very high. 2. Owing to the travel of microwave signal from the sending earth station to the
satellite and then back to the receiving earth station, there is a 270 msec
propagation delay between the sender and receiver of any information.
3. The manner in which a satellite communication system works, any data sent
to the satellite for transmission automatically gets broadcast to all receiving
stations within the satellite's range. Hence, special security measures are needed to
prevent unauthorized tampering of information.
Atmospheric disturbances like thunder and lightening affect the K u-band
transmission of a satellite communication system. Hence C-band transmission is
recommended during bad weather.
Optical fibers are hair-thin threads of glass or plastic that can serve as a data
transmission medium as copper wires or coaxial cables. The basic difference is
that optical fibers transmit light signals instead of electrical signals. Because light
travels much faster than electricity, optical fibers can transmit data at much higher
speed than copper wires or coaxial cables, and also with no significant loss of
intensity over very long distances.
Optical fibers are made of glass, plastic or silica. Plastic fibers are least efficient,
but tend to be cheaper and more rugged. Glass or silica fibers are much smaller,
and their lower attenuation makes them more suited for very high capacity
Physically, a fiber-optic cable consists of three concentric layers - the inner core, a
cladding around it, and the outer protective coating. The inner core, which has a
diameter of 8 to 200 micrometers, consists of a bunch of optical fibers. The
cladding around it is made of plastic or glass and has a refractive index less than
that of the core. The c...
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This document was uploaded on 04/07/2014.
- Spring '14