Their bandwidths are typically in the range of 200

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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 disadvantages: 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. 4. 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 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 channels. 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.

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