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Unformatted text preview: haracteristics of light propagation depend primarily on the
fiber size, its construction, the refractive index profile, and the nature of the light
source. The outer protective coating is made up of plastic.
The main components of an optical fiber communication system are shown in
Figure 17.7. Towards its source side is a converter that converts electrical signals
into light waves. The converter uses either a light-emitting diode (LED) or a laser
diode to convert electric signals into light signals. These light waves are then
transmitted over the optical fiber to the receiver's end. At the receiver's end,
another converter is placed that detects the light waves and converts them back to
electrical signals. It uses photoelectric diodes for this purpose. These electric
signals are then amplified using an amplifier and sent to the receiver.
Optical fibers have the following advantages: 1. Large bandwidth. Optical fibers can transmit massive amounts of data at very
high speed and long distances. They can have bandwidths 10 to 100 times greater
than the best coaxial cables. Their bandwidths are typically in the range of 200
MHz per Km to 3 GHz per Km. A fiber-optic cable consisting of a bunch of 10
optical fibers can accommodate more than 200,000 voice channels.
2. Low loss. As compared to electrical signals, light signals can travel at very
high speed with no significant loss of intensity over long distances. In case of use
of data transmission medium that use electrical signals for transmitting data, such
as copper wires or coaxial cables, electrical signals have to be intercepted and
amplified by repeaters at short intervals along the way. Light signals flowing
through a fiber-optic cable also must be amplified, but much less so that of
electrical signals. The implication is that signal repeaters need not be placed so
close together, which reduces the cost of an optical fiber communication system.
Immunity to electromagnetic interference.
Because they are made of
insulators, optical fiber transmissions are not affected by magnetic or electrical
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- Spring '14