Fiber Optic Cables
 Fiber
optic cables are similar in function to copper wires, but use light
instead of electricity to transmit data. Because of the speed and
reliability of such a method, fiber optic cables allow vast amounts
of data to be transmitted over much greater distances, without the
requirement for "repeaters" or "amplifiers"
between the transmitter and the receiver, and offering many more
applications to take advantage of the link.
Fiber optics are manufactured from a specially-designed
glass that utilises a principle known as Total Internal Reflection.
This allows thin beams of light to be sent over the fiber without
loss or interference. The coded light pulses are generated by Light
Emitting Diodes (LEDs) or Injection-Laser Diodes (ILDs) and focused
on one end of the fiber using a tiny lens. At the other end an optical
receiver picks up these coded light pulses and translates them back
into electrical pulses for a computer or other device to understand.
There are two basic types of fiber optic cabling
- Multi-Mode Fibre (MMF) and Single Mode Fiber (SMF). MMF is a cost-effective
type of fibre designed to carry data over short-medium distances.
SMF is a more expensive type suitable for long distance data transit,
such as international links. You should contact your supplier to
discuss your requirements before choosing between these two basic
types.
Fiber optic cables usually consist of five elements;
the optical core, optical cladding, a buffer material, a strengthening
sheath for protection and finally the outer jacket.
Today fiber optics usually have an attenuation
range of 0.5dB/km to 1000dB/km - this describes the amount of light
lost over a single kilometre and hence how suitable a particular
fibre strand is for a particular application.
Bandwidth is also an issue, that is the amount
of concurrent information that can be transmitted over a fibre.
The greater the bandwidth, the more data it can transmit at any
one time. The largest known bandwidth at the moment for fiber is
2.5Gb/sec, enough for 40000 concurrent telephone conversations or
250 television channels. It would be enough to transmit the entire
contents of the average PC hard disk in about 18 seconds.
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