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Fibre Optics: Communications (telephone, cable TV)

Fibre-optic cables use light to transmit information over great distances at high speed.

They are used widely in telecommunications because of their many advantages over copper cable.They are smaller, cheaper (overall) because you can snd more information with less 'degradation' or signal loss than other kinds of cables. Today these cables are found in local cable TV and internet connections and most international telephone networks.

The fibres used in long-distance telecommunications are made of very pure glass rather than plastic, because glass does not absorb the enegy of the light signals as much as plastic does. For shorter distances, plastic is often used as it is cheaper.

For very short distances, fibre-optics are not the best choice. Cables such as copper wires and coaxial cable, which transit information using electricity are easier to join together or splice into new circuits. In very short distances, there is very little need for the speed and huge volumes of transmission that fibre optic cables can offer

A Telecommunications Link is the simplest of fibre optic systems.

It consists basically of a transducer (to change the electrical signal into light energy), a transmitter (that generates light pulses to travel along the fibre) , a fibre link and a receiver to detect the light gignals and transfer them into electrical output.

The transmitter will normally be equipped with a laser diode that usually has an output wavelength of 1300nm or 1500nm.

The fibre link will be made of single lengths of optical fibres 2km in length, which are fusion spliced (joined) together. The link will be able to carry thousands of telephone conversations simultaneously by means of time division multiplexing.

This basically means that the data in multiple conversations is split up and sent down the cable. When it reaches the other end of the cable, the individual conversations This would not be possible with copper cabling.