What is Fibre Optic Cable? Theory, Construction, Advantages & Disadvantages

Fibre Optic Cable carry light signals instead of the electric signals. They are used for light and infrared transmissions.

Fig. 1: Construction of Fibre Optic Cable.

Fibre Optic Cable Construction

Fig. 1 shows the construction of an optical fibre cable. The diameter of fibre optic cables is only a fraction of an inch. A fibre optic cable can have a single fibre or a bundle of fibres to carry the information in the form of light.

The inner core carries light and is made of either plastic or glass. It is surrounded by cladding material e.g. a layer of plastic or glass that reflects the light back into core. The refractive index of the core is relatively high and that of the cladding material is low.

This entire assembly is coated with silicon oil and organic material with silica. Then it is covered with a protective inner jacket and outer plastic jacket. They provide mechanical strength to the optical fibre and protect it from mechanical wear and tear. The basic fibre optic communication system consists of three blocks. They are:

Optical Transmitter

It converts the input electrical analog or digital signal into a corresponding light signal. It uses a light emitting diode, or a solid state laser diode for this purpose.

Fibre Optic Cable

It carries the converted signal which is in the form of light from transmitting end to the receiving end. If the distance between the transmitter and receiver large, the fibre optic cables are cascaded one after the other.

Optical Receiver

It converts the received optical signal that is in the form of light, into corresponding electrical signal. It uses photo-detectors like avalanche type or PIN type of photodiode.

Advantages of Fibre Optic Cable

1. Wide bandwidth and high data transmission rates.
2. Good noise immunity.
3. No ground loops and no cross talk inside the cable.
4. Data losses are less.
5. Light in weight with small cable diameter.
6. No shock hazards hence safe and easy installation.
7. They are sturdier and have longer life than coaxial cables.
8. They do not interfere with adjusting cables.

Disadvantages of Fibre Optic Cable

1. The initial cost of incurred is high as compared to that of the copper wires.
2. Skilled and trained operators are required to join together the optical fibre cables.
3. High installation and maintenance cost.