Fibre optic technology relies on th

Fibre optic technology relies on the fact that it is possible to send a light beam along a thin fibre suitably constructed. A fibre optic cable consists of a glass or silica core. The core of the optical fibre is surrounded by a similar material, i.e. glass or silica, called the cladding, that has a refractive index that is slightly lower than that of the core. It is found that even when the cladding has a slightly higher refractive index, the light passing down the core undergoes total internal reflection, and it is thereby contained within the core of the optical fibre.The Outside the cladding there is placed a plastic jacket. This is used to provide protection to the optical fibre itself. In addition to this, optical fibres are usually grouped together in bundles and these are protected by an overall outer sheath. This not only provides further protection but also serves to keep the optical fibres together.