Define term practical optical fibre in short.

Optical fibre:

A practical optical fibre has in common three coaxial areas. The innermost area is the light guiding region termed as the core. This is surrounded through a coaxial middle region termed as the cladding. The outermost coaxial area is termed as the sheath. The refractive index of cladding is all the time lower than that of core. The purpose of the cladding is to make the light to be restricted to the core. Light launched within the core and striking the core to cladding interface at larger than critical angle will be reflected back within the core. As the angles of incidence and reflection are equivalent, the light will continue to rebound and propagate by the fibre. There sheath protects the cladding and the core by abrasions, contaminations and the injurious affects of moisture. Moreover, it raises the mechanical strength of the fibre.