Write a note on optical fibre.

Explanation

(i) Optical fibres consists of inner part called core and outer part called cladding (or) sleeving.
(ii)Transmitting signals through optical fibres is possible due to the phenomenon of total internal reflection.
(iii) The refractive index of the material of the core must be higher than that of the cladding for total internal reflection to happen.
(iv) Signal in the form of light is made to incident inside the core-cladding boundary at an angle greater than the critical angle.
(v) Hence, it undergoes repeated total internal reflections along the length of the fibre without undergoing any refraction.
(vi) The light travels inside the core with no appreciable loss in the intensity of the light.
(vii) Even while bending the optic fiber, total internal reflection is ensured at every reflection.
(viii) To ensure the critical angle incidence in the core-cladding boundary inside the optical fibre, the light should be incident at a certain angle at the end of the optical fiber while entering in to it. This angle is called acceptance angle. It depends on the refractive indices of the core `n_1` cladding `n_2` and the outer medium `n_3` .