Explanation

(b) Some of the characteristics of an optical fibre are as follows.
(i) This works on the principle of total internal reflection.
(ii) It consists of core made up of glass/silica/plastic with refractive index $n_{1},$ which is
surrounded by a glass or plastic cladding with refractive index $n_{2}\left( n_{2} > n_{1} \right).$ The
refractive index of cladding can be either changing abruptly or gradually changing
(Graded index fibre).
(iii) There is a very little transmission loss through optical fibres.
(iv) There is no interference from stray electric and magnetic fields to the signals
through optical fibres.