How does the optical fiber work?

optical fibre use the phenomenon of total internal reflection.In optical fibres glass of high refractive index is coated with a thin layer of glass of lower refractive index .the rays of light entering through its one end strickes the interference between the 2 glass surfaces at an angle greater than critical angle .this ray will be totally reflected along the whole length of fibre. light can thus travel the length of fibre and emerges from its another end without loss of intensity.