Why interference doesnot occur in optical fibres?

Fiber has a core and a cladding; light reflect on the transition surface between the core and the cladding Light is transmitted by total reflection inside the fiber, that means that no light is refracted, so the light keep inside the fiber. External light cannot o inside the fiber unless it is injected with the proper angle at one end of the fiber. Electromagnetic radiation cannot affect the light inside the fiber. Transmitted light is 'analogical' no digital transmission exist, because even transmitting pulses (digital signal), those pulses disperse at the distance depending on 'transmission modes'. There mono mode fiber and multi-mode fiber, generally multi.mode are preferred, and they are build with gradual o stepped refraction index to compensate ray length, (in order to diminish ray dispersion over distance). A ray dispersed could suffer it own interference. Transmission could be by 'pure' pulses, or by frequencies (different colors) where you have several channels on the same ...  more