Fiber-optic communications is the method of transmitting data from one point to another by sending pulses of light through an optical fiber. Optical fiber is a waveguide made of very thin tubes of glass whose diameter is of the order of a few micrometers. Here the optical fiber works on the principle of ‘Total Internal Reflection’.
A block diagram of a fiber-optic communication system is shown below.

The process of communicating using an optical fiber involves the following -
a) Converting electrical signal to optical signal at the transmitter.
b) Transmission of optical signal to the cable.
c) Relaying the signal through the optical-fiber.
d) Receiving the optical signal at the detector.
e) Converting the optical signal back to the electrical signal at the receiver.