Communication systems that use high carrier frequencies in the near IR region of visible spectrum are called optical communication systems or general light wave systems. Light wave system that employs optical fibre as channel for information transmission is called ‘fibre Optics Communication Systems’. The technology to which light is propagated through very fine cylindrical hair like transparent fibres is called fibre optics. Optical communication system or light wave system can be broadly classified based on the nature of the communication channel into two.

It is used in fiber optic communication system. It receives the optical signal in electric form. It performs reshaping and amplification operations before retransmission. Due to signal reconstruction before amplification, signal is less distorted.

To compensate for signal degradation in long distance convert optical signal to electrical signal, restores the signal used then converting back to optical signal for further transmission. This method increases cost, complexity and reduces operational bandwidth. Optical amplifiers simply amplify the optical signal. They provide improved SNR due to all optical domain operation.