Optical communication has a significant presence in the telecommunications and data networking sectors. Optical communication is an essential part of telecommunication systems, data processing and networking. It can be performed visually or by usingaelectronic devices.a It consists of a transmitter that encodes any information into an optical signal, a channel that carries the signal to its desired destination, and a receiver that reproduces that information from the received optical signal. This book deals with the basic concepts, components, systems, networks, signal processing, etc. In the past few decades, optical mechanism and other improved signal processing functions have been considered in-depth for optical communications systems. The book also explains MIMO system thoroughly. We intend to help our readers with the compilation of researches and theories mentioned in this book.