The aim of this book is to provide a comprehensive idea about high-speed optical communication streams. In recent years, optical devices and other enhanced signal processing functions are also considered in depth for high-speed communications systems. Commonly used optical devices are light emitting diodes and photodetectors. Advances in dense optical communication system is very much useful in telecommunication systems, data processing and networking. It consists of a transmitter that encodes a message into an optical signal, a channel that carries this optical signal to its desired destination, and a receiver that reproduces the message from the received optical signal. Further, this book is also targeted at research, development and design engineers from the teams in manufacturing industry, academia and telecommunication industries.