Essential information regarding the field of optical amplifiers has been elucidated in this book. The increase in information traffic at an explosive pace accounts for a crucial role of optics in meeting the demand of data processing and super-fast computing. Optical amplifiers play an essential role in optical communication field. This book provides insight into the advanced functionalities of optical amplifiers and the related newly developing applications, like optical packet switching architectures, high speed switches, SOA in the next generation of optical access network, microwave photonic system, frequency encoded all-optical logic processors etc. It also provides evaluation of variation of material gain of QD structure and technology for improving the gain and noise figure of EDFA among other supporting topics. These topics provide comprehensive understanding of optical amplifiers in contemporary scenario for the reference of academicians and researchers.