The optical fiber is the enabling and promising technology used in almost all the trunk lines of existing networks.In optical fiber communication, the attenuation is the major limiting factor imposed by optical components or by fiber itself which degrades the system performance and limits the reach of the signals.To compensate attenuation factor the optical amplifiers boosts the signals without going through the costly conversions from optical to electrical signal and vice versa. But due to the various non-linear effects and phase noise present in the optical amplifier, its use is restricted to limited applications in optical communications. This books addresses various aspects of conventional and hybrid optical amplifiers including gain bandwidth, gain flatness, transient effect, crosstalk etc. The continuing research on optical amplifiers and their applications justifies the need for the book. An intuitive and understandable monograph, it guides the reader through many aspects of the fiber amplifier field.