The semiconductor optical amplifier (SOA) has emerged as an important component in many optical fiber communication, switching and signal processing systems. Besides its basic use as an in-line amplifier, SOAs have found use in a myriad of applications. Semiconductor Optical Amplifiers provides a comprehensive and detailed treatment of the design and applications of SOAs. Key areas covered include: * Historical background. * SOA principles - theory of amplification, gain, noise, noise figure, polarisation dependence, spectral bandwidth, dynamics. * SOA structures - travelling-wave, Fabry-Perot, DBR, DFB, multi-section, twin-guide, polarisation insensitive configurations, low-reflectivity coatings, angled facets, high-power devices, gain clamped devices, SOA packaging. * Bulk and quantum-well semiconductor materials. * Static and dynamic modelling - travelling-wave equations, recombination mechanisms, analytical approximations and computer modelling techniques. SOA optimisation, slow and fast pulse amplification. * Applications in optical communication systems - direct detection and coherent receivers, amplified light detection statistics, preamplifier, in-line amplifier, booster amplifier, amplifier chains, SOA based optical network topologies, TDM, WDM, soliton transmission, system experiments, analog systems. * Non-linear behaviour - cross-gain modulation, self-phase and cross-phase modulation, four-wave mixing, frequency chirping, bistability. * Functional applications - intensity modulator, phase modulator, switch, add/drop multiplexer, wavelength converter, in-line detector, dispersion compensator, pulse-shaper, all-optical clock recovery, loop mirror configurations, logic functions. * SOA photonic integrated circuits. * Current developments and future prospects. Semiconductor Optical Amplifiers is an invaluable information source for researchers and engineers involved in SOA and optical systems design and manufacturing. It is also useful to graduate students, in optoelectronics, optical communications and optical engineering, entering this rapidly growing and exciting field of research and development.