半导体光放大器(SOA)中非线性系数约为普通光纤的109倍，为光子晶体光纤的107倍。有4种光-光互作用，即交叉增益调制、交叉相位调制、交叉偏振调制和四波混频，可以灵活地组成各种光信号处理器件，如波长变换器、全光触发器、全光逻辑、全光时钟恢复、全光缓存器，正成为整个光信号处理的基础。介绍了这些技术的同时，分析当前应用的制约因素，指出半导体光放大器集成是下一步发展的必然趋势。

In semiconductor optical amplifier(SOA) the nonlinearity coefficient is about 109 times of that in commercial optical fiber, and about 107 times in photonic crystal. There are four kinds of interaction of two beams of light: cross gain modulation, cross phase modulation, cross state of polarization modulation, and four wave mixing. Based on the different interation, many kinds of all-optical processing devices can be made up, such as wavelength converter, all-optical flip-flop, all-optical logic devices, all-optical clock recovery, all-optical buffer. Now SOA is the basic of whole optical signal processing. This paper reviews various applications of SOA, analyses its limitation in applications, and point out that integration of SOA is the development trend.