摘要： In the stimulated scattering processes covered in Chapters 8 and 9, optical ?bers play an active role in the sense that the process depends on molecular vibrations or density variations of silica. In a separate class of nonlinear phenomena, optical ?bers play a passive role except for mediating interaction among several optical waves. Such nonlinear processes are referred to as parametric processes, because they involve modulation of a medium parameter, such as the refractive index, and require phase-matching before they can build up along the ?ber. Among these, four-wave mixing (FWM) plays the dominant role. FWM has attracted considerable attention as it is useful for a variety of applications. We discuss the origin of FWM in Section 10.1 before developing a simple scalar theory of this process in Section 10.2. The techniques used for phase-matching are covered in Section 10.3. The focus of Section 10.4 is on parametric ampli?cation, and the polarization effects related to this process are discussed in Section 10.5. Some applications of FWM are covered in Section 10.6.