SUMMARYThe four-wave mixing (FWM) used in optical fibers is expected to be a simple wavelength conversion technique for ultrafast optical signals. Highly efficient generation of stable FWM light is desired. FWM efficiency depends on the zero-dispersion wavelength of the fiber, the wavelength of the pump light, and the wavelength of the signal light, and reaches its maximum efficiency when the pump wavelength and zero-dispersion wavelength match in degenerate FWM. However, the zero-dispersion wavelength fluctuates in the longitudinal direction in actual optical fibers, and these changes affect the FWM generation characteristics.In this paper, we analyze FWM generation that accounts for the zero-dispersion wavelength fluctuations in the longitudinal direction of the optical fibers and explain the theory of the dependence of the FWM efficiency on the pump wavelength. In addition, by conducting FWM generation experiments, we demonstrate the differences in the characteristics of the optical fibers and clearly show the relationship between the FWM generation characteristics and zero-dispersion wavelength distribution.