Modulation instability induced by cross-phase modulation in decreasing dispersion fiber

Modulation instability induced by the cross-phase modulation in a decreasing dispersion fiber (DDF) is investigated. The expression of the dispersion relation is obtained when the fiber loss and the walk-off effect are taken into account. The results show that the gain spectrum of the DDF is much broader than that of the ordinary optical fibers, and the gain spectral width will increase with the propagation distance when the dispersion decreasing parameter is greater than the fiber loss coefficient. The results also show that a small walk-off effect will increase the range and the maximum value of the gain spectrum in the fiber.