Modulation instability gain spectrum of cross-phase modulation in decreasing dispersion fiber

Modulation instability gain spectrum resulted from cross-phase modulation(XPM) in decreasing dispersion fiber (DDF) is presented from nonlinear Schrodinger equation. The results show that XPM-induced modulation instability exists not only in the anomalous-dispersion regime but also in the normal dispersion regime; what's more,the spectrum width of the former is wider than that of the latter. The spectrum width in DDF is wider than that of in ordinary dispersion fiber(ODF) and the gain peak is also higher. DDF is a good dispersion medium to produce modulation instability of XPM.