Modulation Instability In Decreasing Dispersion Fibers

Starting from the nonlinear Schrodinger equation governing the propagation of optical pulses in optical fibers, modulation instability in decreasing dispersion fiber is analytically investigated. The synthetic effects of dispersion parameter, slowly decreasing dispersion parameter, incident power, propagation distance, loss coefficient, nonlinear coefficient, etc. on the gain spectrum of modulation instability are analyzed. Furthermore, gain spectra of modulation instability in the ideal fiber, loss fiber and decreasing dispersion fiber are calculated and compared. The gain spectrum of decreasing dispersion fiber is much broader than that of ordinary optical fibers The broad gain bandwidth can be obtained by selecting the dispersion parameter of decreasing dispersion fiber. Accordingly, the decreasing dispersion fiber in anomalous dispersion regime is good kind of fiber to produce modulation instability. This research result shows that a new method can be obtained to generate the broadband spectrum of modulation instability in the fibers with slowly decreasing dispersion which is promising to produce the ultra short pulses and so on.