Taken into account second order dispersion and self-phase modulation in the normal-dispersion region of single-mode fibers by means of Fourier-transform algorithm,the results show that negative initial chirps can be compressed owing to normal GVD,we also show that SPM degrades pules compression.

Second order dispersion and self-phase modulation in the normal-dispersion region of single-mode fibers are analyzed by means of Fourier-transform algorithm.

In the anomalous dispersion regime of fiber gratings, optical pulse can come into being bright solitons by a careful control of SPM、XPM and GVD, in the normal dispersion regime of fiber gratings can allowed transmission of dark solitons.

We suggest that a three-level cascade medium be used to achieve the switching from normal dispersion to anomalous dispersion.

Taken into account second and third order dispersion in the anomalous dispersion regime of the single mode fibers for an initial chirped Gaussian pulse, an analytic exproxission of the dispersion induced chirp is obtained .

In the anomalous dispersion regime of fiber gratings, optical pulse can come into being bright solitons by a careful control of SPM、XPM and GVD, in the normal dispersion regime of fiber gratings can allowed transmission of dark solitons.