Stable soliton propagation with self-frequency shift

We investigate the propagation of ultrashort solitons in fiber-optic systems in the presence of the soliton self-frequency shift effect. It is demonstrated that both the self-frequency shift and the background instability can be effectively controlled using spectral filters of moderate strength together with nonlinear gain proportional to the second and fourth power of the amplitude. These results are verified both for plain pulses and for composite pulses. In the last case, however, an asymmetry of the pulse induced by the Raman effect is observed.