Effect of intrapulse Raman scattering on soliton-effect pulse compression

Optical fibers can be used for pulse compression in the wavelength region of anomalous group-velocity dispersion by exploiting the periodic evolution of the higher-order solitons which undergo an initial pulse-narrowing stage. By choosing the fiber length judiciously, the pulse is made to exit out of the fiber when it is narrowest. The optimum fiber length and the compression factor are obtained by solving the nonlinear Schrodinger equation (NSE).1 The predictions of the NSE are accurate for picosecond pulses but need modification for femtosecond input pulses as several higher-order nonlinear effects become important for such short pulses. The most important among them is intrapulse stimulated Raman scattering, a phenomenon responsible for the soliton self-frequency shift and soliton decay. In this paper, we study numerically the effect of intrapulse Raman scattering on soliton-effect pulse compression by solving the generalized NSE. Even though the pulse evolution is no longer periodic, the input pulse is compressed significantly at an optimum fiber length. The compression factor is larger than that occurring without the Raman effect. Furthermore, the compressed pulse is generally pedestal-free.