Intrapulse stimulated Raman scattering and ultrashort solitons in optical fibers

Intrapulse stimulated Raman scattering (ISRS) is an important physical phenomenon responsible for the self-induced frequency shift of solitons in optical fibers. ISRS is generally treated as a perturbation term in the nonlinear Schrodinger equation, an approximation that breaks down for ultrashort optical pulses. The authors obtain the solitary-wave solutions of the nonlinear Schrodinger equation by including both ISRS and self-steepening. These solutions do not correspond to optical pulses but represent optical fronts or optical shocks. The properties of ISRS-supported optical shocks are discussed in detail.