Nonlinear Fitting of the Complex Raman Gain Profile in Single-Mode Optical Fibers

The new decomposition approach for the Raman gain spectrum approximation in an arbitrary optical fiber is presented in this paper. A nonlinear fitting procedure of the Raman gain profile based on the Levenberg-Marquardt method was applied, which provides a nearly perfect match for the observed Raman gain spectra in silica-based fibers. The optimal set of Raman gain parameters is reduced to simple analytical expressions that can be integrated and differentiated in symbolic form, and can be easily evaluated numerically. The results of simulations of stimulated Raman gain spectra in several widely used fibers are presented