Raman effect contribution to cross-phase modulation in nonpolarization-preserving fibers

The contribution of the Raman effect to the cross-phase modulation (XPM) st rength in fibers with randomly varying birefringence is calculated taking a ccount of different symmetry rules for the Kerr and Raman susceptibilities. The averaging factors for the Kerr contribution to the nonlinear index are shown to be different from those for the parallel and perpendicular Raman contributions. The XPM strength is calculated as a function of a frequency shift between pulses, and a fiber core composition for a randomly polarized and depolarized light. In pure silica fibers, the XPM coefficient is shown to decrease more than 27% at the peak of the Raman gain compared to the ca se of co-polarized waves in polarization-preserving fibers. (C) 2000 Publis hed by Elsevier Science B.V.