Investigation of Spontaneous Raman Scattering in Few-Mode Fibers: Dependence on Polarization and Spatial Modes

We study Raman gain in few-mode fibers (FMFs) by measuring spontaneous Raman scattering in polarization-maintaining FMF, mode-maintaining FMF and common FMF. The results show that the intensities of spontaneous Raman scattering in different polarization and spatial modes are affected by vector mode coupling of the degenerate modes in FMFs, which weakens the polarization- and spatial-mode dependence of Raman gain. Our investigation can be used for developing the FMF-based nonlinear-optical devices and sub-systems.