Understanding the formation of the SRS Stokes spectrum in fused silica fibers

Spectral characteristics of stimulated Raman scattering (SRS) in optical fibers are examined in a regime (nanosecond pulses or longer) for which effects such a self-phase modulation, cross-phase modulation, and group velocity dispersion are negligible. An XeF excimer laser was used to pump a multimode fused silica UV optical fiber to observe SRS multiple-order Stokes generation. A theoretical model in which SRS is the only nonlinear effect induced was developed to simulate the SRS spectra of excimer laser pumped silica fibers. Good agreement has been achieved on spectral characteristics of SRS between the computer simulation and experimental results, which clarifies several puzzling features observed in experiment. The most important parameters to the evolution of SRS spectra in fibers were found to be the Raman gain curve, and the linewidth and temporal profile of the input pump.>