Effect of pump laser mode structure on the gain of forward pumped Raman fibre amplifier in the presence of stimulated Brillouin scattering

The first experimental results on the variation of forward linear Raman gain with pump power in the presence of stimulated Brillouin scattering (SBS) for a different number of longitudinal modes of the pump laser are reported. The experimental results are in agreement with numerical simulations using a shooting method. The results presented have significant implications for optimising the design of semiconductor pump lasers for Raman fibre amplifiers.