Amplified Spontaneous Emission and Rayleigh Scattering in Few-Mode Fiber Raman Amplifiers

A theoretical model of noise-amplified spontaneous emission and Rayleigh backscattering-in few-mode fiber Raman amplifiers is presented in this letter. Based on this model, the equalization of the signal modal gain determines the equalization of the noise modal gain. The model can also be used to predict the mode-dependent optical signal-noise ratio. The theoretical results of this model are consistent with reported experimental results.