Amplified spontaneous Raman scattering in fiber Raman amplifiers

Amplified spontaneous Raman scattered light power in forward and backward Raman amplifiers is theoretically and experimentally studied under the assumption of the constant Raman gain coefficient in the bandwidth of an optical filter. On the basis of the results, the power ratio of the amplified signal to amplified spontaneous scattering is discussed. As a result, it is clarified that the effect of amplified spontaneous Raman scattering on the signal to noise ratio for backward Raman scattering is larger than for forward Raman scattering.