Pump-to-Stokes RIN transfer in Raman fiber lasers and its impact on the performance of co-pumped Raman amplifiers

We show experimentally and numerically that pump-to-Stokes transfer of relative intensity noise (RIN) makes a significant contribution to the output RIN of Raman fiber lasers (RFLs). We theoretically investigate the penalty in the signal-quality factor induced by a noisy RFL pump in a co-pumped Raman-amplified transmission span, where the noise on the RFL output is caused by pump-to-Stokes transfer of RIN. This penalty can be kept low by a proper design of the RFL, in particular by using high-reflectivity output couplers, high-gain Raman fibers and optimizing the RFL fiber length.