Relative intensity noise transfer in fiber raman amplifiers with multiple coherent or incoherent pumps

Fiber Raman amplifiers (FRAs) suffer from relative intensity noise (RIN) transfer from pumps to signals. RIN transfer for FRAs with single pump to one signal was well investigated. However, RIN transfer for FRAs with multiple pumps to multiple signals has not been investigated so far. We used an equivalent modulation index to evaluate RIN transfer for FRAs with multiple pumps. As such, a general RIN transfer function of multiple pumps to multiple signals for FRAs with multiple pumps is derived. The model is verified with approximate calculations with an analytical model. Based on the model we first investigated DC RIN transfer including signal to signal transfer. It is shown that longer wavelength signals suffer from a larger DC RIN transfer. Also FRAs using incoherent pumps suffer from a larger DC RIN transfer. The full characteristics of RIN transfer are compared for FRAs in non-pump depletion and depletion regime