Simple numerical characterization of double Rayleigh scattering noise in fiber Raman amplifiers

We proposed a method to calculate the double Rayleigh scattering (DRS) noise easily by separating signal part and noise part in signal evolution equations of fibre Raman amplifiers (FRAs). The result was compared with constant gain approximation and it shows reasonable agreements. The DRS noises were compared in cases of forward pumping and backward pumping. The DRS noise of each channel in WDM transmission was calculated and it would be helpful to estimate the power penalty resulted from the DRS noise in long-haul WDM transmission.