Comparison of pumping schemes of fiber Raman amplifiers bidirectionally pumped at multiple wavelengths

In this paper we evaluate the influence of pumping schemes on the performance of fiber Raman amplifier bidirectionally pumped at multiple wavelengths. The numerical model we used includes bi-directional interactions between all signal and pumping wavelengths induced by stimulated Raman scattering, spontaneous Raman scattering and Rayleigh backscattering. We develop a effective algorithm to numerically solve the equations and show that by changing the ratio of forward to backward pumping power for each wavelength we can get very good tradeoff between gain flatness, optical signal to noise ratio and nonlinear effects.