I am also attaching link of a paper which may be very useful to you. It It is based on the amplifier spectral equalization by adjusting the flexible gain profile of a multi-pump Raman amplification stage to compensate the Erbium-doped stage gain variation within the C-band. In order to increase the pump power efficiency, the Erbium-doped fiber section recycles the residual Raman pump. Three different cases considering, respectively, one, two, and three pumps are analyzed to demonstrate the effectiveness of the proposed technique. The characterization of the Raman+EDFA hybrid amplifier has been performed in terms of global gain, ripple, and noise figure. The proposed optimization method for the Raman pump sets allows ripple figures to be reduced by half of their original values in single pumped configurations. Our results also suggest that two pump lasers is the best configuration when the maximum gain, minimum ripple, and pump power efficiency are simultaneously considered.
http://www.scielo.br/pdf/jmoea/v9n2/v9n2a04.pdf
The results results demonstrate that this kind of hybrid amplifier, with the properly chosen pump wavelengths and powers, enables the design of broadband devices with enhanced power conversion efficiency. Optimal EDF length studies, considering specific input signal power levels, could lead to even better results as the EDFA gain saturation condition could be avoided.
Hope it helps.
Regards