An approximated technique to quickly optimize the gain
profile of multi-pump broadband hybrid amplifiers under residual
pump recycling in WDM systems is proposed. 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.
