Optimal design of a DFRA considering pump-to-pump FWM

When a DFRA is implemented over a fiber with low chromatic dispersion around the pumping wavelengths, new waves (pumps) appear due to four-wave mixing (FWM) processes. This phenomenon is highly efficient when the phase mismatch of amplifier pump wavelengths is satisfied, so these new pumps can cause both a loss of flatness on the spectral gain and a reduction of DFRA gain, degrading WDM system performance. This work presents a new design method for a DFRA considering these new pumps in order to obtain a flat-gain profile. A two stage optimization algorithm is presented. First, a genetic algorithm is developed to obtain power integral optimal values for a fixed wavelength pump allocation, and secondly, an iterative proportional-integrative process is applied to obtain the input power of each pump from the optimal power integral obtained in the previous step. It was shown that this method can decrease the DFRA gain ripple from 4.67 dB to 0.85 dB, in a 20 nm bandwidth, for a non-degenerate FWM process.