A Novel Dispersionless Comb Gain Equalizer for Fiber-Optical Parametric Amplifier

Abstract

In this article, we propose a novel superstructure fiber Bragg grating (SFBG)-based comb gain equalizer for fiber-optical parametric amplifiers (FOPAs). The target spectrum of the gain equalizer is obtained by two steps. Initially, we calculate the spectrum according to the inverse of the gain spectrum of the FOPA. Then we apply a channel-by-channel windowing method to shape each channel and adopt a Gaussian hypergeometric function to describe the rising and descending edges of each channel. The SFBG is finally synthesized with layer-peeling inverse scattering technique. Using the designed SFBG, the gain variation of the FOPA is flattened to be within ±0.4 dB for 16 ITU channels and the best channel isolation is as high as 35 dB. It should be pointed out that the proposed method could also be used to design gain equalizers for other optical amplifiers.