Brillouin Controlled Phase Matching in Optical Parametric Processing of Coherent Signals

We demonstrate the recovery of phase-matched condition in fiber-based four-wave mixing (FWM) using gain-transparent stimulated Brillouin scattering (SBS). The phase term introduced by SBS offers additional FWM conversion efficiency (CE). Our approach is implemented in a coherent communication system using a 10-Gbaud/s QPSK signal in the proof of concept experiment. A CE enhancement of ~11 dB has been achieved. As a result of optical signal-to-noise ratio enhancement, the Q factor is improved by 5.4 dB. Compared with directly detected signals, coherent signals are highly susceptible to phase noise. Therefore, we further evaluate possible phase noise degradation caused by SBS on the FWM pump, emphasizing on the frequency range of interest in our coherent system. The results are compared with those obtained from the conventional FWM configuration, confirming that the impact of SBS on the phase noise is insignificant.