SBS-enhanced FWM for polarization division multiplexed signals in coherent communication systems.

Stimulated Brillouin scattering (SBS) is applied to improve the performance of polarization insensitive four-wave mixing (FWM) realized with two orthogonal pumps. By manipulating the phase matching condition with SBS-induced phase change, we achieve conversion efficiency improvement up to 6 dB with negligible polarization dependence. Our approach is implemented in a coherent communication system where polarization division multiplexing (PDM) quadrature phase shift keying (QPSK) signal is applied. The quality of the converted idler is evaluated in both back-to-back (BtB) and transmission systems. Our experimental results show that the converted signal enjoys an improved conversion efficiency with negligible polarization-induced distortion. The SBS-enhanced Q factor leads to an extension of the transmission distance by 240 km. The results indicate that SBS-enhanced FWM can accommodate the advanced modulation formats and multiplexing schemes in today's optical networks.