Polarization insensitive coherent detection for Brillouin scattering spectrum in BOTDR

The technique of time domain polarization diversity (TDPD) is proposed to reduce the polarization-induced fading in the coherent detection system of Brillouin optical time domain reflectometry (BOTDR). TDPD is implemented by a simple non-feedback polarization controller on the local light and with little change on the original architecture of BOTDR. Theoretically, the system with TDPD is insensitive to the random states of polarization of the Brillouin backscattered light. It is experimentally shown that the amplitude fluctuation of the detected signal with TDPD is 4.2 times less than that without TDPD.