在布里渊光时域反射计(BOTDR)的相干检测系统中,为减小偏振失配对布里渊谱测量精度的影响,针对后向布里渊散射光偏振态沿光纤随机变化,而同一记录点在重复采样周期内几乎不变的特点,结合偏振分集和扩展的思想,提出了实现简单而有效的时域偏振分集技术。理论分析表明,不管布里渊散射信号光的偏振态如何随机变化,采用该技术有较稳定的信号光功率与本振光被外差接收,接收信号对偏振态随机变化不敏感。系统实际上可基本不改变原系统体系,只对本振光施以无循环反馈的简单偏振控制。在布里渊时域反射计系统中实验对比了采用与不采用该技术的结果,表明前者的接收信号功率幅度约是后者的四分之一,抑制幅度起伏效果明显。

In order to reduce the effect of polarization mismatch on detection of Brillouin scattering spectrum in the coherent detection system for Brillouin optical time-domain reflectometry (BOTDR), based on the feature of Brillouin scattering light and the principles of the polarization spreading and the polarization diversity, the time-domain polarization diversity (TDPD) technique is introduced. The TDPD is implemented easily and effectively for BOTDR. The theoretical analysis shows that with TDPD more than half of signal power is heterodyned with the local light no matter how their polarizations vary, and the received signals are insensitive to the random variation of the polarization of Brillouin backscattering light. The TDPD is implemented by performing simple and non-feedback polarization control on the local light, and the original architecture of BOTDR is less changed. The comparison between the system with and without TDPD shows that the fluctuation of the received signal light power with TDPD is 4.2 times less than that without TDPD.