电力悬空光缆中光子偏振态易受外界快速无规则扰动影响,导致偏振编码量子密钥分发(QKD)系统成码率降低甚至无法成码,为对抗链路中偏振态的快速变化,设计了高速偏振反馈系统(FPF),介绍了该系统的工作原理。重点研究了系统中关键的偏振反馈算法,包括对偏振收敛程度评价函数及搜索算法的选取,偏振反馈周期与成码周期的监测条件的选取,以及监测阈值的自适应选取。整个系统在实际悬空光纤上进行了实测,测试结果表明该系统和算法能够解决中远距离悬空光缆中QKD成码难的问题。

Photon polarization state in aerial fiber for power grid is susceptible to the rapid external random disturbances, which leads to low coding rate of polarization-coded quantum key distribution (QKD) system or even zero coding rate. To counter the rapid change of polarization state in the link, we design polarization feedback system (FPF), and describe the working principle of the system. The key polarization feedback algorithms in the system are studied, including the selection of evaluation function and search algorithm of polarization convergence, the selection of monitoring conditions of polarization feedback cycle and coding cycle, and the adaptive selection of monitoring threshold. The whole system is measured on actual aerial fibers. The test results show that the system and algorithm can solve the problem of QKD code in intermediate-distance installed aerial fiber.