在光纤中传输的光信号,其偏振态(SOP)会受到外界环境的影响而发生随机变化,因此在偏振复用光纤通信系统、偏振编码光纤量子密钥分发(QKD)等系统中,需要插入光纤信道偏振补偿模块对光纤中随机双折射效应引起的偏振态变化进行实时补偿,以保证相应通信系统能够正常工作。根据波分复用光纤信道偏振补偿的理论模型,实现了偏振态相互共轭的两路参考光的制备,采用集成化的偏振探测器对实时变化的偏振态进行检测。在此基础上,提出了一种可以实时补偿光纤信道偏振变化的实验系统,该系统可以应用于偏振复用的光纤通信系统中,也可应用于光纤QKD系统中。实验数据表明,所设计的实验系统可以保障QKD在5 km传输距离下连续稳定运行8 h以上,量子比特误码率为1.96%。

The polarization states of the optical signals transmitted through optical fibers change randomly because of the influence of the external environment. Therefore, a real-time polarization compensation module must be inserted into the optical fiber communication systems, such as the polarization multiplexing communication system and the polarization encoding fiber quantum key distribution(QKD) system, to compensate the polarization changes that can be attributed to the random birefringence effect in optical fibers. Thus, the stable operation of the corresponding communication system can be ensured. In this study, an experimental system that can compensate for the variation of the polarization states in real time is proposed according to the polarization compensation system based on wavelength-division multiplexing in optical fibers. In this system, two reference lights with conjugated polarization states are prepared and an integrated polarization detector is used for detecting the changing polarization states in real time. This system can be applied to the optical fiber communication systems. The experimental results show that when this system is applied to a QKD system, continuous and stable operation can be achieved at a transmission distance of 5 km for more than 8 h with a quantum bit error rate of 1.96%.