A Real-Time Polarization Compensation System Based on Wavelength-Division Multiplexing for Optical Fiber Communication Systems

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 arc 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%.