针对光纤量子密钥分发(QKD)系统中信号同步的关键问题,提出了一种光同步方案。 发送方通过现场可编 程门阵列(FPGA)产生一定特征的同步脉冲序列驱动同步激光器,产生的同步光和信号光耦合到一根光纤传给 接收方。接收方对同步光进行高速甄别,甄别出的同步脉冲经过高精度延时调整后作为门控信号提供给单光子 探测器；同时在FPGA内使用高频时钟采样同步脉冲序列用以编码,使得双方达到严格同步。该方案具有高精度、 低成本、容错性好的特点,已经成功应用于城域量子通信网络。

A light synchronization scheme to solve the key problem of signal synchronization in quantum key distribution (QKD) system is proposed. At side of the transmitter, the field-programmable gate array (FPGA) chip produces a synchronization pulse sequence of certain pattern. The pulse sequence drives laser to transmit sync light through one fiber along with signal light to the receiver. The sync light reverts to sync pulse sequence through fast discrimination at side of the receiver, and the pulses are provided to the single-photon detector as gate after high-precision delay adjustment. Simultaneously, the receiver uses a high-frequency clock to sample the sync pulse sequence in FPGA for encoding, synchronizing the transmitter and receiver. The scheme has a high-precision, low-cost, high fault tolerance feature, and was successfully applied to metro quantum communication network.