量子密钥分发系统中高精度同步方案设计

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。接收方经过高速甄别后使用高频时钟来“采样”接收到的同步脉冲序列，使得双方达到严格同步；同时经过高精度延时调整后提供给单光子探测器作为门控信号，最大限度地去除暗计数。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。

Design of high-precision synchronization in quantum key distribution system

A light synchronization scheme to solve the key problem of signal synchronization in Quantum Key Distribution (QKD) system is proposed. At side of Transmitter, a field-programmable gate array (FPGA) chip is used to produce a synchronization pulse sequence which has certain characteristics to drive laser to transmit sync light pulse through one fiber coupled with signal light. A PIN-TIA is used to receive the sync light which is converted to electrical pulse that is used as gate control signal to the single-photon detectors after discriminating and delay adjusting. Simultaneously a high-frequency clock is used to sample the sync pulse sequence, synchronized the transmitter and receiver. The scheme has a high-precision, low-cost, high fault tolerance feature, and has been successfully applied to metro quantum communication network.