基于保护时隙的一倍时隙频率采样光PPM时钟同步技术

Clock Synchronization Technology for Pulse Position Modulation with Guard Time at Sampling Frequency of 1 Slot

针对一倍时隙频率异步采样的脉冲位置调制(PPM)系统,提出一种基于保护时隙的时钟同步技术。在发送端每个PPM信号中安排一个或多个保护时隙,根据保护时隙位置只有背景光子,而其他时隙既有背景光子也有信号光子的特性实现时钟同步。在接收端,将采样输出的数据以PPM信号中时隙个数为周期进行统计计数,基于保护时隙的统计分布特性对定时偏差进行粗同步,通过插值匹配搜索方式完成定时精同步。仿真结果表明,所提方法能够在大定时偏差范围内实现有效同步,适当增加保护时隙数或增大统计数据量能获得较为理想的系统误码性能。

Aiming at the pulse position modulation （PPM） system of asynchronous sampling at sampling frequency of 1 slot, we propose a clock synchronization technique based on guard time. One or more guard time are inserted into each PPM signal in the transmitter. Based on the fact that there are only background photons in these guard time, while other slots have the characteristics of both background photons and signal pho：ons, we achieve clock synchronization. At the receiving end, the sampling data is counted periodically with the number of slots in PPM signal. Then, the coarse timing synchronization is carried out based on the statistical distribution characteristics of photon in guard time. Finally, the interpolation matching search method is used for the fine timing synchronization. The simulation results show that the proposed method can achieve efficient synchronization within the scope of large timing offset, and increasing the number of guard time or increasing the amount of statistics can achieve ideal system bit error performance.