脉冲展宽对深空激光通信的影响与补偿研究

深空激光通信系统下行链路的脉冲位置调制PPM（Pulse Position Modulation）信号在经过大气信道传输和单光子探测器接收时，将出现脉冲展宽效应，引起通信系统性能下降。分析了大气信道中的淡积云云层散射、大气湍流与气溶胶散射和单光子探测器的抖动特性所引起的脉冲展宽效应。在此基础上，仿真分析了淡积云云层物理厚度对不同PPM调制阶数下通信速率的影响，并研究了单光子探测器引起的脉冲展宽产生的抖动损失。为补偿脉冲展宽的影响，提出了一种基于时隙似然比解调的补偿方法，通过仿真验证了该方法能够有效降低深空PPM激光通信链路中脉冲展宽对通信误码率的影响。该研究对分析和提升深空PPM激光通信系统的链路性能具有一定的参考意义。

Analysis of pulse broadening effect and compensation on deep space laser communication system

In the deep-space laser communication downlink, the pulse position modulation (PPM) laser signal will have a pulse broadening effect when it is transmitted through the atmospheric channel and received by the single-photon detector, and causes the performance of the communication system to decrease. This paper analyzes the pulse broadening effect caused by light cumulus cloud scattering, atmospheric turbulence and aerosol scattering in the atmospheric channel and the jitter characteristics of the single photon detector. On this basis, this paper analyzes the effect of the physical thickness of the pale cumulus cloud on the communication rate under different PPM modulation orders and the jitter loss caused by the pulse broadening of the single photon detector. To compensate the effect of pulse broadening, a method based on likelihood ratio demodulation is proposed which reduce the effect of pulse broadening on communication BER through simulation verification. This research has certain reference significance for analyzing and evaluating the link performance of deep space PPM laser communication system.