高功率、超远距离的光通信需要选择合适的调制解调方式,调制方式的选择是由系统的信道特性来决定的。PPM(Pulse Position Modulation)调制由于其功率利用率较高、传输效率高和抗干扰能力强等优点在光通信系统中被广泛应用。介绍了PPM的三种调制形式,并且对PPM调制系统的组成进行了研究,着重分析了PPM的调制性能,包括信号功率谱密度、信号的传输效率及误码率,证明PPM调制在保证一定的速率和传输功率尽可能小的要求下,是空间激光通信系统的最佳选择。 High power, long-distance optical communications need to select the appropriate mode of modulation and demodulation, the choice of modulation is determined by the system’s channel characteristics. PPM (Pulse Position Modulation) modulation is widely used in optical communication systems due to its advantages of high power utilization, high transmission efficiency and strong anti-interference ability. This paper introduces three kinds of modulation forms of PPM, and studies the composition of PPM modulation system. The modulation performance of PPM is analyzed emphatically, including signal power spectral density, signal transmission efficiency and bit error rate. It is proved that PPM modulation can guarantee a certain With the lowest possible speed and transmission power, it is the best choice for a space laser communication system.