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。

Optical communication with high-power and ultra-long distance needs appropriate modulation and demodulation. The modulation mode depends on the channel characteristics of the system. PPM (Pulse Position Modulation) is widely used in optical communication systems because of its high power efficiency, high transmission efficiency and anti-jamming ability, etc. In this paper, three PPM formats are presented, and the composition of the PPM modulation system is studied with the focus on the modulation performance of PPM, including the signal power spectral density, signal transmission efficiency and the bit error rate (BER). The results show that PPM is the best choice for space laser communication system under a certain rate and transmission power as small as possible.