从理论和实验两方面对自由空间光通信中常用的两种调制方式进行性能比较分析，旨在找出一种最适合的调制方法抑制大气湍流。在分析GammaGamma信道下OOK（开关键控）和DPSK（差分相移键控）调制的误码率时，将广义超几何方法引入分析。利用Matlab软件搭建系统，通过实验可知，采取相干及平衡探测的DPSK调制时性能要比基于OOK调制的直接探测高出3.21 dB；通过对双管平衡探测和单管探测进行实验，结果表明，双管平衡探测的信噪比优于单管探测，约提高21.6 dB。因此，基于DPSK平衡探测的相干通信方案具有可行性和优越性。

This paper makes a comparative analysis of the performances of two modulation modes commonly used in free space optical communications theoretically and experimentally, aimed at finding an optimal modulation method for suppressing atmospheric turbulences. In analyzing the BER of OOK and DPSK modulations in GammaGamma channels, it introduces the generalized hypergeometric method to the analysis and establishes a system for simulation by using Marlab. The experimental results indicate that the performance of DPSK modulationbased coherent and balanced detection is 3.21 dB higher than that of OOK modulationbased direct detection and that in the comparison between the dualtube balanced detection and the singletube detection, the former is superior in BER, about 21.6 dB higher, verifying that DPSK balanced detectionbased scheme is feasible and superior.