在自由空间光通信(FSO)中,由系统设计以及大气湍流所引起的光强闪烁和相位起伏会造成圆偏振控制误差，这严重影响圆偏振位移键控(CPolSK)通信系统的性能。因此，基于Gamma-Gamma大气信道模型，在较全面考虑光强起伏、相位噪声和圆偏振控制误差三个参数的基础上，建立了CPolSK系统信道的数学统计模型，推导了平均信道容量的闭合表达式，仿真研究了误码率在连续相位噪声下的性能以及三个参数对信道容量的影响。结果表明，光强起伏的增强和相位噪声的增大均会导致CPolSK系统性能的劣化，而提高平均信噪比在一定程度上能够改善系统性能。特别地，当圆偏振控制误差大于8°时，CPolSK系统的平均信道容量显著下降。

Circular polarization control error caused by system design and intensity fluctuation as well as phase noise induced during the transmission of optical signal in atmospheric turbulence will directly lead to performance impairments of circular polarization shift keying(CPolSK) system in FSO. Therefore, on the basis of roundly considering the three parameters, which are the intensity scintillation, the phase noise and the circular polarization control error, the mathematical statistical model of the CPolSK system channel was established based on the Gamma-Gamma atmospheric channel model, and the closed expression of the average channel capacity was derived. Simulations were given to analyze the effects of intensity scintillation, phase fluctuation and circular polarization control error on channel capacity of CPolSK system. Results show that the increase of both intensity fluctuation and phase noise will cause the degradation of the channel capacity, while raising the average SNR can improve the channel capacity in a certain degree. It is also noted that the average channel capacity will significantly decrease when the circular polarization control error is larger than 8°.