自由空间光通信(FSO)是一种通过激光在无需光纤的情况下实现双向信息传输的通信系统。它具有带宽宽、保密性好、抗干扰性强、无需频率申请、体积小、功耗低等特点。尽管FSO通信系统有较高的安全性，但波束溢出还是会威胁到通信的安全，在通信中采用混沌加密的方式可有效地提高系统的安全性。采用差分混沌键控(DCSK)的Gamma-Gamma湍流模型来提高FSO通信系统的安全性，推导了系统误码率的表达式。通过空间信道图像数据的传输，对接收到的数据进行统计直方图、像素相关性和明文敏感性分析，结果表明系统具有很好的保密性能。

Free space optical communication(FSO) is a communication system that realizes two-way information transmission through laser without optical fiber. It has the characteristics of wide bandwidth, good confidentiality, strong anti-interference, no frequency application, small size and low power consumption. Despite the high security of the FSO communication system, beam overflow still threatens the security of the communication. The use of chaotic encryption in communication can effectively improve the security of the system. In this paper, the differential chaos keying(DCSK) Gamma-Gamma turbulence model was used to improve the security of the FSO communication system, the expression of the system bit error rate was derived. Through the image data transmission of spatial channel, and the statistical histogram, pixel correlation and plaintext sensitivity were analyzed on the received data, the results show that the system has good security performance.