自由空间光通信的物理层安全与光编码方法研究

随着计算资源和窃听手段的发展，FSO系统的安全性问题日益突出并亟待解决。本项目以信息论为理论基础，通过建立FSO-OCDMA和时/码分集FSO系统的信道转移概率矩阵，首次定量研究基于光编码的FSO物理层安全性能，包括平均安全容量、安全通信概率和安全泄露因子等指标。创新性地提出一种解决FSO系统物理层安全性与可靠性的光编码理论与方法，建立时/频域零相关区二维光地址码的理论界，并研究相应的构造算法。在时/频域零相关区二维光正交码的基础上，研究新型的时/码分集FSO系统，不仅解决FSO系统的物理层安全性，而且完全消除时/码分集FSO系统的多址干扰，有效克服大气湍流效应导致的信号衰落。最后，对基于时/频域零相关区光编码的时/码分集高速FSO系统进行仿真与实验研究，同时研究其误码率与物理层安全性性能。本项目通过新型的光编码方法与时/码分集机制，将有效解决FSO系统的物理层安全性与可靠性。

With the development of computing resources and eavesdropping means, the security problems of free-space optical( FSO) system have become increasingly prominent and urgent. Based on the information theory, this project will establish channel transtion-probablity matrix of FSO-OCDMA and time/code diversity FSO system. The safety performances of physical layer of optical encoding FSO system are first quantitative analyzed, including the average security capacity, safety communication probability and safety factors of leakage. Optical encoding theory and method are proposed to solve the safety and reliability of FSO physical layer. Theoretical boundary of time/frequency zero correlation zone two-dimensional optical code is established, and corresponding algorithms is studied. Based on the time/frequency zero correlation zone two-dimensional optical code, novel scheme of time/code diversity FSO system is proposed. It can not only solve the physical layer safety, but also completely eliminate the multiple access interference of time/code diversity FSO system, which can effectively overcome the signal fading caused by atmospheric turbulence. Finally, simulation and experimental are studied based on the time/frequency zero correlation zone two-dimensional optical code and high speed time/code diversity FSO system, and bit error rate and physical layer security performance are analyzed. Through the novel optical encoding method and time/code diversity mechanism, this project will effectively solve the physical layer security and reliability of FSO system.