非直视紫外光通信能够在复杂环境和特殊地形下工作,但大气吸收、 散射及湍流会造成信号强度的快速衰减,从而极大地限制了传输距离。协同中继是克服这一缺点、扩大通信范围的有效手段。 针对大气湍流条件下非共面中继辅助紫外散射系统,推导获得了译码转发(DF)和放大转发(AF)两种协议下中断概率的闭式表达式。 通过蒙特卡洛仿真,验证了理论分析结果的正确性。仿真结果表明:DF的中断性能优于AF, 且光发送功率越大、 接收仰角和偏轴角越小,系统的中断性能越好。偏轴角不同,中断概率随发送仰角的变化规律不同。

The two-dimensional (2D) compound parabolic concentrator's (CPC) characteristics are analyzed. It is shown that CPC's height is taller and its light collecting ability is stronger with the CPC's field of view decreasing when the bottom radius is unchanged. According to the ZEMAX analysis, CPC is good at collecting optical signal, and the antenna combining CPC with hemispherical lens can gather more optical signal than a single CPC or CPCs combined in series. The light propagation of scattering optical communication based on multiple scattering is simulated by Monte Carlo method, and the results show that using CPC as receiving antenna can strengthen communication system's signal collecting ability and increase its communication distance.

本文推导了复合抛物面聚光器的轮廓曲线方程,分析表明,复合抛物面聚光器的结构决定于视场和底部半径两个参量,其底部半径一定时,视场越小,高度越大、聚光能力越强;复合抛物面聚光器的截取比越大,聚光能力越强;随着视场的增大,复合抛物面聚光器的聚光能力受截取比的影响减小。利用基于多次散射的蒙特卡罗模型对光散射通信的传输进行模拟,结果表明,复合抛物面聚光器应用于光散射通信的接收天线,能增加对光信号的采集,有助于增加通信距离。

利用大气对光的散射作用可以实现非视线通信。在单次散射假定下，研究了非视线光散射通信系统的大气传输模型。利用该模型分析了光源发散角、接收视场和收发仰角等系统几何参数与接收散射光能量之间的关系; 重点讨论了大气分子散射和气溶胶散射各自对接收散射光能量的贡献。结果表明当系统的收发仰角较大时，接收光能量主要来自大气分子散射; 反之，气溶胶散射则成为接收光能量的主要部分。对于工作在日盲紫外光谱区的非视线通信系统，增加接收视场可以有效地增大系统的信噪比。发现在两种典型的收发仰角情况下，接收散射光能量随光源发散角的变化趋势是相反的，这说明光源发散角要根据实际的应用场合设计确定。

Multipath-induced pulse broadening in a non-line-of-sight (NLOS) optical scattering channel is investigated. Expressions for impulse response and digital signal-to-noise ratio (DSNR) penalty induced by intersymbol interference (ISI) of a NLOS ultraviolet (UV) scattering communication are introduced based on a single-scattering model, and simulated results for some typical atmospheric condition and configuration of geometry are given in the paper. It is shown that the multipath dispersion is one of the most important factors limiting the system performances, and return-to-zero (RZ) format is more suitable for the optical scattering communications than non-return-to-zero (NRZ) format. The method proposed here can be used to predict available bandwidth and data rate of the communication system operating in a NLOS optical scattering channel.