Djordjevic Goran T, Petkovic Milica I, Spasic Miodrag, Antic Dragan S
Opt Express. 2016 Jan 11;24(1):219-30. doi: 10.1364/OE.24.000219.
In this paper, we analyze the outage capacity performance of free-space optical (FSO) systems. More precisely, taking the stochastic temporary blockage of the laser beam, atmospheric turbulence, misalignment between transmitter laser and receiver photodiode and path loss into account, we derive novel accurate analytical expressions for the outage capacity. The intensity fluctuations of the received signal are modeled by a Gamma-Gamma distribution with parameters directly related to the wide range of atmospheric conditions. The analytical results are validated by Monte Carlo simulations. Furthermore, when the intensity fluctuations are caused only by atmospheric turbulence, derived expressions are reduced to the simpler forms already presented in literature. The numerical and simulation results show that the link blockage causes appearance of the outage floor that is a significant energetic characteristic of an FSO system. The results also show that there exists an optimal value of the laser beam radius at the waist for minimizing outage probability in order to achieve the specified outage capacity. This optimal value depends on atmospheric turbulence strength and standard deviation of pointing errors, but it is also strongly dependent on the probability of link blockage.
在本文中，我们分析了自由空间光（FSO）系统的中断容量性能。更确切地说，考虑到激光束的随机临时阻塞、大气湍流、发射机激光器与接收机光电二极管之间的对准误差以及路径损耗，我们推导出了中断容量的新颖精确解析表达式。接收信号的强度波动由伽马-伽马分布建模，其参数与广泛的大气条件直接相关。解析结果通过蒙特卡罗模拟进行了验证。此外，当强度波动仅由大气湍流引起时，推导的表达式简化为文献中已给出的更简单形式。数值和模拟结果表明，链路阻塞导致了中断基底的出现，这是FSO系统的一个重要能量特征。结果还表明，为了实现指定的中断容量，存在一个使中断概率最小化的腰部激光束半径的最优值。这个最优值取决于大气湍流强度和指向误差的标准差，但它也强烈依赖于链路阻塞的概率。
