雾是影响自由空间光通信性能的不可避免的天气因素, 选择合适的激光波长可以有效的降低其影响。文中针对薄雾、雾、霾三种大气能见度, 在不同传播距离条件下, 计算分析了均处于大气吸收窗口的中红外波长3.8 ?滋m和近红外波长1.55 ?滋m的传输特性。利用Monte Carlo方法对大量光子沿水平方向的传播特性进行数值模拟, 俄罗斯轮盘赌法判定光子是否“湮灭”。计算不同接收面半径和相对光强的关系, 不同大气能见度和不同传输距离下光子的透过率。结果表明3.8 ?滋m波长相对于1.55 ?滋m波长, 在同样的接收面半径下光强更集中, 同样的传播距离下光子透过率更高, 更不易受大气能见度的影响, 所以3.8 ?滋m波长比1.55 ?滋m更适合在雾中进行水平链路的自由空间光通信。

Fog is an inevitable weather factor affecting the performance of free space optical communication. Selecting the appropriate laser wavelength can effectively reduce the influence. Three atmospheric visibility of mist, fog, haze were considered in this paper. The transmission characteristic of mid-wave IR wavelength at 3.8 μm was compared with the traditional near-infrared wavelength at 1.55 μm that both belong to atmospheric transmission windows. Using Monte Carlo method, the propagation of a large number of photons along the horizontal direction was numerically simulated. Relationship between the relative light intensity and different receiving surface radius, photon transmittance under different transmission distance and different atmospheric visibility were worked out. The result reveals that the mid-wave IR wavelength at 3.8 μm, the light intensity is more concentrated under the same radius of receiving surface, and photon transmission is higher under the same propagation distance and less affected by atmospheric visibility. The wavelength at 3.8 μm is more suitable for horizontal link of free space optical communication in the fog than 1.55 μm.