Scintillation index of multimode laser beams used for communication systems in vertical paths of weak atmospheric turbulent medium are examined by employing the Rytov method. On-axis scintillation index is examined versus the source size, propagation distance and zenith angle for vertical link including uplink and downlink. At the selected values of source sizes and propagation distances, scintillation responses of multimode laser beams are evaluated. In general, it is found for both uplink and downlink that the laser beam with multimode content has larger scintillation noise as compared to a Gaussian laser beam. However, for the downlink at L=700 km, at the chosen parameters, the multimode beam possessing larger mode content, is found to attain slightly smaller scintillations.

采用Rytov方法研究了用于通信系统的多模激光束在弱大气湍流介质垂直路径中的闪烁指数。针对垂直链路（包括上行链路和下行链路），检查轴上闪烁指数与源尺寸、传播距离和天顶角的关系。在选定的光源尺寸和传播距离值下，评估多模激光束的闪烁响应。通常，对于上行链路和下行链路，具有多模成分的激光束与高斯激光束相比具有更大的闪烁噪声。然而，对于L = 700 km 处的下行链路，在所选参数下，发现具有较大模式内容的多模波束获得稍小的闪烁。