Experimental Coupling Loss Analysis of Free Space Optical Link under different Weather Conditions

The coupling efficiency of a free space optical (FSO) prototype based on fiber coupling technology was analyzed for different distances, combining numerical simulation and measurements under different weather conditions. When unaffected by the weather, the measurements are in good agreement with the simulated results. Based on the measurements for a distance of 60 meter, the impact of different weather conditions on the FSO link was assessed. The result shows that the link loss differs greatly under these three weather conditions, i.e., snow, rain and cloud. Combined with empirical formulas for the specific attenuation of snow and rain, the physical mechanism was inferred. The results indicate that the high attenuation in times of rain and cloud should be ascribed to the water vapor absorption in the near-infrared region, which needs further investigating.