The transmission of a free-space optical (FSO) beam through the atmosphere is influenced by several factors: chief among them are weather conditions such as fog, rain, and snow. In the design of FSO communication systems, it is necessary to determine the weather dependence of the system and derive a relation between the weather parameters and performance of the FSO communication systems. From our experiments, we have established that the link-operating rate, which is an important parameter for overall FSO-communication-system performance, cannot be estimated using the cumulative-distribution probability of the visibility data. A technique of estimating short-term FSO-link performance characteristics is required. Using this approach, a method for approximating an FSO link-operating rate is proposed for the western Kanto area in Japan, where the link-performance deterioration is mostly a result of rain. The method is based on the analysis of short-term recorded rain intensity and visibility data. The estimated FSO link-operating rate is shown to have a good conformance with the experimental measured result.
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