An Efficient Visibility Prediction Framework for Free-Space Optical Systems

Free-Space Optical (FSO) systems are greatly affected by fog conditions, which cause very high attenuation over considerable amounts of time. Therefore, some models have been adopted by the designers of FSO links, which take into account visibility values in order to compute the attenuation due to fog. However, the visibility distribution for an FSO link site may not be available. In this paper we propose a simple but reliable framework that estimates the visibility distribution and has a single statistical input: the number of foggy hours per year. The proposed tool is evaluated using real visibility data from a large variety of sites with different climates within the Portuguese territory. The results show that the predicted visibility distributions considerably agree with the real data for all sites, as well as they are robust for cases where the available fog statistics are not the most accurate, proving that the simple metric proposed herein is an easy-to-use, valid and robust tool to take into account when designing FSO systems.