Combination of two visibility sensors to predict fog attenuation on FSO links

The Institute of Atmospheric Physics in Prague is performing research of FSO signal propagation. This study is concerning the fog impact on signal attenuation. It compares three formulas estimating fog attenuation from visibility. Special sight is given to usage of two visibility sensor data. It is shown that their combination slightly improves the fog attenuation estimation. It was experimentally proved that the visibility data from lower sensor of our slant path are correlated better with FSO link attenuation in comparison with upper sensor data. Another significant benefit of using two sensors is also the determination if there cloudiness or fog occurs.