Rain attenuation measurement and prediction on parallel 860-nm free space optical and 58-GHz millimeter-wave paths

Abstract

Attenuation of electromagnetic waves at 860 nm and 58 GHz due to scattering in rain is measured on the terrestrial paths simultaneously with rain intensity. The relationship between rain intensity and rain attenuation of light is analyzed using the Marshal-Palmer drop size distribution model and the Mie scattering theory. The pertinent power law model is derived from drop size distribution parameters. An empirical composite power law model is proposed and fitted to the dataset extracted from rain attenuation events recorded during a seven-year experiment in Prague. Observed average rain attenuation of light at intensities larger than about 5 mm/h is lower than attenuation predicted by standard models. Rain attenuation measured at 58 GHz is larger than attenuation at 860 nm for rain intensities in the range from 0.1 to 100 mm/h.