Simulating atmospheric free-space optical propagation: rainfall attenuation

Maha Achour

doi:10.1117/12.464100

26 April 2002 Simulating atmospheric free-space optical propagation: rainfall attenuation

Maha Achour

Proceedings Volume 4635, Free-Space Laser Communication Technologies XIV; (2002) https://doi.org/10.1117/12.464100
Event: High-Power Lasers and Applications, 2002, San Jose, California, United States

Abstract

With recent advances and interest in Free-Space Optics (FSO) for commercial deployments, more attention has been placed on FSO weather effects and the availability of global weather databases. The Meteorological Visual Range (Visibility) is considered one of the main weather parameters necessary to estimate FSO attenuation due to haze, fog and low clouds. Proper understanding of visibility measurements conducted throughout the years is essential. Unfortunately, such information is missing from most of the databases, leaving FSO players no choice but to use the standard visibility equation based on 2% contrast and other assumptions on the source luminance and its background. Another challenge is that visibility is measured using the visual wavelength of 550 nm. Extrapolating the measured attenuations to longer infrared wavelengths is not trivial and involves extensive experimentations. Scattering of electromagnetic waves by spherical droplets of different sizes is considered to simulate FSO scattering effects. This paper serves as an introduction to a series of publications regarding simulation of FSO atmospheric propagation. This first part focuses on attenuation due to rainfall. Additional weather parameters, such as rainfall rate, temperature and relative humidity are considered to effectively build the rain model. Comparison with already published experimental measurement is performed to validate the model. The scattering cross section due to rain is derived from the density of different raindrop sizes and the raindrops fall velocity is derived from the overall rainfall rate. Absorption due the presence of water vapor is computed using the temperature and relative humidity measurements.

Citation Download Citation

Maha Achour "Simulating atmospheric free-space optical propagation: rainfall attenuation", Proc. SPIE 4635, Free-Space Laser Communication Technologies XIV, (26 April 2002); https://doi.org/10.1117/12.464100

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