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9 December 2002 Visibility in low clouds and its impact on FSO links
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Fog and low clouds are the two atmospheric elements with the greatest impact on the performance of a free space optical (FSO) network. Predicting the effects of low clouds and ground based fog on FSO equipment performance is a challenging exercise. Usually, surface visibility records from airports in proximity to the deployment area are used to calculate the link availability. However, very little data are available on visibility within clouds, which have a larger impact on elevated links. To estimate the visibility in low clouds we have deployed visibility sensors at three different heights (33, 119, 188 meters above mean sea level) and a ceilometer in San Francisco from June to October of 2001. The data collected show substantial difference between the visibility reported at San Francisco International Airport (SFO) and the visibility recorded by our sensors in downtown San Francisco. More importantly, the data indicate a greater prevalence of low clouds downtown than at the airport.
© (2002) COPYRIGHT Society of Photo-Optical Instrumentation Engineers (SPIE). Downloading of the abstract is permitted for personal use only.
M. Ammar Al-Habash, Janae Nash, Jeff Baars, Michael Witiw, Kenneth W. Fischer, and Kenneth N. Desmet "Visibility in low clouds and its impact on FSO links", Proc. SPIE 4821, Free-Space Laser Communication and Laser Imaging II, (9 December 2002);

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