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Proceedings Paper

Effects of low clouds on terrestrial free-space optics availability
Author(s): Jeff Baars; Michael Witiw; Ammar Al-Habash; Kenneth W. Fischer
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Paper Abstract

Meteorological visibility data are the most commonly used data to estimate terrestrial Free Space Optics (FSO) availability in a given city. Visibility data can be used to estimate transmission efficiency at desired IR wavelengths using a semi-empirical equation, and are often archived over many years allowing the calculation of long-term averages of availability. However, these data are taken at near-surface levels (historically within a few meters of the surface) and are therefore only appropriate for estimating FSO availability near the surface. Examination of long term cloud observations, including percent frequency of cloud ceilings occurring at various heights above the ground, show the importance of including low clouds into the consideration of FSO availability for any situation above about 30-m above ground level (AGL). In most locations, low clouds occurring very near the surface are relatively common -- more so than surface-based fog (which is measured in terms of visibility). Thus, FSO availability will decrease with height, sometimes dramatically, in most cities. Cloud data is also archived over long periods of record and can thus be used to calculate long-term averages of availability.

Paper Details

Date Published: 26 April 2002
PDF: 8 pages
Proc. SPIE 4635, Free-Space Laser Communication Technologies XIV, (26 April 2002); doi: 10.1117/12.464098
Show Author Affiliations
Jeff Baars, Terabeam Corp. (United States)
Michael Witiw, Terabeam Corp. (United States)
Ammar Al-Habash, Terabeam Corp. (United States)
Kenneth W. Fischer, Terabeam Corp. (United States)

Published in SPIE Proceedings Vol. 4635:
Free-Space Laser Communication Technologies XIV
G. Stephen Mecherle, Editor(s)

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