Analysis of fog attenuation events at 850 nm measured on an 853 m path

摘要

The specific results of a propagation study carried out on a free space optical link working at 850 nm on an 853 m long terrestrial path over a 4-year period from August 2004 to July 2008 are presented. The records of both the observed fade events and the concurrent meteorological conditions were processed. Individual recorded attenuation events were classified according to the types of individual hydrometeors (rain, rain with hail, snow and fog) that occurred. Fog attenuation events were analyzed in detail and were subdivided into the attenuation events due to fog only, and to combinations of fog with rain, fog with snow, and fog with rain and snow, respectively. The cumulative distributions of attenuation due to fog events for four individual year periods, the entire 4-year period, the individual worst months and the average worst month from the four-year period are presented. It is shown that not only attenuation due to fog only but also attenuation due to fog combined with other hydrometeors may have a significant impact on the attenuation of the optical beam. The assessments of availability performance and error performance parameters are given. The use of measured visibility data for the calculation of attenuation is discussed.