Probabilistic Model for Free-Space Optical Links Under Continental Fog Conditions
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The error characteristics of a free-space optical (FSO) channel are signiﬁcantly different from the ﬁber based optical links and thus require a deep physical understanding of the propagation channel. In particular different fog conditions greatly inﬂuence the optical transmissions and thus a channel model is required to estimate the detrimental fog effects. In this paper we shall present the probabilistic model for radiation fog from the measured data over a 80 m FSO link installed at Graz, Austria. The fog events are classiﬁed into thick fog, moderate fog, light fog and general fog based on the international code of visibility range. We applied some probability distribution functions (PDFs) such as Kumaraswamy, Johnson SB and Logistic distribution, to the actual measured optical attenuations. The performance of each distribution is evaluated by Q-Q and P-P plots. It is found that Kumaraswamy distribution is the best ﬁt for general fog, while Logistic distribution is the optimum choice for thick fog. On the other hand, Johnson SB distribution best ﬁts the moderate and light fog related measured attenuation data. The difference in these probabilistic models and the resultant variation in the received signal strength under different fog types needs to be considered in designing an efﬁcient FSO system.
KeywordsFree Space Optics (FSO), optical attenuations, Mie scattering, Probability Density Function (PDF), visibility, channel modeling.
Document typePeer reviewed
Document versionFinal PDF
SourceRadioengineering. 2010, vol. 19, č. 3, s. 460-465. ISSN 1210-2512
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