Estimation of optical attenuation in reduced visibility conditions in different environments across free space optics link

Abstract

Low‐visibility events detected in the city of Milan (Italy) and in the mountainous site of Milešovka (Czech Republic) during several months are analysed to compare optical attenuation measurements collected by a laser link and by a visibility sensor. General guidelines for data processing and automatic event identification are given. In Milan, the visibility sensor is a valuable support to estimate link attenuation during moderate radiation fogs or when it is raining, provided data are averaged in time. In Milešovka, the propagation conditions are challenging and the effect of the inhomogeneous distribution of fog (cloud) limit the usefulness of visibility measurements. In the case of snowfalls, that can produce high‐attenuation values, the agreement between the two measurements is poor.

FSO Path Loss Model Based on the Visibility

“…Possible issues with the results of [19] are that: 1) the dataset includes very different path lengths (from 17 m to 2.6 km), and 2) best fit lines at the three wavelengths are drawn from different datasets. Recent measurements in the first optical window indicate that γ = K/V, with K = 13 or K = 17, depending on the visibility sensor, fits the data fairly well, regardless of the environment and of the path length [39], [40], even though there are exceptions. The results at 1.550 μm are different and sometimes disagree to each other.…”

Cost-Efficient Hybrid WDM-MDM-Ro-FSO System for Broadband Services in Hospitals

“…However, Ro-FSO faces challenges of atmospheric turbulences such as scintillations, fog, rain, snow, etc. affecting the signal to noise ratio [9]. These atmospheric turbulences increase attenuation in the transmission path which results in shutdown of the network.…”