| Popis: |
Free Space Optical (FSO) systems offer tremendous channel capacity, which can significantly contribute to the bandwidthhungry next generation networks. FSO technology is certainly highly vulnerable to atmospheric Mie scattering, which leads to severe degradation of the established optical communication link. To address this key-issue, the current paper is focused on detailed investigation of the fog effect using artificially built fog environment. Low-visibility conditions are adjusted within a 50 m long corridor covered with PVC and including two artificial fog machines and a signal flare. The Particle Size Distributions (PSDs) of the simulated fog are measured with a sophisticated and so-called “Spraytec” device provided by Malvern Instruments Company. Once the main characteristics of the artificial fog are assessed, the measurements are compared with an empirical estimated fog model using modified gamma function. The comparison is accomplished in terms of theoretically defined PSDs where both radiation as well as advection fog modelling are taken into account. In order to calculate the relevant FSO channel attenuation only based on our measured fog PSDs, Mie theory is applied. For this purpose, Mie scattering efficiencies of a fog water sphere with arbitrary radius and refractive index are shown and examined. Respectively, apart from the presented figures with comparison of various PSDs, also the specific attenuation in dependence on fog particles size is introduced and discussed. Taking into account that particle density of the artificial fog can be manually setup in accordance with the applied theoretical models, our simulations offer attenuation up to 210 dB/km in the presence of continental moderate and dense fog effects. Consequently, we have the possibility to simulate significantly well various fog conditions in artificially simulated environment. |
