Characterization of Fog and Snow Attenuations for Free-Space Optical Propagation

Abstract

<p class="MsoNormal" style="margin: 0cm 0cm 0pt; layout-grid-mode: char;"><span style="layout-grid-mode: line; font-family: ";Arial";,";sans-serif";; mso-bidi-font-weight: bold;"><span style="font-size: x-small;">Free Space Optics (FSO) is now a well established access technology, better known for its robustness in transmitting large data volumes in an energy efficient manner. However the BER performance of a FSO ground-link is adversely affected by cloud coverage, harsh weather conditions, and atmospheric turbulence. Fog, clouds and dry snow play a detrimental role by attenuating optical energy transmitted in terrestrial free-space and thus decrease the link availability and reliability. We measured the time variation of received optical signal level during continental fog and dry snowfall over a link distance of 80 m. We perform a detailed analysis of the continental fog and dry snow attenuation results and further characterise them by presenting some useful attenuation statistics and also showing their comparison with the corresponding measured density values collected by a particle sensor device. We propose also an empirical relationship between temperature, relative humidity and optical attenuation values for the continental fog case based on standard curve fitting technique. <em></em></span></span></p&gt

Effect of Clear Atmospheric Turbulence on Quality of Free Space Optical Communications in Western Asia

“…Although their concentration is closely related to the optical visibility, there is no single particle dimension distribution for a given visibility [28]. Due to the fact that the visibility is an easily obtainable parameter, either from airport or weather data, the scattering coefficient can be expressed according to visibility and wavelength by the following expression [5]:…”

Experimental study of bit error rate of free space optics communications in laboratory controlled turbulence

“…In a cloudy condition, the optical loss could be much higher than 50 dB/km. Rain drop could also attenuate the transmitted signal by about 20-30 dB/km at a rain rate of 150 mm/h [4], whereas attenuation due to snow could be greater than 45 dB/km [5].…”

Performance Analysis of 16 × 2.5Gb/s FSO System for the Most Critical Weather Conditions

“…S. Awan et al [11] investigated impact of fog, rain and snow effects and evaluate their performance on the basis of attenuation data collected for the optical pulse propagated through the troposphere and it was found that fog is the most limiting factor. Horwath et al [12] measured the time variation of received optical signal level during continental fog and dry snowfall over a link distance of 80m. Wang et al [13] studied and compared the BER performance of several widely used modulation formats under different atmospheric turbulence scenarios with and without SDRT.…”