Mitigating Fog Attenuation with Acoustic Waves in Free-Space Optical Systems

This paper presents exploration of an acoustic wave strategy (AWS) for mitigating fog-induced attenuation in free space optical (FSO) systems. Experiments using a dedicated fog chamber were conducted to evaluate the link performance in terms of optical power recovery, attenuation reduction, and visibility improvement under acoustic frequencies. Results demonstrate that the AWS significantly accelerates the channel’s recovery and enhances the received signals’ strength in dense fog conditions. At a frequency of 450 Hz, the recovery time to reach the maximum received optical power was reduced by more than 4 minutes compared to that in the non-acoustic operation. At 1.2 kHz, the received power exceeded the baseline level observed without acoustic excitation. The attenuation was decreased in the first 7 minutes of acoustic action from 180 to 11 dB/km at 450 Hz and 180 to 25 dB/km at 1.2 kHz. Within the same 7-minute timeframe, visibility was improved from 0.2 to 1.7 km at 450 Hz and 0.2 to 0.8 km at 1.2 kHz. A visibility prediction model incorporating acoustic frequency was proposed to assess and highlight any potential gains to an FSO link. In brief, this study demonstrates that acoustic excitation serves as an effective active mitigation technique for enhancing the robustness of FSO links under fog-affected conditions.