Data Acquisition of Atmospherically Induced Optical Signal Fluctuations

Abstract

Free-space optical (FSO) communication offers a cost-effective, high-bandwidth, and high-security [1] solution for diverse communication scenarios, attracting growing interest [2]. However, a significant challenge for FSO links is signal fluctuation, quantified by the power scintillation index (PSI) [3]. This fluctuation manifests as signal fading, which severely degrades link performance[4]. To mitigate this issue, transmitter diversity can be employed in FSO systems [5]. This study investigates the PSI and fading characteristics of FSO links utilizing double transmitters with three different divergence angle application over weak turbulence, log-normal atmospheric fading channels in a ground-to-ground horizontal link of 350 meters. We assume independent channels for our analysis, which leverages an approximation for the sum of uncorrelated log-normal random variables. To verify the lack of correlation between the two beams, additional measurements were conducted prior to the main data collection. The core investigation focuses on the performance improvements offered by the double transmitter configuration for each divergence angle. This evaluation will involve comparing PSI values and fade occurrence with a single transmitter setup. Additionally, the double transmitter performance across the different divergence angles were evaluated. Both numerical simulations and measurement data will be used to support this comprehensive evaluation. Additionally, a lightweight, standalone optical receiver system is also presented for further studies.