Performance Enhancement of FSO Communication System Under Rainy Weather Environment Using a Novel Encryption Technique

Free Space Optics (FSO) has emerged as a viable solution to meet the growing demand for high bandwidth, secure data transmission, and high speed. However, the FSO system is highly susceptible to environmental factors, with precipitation in particular having a significant impact on FSO links. Optical loss, phase fluctuation, and multipath fading of the received optical power are all caused by these external factors. From this perspective, to improve the system's performance in such conditions, a novel image encryption technique based on the Choquet Fuzzy Integral (CFI) in conjunction with the integer wavelet transform is proposed. The security of the proposed method is demonstrated via analysis security on the one, and its efficacy in terms of transmission performance of an encrypted image over an FSO channel exposed to rainy weather conditions is analyzed on the other. Authentic meteorological data from two distinct cities are considered to demonstrate the model's real-world applicability: Alexandria, Egypt, in Africa, and Jeddah, Kingdom of Saudi Arabia (KSA), in Asia. To evaluate the system's performance, a variety of metrics such as FSO range, Signal-to-Noise Ratio (SNR), Peak Signal-to-Noise Ratio (PSNR), and the Structural Similarity Index Method (SSIM) are used. Furthermore, the findings from studying the impact of weather conditions reveal that, as the intensity of rainfall increases, the encrypted image experiences a reduction in its propagation range within the FSO channel. For example, under heavy rain (HR) conditions, the maximum FSO range for high-quality received encrypted images is 1055 m, which extends to 2290 m as rain intensity decreases (for light rain). In terms of the two cities, Jeddah, with its lower average rainfall intensity compared to Alexandria, allows the encrypted image to travel an additional 2400 m.