# Fuzzy Logic-Based Performance Enhancement of FSO Systems Under Adverse Weather Conditions
## 1 Introduction
### Existing Works  
To enhance the FSO transmission capacity, multiplexing techniques like orthogonal frequency multiplexing (OFDM), wavelength division multiplexing (WDM), and OCDMA are utilized in FSO systems [8; 9]. High-data-rate FSO systems are affected by various impairments that reduce transmission signal quality. These impairments have been reported to increase the risk of an optical transmission system error, but the impact is not severe over considerably long distances [10]. The results reveal that 1550 nm FSO wavelengths are less affected by atmospheric attenuation. Furthermore, the 1550 nm wavelength can support a 2.5 Gbps error-free transmission in clear weather conditions with BER = \(10^{-9}\). Short link-reach between the transmitter and receiver can further optimize the FSO system transmission parameters or components [11]. Spectral amplitude coding optical code-division multiple-access (SAC-OCDMA) codes are employed in free-space optical communication systems to mitigate multiple-access interference. Different categories of codes have been suggested, and their effectiveness has been assessed in diverse weather circumstances. Successful transmission of high data rates has been achieved, where the performance is influenced by the selection of the detection method and receiver [12; 13]. In [14], the authors theoretically and experimentally studied the spectral attenuation of FSO communication systems operating across visible and near-infrared (NIR) wavelengths under fog and smoke conditions, using a controlled laboratory atmospheric chamber of 5.5 m. A new wavelength-dependent empirical model was proposed, demonstrating closer agreement with measured attenuation data than conventional models, such as models of [PERSON] and [PERSON]. Furthermore, the study provided insights into optimal wavelength selection for FSO systems operating in dense fog. In [15], the authors evaluated the performance of FSO systems under different line-coding schemes, including return-to-zero (RZ), carrier-suppressed RZ (CSRZ), and non-return-to-zero (NRZ)at a data rate of 2.5 Gbps. A 4 \(\times\) 4 multi-input-multi-output (MIMO) FSO system was also investigated, showing that a combination of MIMO and RZ modulation could significantly extend the propagation distance of the FSO link. In [16], a performance comparison of PSO systems using pulse-position modulation (PPM), RZ, and NRZ coding schemes was carried out. The study further analyzed the impact of varying transmitted power levels, concluding that PPM modulation achieved the greatest improvement in BER performance with increased transmitter power compared to other schemes. While the aforementioned techniques focus on enhancing transmission efficiency and coding robustness, another line of research explores the use of intelligent control methods to mitigate environmental effects in real time. Among these, fuzzy logic has emerged as a powerful tool for adaptive decision-making in optical systems, particularly under uncertain and variable weather conditions. Fuzzy logic has been used for various aspects in optical communication systems [17]. One application is to evaluate the different sensing resource allocations in fiber-optic communication networks [1]. Similarly, it is used in the integrated routing and wavelength assignment method for Optical Network-on-Chip (ONoC), where fuzzy logic is used to consider multiple performance factors such as OSNR, traffic distribution, waiting delay, and wavelength utilization [2]. Fuzzy logic is also used in mitigating the adverse effects of weather conditions on FSO communication (FSOC) systems by implementing an adaptive fuzzy logic controller (AFLC) for laser beam alignment and tracking. Additionally, fuzzy logic is utilized in the creation of effective optical logic systems, where light emitters of different colors are used as fuzzy variables for logical information processing [18].