## 1 Introduction
Consequently, it is relatively easy for jammer to determine the operational wavelength of dedicated FSO communication links; (2) To mitigate the impact of fading effects such as AT and PE on FSO systems, it is common practice to increase the receiver aperture Field-of-View (FoV) [22]. Enlarging the receiver FOV also makes it feasible to jam optical beams. Many terrestrial applications, such as storage area networks and enterprise connectivity, require aperture averaging and a wide FoV to mitigate the effects of building sway, seismic activity, or physical obstruction, even when the transceiver is stationary [23]. In the satellite communication, a wider FoV is particularly crucial due to the mobility of transceivers and their significant distance from each other [24]; (3) In FSO communication, which belongs to LoS communication, communication antennas are typically installed at the top of buildings along streets or in elevated and easily accessible locations to avoid obstructions [21]. Consequently, malicious jammers may easily identify the locations for jamming. Researchers have proposed analytical models and methods to mitigate malicious jamming, analyze its impact on the communication performance of FSO systems. In [25] the authors investigated the impact of pulse jamming on FSO systems, focusing primarily on the system's Bit Error Rate (BER) and Outage Probability (OP). The study explored the impact of jamming on the system using different receiver apertures in [25]. In [24], an examination was conducted to analyze the impact of jamming on FSO systems, including both single-input single-output (SISO) setups and multiple-input single-output (MISO) configurations. The study assessed the efficacy of these systems by examining the BER and OP in the presence of negative exponential atmospheric turbulence. In [26], A Buffer-Aided Relaying Approach is employed to mitigate jamming in FSO cooperative networks. In [27], [PERSON] et al. explore the consequences of jamming instigated by a malicious UAV on the performance of an FSO communication system. They utilize a trustworthy UAV as a relay and incorporate an intelligent reflecting surface to improve signal coverage. However, in all of these works, research on FSO jamming and mitigation techniques is primarily focused on single-hop systems. Furthermore, while literature has conducted jamming mitigation analysis using MISO for single-hop systems, SIMO is relatively easier to implement compared to MISO. Therefore, this prompts us to delve into examining the ABER of dual-hop FSO systems supported by RIS in the presence of jamming. Additionally, we aim to evaluate the improvement of ABER under different jamming scenarios utilizing SIMO technology. In summary, the key contributions of this study can be outlined as follows:  
* The closed-form expression of the PDF of the legitimate channel in the RIS-assisted dual-hop FSO system is derived. Additionally, The PDF of the UAV jamming receiver and the RIS channel is derived. Novel closed-form expressions for the end-to-end ABER in both jamming scenarios have been derived based on the obtained link statistics. These expressions are derived considering the impact of non-Gaussian additive noise, which varies depending on the jammer's location. * The closed-form PDF of the legitimate channel in a 1 \(\times\) N SIMO-FSO system and the channels under various jamming scenarios were derived using Mellin transforms to mitigate the impact of jamming. Analytical expressions for the end-to-end ABER in the two jamming scenarios were subsequently provided. * A comprehensive system ABER analysis is conducted in terms of atmospheric turbulence strength, N (the number of receiving apertures), the probability of jamming and different RIS positions. Moreover, some useful insights are obtained. The rest of the paper is organized as follows. The FSO system, along with the jammer and optical channel models, is introduced in Section 2. In Section 3, The closed-form expressions for ABER in the SISO System are derived.