## 1 Introduction  
The progressively demanding criteria of fifth-generation (5G) mobile communications sparked the deployment of high-throughput short-range links and mesh topologies to cater to the increased user capacity and to reduce energy consumption [1, 2]. The sub-10 GHz radio frequency (RF) band is almost exhausted and strictly regulated. Consequently, scientific research is moving towards the incorporation of millimeter and nanometer wavelengths [1, 2]. Optical wireless communications (OWC) operate similarly to fiber optics by modulating a coherent laser beam that propagates point to point and by line of sight [2, 3, 4, 5, 6]. Free-space optical (FSO) technology has excellent backhauling capabilities of ultra-fast transfer of traffic between antenna towers and small cells [2, 3, 4, 5, 6]. FSO also mitigates the last mile problem, i.e., congestion in the component linking the user to the Cloud/Internet [2, 3, 4, 5, 6]. Satellite communications (SatComs) cover a large portion of the Earth, including remote locations, and enable a vast variety of forecasting and broadcasting applications [6, 7]. Yet, the cost of designing and manufacturing them is substantial, satellite debris causes \"space pollution\", and a satellite constellation requires numerous satellites in addition to very quick handovers to guarantee visibility and continuity [6, 7]. Especially for high-speed SatComs, FSO systems have exhibited great potential due to their easy installment (<30 min), their operation with low initial expense and maintenance, no licensing requirements like RF systems, and their secure connections due to their large antenna gains,allowing several FSO links to be deployed in parallel and in proximity [2; 3; 4; 5; 6]. Nevertheless, they demand advanced pointing, acquisition, and tracking components. The process of creating a private encryption key between two parties is known as quantum key distribution (QKD) [7]. Fundamentally, QKD is an optical technology that can supply encryption keys for any two locations connected by an optical link [7]. The application of QKD over optical fiber, on the other hand, is restricted by exponential fiber losses. In this setting, QKD over satellites is becoming more popular. The capacity to put up robust optical links and guarantee a minimal quantum bit error rate (QBER) by overcoming numerous transmission obstructions is critical to the success of QKD over satellites [7]. However, the FSO beam is susceptible to various problematic atmospheric phenomena, i.e., absorption, scattering, cirrus clouds, and turbulence [2; 3; 4; 5; 6]. Physical obstructions, geometric losses, and the blockage of the link caused by cloud occurrence are some of the difficulties [8; 9]. For mitigating the cloud occlusion, site diversity can be used [8]. Received irradiance scintillation is created from rapid changes in wind speed, pressure, and temperature, which in turn induce changes in the refractive index [10; 11; 12]. The impact of scintillation depends primarily upon the time of day, the elevation angle of the link, and the altitude of the station [10; 11; 12]. In the daytime, at low elevation angles and low-altitude stations (denser atmosphere), turbulence is more extreme [10; 11; 12]. In [10; 11; 12], the power allocation (PA) problem is investigated for optical satellite downlinks under weak turbulence and solved using a Karush-Kuhn-Tucker (KKT), water-filling-inspired algorithm. However, the reported methodology depends on the knowledge of the system and channel model. In [13; 14], a radio-on-FSO (RoFSO) wavelength multiplexing scenario is considered where the channel model is assumed unknown. The developed model-free primal-dual deep learning algorithm (PDDL) strongly converges to the precise solution derived from the model-based algorithm. In both studies, however, synthetic data were employed while the optical satellite-to-ground scenario was not explored.