## 1 Introduction
GEO was the preferred technology used by satellite operators to execute their commercial satellite communication systems due to the advantages of fixed position relative to the Earth, coverage, and practically constant latency [8]. However, communication systems encounter multiple issues. The first issue is a bad user experience caused by high latency and channel attenuation. Second, it is inappropriate for mobile communications at high latitudes, not least because the elevation angle (the angle between the user's satellite and the horizon) of the user equipment is so narrow that terrain shelter should not be disregarded. Also, the system's coverage and capacity are constrained by a lack of orbital and frequency resources. Finally, the costs of satellite launch and operation are relatively high. Few missions were established between the GEO to ground. A Laser Communication Experiment (LCE) aboard the Japanese Engineering Test Satellite-VI (ETS-VI) was an example of the bi-directional laser communications link between the GEO and ground station [8; 9]. Even though medium Earth orbit (MEO) satellite communications have a shorter propagation delay than GEO (closer to the Earth than GEO satellites, with distances ranging from 2000 km to 20,000 km), more MEO satellites are required to continually cover the region. It also requires a higher transmit power than low Earth orbit (LEO) systems to overcome path loss and other atmospheric losses [10]. O3b/SES \"other 3 billion\" has launched over 15 MEO satellites to provide Ka-band communication services [11], while Laser Light Communications plans to create an all-optical worldwide MEO communications network [10; 11]. Unlike their GEO and MEO predecessors, LEO satellites orbit between 500 and 2000 km above the Earth's surface [12]. This low altitude translates into a variety of advantages, making LEO a suitable candidate for the satellite communication business, which include lower latency, reduced signal path loss, and lower production and launch costs. Prior demonstrations have successfully established FSO communication links between LEO to Ground Station. Examples include the Laser Utilizing Communications Equipment (LUCE) [13], Optical Payload for Lasecomm Science (OPALS), and Test LCTlinks facilitate optical communication capabilities from entities like the International Space Station (ISS) or LEO satellites to terrestrial stations [12]. The next section will further discuss these demonstrations and what they mean for future FSO communication installations employing LEO satellites. The potential applications of FSO communication systems extend beyond traditional point-to-point links and established orbital altitudes. As shown in Figure 1, FSO can facilitate various array of interconnected links across different communication paths, including (i) Satellite-to-Satellite Links, as it may involves connections between LEO to GEO Satellite, which is established through the Semiconductor-laser Inter-satellite Link Experiment (SILEX) and the European Data Relay System (EDRS) [14; 15]. Inter-satellite Links (ISLs) between satellites positioned in various orbits, including LEO, MEO, and GEO, are demonstrated by the Optical Inter-Orbit Communications Engineering Test Satellite (OICETS) and SILEX, with the Laser Communications Relay Demonstration (LCRD) showcasing optical inter-satellite links bridging LEO and geosynchronous orbit [16; 17]. In addition ground to deep space connections were demonstrated by the Lunar Laser Communication Demonstration (LLCD) and Laser Communications Relay Demonstration (LCRD), showcasing optical communication capabilities from terrestrial stations to lunar orbit and deeper space regions [7; 18; 19]. (ii) Air-to-Ground/Ground-to-Air Link establishes a bidirectional laser communication between aircraft and LEO satellites, enabled by the Optical Communications and Sensor Demonstration (OCSD) [20].