## 2 Related Work and Problem Description
### Low Earth Orbit Satellite Routing and Optical Laser Interconnection  
In the past few decades, both domestic and international researchers have conducted extensive studies on satellite routing algorithms for Low Earth Orbit satellite constellations, making significant contributions to the continuous improvement and development of satellite routing. Early routing schemes can be mainly classified into two categories: virtual topology and virtual nodes. Virtual topology involves the temporal virtualization of the network structure, discretizing the orbital motion into a series of time slots, with each time slot referred to as a snapshot. Within each snapshot, due to the short period, the topology of the satellite network is considered stable or quasi-static, with changes occurring only at the junctions of snapshots. In each snapshot, different satellite nodes are interconnected, indicating \begin{table}
\begin{tabular}{c c c} \hline
**Classification** & **Orbital Altitude** & **Role** \\ \hline LEO & 500–1500 km & Earth observation satellites, space stations, broadband network services \\ MEO & 1500–35,786 km & Global short message communication, international search and rescue services \\ HEO & Remote location higher than 36,000 km & Strategic and theater surveillance of the Arctic region \\ GEO & 35,786 km & Positioning, navigation, timing services, “bent-pipe” communication, meteorological observation, and other services \\ \hline \end{tabular}
\end{table} 
Table 1: Satellite classification table based on orbital altitude. the establishment of communication links for data transmission. It is worth noting that each snapshot contains replicas of all satellite nodes, consuming a significant amount of onboard storage space. With the rapid increase in the number of satellites and the rapid expansion of constellation size, the interconnections between satellites have become more frequent, increasing the pressure on onboard storage and maintenance, leading to an increase in onboard task burden. This poses significant challenges and pressures on resource-constrained Low Earth Orbit small satellite networks. Reference [19] proposes a region-based satellite routing algorithm. Its core involves dividing satellite regions based on topological properties and implementing a distributed subdomain routing mechanism. Satellite nodes establish and maintain routing tables within domains and inter-domain routing tables. When there are topological changes, only a few intra-domain routing tables need to be updated, while inter-domain routing tables are updated only when inter-domain neighbor relationships change. This approach enables fast rerouting in dynamic networks. Virtual nodes involve virtualizing the satellite network into fixed-coordinate virtual nodes, assuming that the entire Earth's surface can be covered by the Low Earth Orbit satellite constellation. The logical positions within the constellation remain unchanged, and when a satellite is relocated, its position is inherited by the nearest satellite. Specific routing decisions are calculated by relevant controllers, but a potential issue that arises with a substantial increase in traffic is the occurrence of link congestion, resulting in a decline in algorithm performance [20]. In the context of virtual node technology, regarding the issue of link failures in satellite networks, [PERSON] et al. proposed a dual-layer satellite network routing algorithm based on priority and fault probability. This algorithm considers business classification and link failure probabilities to meet various Quality of Service (QoS) requirements for different services [21]. Inter-satellite links (ISLs) play a crucial role in satellite networks, with two methods of communication: microwave and laser communication.