Laser Intersatellite Link Range in Free-Space Optical Satellite Networks: Impact on Latency

Laser communication terminals for establishing laser intersatellite links (LISLs) are in high demand by companies, such as SpaceX and Telesat, who want to equip their satellites with LISLs to realize free-space optical satellite networks (FSOSNs). Such terminals offer LISLs with ranges spanning from 4500 to 45,000 km. How does LISL range affect network latency in FSOSNs? To investigate this effect, we employ the satellite constellation for Phase I of SpaceX's Starlink, and examine six different LISL ranges for satellites in this constellation in three different scenarios for long-distance intercontinental data communications. We observe that the satellite connectivity and thereby the network connectivity improves with an increase in the LISL range as more and farther satellites become available within the LISL range of a satellite. A higher LISL range leads to better shortest paths offering lower average network latency. Furthermore, improvement in average network latency with increase in LISL range is seen in all scenarios.