Low-earth orbit free-space optical communication networks using all-optical relays

Low Earth Orbit (LEO) satellite mesh networks provide a promising avenue toward low-latency free-space optical communications. Most free-space laser communication systems rely on point-to-point links that require optical-to-electrical-to-optical (OEO) conversion to receive and regenerate optical signals at each node within the communication system. OEO regeneration processes introduce both latency and additional power consumption while limiting the data throughput of the system as the number of nodes increases. These drawbacks render OEO-based links nonideal for use in LEO satellite mesh networks of which large amounts of data and limited satellite resources demand several high data capacity nodes to provide more frequent connectivity to ground stations around the globe. All-optical relays (AORs), in which an optical signal is received, passed through a fiber amplifier, and immediately transmitted to another node in the system, bypass OEO regeneration and yield significantly reduced latency in long-haul fiber communication systems. Moreover, wavelength division multiplexed (WDM) versions of AOR systems facilitate increased data capacity without a significant increase in power consumption. In this work, we adapt standard optical fiber telecommunications analysis used for terrestrial long haul all-optical relays to LEO free-space laser satellite communication systems. Within this framework, we investigate the impact of effects such as nonlinearities and jitter on span length, channel capacity, and AOR amplifier requirements, and outline a path toward realizing low-latency LEO AOR satellite mesh networks.