Optical satellite networks

Several nongeosynchronous satellite constellation networks providing broad- band access to end-users are currently under development. The use of multig igabit laser intersatellite links (ISLs) is the enabling factor for routing traffic through the space Segment and creating a global space-based optica l backbone network. Optical networking techniques based on wavelength divis ion multiplexing (WDM) ISLs and wavelength routing can allow by-pass of the transit traffic significantly simplifying routing decisions and minimizing processing delays. The paper examines the characteristics of these network s and investigates the applicability of various optical networking schemes based on single hop and multihop approaches. Single hop can be adopted in m edium earth orbit (MEO) systems consisting of 10 to 15 satellites whereas d ouble-hop schemes based on the Matrix lightpath allocation approach ate sui ted for constellations up to 100 satellites, covering the requirements of m ost of the proposed low earth orbit (LEO) systems. Multihop will be require d for some of the very large in number of satellites constellations, Statis tical multiplexing of the transported traffic over the ISLs appears to be a necessary condition to achieve an efficient utilization of the satellite r esources. Traffic routing has to take into account the impact of the varyin g range of the interorbit ISLs on the propagation delays. Although maximum leverage of the technologies developed for fiber optic WDM networks should be made, the technologies to be employed on board the satellites have to be space-qualified that may limit the applicability of some otherwise high-ef ficiency components.