Optical WDM networking in broadband satellite constellations

Laser intersatellite links (ISLs) represent the enabling technology for implementing broadband satellite constellations that use the space segment for networking. Constellations with laser ISLs have the following main properties: The constellation consists of N satellite nodes configured in orbital rings that move geographically very fast ISLs between the satellites in the same and adjacent orbits are maintained continuously. The intra-orbit ISLs range remains constant during the constellation propagation, whereas the inter-orbit ISLs range changes periodically in a deterministic fashion. As a consequence, although the geographic topology of the constellation changes continuously, the network physical topology (i.e. connectivity) remains fixed. Such networks can be considered as single fiber networks with continuously varying node sourced/sunk traffic. The latter constitutes a major issue to be addressed when modeling constellations because the rate of change is very fast. As an example, a satellite may be required, at some instances in time, to process multigigabit traffic above hot spots, whereas a few minutes later it may be above an ocean area with negligible uplink load. The connection traffic changes are even more intense since they reflect the geographic coverage changes of both the source and the destination satellites.