Scalability of wavelength division multiplexed optical passive star networks with range limited tunable transceivers

The number of stations attached to a single optical passive star is limited by current state of the art in optical technology. Also, the wavelength range of tunable optical transceivers is limited by current technology. Many high performance computing applications require the use of large size regular topologies for communication between computing nodes. Scalability of passive star networks built with these two limitations becomes an important issue for building larger networks. This is the subject of our study in this paper. In a previous related work we explored the design issues for networks built on a single passive star employing transceivers of a limited tuning range. Here we extend that study by considering the problem of connecting several optical passive stars, each embedded with a given virtual topology, to create larger aggregate networks. The design issues are analyzed and a number of design rules are proposed for building such aggregate networks. We study the scalability of embedded optical passive stars by considering the most commonly employed virtual topologies-complete graph, mesh and hypercube.