Design of WDM Networks Exploiting OTDM and Light-Splitters

Wavelength routed optical networks allow to design a logical topology, comprising lightpaths and routers, which is overlayed on the physical topology, comprising optical fibers and optical cross-connects, by solving a Routing and Wavelength Assignment (RWA) problem. In this paper we extend the concept of lightpath to the one of Super-LightTree, which uses a simple bit level Time Division Multiplexing that can be directly implemented in the optical domain, to split the wavelength bandwidth over a tree among more than one traffic flow. This allows to design logical topologies with an increased number of logical links, thus reducing the average distance among nodes, i.e., the number of electro-optic and opto-electronic conversions, and the traffic congestion on logical links. At the same time, this reduces the number of wavelengths required to solve the RWA problem. Being the Super-LightTree RWA problem computationally intractable, we propose two heuristics for which we show that the number of wavelengths required to overlay a given logical topology on a given physical topology is reduced by more that 70% using Super-LightTrees.