On the use of terminal and inline conversion in planar optical interconnection networks

Optical wavelength converters (WCs) are used in the design of most optical interconnection networks to improve blocking performance. Typical network architectures make use of WCs at the terminal of the network (i.e., at the input and/or output ports). Recently, inline conversion has been introduced where WCs are deployed and shared between the stages of the network. Sharing conversion among stages can lead to architectures with reduced complexity and hence lower cost. However, sharing inline conversion requires crossovers of interstage links to enter and exit the shared inline converters. As a result, inline conversion can be difficult to implement in planar switching networks with no crossover between interstage links. In this paper, we study, for the first time to the best of our knowledge, the use of combined terminal and inline WCs in planar optical interconnection networks. In particular, we show that terminal conversion has limited scalability even when fixed-range WCs are used. Accordingly, we propose a new design approach that improves scalability while preserving the noncrossover property of planar interconnection networks. It is shown that all conversion processes in the new design are independent of the number of wavelengths in the network, and hence high scalability is achieved.