Evaluation of a buffered time-wavelength cross-connect with sparse wavelength converters

In traditional optical wavelength routed networks, the entire bandwidth of a channel is not exploited. To achieve finer granularity in the wavelength domain and avoid the bottle-neck of electrical processing, optical time division multiplexing can be used on each wavelength. In such a Time-Wavelength-Switched Network, an optical cross-connect (OXC) would switch time-wavelength slots. Fiber delay lines (FDLs) and wavelength converters can be further utilized to improve the connection slot scheduling and decrease the connection blocking probability. In this paper, we consider an OXC equipped with FDLs and sparse wavelength converters (limited number of full range converters), under two different scenarios: shared per link and shared per cross-connect. We propose several cross-connect architectures and develop model formulations that can be used to solve the scheduling problem. We also incorporate FDL feedback provision in these architectures. Results show that using sparse converters along with FDLs could provide significant benefits.