Buffered time-wavelength cross-connects: Architectures and performance evaluation

An all-optical approach to reduce the speed mismatch between electronic sources and high-speed wavelength channels is to time-division multiplex low-capacity circuits onto each wavelength. In such a Time-Wavelength-Switched Network (TWSN), the optical crossconnects (OXCs) are configured to switch time-wavelength-slots within the network. The OXCs can be deployed with a bank of fiber delay lines (FDLs) to improve the connection slot scheduling and decrease the connection blocking probability. In this paper, we consider the two broad scenarios of sharing a bank of FDLs: shared per output link (SPL) and shared per crossconnect (SPC). We present several OXC architectures and develop graph formulations that can be used to optimally solve the scheduling problem. We also incorporate wavelength conversion and feedback in these architectures and study the impact of various FDL configurations on a crossconnect’s performance. Results using numerical simulations show that the FDL configuration does in fact affect the performance of the OXC. We also evaluate the performance of an OXC equipped with an FDL bank for both the SPL and SPC scenarios by considering sparse wavelength converters (limited number of full range wavelength converters). Results show that using sparse converters along with FDLs could provide significant benefits.