Efficient Sharing of Fixed Wavelength Converters in Clos-Type Wavelength Interchanging Cross Connects

Several structures of sharing wavelength converters (WCs) have been proposed for wavelength interchanging cross connects, including share-per-node (SPN), share-per-link (SPL), and share-per-wavelength (SPW). Among them, SPN has the highest sharing efficiency but at the expense of a complex switch fabric. In this paper, we investigate the Clos-type SPN and SPL structures and propose a novel structure, which is termed as C-SPW, to share fixed WCs based on the Clos network. The comparative simulations show that the sharing of fixed WCs in C-SPW can achieve similar drop probability (DP) with the sharing of tunable ones in Clos-type SPN under synchronous uniform traffic. The reason is that the fixed WCs in C-SPW can be accessible by all incoming packets, instead of a subset of them. Furthermore, an analytical model is derived to calculate the DP and converter utilization rate when C-SPW is operated in a synchronous mode under uniform traffic. The proposed analytical model fits well with the simulation results.