Placements of shared wavelength converter groups inside a cost-effective permuted clos network

The Clos network is used for optical cross-connect and optical packet switch node, and has a large number of crosspoints if the number of wavelengths per fiber is more than that of fibers per node. In this letter, we propose a cost-effective permuted Clos network to reduce the number of crosspoints. We further investigate the placement of fixed wavelength converter groups (WCGs) shared inside the permuted Clos network. On the contrary, a normal Clos network has to be equipped with expensive tunable WCGs. The simulation result implies that equipment of about 50% WCGs achieves similar performance as the full wavelength interchanging node does.