Abstract: The three-stage Clos networks remain the most popular solution to many practical switching systems to date. The aim of this paper is to show that the modular structure of Clos networks is invariant with respect to the technological changes. Due to the wavelength routing property of arrayed-waveguide gratings (AWGs), non-blocking and contention-free wavelength-division-multiplexing (WDM) switches require that two calls carried by the same wavelength must be connected by separated links; otherwise, they must be carried by different wavelengths. Thus, in addition to the non-blocking condition, the challenge of the design of AWG-based multistage switching networks is to scale down the wavelength granularity and to reduce the conversion range of tunable wavelength converters (TWCs). We devise a logic scheme to partition the WDM switch network into wavelength autonomous cells and show that the wavelength scalability problem can be solved by recursively reusing similar, but smaller, set of wavelengths in different cells. Furthermore, we prove that the rearrangeably non-blocking (RNB) condition and route assignments in these AWG-based three-stage networks are consistent with that of classical Clos networks. Thus, the optimal AWG-based non-blocking Clos networks also can achieve 100% utilization when all input and output wavelength channels are busy. 

Abstract: Future switching and interconnection fabrics inside switching equipment, high-performance computers and datacenters will require more throughput and more energy efficiency. Optical technology provides many opportunities of improvement of both features compared to electronic counterparts. This work defines a procedure to design the architecture of optical multistage switching networks. Modularity of the implementation is the primary concern, allowing for the construction of a genericsize fabric by the simple cascading of multiple stage-modules. In this paper we show in details the application of the approach to a family of banyan networks. The designed architecture can be exploited for various implementation technologies, as, for instance, integrated optics with micro-ring resonators, free-space optics with 2-D MEMS, networks on chip.