AWG-based Non-blocking Clos Networks

TL;DR

This paper demonstrates that AWG-based three-stage Clos networks can be designed to be non-blocking and scalable, maintaining classical properties while optimizing wavelength usage in WDM switching systems.

Contribution

It introduces a wavelength partitioning scheme and recursive wavelength reuse method, ensuring non-blocking and scalable AWG-based Clos networks.

Findings

Achieves 100% utilization in AWG-based non-blocking Clos networks.

Provides a wavelength partitioning scheme for scalability.

Proves the equivalence of AWG-based and classical Clos network properties.

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.