Increasing Capacity of the Clos Structure for Optical Switching Networks

Abstract

Clos networks are widely used as an efficient physical structure due to their nonblocking property. However, in strictly nonblocking networks composed of ordinary optical switches (switches with equal numbers of input/output ports), we find that a substantial fraction of ports can remain unused, which decreases the efficiency of Clos networks. This inefficiency comes from the implicit restriction that the two ''sides'' of switches have distinct roles, i.e., ports on one side are connected to endpoints (terminals) while those on the other side are linked to switches. Removing this restriction brings greater freedom in structuring the network and can increase the capacity without losing the strictly nonblocking property. This paper proposes a new physical structure and provides several theorems that address network capacity. Numerical experiments show that our structure increases the capacity by up to about 30%.