From Small to Large: Clos Network for Scaling All-Optical Switching

To cater to the demands of rapidly growing Internet traffic, backbone networks need high-degree reconfigurable optical add/drop multiplexers (ROADMs) to simultaneously support multiple pairs of bi-directional bers on each link. However, the traditional ROADM architecture based on the Spanke network is too complex to be directly scaled up to construct high-degree ROADMs. Because of this, Clos networks are considered as promising alternatives for constructing large-scale ROADMs. In this article, we look at a next-generation Clos-based ROADM architecture and show that it indeed provides better blocking performance with lower element and fiber complexities compared with a traditional Spanke-based (i.e., fully connected in the backplane) ROADM architecture. We also compare insertion loss, power consumption, and system cost of these architectures, which further illustrates the potential of the Clos-based ROADMs.