Low-Latency Interconnect Optical Network Switch (LIONS)

Abstract

This chapter discusses experimental demonstrations of a category of optical switches named low-latency interconnect optical network switches (LIONSs). These switches are based on wavelength routing in arrayed waveguide grating routers (AWGRs). There can be both active and passive implementations for intra- and inter-rack communication in data center and HPC networks. In active LIONS architectures, the switching operation is completely performed in optical domain on the fly without any buffering at the switch. In passive LIONS architectures, the switching operation is performed both in electrical and optical domains. In both passive and active implementations, the unique features of wavelength routing and multiplexing in AWGR allow to build a very low-latency and high-bandwidth switch. First, we demonstrated an active LIONS with loopback buffer scheme (LB-LIONS) and compared the experimental results with networking simulation results. This comparison allowed to validate the correctness of the simulation framework and results. Second, by introducing an all-optical token scheme for optical contention resolution and an all-optical negative acknowledgment technique, we experimentally demonstrated alternative active switch architectures (TOKEN-LIONS and TONAK-LIONS) capable of handling contention resolution in the optical domain while removing the needs of using the loopback buffer as well as the centralized control plane. For what concerns passive LIONS architectures, we carried out experiments for hierarchical all-to-all interconnection between data center servers, racks, and clusters with flexible bandwidth allocation to reduce the congestion created by hot spots in the network.