<p>An architecture is described for a switch that is suitable for future large-scale packet-convergence networks. This optically interconnected multi-stage ATM switch architecture (OPTIMA) is a multi-stage switch architecture, and an OPTIMA switch can perform two types of QoS switching. The architecture is scalable - switching capacity can be expanded by interconnecting identical unit switches, without causing degradation in switching performance, because of the switch's route-control mechanism for high-priority traffic and its self-load balancing mechanism for low-priority traffic. Analysis and simulation demonstrated that an OPTIMA switch has high-performance switching capability. Also described is the hardware architecture for the 640 Gbit/s OPTIMA switching system. The OPTIMA switch is suitable for use as a backbone node in future packet-convergence networks.</p>