Efficient routing in TDM optically interconnected multiprocessor systems

Routing performance of optical interconnection networks is limited by the complexity of switches and the connectivity of the networks. One way to overcome these limitations is to allocate the network bandwidth in a time-division multiplexed (TDM) way. More specifically, an appropriate subset of input-to-output connections can be established during a time slot and all possible connections are established within several time slots. That is, the network is reconfigured with time division multiplexing at an appropriate degree to emulate a fully connected network. Message routing can be done by selecting an appropriate time slot in which the required connection is established. However, the connection latency, which is equal to the multiplexing degree, may be prohibitive in a large network. To reduce the latency, only a subset of all possible connections needs to be established in the network with time-division multiplexing as required by applications. Network reconfiguration with TDM may be done either statically or dynamically. Static reconfiguration can be based on compile time analysis of an application program, while dynamic reconfiguration is controlled at run time. With time-multiplexing, several virtual networks are created in the time domain and the control overhead can be amortized over the number of virtual networks. Simulation studies have been carried out and results show that dynamic reconfiguration with TDM can effectively ease the communication bottlenecks.