A Time Domain Approach for Avoiding Crosstalk in Optical Blocking Multistage Interconnection Networks

Crosstalk in Multistage Interconnection Networks can be avoided by ensuring that a switch is not used by two connections simultaneously. In order to support crosstalk-free communications among N inputs and N outputs, a space domain approach dilates an NxN network into one that is essentially equivalent to a 2Nx2N network. Path conflicts, however may still exist in dilated networks. This paper proposes a time domain approach for avoiding crosstalk. Such an approach can be regarded as “dilating” a network in time, instead of space. More specifically, the connections that need to use the same switch are established during different time slots. This way, path conflicts are automatically avoided. The time domain dilation is useful for overcoming the limits on the network size while utilizing the high bandwidth of optical interconnects. We study the set of permutations whose crosstalk-free connections can be established in just two time slots using the time domain approach. While the space domain approach trades hardware complexity for crosstalk-free communications, the time domain approach trades time complexity. We compare the proposed time domain to the space domain approach by analyzing the tradeoffs involved in these two approaches. 0733-8724/94#04.00