An evaluation of the time domain approach for crosstalk free communication in photonic switches

First-order crosstalk in Multistage Interconnection Networks (MINs) can be avoided by ensuring only one input of each switch is active at a given time, in other words, no two connections can use the same switch simultaneously. A space domain approach dilates an N-by-N network into one that is essentially equivalent to a 2N-by-2N network [1]. The time domain approach proposed in [2] extends the "dilation" concept from space to time to avoid crosstalk by establishing the connections sharing the same switch in different time slots. This paper studies the tradeoffs of these two approaches in two different MINs, namely, Banyan and Benes, under both individual and stage switch control. Theoretical analysis showed that in a Banyan with stage control, the set of N-by-N permutations whose connections can be established crosstalk free in two time slots using the time domain approach is more than the set of permutations that can be realized in one time slot using the space domain approach. In addition, simulation results showed that given the same set of one-to-one or one-to-many connections, the number of time slots needed by the time-domain approach is less than twice of that needed by the space-domain approach.