Nonblocking optical MINs under crosstalk-free constraint

Vertical stacking is a novel scheme in creating nonblocking multistage interconnection networks (MINs). Available results indicate that under the crosstalk-free constraint, the hardware cost is high for a strictly nonblocking optical MIN based on the scheme. Packing strategy is a commonly used routing strategy for reducing network hardware. In this paper, we look into the nonblocking conditions for crosstalk-free optical MINs under packing strategy. It is shown that packing strategy is very efficient in reducing the hardware cost of a nonblocking optical MIN under the crosstalk-free constraint. The results in the paper will be useful in designing optical MINs.