Nonblocking self-routing switching networks

We investigate a class of binary self-routing switches, characterized by the way they function. These switches can describe for example the functional aspects of some recently developed self-routing photonic switches. First we show that, within this class, essentially we only need to consider the four possible types of fixed-directory routing switches. Then we determine exactly the minimum number of switches contained in an M-input N-output wide-sense nonblocking self-routing network composed of switches from this class