Fault tolerance study on large scale Benes switches

In this paper, we present methods to enhance the fault tolerance of large-scale optical switches through innovations in architecture and control logic design. A large-scale switch is constructed from a network of 2×2 optical switch elements (SEs). Classic switch network architectures, such as the Benes, are not designed with fault tolerance in mind. There are three major contributions in this paper: 1) we developed an analytical method, referred to as the probability accumulation method, to calculate the average connection blocking probability in a faulty switch network; 2) we provided a fault-aware routing algorithm to effectively circumvent connections from defected SEs in a dilated Benes switch; and 3) we improved the connectivity pattern of the Benes network to further reduce the blocking probability, especially when the SE failure rate is low.