Optical switch matrix with failure protection

The present invention relates to a multi-stage non-blocking optical switch matrix having failure protection. The optical switch includes failure protection in the form of a capacity to provide an alternative route for any connection, including rearrangeable protection to provide alternative routes for multiple connections, as required, and to permit replacement of any failed submatrix module without service interruption. The present invention provides both internal and external protection from system failure in a multi-stage optical switch matrix by providing interconnected modules in a first external stage. The modules are interconnected by rerouting ports for redirecting signals from an input/output port on one external switch module to another external switch module. Protection is further provided through a center stage having a number of center stage switch modules, fully connected to the external modules, equal to twice the number of input/output ports and rerouting ports on an external module. With this structure, a failure at any point in the switch sub-matrices can be avoided, so that rearrangeable non-blocking performance can be obtained. In the case of a failure, a signal can be rerouted, additional signal paths can be rearranged, and faulty modules can be removed and replaced without affecting non-blocking switch performance.