Expanding the switching capabilities of optical crossconnects

Optical-switching technologies exhibit many characteristics that the electronic-switching technologies do not have. One such characteristic lies in switching states. An electronic crosspoint, having open and close as its two switching states, only allows one traversing signal. But an optical-switching crosspoint, such as a directional coupler or a microelectromechanical systems mirror, usually allows two traversing signals. This paper studies how to exploit the characteristic to expand the switching capabilities of an optical switch, and shows new ways of building more crosspoint-efficient rearrangeable nonblocking switches. We show that an optical 2n×2n rearrangeable nonblocking switch can be created by cascading only two n×n optical crossbars.