Optical Switching Using Cascaded Generalised Mach-Zehnder Switches

Optical switches based on planar lightwave technology offer stable and robust means of achieving space-division switching. One form of integrated switch that shows some promise is the generalized Mach-Zehnder optical switch. This switch normally comprises two multimode interference (MMI) couplers connected by an array of phase shifters. However, such a switching structure does not possess the non-blocking characteristics required in most communication applications. In this paper it is shown that, if the architecture is extended to include additional MMI couplers, then the resultant cascaded generalised Mach-Zehnder switch can provide improved blocking characteristics.