Cascaded microring resonators for crosstalk reduction and spectrum cleanupin add-drop filters

The role of cascaded filters fort spectrum cleanup and crosstalk reduction in add-drop filters is addressed experimentally for microring resonator cro ss-grid technology. The fabricated devices consist of glass microring reson ators 10 mu m in radius vertically integrated above a cross-grid waveguide array. Sharper linewidth rolloff and flattened passband responses are obser ved. The ratio of 15 to 3 dB bandwidth of a cascaded double filter is reduc ed by a factor of 3 compared with the single-filter case. Because of the ve ry small dimensions of the resonators, the use of multiple biters to improv e the spectral response consumes negligible chip space.