Compact tunable microwave photonic filters based on cascaded microring resonators

We propose and experimentally demonstrate a simple photonic approach to achieving tunable and reconfigurable bandpass microwave photonic filters (MPFs) based on cascaded microring resonators (CMRRs). The optical spectrum of the silicon CMRRs could offer two bandpass responses to separately filter the optical carrier and one of the sidebands generated by the phase modulation. Thus we could achieve a bandpass MPF. Moreover, as the central frequencies and bandwidths of the two bandpass responses can be tuned by simply adjusting the voltages applied on one MRR, tunable and reconfigurable MPFs could be successfully achieved. A proof-of-concept experiment illustrates a central frequency tuning range from 19 GHz to 40 GHz, and a wide bandwidth tuning range from 5.5 GHz to 17.5 GHz.