Reconfigurable Bandpass Microwave Photonic Filter Based on Cascaded Second-Order CROWs

The microwave photonic filter (MPF) integrates photonic and microwave technology to carry out a variety of microwave band filtering applications. The advantages of the MPF in terms of flexibility have attracted a great deal of interest. Here, we propose and demonstrate a tunable and reconfigurable bandpass microwave photonic filter (BMPF) based on silicon-on-insulator (SOI). The BMPF is implemented by cascading two 2nd-order coupled resonator optical waveguides (CROW). Each microring resonator (MRR) of the CROW is designed with tunable coupling regions, enabling the BMPF with both wide frequency tunability and exceptional reconfigurability. Resonance wavelengths of the MRR is able to change to modify the central frequency, and coupling coefficients and resonance wavelengths of the MRRs is able to change to reconfigure the bandwidth. In experiment, the bandwidth of the BMPF is able to adjust from 0.63 to 2.88 GHz while its central frequency is modified between 4 and 36 GHz. The BMPF's rejection ratio is able to reach up to 38.65 dB during the adjustment. The achieved flexibly BMPF is possibly applicable to radar, sensor networks, microwave signal processing and communications.