Tunable band-pass microwave photonic filter with ultra-wide bandwidth and frequency tuning range based on cascaded tunable high- <i>Q</i> silicon micro-ring resonators

This work presents a tunable band-pass microwave photonic filter (MPF) with good overall performance based on two cascaded high- Q silicon micro-ring resonators (MRRs). A phase compensation technique based on unbalanced filtering is proposed to overcome the out-of-band RF rejection ratio degradation due to phase perturbation caused by adjacent MRR resonance orders. The experiment results show the RF rejection ratio can be enhanced by about 23.70 dB. Also, a bandwidth compression method is developed to break the microwave photonic filter’s bandwidth limitation, which is constrained by the optical bandwidth of the used micro-ring resonators. Moreover, combined with tunable over-coupled and under-coupled working regimes of the micro-ring resonators, an ultra-large bandwidth tuning of 0.51–18.61 GHz is obtained. Furthermore, by simply changing the resonance frequencies of the two micro-ring resonators simultaneously, a large frequency tuning range of 0.84–41.06 GHz is achieved. These proposed approaches enable a band-pass MPF with simultaneous wide bandwidth reconfigurability, broad frequency tuning range, and enhanced out-of-band RF rejection. The demonstrated reconfigurable band-pass microwave photonic filter could have great potentials in diverse microwave photonic signal processing systems.