Wideband and Continuously Tunable Microwave Photonic Phase Shifter Based on an Active InP/InGaAsP Microring Resonator

We propose and experimentally demonstrate a wideband and continuously tunable microwave photonic (MWP) phase shifter based on an active InP/InGaAsP microring resonator (MRR) incorporating two semiconductor optical amplifiers (SOAs) and a phase modulator (PM). By tuning the gain provided by the SOAs, the loss in the ring cavity can be compensated and the extinction ratio of a resonance is decreased to nearly 0 dB, while maintaining the optical phase shift range of nearly 2π within the resonance bandwidth. A theoretical analysis is performed. The key advantages of using the proposed MRR to achieve a microwave phase shifter are that the power variation at the output of the phase shifter is minimized during phase tuning and the microwave phase can be continuously tuned by tuning the PM in the MRR theoretically. The proposed phase shifter is experimentally demonstrated. A continuously tunable microwave phase shift over a phase tuning range of 291° from 5 GHz to 20 GHz by tuning the injection current to the PM is implemented. The microwave power variation is lower than 5 dB.