All-Optical Microwave Photonic Filter Based on Electrooptic Phase Modulator and Detuned Wavelength Division De-Multiplexer

We theoretically and experimentally investigate a microwave photonic filter with an electrooptic phase modulator and an array waveguide grating, which acts as a detuned two-channel wavelength division de-multiplexer. In the experiment, a microwave notch filter with a QN factor of 236 and a rejection ratio of 31 dB is obtained by introducing microwave subtraction directly in optical domain. The parameter QN factor is defined to measure the rejection selectivity of a microwave notch filter and corresponding to the Q factor in a microwave bandpass filter. A microwave bandpass filter with a Q factor of 245 and a rejection ratio of 38 dB is also obtained. The relationship between the Q factor of the microwave bandpass filter and the QN factor of the microwave notch filter is measured. The variations of Q and QN versus the detuning of the tunable optical bandpass filter (TOBF), which is incorporated in the recirculating delay line loop, is also measured and discussed. Simulation results about the influences of the wavelength division de-multiplexer and TOBF on the microwave frequency response are also presented and analyzed.