Cascaded Optical Microring Resonator Based Auto-Correction Assisted High Resolution Microwave Photonic Sensor

We propose a new microwave photonic (MWP) sensor based on cascaded silicon-on-insulator microring resonators (MRRs) with the incorporation of a seamless auto-corrective MWP sideband processing scheme to achieve multi-parameter sensing with high sensitivity and high-resolution. By using two MRRs with different waveguide widths, we take advantage of the resulted dual resonances which are not only distinct, but also exhibit different sensitivities. A multi-parameter sensing model can thus be established by deriving the difference in the sensitivity slope of the resonance notch shifts. The technique enables dynamic MWP sideband processing to actively compensate for variations in the optical resonances where limited extinction ratios in the optical domain are mapped instantaneously into ultra-high rejection ratios in the RF spectrum. We then demonstrate the cascaded optical MRR based auto-correction assisted MWP sensor for the environmental sensing of both humidity and temperature variations. Besides negligible hysteresis effect, the humidity sensitivity of the sensor reached over 291 MHz/%RH for both MRRs, which is over 3.5 times that of the microdisk-based humidity sensor. With the aid of the seamless auto-correction mechanism, the dual RF notches with albeit different but very high sensitivities are well maintained over 50 dB of rejection ratio, thus preserving a consistently high resolution throughout the whole sensing range. Additionally, a complete sensing model for measuring both parameters is also established and verified experimentally. Results show the capability of the proposed high-resolution sensor scheme for independent measurand detection for multi-parameter sensing applications.