Microwave-photonic interferometer based on FLRD for simultaneous sensing of loss and temperature

The optical carrier-based microwave interferometry (OCMI) system for simultaneous loss and temperature measurement is proposed and demonstrated experimentally, which is implemented with the fiber loop ringdown (FLRD). By multiplexing the phase spectra of low and high radio frequencies (RF), the independent sensing of loss and temperature is achieved. With the advantages of robustness and immunity to crosstalk, the sensitivity of transmittance and temperature are at -0.4942 rad and -14.05 kHz/degrees C. The stability and tunable sensitivity of the sensing system are investigated and demonstrated by the numerical analysis and experiments. The principle of phase-shift FLRD is ameliorated by numerical investigation, verified by the experiment results. The independent sensing of loss and temperature is achieved by recording the phase spectra of low and high radio frequencies (RF), where the insensitive points play a vital role and provide a potential approach for multiplexing.