Multi-Point and High-Sensitivity Hydrogen Sensor Based on OFDR and Fiber-Tip Microcavities

A high sensitivity, multi- area hydrogen sensing technology is proposed. It employs Pd-coated Fabry-Perot (FP) microcavities as high-sensitivity hydrogen sensing units, and uses optical frequency domain reflectometry (OFDR) to measure the spectra of multiple FP microcavities at the same time, so as to achieve multi-point and high-sensitivity hydrogen concentration measurement. In the demonstration experiment, five FP hydrogen sensing units are prepared based on nanofabrication technology. With OFDR, the spectra of FP cavities at 0-4% hydrogen concentration are measured, achieving a hydrogen sensing with a sensitivity of ∼1 nm/%, and the response time of 12.6 s. The scheme retains the advantages of high sensitivity and fast sensing of the conventional FP hydrogen sensor based on wavelength division multiplexing (WDM), and effectively solves the problem of multiplexing deficiency of the WDM-based sensor due to the bandwidth limitation of light source. It can realize the hydrogen leakage monitoring of multiple areas in space with a maximum number of sensing points up to thousands and a coverage of kilometers.