Integrated and Robust Fabry–Perot Humidity Sensor Based on Metal–Organic Framework onto Fiber-Optic Facet

An integrated and robust fiber-optic Fabry–Perot (FP) humidity sensor based on the metal–organic framework (MOF) material FIR-53 is presented and characterized for the first time, along with its implementation method. Noticeably, the FIR-53 crystal was chosen as the moisture-sensitive material, due to its large porosity and chemical tailorability. By connecting the single-mode fiber (SMF) with FIR-53 using polydimethylsiloxane (PDMS) rationally, our sensor, whose FP cavity was formed by FIR-53, monitors the spectrum peak shift caused by humidity change. The experiments revealed that the proposed sensor had a sensitivity of 315 pm/% relative humidity (RH) in the range of 10%–90% RH, and also good linearity, reversibility, long-time stability, and antihigh-temperature interference resistance. To summarize, the proposed sensor has the advantages of easy fabrication and low cost, and is highly sensitive to humidity, which is going to have significant potential in the field of humidity sensing and promote the research and application of new fiber-optic sensors for humidity.