Ni-MOF-74 film coated optical microfiber CO sensor cascaded with spiral fiber grating temperature compensator

Metal-organic framework (MOF) material is a good carbon monoxide (CO) storage material. This paper proposed a composite optical fiber structure based on spiral fiber grating (SFG) and tapered microfiber (TMF), which can realize the simultaneous sensing of CO concentration and temperature by coating different functional films. The refractive index (RI) of Ni-MOF-74 coated on tapered microfiber can be changed by absorbing CO molecules. The thermal expansion of Ultraviolet (UV) glue will change the period of the spiral fiber grating. Based on the above mechanism, the research shows that the CO sensitivity of the optical microfiber can reach 64.11 pm/ppm, and the temperature sensitivity is -30.1 pm/degree celsius. The temperature sensitivity of the spiral fiber grating can reach 294 pm/degree celsius, which can effectively compensate for the temperature sensitivity of the microfiber. This composite structure has a good application prospect in accurate CO gas concentration measurement.