Fiber-optical methane sensor, with its lower cost, higher sensitivity and distributed sensing capability, has been developed in recently years based on various technologies, such as evanescent wave fiber sensor, photonic crystal fiber sensor, and long-period fiber. Fiber-optical methane sensor, with its lower cost, higher sensitivity and distributed sensing capability, has been developed in recently years based on various technologies, such as evanescent wave fiber sensor, photonic crystal fiber sensor, and long-period fiber. In this paper, based on the multimode interference structure fiber and the sensitive advantages of a zeolitic imidazolate framework-8/Polydimethylsiloxane (ZIF-8/PDMS)-sensitive film in methane detection, a methane sensor based on an interferometer induced by multimode interference is designed and. Abstract—An active optical fiber gas sensor was developed in a cobalt-doped single mode fiber. This fiber can be heated up to a few hundred degrees Celsius by a heating laser, and a fiber Bragg grating (FBG) was fabricated inside this fiber as a thermometer. The Bragg wavelength of the FBG is. A novel fibre-optic methane detection system was proposed, which involved sampled fibre grating and improved differential absorption detection technique. In order to develop an accurate monitoring method for methane gas concentration at different locations in a mine environment, a non-source optical fiber sensor for multi-point methane detection has been developed in this paper. The sensor is constructed by depositing a thin styrene-acrylonitrile (SAN) film containing the new compound cryptophane-E- (OEt)<sub>6</sub> onto the cladding surface of the LPFG.
