Fiber-optic flammable vapor sensor based on a porous cholesteric liquid crystal film

In this study, we present an all-fiber sensor based on porous cholesteric liquid crystal film (CLCF) coated on the cross-section of an optical fiber ferrule for real-time monitoring of flammable vapors in industrial environments. Reflection band shifts according to the concentration of gases were measured using a broadband wavelength-swept laser, and the sensitivity were 3.19 pm/ppm, 4.88 pm/ppm, and 6.61 pm/ppm were obtained for acetone, toluene, and benzene vapors, respectively, with benzene vapor showing the highest sensitivity. Compared to nonporous CLCFs, the porous CLCF showed six times higher sensitivity. This sensor, which operates passively without a battery, is immune to electromagnetic interference, suggesting its potential as a reliable sensor.