Miniature optical fiber sensor based on polypyrrole for detection of VOCs

A volatile organic compounds (VOCs) sensor based on intrinsic Fabry-Perot interferometer (IFPI) coated with polypyrrole thin film was proposed and experimentally demonstrated. The IFPI consists a section of hollow-core fiber (HCF) sandwiched between two single mode fiber. The polypyrrole is formed chemically via interfacial polymerization technique and coated directly onto the fiber. As the isopropanol vapor got absorbed by the film, the reflection spectrum of IFPI changes due to the refractive index (RI) variation of the film. The proposed sensor achieves a sensitivity of 0.0423 dB/ppm with a wide concentration range of isopropanol vapor from 65 to 455 ppm.