Hollow-Core Anti-Resonant Fiber Sensor for Simultaneous Measurement of CH 4 and C 2 H 2

This paper presents an all-fiber novel gas sensor for simultaneous dual-gas detection of methane (CH₄) and acetylene (C₂H₂), which integrates a hollow-core anti-resonant fiber (HC ARF) with tunable diode laser absorption spectroscopy (TDLAS). The sensor employs a self-fabricated, large-core HC-ARF (0.75m) and a uniquely designed coupling unit to achieve a fully fiber optic architecture, offering a rapid response time of 9.4 s. The system demonstrated concentration sensitivities of 0.0006 V/ppm (R² = 99.95%) for CH₄ and 0.0019 V/ppm (R² = 99.96%) for C₂H₂. The minimum detection limit (MDL), derived from experimental standard deviation, was 36 ppm for CH₄ and 4.2 ppm for C₂H₂. Furthermore, Allan deviation analysis enabled the optimization of the MDL to 0.63 ppm (at an integration time of 7.93 s) for CH₄ and 0.08 ppm (at 9.57 s) for C₂H₂. The sensor was successfully deployed in a laboratory-simulated industrial gas leak scenario, which was proved capable of real-time concentration monitoring and precise leak localization. The detection limit of the proposed sensor can be further improved by selecting gas absorption lines with higher intensity or by using a longer HC-ARF.