This study presents an innovative methane gas sensor design based on anti-resonant hollow-core fiber (AR-HCF) technology, optimized for high-precision detection at 3.3 \(\:\:{\upmu\:}\text{m}\) . Our numerical analysis explores the geometric optimization of the AR-HCF’s structural parameters, incorporating real-world component specifications. The proposed design features a 65 \(\:\:{\upmu\:}\text{m}\) diameter hollow core surrounded by seven silica rings. We achieved significant improvements in confinement loss and optical power distribution through progressive structural modifications. The optimized structure demonstrated a confinement loss of \(\:1.85\times\:{10}^{-4}\:\text{d}\text{B}/\text{m}\) and over 95% optical power confinement in the hollow core. Our model predicts a relative sensitivity of \(\:0.1745\:\text{A}\text{U}/\text{p}\text{p}\text{m}\) , a response time of 5.4 s, and a theoretical detection threshold of 2.24 ppm. The limit of detection (LoD) was estimated to be 3.8 ppbv, and the normalized noise equivalent absorption (NNEA) coefficient was \(\:1.22\times\:{10}^{-10}\:\text{W} \; {\text{c}\text{m}}^{-1} \; {\text{H}\text{z}}^{-1/2}\) . The sensor response exhibited excellent linearity over its operating range, with an R2 value of 0.9917 in the critical concentration range. These findings highlight the potential of our AR-HCF-based methane sensor design for real-time gas monitoring applications.
