Dual gas sensor based on anti-resonant hollow-core fiber for detection of CO2 and CH4 with different absorption lines

The simultaneous detection of a mixture of two gases with the aid of unique and excellent capabilities of anti-resonance hollow-core fibers (AR-HCF), is numerically investigated in this article. Low-loss transmission bands in near and mid-infrared, which correspond to the transition of methane (CH[Formula: see text] and carbon dioxide (CO[Formula: see text], are considered in this work. Reasonable consideration of structural parameters has caused the low-loss transmission band covering 1.57 [Formula: see text]m and 3.33 [Formula: see text]m wavelengths. The second harmonics caused by the interaction of the laser beam and the gas sample inside the hollow core of the fiber were analyzed utilizing the fast Fourier transform (FFT) method. The maximum amplitude for the corresponding frequency at the determined concentration has reached 3002 [Formula: see text] for CH 4 and 6381 [Formula: see text] for CO 2 . Enhancement of the inhibited coupling between the fundamental mode and some of the cladding modes and leakage loss reduction, extra capillary tubes nested inside the silica tubes forming the fiber cladding. The simulation results confirm the suitability of the proposed structure for efficient utilization in gas sensing applications for two different spectral ranges in the near and mid-infrared. Benefiting from a large hollow core, very low background noise and anti-resonance properties, high sensitivity of about 99.6% and confinement loss of 0.127 dB/m were obtained.