Optical sensor based on an anti-resonant hollow-core fiber for simultaneous detection of methane, carbon monoxide, and nitrogen monoxide: proposal and simulation

This work demonstrates the potential application of anti-resonant hollow-core fibers (AR-HCFs) as efficient sensors to simultaneously monitor three gases: methane, carbon monoxide, and nitrogen monoxide. Two AR-HCFs were investigated, one made of silicon dioxide and the other of indium (III) fluoride, to demonstrate the impact of the building material on fiber performance over a wide wavelength range. With the controlled insertion of holes into these fibers, the gas present in the environment can reach the hollow core of the fiber, being able to interact with the propagating light in the fiber. This light–gas interaction, when performed in different spectral regions where certain gases have high absorption, allows simultaneous monitoring of low concentrations of gases present in the environment by direct absorption spectroscopy. The wide wavelength range with low optical losses offered by AR-HCFs makes them suitable for this type of application. The simulation results show low insertion loss and a linear behavior of the optical absorption as a function of gas concentration for the three gases of interest, enabling the application of such sensors in the health, industrial, and environmental areas for precise monitoring of low concentrations of gases.