Mid-Infrared Hollow-Core Waveguide Gas Sensor for Low-Concentration Sulfur Hexafluor Detection

Sulfur hexafluoride gas (SF6) is widely used in various electrical insulating equipment in the electric power industry. In this paper, a novel mid-infrared hollow-core fiber (HCF) gas sensor based on infrared spectral absorption is proposed for low-concentration SF6 leakage detection. The fiber was coupled with the mid-infrared source and detector directly through a mechanical process interface. With a narrow filter, target gas absorption band light was filtered out. The optimal length of the optical fiber is derived by theoretical modeling and optimization solutions. The experimental results show that the sensor has sub-ppm measurement limitation for SF6 gas by utilizing a Lab-view-based digital dual-phase lock-in amplifier. The calibration results of SF6 standard gas at concentrations of 0.5 ppm, 2.45 ppm, 4.9 ppm, and 9.92 ppm show that the detection error of the sensor is less than 1%. Repeatability test results show the sensor can achieve high stability and low zero drift. It provides a compact and low-cost solution for low-concentration SF6 detection in the environment.