Opt Express. 2023 Jan 30;31(3):3685-3697. doi: 10.1364/OE.479963.
For over a decade hollow-core fibers have been used in optical gas sensors in the role of gas cells. However, very few examples of actual real-life applications of those sensors have been demonstrated so far. In this paper, we present a highly-sensitive hollow-core fiber based methane sensor. Mid-infrared distributed feedback interband cascade laser operating near 3.27 µm is used to detect gas inside anti-resonant hollow-core fiber. R(3) line near 3057.71 cm located in ν band of methane is targeted. Compact, lens-free optical setup with an all-silica negative curvature hollow-core fiber as the gas cell is demonstrated. Using wavelength modulation spectroscopy and 7.5-m-long fiber the detection limit as low as 1.54 ppbv (at 20 s) is obtained. The demonstrated system is applied for a week-long continuous monitoring of ambient methane and water vapor in atmospheric air at ground level. Diurnal cycles in methane concentrations are observed, what proves the sensor's usability in environmental monitoring.
十多年来，空心光纤一直被用于光学气体传感器中作为气体池。然而，到目前为止，这些传感器的实际应用实例非常少。在本文中，我们提出了一种基于空心光纤的高灵敏度甲烷传感器。中红外分布式反馈级联激光器在近 3.27 μm 处工作，用于检测抗共振空心光纤内的气体。目标是检测位于甲烷 ν 带的 R(3)线，其中心波长为 3057.71 cm。我们展示了一种紧凑的无透镜光学装置，其中使用了作为气体池的全硅负曲率空心光纤。使用波长调制光谱和 7.5 米长的光纤，我们获得了低至 1.54 ppbv（20 s）的检测极限。所展示的系统被应用于地面大气中环境甲烷和水蒸气的长达一周的连续监测。观察到了甲烷浓度的昼夜循环，这证明了该传感器在环境监测中的可用性。
