In this article, a mid-infrared all-fiber light-induced thermoelastic spectroscopy (LITES) sensor based on a hollow-core anti-resonant fiber (HC-ARF) was reported for the first time. The HC-ARF was applied as a light transmission medium and gas chamber. The constructed all-fiber structure has merits of low loss, easy optical alignment, good system stability, reduced sensor size and cost. The mid-infrared transmission structure can be utilized to target the strongest gas absorption lines. The reversely-tapered SM1950 fiber and the HC-ARF were spatially butt-coupled with a V-shaped groove between the two fibers to facilitate gas entry. Carbon monoxide (CO) with an absorption line at 4291.50 cm (2.33 μm) was chosen as the target gas to verify the sensing performance. The experimental results showed that the all-fiber LITES sensor based on HC-ARF had an excellent linear response to CO concentration. Allan deviation analysis indicated that the system had excellent long-term stability. A minimum detection limit (MDL) of 3.85 ppm can be obtained when the average time was 100 s.

中文翻译：

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基于空心反谐振光纤的中红外全光纤光致热弹光谱传感器

本文首次报道了一种基于空心反谐振光纤（HC-ARF）的中红外全光纤光致热弹性光谱（LITES）传感器。HC-ARF用作光传输介质和气室。所构建的全光纤结构具有损耗低、易于光学对准、系统稳定性好、减小传感器尺寸和成本等优点。中红外传输结构可用于瞄准最强的气体吸收线。反向锥形 SM1950 光纤和 HC-ARF 在空间上对接耦合，两根光纤之间有一个 V 形凹槽，以促进气体进入。选择吸收线为 4291.50 cm (2.33 μm) 的一氧化碳 (CO) 作为目标气体来验证传感性能。实验结果表明，基于HC-ARF的全光纤LITES传感器对CO浓度具有优异的线性响应。Allan偏差分析表明系统具有良好的长期稳定性。当平均时间为100 s时，可以获得3.85 ppm的最低检测限（MDL）。