介绍了一种基于空芯光子晶体光纤(HC-PCF)气体吸收腔的气体检测系统。采用20 μm芯径、40 cm长的HC-PCF作为气体吸收腔,利用连接套管实现HC-PCF和单模光纤(SMF)的对接。连接套管上留有50 μm的缝隙,使环境气体可通过缝隙扩散进入HC-PCF吸收腔。结合可调谐光纤环形激光器构建了全光纤气体检测系统。光纤激光器输出的高功率、窄带宽探测光对待测气体具有很好的选择性,克服了传统检测方法中常见的交叉敏感现象。以乙炔气体为测量对象,对该系统测量性能进行实验验证。实验结果表明,在自然扩散条件下,乙炔气体在HC-PCF气体腔内的扩散时间约为6 min,系统响应与乙炔气体体积分数近似呈线性关系,最低检测限为0.1%。

A fiber gas sensing system using hollow-core photonic crystal fiber (HC-PCF) as gas cell is introduced.The gas cell is made by a HC-PCF with length of 40 cm and core diameter of 20 μm.The HC-PCF is connected with a single mode fiber (SMF) by a connector.There is a 50 μm gap on the connector,from which the environmental gas can diffuse into HC-PCF cell.Combining with wavelength tunable fiber ring laser technology,a compact and a real all-optical-fiber gas sensing system is proposed.Because of the characteristic of high power and narrow wavelength width of the probing light emitting from the fiber ring laser the system can detect gas with high sensing selectivity and thus the cross-effects usually encountered in the ordinary gas sensing method are reduced greatly.The properties of the system are demonstrated experimentally by detection of acetylene (C2H2).The experimental results demonstrate that the time for acetylene diffusing into the proposed HC-PCF gas chamber is proximately 6 min under natural free diffusion conditions.Approximate linear relation between the system responses and the acetylene volume fraction are experimentally demonstrated and the minimal detectable volume fraction of acetylene of 0.1% is also achieved by experiments.