Lou Xiutao, Feng Yabo, Chen Chen, Dong Yongkang
Opt Express. 2020 Mar 16;28(6):9014-9026. doi: 10.1364/OE.389746.
We present an innovative spectroscopic method based on coherent optical frequency-modulated continuous-wave (FMCW) interferometry that can realize multi-point gas detection with high spatial resolution, high sensitivity, and high selectivity. This method takes full advantage of the intrinsic capability of spatial localization of the coherent FMCW, meanwhile efficiently decodes the spectral information from the reflected optical signals. Gas sensors are deployed by adopting bus topology, i.e., distributed along a single backbone fiber in the measurement arm of the FMCW interferometer. For validation, a multi-point acetylene gas sensing system with three sensing nodes is experimentally demonstrated. The transmission spectra of the three gas sensors are accurately extracted, and their corresponding gas concentrations are efficiently retrieved with a low crosstalk below -30 dB. The demonstrated system achieves a sensitivity of 55 ppm (noise equivalent absorbance of 0.004) over a distance of 52 m, with a sensing spatial resolution of 30 cm and a spectral resolution of 0.5 GHz. Our proposed method promotes a novel way for the development of multi-point spectroscopic gas sensing systems for challenging applications such as gas leakage detection and gas emission monitoring, where spatially resolved chemical analysis over a large area is required.
我们提出了一种基于相干光学频率调制连续波（FMCW）干涉测量法的创新光谱方法，该方法能够实现具有高空间分辨率、高灵敏度和高选择性的多点气体检测。此方法充分利用了相干FMCW固有的空间定位能力，同时有效地从反射光信号中解码光谱信息。气体传感器采用总线拓扑结构进行部署，即在FMCW干涉仪测量臂中的单根主干光纤上分布式布置。为进行验证，通过实验展示了一个具有三个传感节点的多点乙炔气体传感系统。准确提取了三个气体传感器的透射光谱，并以低于-30 dB的低串扰有效地获取了它们相应的气体浓度。所展示的系统在52 m的距离上实现了55 ppm的灵敏度（噪声等效吸光度为0.004），传感空间分辨率为30 cm，光谱分辨率为0.5 GHz。我们提出的方法为开发用于诸如气体泄漏检测和气体排放监测等具有挑战性应用的多点光谱气体传感系统开辟了一条新途径，这些应用需要在大面积上进行空间分辨化学分析。
