All-Fiber Photoacoustic Gas Sensing with Interferometric Location

Photoacoustic spectroscopy (PAS) is a promising gas detection technique with high sensitivity, fast response, and good stability. Frequency-modulated continuous-wave (FMCW) interferometry offers precise distance detection with high spatial resolution. The combination of PAS and FMCW may lead to an optical technique for the simultaneous extraction of gas concentration and location information. Herein, we demonstrate this technique in an all-fiber sensing system by blending a fiber-pigtailed PAS sensor with an FMCW interferometer. As an example, we have measured the methane concentration and location by employing time-division multiplexing, showing a minimum detection limit of 28 ppm and a spatial resolution of 3.87 mm over a distance of similar to 4.9 m. This study enables the realization of a versatile technique for multiparameter gas sensing in gas leakage detection and gas emission monitoring.