Single-shot, multi-point remote gas sensing by a linearly chirped laser pulse

We present a spectroscopic method that employs a single linearly chirped laser pulse (LCLP) generated by external modulation to realize long-distance multi-point gas sensing. Even without frequency-chirping calibration, accurate single-shot spectral measurement is rendered possible by the high linearity of intrapulse chirping (linearity error of ∼10⁻⁴). Utilizing the LCLP’s built-in capacity of time-division-multiplexing, high measurement sensitivity is guaranteed by introducing a multichannel intensity noise compensation mechanism. As proof of concept, this method is experimentally demonstrated by three acetylene gas sensing nodes using an LCLP of 100-ns pulse width and 20-GHz chirping range, achieving a time resolution of 280 µs with 90-ppm sensitivity and a spatial resolution of 25 m over a 25-km sensing distance. Having the advantages of high time resolution, high spatial resolution, and accurate spectral measurement, our proposed method promotes a novel, to the best of our knowledge, way of developing spectroscopic gas sensing systems for challenging applications where spatially resolved gas analysis with fast response over a long distance is required.