Multipoint dispersion spectroscopic gas sensing by optical FMCW interferometry.

We present a novel, to the best of our knowledge, multipoint gas-sensing method based on dispersion spectroscopy using optical frequency-modulated continuous-wave (FMCW) techniques. By taking advantage of the optical FMCW's excellent multiplexing capability with high spatial resolution, the phase noise in the retrieved dispersion signal is efficiently suppressed. As a proof of concept, this method is experimentally demonstrated with three acetylene gas-sensing nodes, achieving a sensitivity of 30 ppm, a sensing spatial resolution of 30 cm, and a linear dynamic range of more than 3 orders of magnitude. Having advantages of high sensitivity, high spatial resolution, large dynamic range, and immunity to light power variation, the proposed method promotes a novel way for the development of long-distance multipoint spectroscopic gas sensors.