Dual-sideband heterodyne of dispersion spectroscopy based on phase-sensitive detection

Abstract

A methane sensor based on dispersion spectroscopy is presented in this paper. A standard Mach–Zehnder modulator working in carrier suppression mode is adopted to generate a spectrum of a carrier and two sidebands. We aim at detecting the phase shift of the beatnote generated by the two sidebands in a methane concentration evaluation process. We put forward an analytical model to describe the dual-sideband heterodyne scheme and carry out experiments to demonstrate the model. Long-term tests show that the sensor has a minimum detection limit of $0.4\mathrm{ppm}·{\mathrm{mHz}}^{-0.5}$ at an average time of 1 s. And in the condition of 1 atm and room temperature, a linear measurement range from 0.4 to $44955\mathrm{ppm}·\mathrm{m}$ is achieved.

© 2016 Optical Society of America

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