On-line measurement of atmospheric oxygen by an open-path OA-ICOS based sensor with high accuracy at ambient pressure

Abstract

In this paper, a compact optical oxygen (O2) sensor system was demonstrated based on off-axis integrated cavity output spectroscopy (OA-ICOS). Light from a distributed feedback laser near 761 nm was coupled into an open-path F-P cavity by off-axis configuration. To address the challenges of changing field environments for open-path configuration, the influence of pressure on the sensor system was studied. A linewidth enhancement factor (δ) was proposed to measure the ambient pressure and a pressure correction method was developed to improve the measurement accuracy. A minimum detection limit of 0.0038% was obtained for an optimum averaging time of 20 s under 760 Torr. Indoor and outdoor O2 concentration measurements were conducted and the sensing applicability of the sensors system at ambient pressure was verified. The demonstrated sensor system allows operation without a vacuum pump and a pressure controller combine with the self-developed laser driver and digital lock-in amplifier, which has advantages of reduced size, low power consumption, low cost and has wide application prospect for O2 sensing in field environments.