Stability study on high sensitive CO monitoring in near-infrared

CO is an indicative gas of coal spontaneous combustion warning and mine production safety instruction, whose detection process generally requires fiber long-haul transmission. However, currently, the communication fiber windows are mainly in the near-infrared band, so it is very significance to realize highly sensitive CO detection at near-infrared band. Tunable diode laser absorption spectroscopy (TDLAS) technology has advantages of high sensitivity, high resolution, fast response ability and no-contact, which has been widely used in air pollution monitoring, industrial and agricultural production process control, and many other fields. Long-path multi-pass cell can effectively improve the TDLAS detection capabilities, at the same time, the whole system is more compact. In this paper, 1566.64 nm DFB laser and the novel multi-pass cell with an optical path 56.7 m are used to detect different CO concentrations in long-term, while the system stability and linearity are analyzed. In addition, the detection limit is 0.25 ppmv with 30 s integration time by calculating the Allan variance. It means that we have primarily achieved highly sensitive detection of CO in the near-infrared bands.