A Dual-Laser Sensor Based on Off-Axis Integrated Cavity Output Spectroscopy and Time-Division Multiplexing Method

Abstract

In this article, a compact dual-laser sensor based on an off-axis integrated-cavity output spectroscopy and time-division multiplexing method is reported. A complete dual-channel optical structure is developed and integrated on an optical cavity, which allows two distributed feedback (DFB) lasers operating at wavelengths of 1603 nm and 1651 nm to measure the concentration of CO2 and CH4, simultaneously. Performances of the dual-laser sensor are experimentally evaluated by using standard air (with a mixture of CO2 and CH4). The limit of detection (LoD) is 0.271 ppm and 1.743 ppb at a 20 s for CO2 and CH4, respectively, and the noise equivalent absorption sensitivities are 2.68 × 10−10 cm−1 Hz−1/2 and 3.88 × 10−10 cm−1 Hz−1/2, respectively. Together with a commercial instrument, the dual-laser sensor is used to measure CO2 and CH4 concentration over 120 h and verify the regular operation of the sensor for the detection of ambient air. Furthermore, a first-order exponential moving average algorithm is implemented as an effective digital filtering method to estimate the gas concentration.

Recent advances and applications of off‐axis integrated cavity output spectroscopy

“…The detected signal based on time-division multiplexing method. 68 F I G U R E 21 Photograph of the smog chamber by Zhao et al 72 and composition of atmospheric aerosols produced from gaseous precursors and photo-oxidant chemistry chemical mechanisms, and kinetics studies. The successful coupling of the OA-ICOS device in the smog chamber provides a higher gas-phase detection sensitivity and a new sight in the study of atmosphere-related problems in a simulation chamber.…”

Vehicle-Deployed Off-Axis Integrated Cavity Output Spectroscopic CH4/C2H6 Sensor System for Mobile Inspection of Natural Gas Leakage

“…To realize quasi-simultaneous detection of CH 4 /C 2 H 6 , the TDM method was used Figure a shows the scan signal sequence of the two lasers, #1 and #2.…”

“…To realize quasi-simultaneous detection of CH 4 /C 2 H 6 , the TDM method was used. 27 Figure 4a shows the scan signal sequence of the two lasers, #1 and #2. In a scan period T, T1 was the scan period of laser #1 and T2 was the scan period of laser #2, covering the absorption lines of CH 4 and C 2 H 6 , respectively.…”

Portable TDLAS Sensor for Online Monitoring of CO2 and H2O Using a Miniaturized Multi-Pass Cell

“…Moreover, it is easily influenced by the presence of other gases. Cavity-ring down spectroscopy (CRDS) and off-axis integrated cavity output spectroscopy (OA-ICOS) have also been increasingly applied for the continuous monitoring of atmospheric CO 2 , CH 4 , and H 2 O [ 8 , 9 , 10 , 11 , 12 , 13 ]. Although CRDS and OA-ICOS sensors have high sensitivity, they require relatively complex setups with laser frequency locking to longitudinal cavity resonances [ 14 ].…”