{"status":"ok","message-type":"work","message-version":"1.0.0","message":{"indexed":{"date-parts":[[2026,3,14]],"date-time":"2026-03-14T18:00:59Z","timestamp":1773511259249,"version":"3.50.1"},"reference-count":32,"publisher":"MDPI AG","issue":"21","license":[{"start":{"date-parts":[[2020,10,30]],"date-time":"2020-10-30T00:00:00Z","timestamp":1604016000000},"content-version":"vor","delay-in-days":0,"URL":"https:\/\/creativecommons.org\/licenses\/by\/4.0\/"}],"funder":[{"DOI":"10.13039\/501100001809","name":"National Natural Science Foundation of China","doi-asserted-by":"publisher","award":["41730103"],"award-info":[{"award-number":["41730103"]}],"id":[{"id":"10.13039\/501100001809","id-type":"DOI","asserted-by":"publisher"}]},{"name":"National Basic Research Program of China (973 Program)","award":["2016YFC0303900"],"award-info":[{"award-number":["2016YFC0303900"]}]},{"name":"National Basic Research Program of China (973 Program)","award":["2017YFC0209700"],"award-info":[{"award-number":["2017YFC0209700"]}]}],"content-domain":{"domain":[],"crossmark-restriction":false},"short-container-title":["Sensors"],"abstract":"<jats:p>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 \u00d7 10\u221210 cm\u22121 Hz\u22121\/2 and 3.88 \u00d7 10\u221210 cm\u22121 Hz\u22121\/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.<\/jats:p>","DOI":"10.3390\/s20216192","type":"journal-article","created":{"date-parts":[[2020,10,30]],"date-time":"2020-10-30T21:34:47Z","timestamp":1604093687000},"page":"6192","update-policy":"https:\/\/doi.org\/10.3390\/mdpi_crossmark_policy","source":"Crossref","is-referenced-by-count":22,"title":["A Dual-Laser Sensor Based on Off-Axis Integrated Cavity Output Spectroscopy and Time-Division Multiplexing Method"],"prefix":"10.3390","volume":"20","author":[{"given":"Kunyang","family":"Wang","sequence":"first","affiliation":[{"name":"Anhui Institute of Optics and Fine Mechanics, Hefei Institutes of Physical Science, Chinese Academy of Sciences, Anhui 230031, China"},{"name":"Science Island Branch of Graduate School, University of Science and Technology of China, Anhui 230031, China"}]},{"given":"Ligang","family":"Shao","sequence":"additional","affiliation":[{"name":"Anhui Institute of Optics and Fine Mechanics, Hefei Institutes of Physical Science, Chinese Academy of Sciences, Anhui 230031, China"}]},{"given":"Jiajin","family":"Chen","sequence":"additional","affiliation":[{"name":"Anhui Institute of Optics and Fine Mechanics, Hefei Institutes of Physical Science, Chinese Academy of Sciences, Anhui 230031, China"}]},{"ORCID":"https:\/\/orcid.org\/0000-0002-9828-5424","authenticated-orcid":false,"given":"Guishi","family":"Wang","sequence":"additional","affiliation":[{"name":"Anhui Institute of Optics and Fine Mechanics, Hefei Institutes of Physical Science, Chinese Academy of Sciences, Anhui 230031, China"}]},{"ORCID":"https:\/\/orcid.org\/0000-0002-5813-5093","authenticated-orcid":false,"given":"Kun","family":"Liu","sequence":"additional","affiliation":[{"name":"Anhui Institute of Optics and Fine Mechanics, Hefei Institutes of Physical Science, Chinese Academy of Sciences, Anhui 230031, China"}]},{"given":"Tu","family":"Tan","sequence":"additional","affiliation":[{"name":"Anhui Institute of Optics and Fine Mechanics, Hefei Institutes of Physical Science, Chinese Academy of Sciences, Anhui 230031, China"}]},{"given":"Jiaoxu","family":"Mei","sequence":"additional","affiliation":[{"name":"Anhui Institute of Optics and Fine Mechanics, Hefei Institutes of Physical Science, Chinese Academy of Sciences, Anhui 230031, China"}]},{"ORCID":"https:\/\/orcid.org\/0000-0001-6141-1039","authenticated-orcid":false,"given":"Weidong","family":"Chen","sequence":"additional","affiliation":[{"name":"Laboratoire de Physicochimie de l\u2019Atmosph\u00e8re, Universit\u00e9 du Littoral C\u00f4te d\u2019Opale, 189A, Av. Maurice Schumann, 59140 Dunkerque, France"}]},{"given":"Xiaoming","family":"Gao","sequence":"additional","affiliation":[{"name":"Anhui Institute of Optics and Fine Mechanics, Hefei Institutes of Physical Science, Chinese Academy of Sciences, Anhui 230031, China"}]}],"member":"1968","published-online":{"date-parts":[[2020,10,30]]},"reference":[{"key":"ref_1","doi-asserted-by":"crossref","first-page":"24559","DOI":"10.1364\/OE.22.024559","article-title":"Time-resolved in situ detection of CO in a shock tube using cavity-enhanced absorption spectroscopy with a quantum-cascade laser near 4.6 mu m","volume":"22","author":"Sun","year":"2014","journal-title":"Opt. Express"},{"key":"ref_2","doi-asserted-by":"crossref","first-page":"8536","DOI":"10.1364\/AO.57.008536","article-title":"Intensity enhancement in off-axis integrated cavity output spectroscopy","volume":"57","author":"Nadeem","year":"2018","journal-title":"Appl. Opt."},{"key":"ref_3","doi-asserted-by":"crossref","first-page":"2947","DOI":"10.1364\/AO.57.002947","article-title":"Modeling the optical field in off-axis integrated-cavity-output spectroscopy using the decentered Gaussian beam model","volume":"57","author":"Shen","year":"2018","journal-title":"Appl. Opt."},{"key":"ref_4","doi-asserted-by":"crossref","first-page":"1345","DOI":"10.1016\/j.proci.2018.06.230","article-title":"Cavity-enhanced absorption spectroscopy for shocktubes: Design and optimization","volume":"37","author":"Chao","year":"2019","journal-title":"Proc. Combust. Inst."},{"key":"ref_5","doi-asserted-by":"crossref","first-page":"1915","DOI":"10.1364\/AO.50.001915","article-title":"Extremely sensitive detection of NO\u2082 employing off-axis integrated cavity output spectroscopy coupled with multiple-line integrated absorption spectroscopy","volume":"50","author":"Rao","year":"2011","journal-title":"Appl. Opt."},{"key":"ref_6","doi-asserted-by":"crossref","first-page":"6085","DOI":"10.1364\/AO.54.006085","article-title":"Real-time trace gas sensor using a multimode diode laser and multiple-line integrated cavity enhanced absorption spectroscopy","volume":"54","author":"Karpf","year":"2015","journal-title":"Appl. Opt."},{"key":"ref_7","doi-asserted-by":"crossref","first-page":"27985","DOI":"10.1364\/OE.22.027985","article-title":"Sensitivity enhancement in off-axis integrated cavity output spectroscopy","volume":"22","author":"Centeno","year":"2014","journal-title":"Opt. Express"},{"key":"ref_8","doi-asserted-by":"crossref","first-page":"413","DOI":"10.1007\/s00340-006-2312-0","article-title":"An off-axis cavity-enhanced absorption spectrometer at 1605 nm for the (CO2)-C-12\/(CO2)-C-13 measurement","volume":"85","author":"Kasyutich","year":"2006","journal-title":"Appl. Phys. B Lasers Opt."},{"key":"ref_9","doi-asserted-by":"crossref","first-page":"467","DOI":"10.1007\/s00340-008-3137-9","article-title":"Design considerations in high-sensitivity off-axis integrated cavity output spectroscopy","volume":"92","author":"Moyer","year":"2008","journal-title":"Appl. Phys. B Lasers Opt."},{"key":"ref_10","doi-asserted-by":"crossref","first-page":"5","DOI":"10.1088\/1612-202X\/aad852","article-title":"Improving the accuracy and sensitivity of(13)C online detection in expiratory air using the TDLAS method in the spectral range of 4860-4880 cm(\u22121)","volume":"15","author":"Kireev","year":"2018","journal-title":"Laser Phys. Lett."},{"key":"ref_11","doi-asserted-by":"crossref","first-page":"8","DOI":"10.1007\/s00340-017-6851-3","article-title":"Detection of shock-heated hydrogen peroxide\u2014(H2O2) by off-axis cavity-enhanced absorption spectroscopy (OA-CEAS)","volume":"123","author":"Alquaity","year":"2017","journal-title":"Appl. Phys. B Lasers Opt."},{"key":"ref_12","doi-asserted-by":"crossref","first-page":"127674","DOI":"10.1016\/j.snb.2020.127674","article-title":"Near-infrared methane sensor system using off-axis integrated cavity output spectroscopy with novel dual-input dual-output coupling scheme for mode noise suppression","volume":"308","author":"Zheng","year":"2020","journal-title":"Sens. Actuators B Chem."},{"key":"ref_13","doi-asserted-by":"crossref","first-page":"128","DOI":"10.1016\/j.snb.2012.04.036","article-title":"Greenhouse gas analyzer for measurements of carbon dioxide, methane, and water vapor aboard an unmanned aerial vehicle","volume":"169","author":"Berman","year":"2012","journal-title":"Sens. Actuators B Chem."},{"key":"ref_14","doi-asserted-by":"crossref","first-page":"2003","DOI":"10.1039\/C8AN02164C","article-title":"A near-infrared C2H2\/CH4 dual-gas sensor system combining off-axis integrated-cavity output spectroscopy and frequency-division-multiplexing-based wavelength modulation spectroscopy","volume":"144","author":"Zheng","year":"2019","journal-title":"Analyst"},{"key":"ref_15","doi-asserted-by":"crossref","first-page":"12137","DOI":"10.1364\/OE.27.012137","article-title":"Wavelength modulation spectroscopy by employing the first harmonic phase angle method","volume":"27","author":"Yang","year":"2019","journal-title":"Opt. Express"},{"key":"ref_16","doi-asserted-by":"crossref","first-page":"132","DOI":"10.1016\/j.pecs.2016.12.002","article-title":"Infrared laser-absorption sensing for combustion gases","volume":"60","author":"Goldenstein","year":"2017","journal-title":"Prog. Energy Combust. Sci."},{"key":"ref_17","doi-asserted-by":"crossref","first-page":"125203","DOI":"10.1088\/0957-0233\/24\/12\/125203","article-title":"Analysis of calibration-free wavelength-scanned wavelength modulation spectroscopy for practical gas sensing using tunable diode lasers","volume":"24","author":"Sun","year":"2013","journal-title":"Meas. Sci. Technol."},{"key":"ref_18","doi-asserted-by":"crossref","first-page":"100","DOI":"10.1016\/j.jqsrt.2013.06.008","article-title":"Diode laser measurements of linestrength and temperature-dependent lineshape parameters of H2O-, CO2-, and N2-perturbed H2O transitions near 2474 and 2482 nm","volume":"130","author":"Goldenstein","year":"2013","journal-title":"J. Quant. Spectrosc. Radiat. Transf."},{"key":"ref_19","doi-asserted-by":"crossref","first-page":"304","DOI":"10.1016\/j.jqsrt.2013.05.023","article-title":"Speed dependence of CH3 Cl-35-O-2 line-broadening parameters probed on rotational transitions: Measurements and semi-classical calculations","volume":"130","author":"Buldyreva","year":"2013","journal-title":"J. Quant. Spectrosc. Radiat. Transf."},{"key":"ref_20","doi-asserted-by":"crossref","first-page":"108","DOI":"10.1016\/j.jqsrt.2015.06.023","article-title":"Measurement of water vapor line strengths in the 1.4\u20132.7 \u00b5m range by tunable diode laser absorption spectroscopy","volume":"165","author":"Klein","year":"2015","journal-title":"J. Quant. Spectrosc. Radiat. Transf."},{"key":"ref_21","doi-asserted-by":"crossref","first-page":"48","DOI":"10.1016\/j.optlaseng.2013.12.005","article-title":"Sensor for headspace pressure and H2O concentration measurements in closed vials by tunable diode laser absorption spectroscopy","volume":"58","author":"Cai","year":"2014","journal-title":"Opt. Lasers Eng."},{"key":"ref_22","doi-asserted-by":"crossref","first-page":"30517","DOI":"10.1364\/OE.27.030517","article-title":"Enhancing off-axis integrated cavity output spectroscopy (OA-ICOS) with radio frequency white noise for gas sensing","volume":"27","author":"Wang","year":"2019","journal-title":"Opt. Express"},{"key":"ref_23","doi-asserted-by":"crossref","first-page":"3298","DOI":"10.1364\/OL.44.003298","article-title":"High-sensitivity off-axis integrated cavity output spectroscopy implementing wavelength modulation and white noise perturbation","volume":"44","author":"Wang","year":"2019","journal-title":"Opt. Lett."},{"key":"ref_24","unstructured":"Engel, G.S., Moyer, E.J., Keutsch, F.N., and Anderson, J.G. (2020, September 15). Innovations in Cavity Enhanced Laser Absorption Spectroscopy: Using in situ Measurements to Probe the Mechanisms Driving Climate Change. Available online: https:\/\/www.researchgate.net\/profile\/E_Moyer\/publication\/237635995_Innovations_in_Cavity_Enhanced_Laser_Absorption_Spectroscopy_Using_in_situ_Measurements_to_Probe_the_Mechanisms_Driving_Climate_Change\/links\/5417c5cb0cf2f48c74a4112a.pdf."},{"key":"ref_25","doi-asserted-by":"crossref","first-page":"4","DOI":"10.1088\/1612-202X\/aacc02","article-title":"Kalman\u2019s method to improve accuracy of online (CO2)-C-13-O-16 measurement in the exhaled human breath using tunable diode laser absorption spectroscopy","volume":"15","author":"Kireev","year":"2018","journal-title":"Laser Phys. Lett."},{"key":"ref_26","doi-asserted-by":"crossref","first-page":"9027","DOI":"10.3390\/s140509027","article-title":"Measurement of the D\/H, O-18\/O-16, and O-17\/O-16 Isotope Ratios in Water by Laser Absorption Spectroscopy at 2.73 mu m","volume":"14","author":"Wu","year":"2014","journal-title":"Sensors"},{"key":"ref_27","doi-asserted-by":"crossref","first-page":"419","DOI":"10.1007\/s00340-008-3125-0","article-title":"Applications of quantum cascade lasers for sensitive trace gas measurements of CO, CH4, N2O and HCHO","volume":"92","author":"Schiller","year":"2008","journal-title":"Appl. Phys. B"},{"key":"ref_28","doi-asserted-by":"crossref","first-page":"35","DOI":"10.1016\/j.snb.2010.02.003","article-title":"Fourier domain local narrow-band signal extraction algorithm and its application to real-time infrared gas detection","volume":"146","author":"Xie","year":"2010","journal-title":"Sens. Actuator B Chem."},{"key":"ref_29","doi-asserted-by":"crossref","first-page":"288","DOI":"10.1016\/j.physa.2013.10.007","article-title":"Following a trend with an exponential moving average: Analytical results for a Gaussian model","volume":"394","author":"Grebenkov","year":"2014","journal-title":"Phys. A Stat. Mech. Appl."},{"key":"ref_30","first-page":"406","article-title":"K-th Moving, Weighted and Exponential Moving Average for Time Series Forecasting Models","volume":"3","author":"Tsokos","year":"2010","journal-title":"Eur. J. Pure Appl. Math."},{"key":"ref_31","doi-asserted-by":"crossref","first-page":"131","DOI":"10.1007\/BF00425997","article-title":"The limits of signal averaging in atmospheric trace-gas monitoring by tunable diode-laser absorption spectroscopy (TDLAS)","volume":"57","author":"Werle","year":"1993","journal-title":"Appl. Phys. B"},{"key":"ref_32","doi-asserted-by":"crossref","first-page":"261","DOI":"10.1007\/s00340-002-0971-z","article-title":"Sensitive absorption measurements in the near-infrared region using off-axis integrated-cavity-output spectroscopy","volume":"75","author":"Baer","year":"2002","journal-title":"Appl. Phys. B Lasers Opt."}],"container-title":["Sensors"],"original-title":[],"language":"en","link":[{"URL":"https:\/\/www.mdpi.com\/1424-8220\/20\/21\/6192\/pdf","content-type":"unspecified","content-version":"vor","intended-application":"similarity-checking"}],"deposited":{"date-parts":[[2025,10,11]],"date-time":"2025-10-11T10:27:13Z","timestamp":1760178433000},"score":1,"resource":{"primary":{"URL":"https:\/\/www.mdpi.com\/1424-8220\/20\/21\/6192"}},"subtitle":[],"short-title":[],"issued":{"date-parts":[[2020,10,30]]},"references-count":32,"journal-issue":{"issue":"21","published-online":{"date-parts":[[2020,11]]}},"alternative-id":["s20216192"],"URL":"https:\/\/doi.org\/10.3390\/s20216192","relation":{},"ISSN":["1424-8220"],"issn-type":[{"value":"1424-8220","type":"electronic"}],"subject":[],"published":{"date-parts":[[2020,10,30]]}}}