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Search Results (6)

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Keywords = off-axis integrated cavity system

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13 pages, 2777 KB  
Article
Improving the Accuracy of Methane Sensor with Dual Measurement Modes Based on Off-Axis Integrated Cavity Output Spectroscopy Using White Noise Perturbation
by Ce Yang, Mingming Wen, Chen Chen, Chunguang Li, Jianyu Huang, Laiyong Song and Yu Li
Appl. Sci. 2025, 15(10), 5562; https://doi.org/10.3390/app15105562 - 15 May 2025
Cited by 1 | Viewed by 923
Abstract
A methane (CH4) sensor based on off-axis integrated cavity output spectroscopy (OA-ICOS) was developed, equipped with two measurement schemes: direct absorption spectroscopy (DAS) and wavelength modulation spectroscopy (WMS). The sensor used an optical resonant cavity composed of two high reflection mirrors [...] Read more.
A methane (CH4) sensor based on off-axis integrated cavity output spectroscopy (OA-ICOS) was developed, equipped with two measurement schemes: direct absorption spectroscopy (DAS) and wavelength modulation spectroscopy (WMS). The sensor used an optical resonant cavity composed of two high reflection mirrors (reflectivity > 99%). With a cavity length of 7 cm, an effective optical path length of 10.8 m and a cavity volume of 8.9 mL were achieved. A distributed feedback laser was used to precisely target the CH4 absorption line near 1.6537 µm. Compared with the original system, the cavity mode noise of the CH4 sensor was further reduced by adding white noise perturbations. The white noise perturbations were generated by the broadband random noise from the signal generator. The special customized narrowband RF noise source was not required. The system complexity and cost could be reduced. In DAS mode, the signal-to-noise ratio (SNR) of the OA-ICOS was 16.2 and the minimum detection limit (MDL) was 2.2 ppm at 117 s. In WMS mode, the SNR of the OA-ICOS was 113.9 and the MDL was 1.2 ppm at 106 s. Compared with the results obtained from the WMS mode and DAS mode, the SNR and MDL was improved 7.0 times and 1.8 times, respectively. The proposed sensor system not only enabled high-accuracy trace gas measurement, but also demonstrated strong potential for applications due to its compact design and low cost. Full article
(This article belongs to the Special Issue Near/Mid-Infrared Lasers: Latest Advances and Applications)
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20 pages, 5581 KB  
Article
Simulation Research and Analysis of Wavelength Modulation Off-Axis Integrated Cavity Output Spectrum Measurement System
by Tao Wu, Xiao Zhang, Xiao Chen, Wangwang Liu, Yan Han, Yubin Zhong, Dan Zhao, Zhen Fang, Linxin Pan, Feiyang Wang and Hang Xu
Sensors 2025, 25(8), 2478; https://doi.org/10.3390/s25082478 - 15 Apr 2025
Viewed by 1107
Abstract
Wavelength modulation spectroscopy off-axis integrated cavity output spectroscopy (WMS-OA-ICOS) is an in situ detection technique suitable for analyzing trace gases in the atmospheres, characterized by its high sensitivity and ease of integration. However, in current practical applications, the design and optimization of WMS-OA-ICOS [...] Read more.
Wavelength modulation spectroscopy off-axis integrated cavity output spectroscopy (WMS-OA-ICOS) is an in situ detection technique suitable for analyzing trace gases in the atmospheres, characterized by its high sensitivity and ease of integration. However, in current practical applications, the design and optimization of WMS-OA-ICOS systems primarily rely on empirical knowledge, lacking systematic quantitative methodologies. To address this limitation, this study conducts comprehensive modeling and simulation research on WMS-OA-ICOS spectroscopy, proposing a novel modeling approach. The spot distribution simulation results obtained from the self-developed model are validated against those generated using Tracepro. Furthermore, based on the self-developed model, an in-depth investigation is conducted into the effects of cavity length tolerance, beam waist matching, modulation depth, and laser linewidth on signal quality. The findings provide valuable insights for designing and optimizing miniaturized systems with high signal-to-noise ratios. Full article
(This article belongs to the Special Issue Spectral Detection Technology, Sensors and Instruments, 2nd Edition)
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14 pages, 8728 KB  
Article
OA−ICOS−Based Oxygen and Carbon Dioxide Sensors for Field Applications in Gas Reflux Chicken Coops
by Weijia Li, Guanyu Lin, Jianing Wang, Jifeng Li, Yulai Sun, Depu Yao, Xiaogang Yan and Zhibin Ban
Sensors 2025, 25(3), 886; https://doi.org/10.3390/s25030886 - 31 Jan 2025
Cited by 2 | Viewed by 1259
Abstract
To facilitate the effective assessment of respiratory entropy during poultry breeding, a novel oxygen (O2) and carbon dioxide (CO2) sensor was developed based on the off−axis integrated cavity output spectroscopy technique, featuring effective absorption optical paths of 15.5 m [...] Read more.
To facilitate the effective assessment of respiratory entropy during poultry breeding, a novel oxygen (O2) and carbon dioxide (CO2) sensor was developed based on the off−axis integrated cavity output spectroscopy technique, featuring effective absorption optical paths of 15.5 m and 8.5 m, respectively. The sensor employs integrated environmental control technology, substantially enhancing detection precision. To improve the instrument’s response speed, the miniaturization of the cavity and structural optimization were implemented, achieving a rapid response time of merely 6.22 s, addressing the stringent requirements for quick responsiveness in poultry respiration thermometry research. A signal processing model tailored for on−site applications was designed, boosting the system’s signal−to−noise ratio by 4.7 times under complex environmental noise conditions. Utilizing Allan variance analysis, the sensor’s detection limits for O2 and CO2 were ascertained to be 2.9 ppm and 7.4 ppb, respectively. A 24−h field application test conducted in Gongzhuling demonstrated that the sensor’s results align with the respiratory characteristics of poultry under normal physiological conditions, validating its extensive potential for application in respiratory analysis, environmental monitoring, and industrial sectors. Full article
(This article belongs to the Section Environmental Sensing)
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15 pages, 3714 KB  
Article
Off-Axis Integral Cavity Carbon Dioxide Gas Sensor Based on Machine-Learning-Based Optimization
by Pengbo Li, Guanyu Lin, Jianbo Chen and Jianing Wang
Sensors 2024, 24(16), 5226; https://doi.org/10.3390/s24165226 - 13 Aug 2024
Cited by 4 | Viewed by 2035
Abstract
Accurately detecting atmospheric carbon dioxide is a vital part of responding to the global greenhouse effect. Conventional off-axis integral cavity detection systems are computationally intensive and susceptible to environmental factors. This study deploys an Extreme Learning Machine model incorporating a cascaded integrator comb [...] Read more.
Accurately detecting atmospheric carbon dioxide is a vital part of responding to the global greenhouse effect. Conventional off-axis integral cavity detection systems are computationally intensive and susceptible to environmental factors. This study deploys an Extreme Learning Machine model incorporating a cascaded integrator comb (CIC) filter into the off-axis integrating cavity. It is shown that appropriate parameters can effectively improve the performance of the instrument in terms of lower detection limit, accuracy, and root mean square deviation. The proposed method is incorporated successfully into a monitoring station situated near an industrial area for detecting atmospheric carbon dioxide (CO2) concentration daily. Full article
(This article belongs to the Section Environmental Sensing)
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11 pages, 4066 KB  
Communication
Multiphysics Coupling Simulation of Off-Axis Integrated Cavity Optical Sensing System
by Xing Tian, Jun Yuan, Shichao Chen, Xile Cao, Tong Mu and Gang Cheng
Photonics 2024, 11(8), 720; https://doi.org/10.3390/photonics11080720 - 31 Jul 2024
Cited by 1 | Viewed by 1586
Abstract
The optical properties of an off-axis integrated cavity system are influenced by both structural deformation and thermal deformation. In this paper, the finite element simulation and analysis software COMSOL multiphysics was used to numerically simulate the optical system. By coupling geometric optics, solid [...] Read more.
The optical properties of an off-axis integrated cavity system are influenced by both structural deformation and thermal deformation. In this paper, the finite element simulation and analysis software COMSOL multiphysics was used to numerically simulate the optical system. By coupling geometric optics, solid mechanics, and solid heat transfer and conducting parametric temperature scanning, a multiphysics simulation of the off-axis integrated cavity optical sensing system was achieved. The effects of different temperature conditions on the stress field, displacement field, and optical mirrors were analyzed, and changes in optical properties were assessed using ray trajectories and point diagrams. Additionally, optical simulation software was used to simulate and optimize the experimental optical path, obtaining the distribution of light spots on the detector surface. This provides a theoretical basis for the subsequent optimization of the off-axis integrated cavity optical system. Full article
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12 pages, 2730 KB  
Article
Measurement of CO2 by Wavelength Modulated Reinjection Off-Axis Integrated Cavity Output Spectroscopy at 2 μm
by Zihao Yuan, Yinbo Huang, Xingji Lu, Jun Huang, Qiang Liu, Gang Qi and Zhensong Cao
Atmosphere 2021, 12(10), 1247; https://doi.org/10.3390/atmos12101247 - 25 Sep 2021
Cited by 12 | Viewed by 3247
Abstract
A high sensitivity wavelength modulated reinjection off-axis integrated cavity output spectroscopy (WM-RE-OA-ICOS) experimental setup was built at a 2 μm band. On the basis of an off-axis integrated output spectroscopy (OA-ICOS), combined with an optical reinjection (RE) approach to improve signal intensity, and [...] Read more.
A high sensitivity wavelength modulated reinjection off-axis integrated cavity output spectroscopy (WM-RE-OA-ICOS) experimental setup was built at a 2 μm band. On the basis of an off-axis integrated output spectroscopy (OA-ICOS), combined with an optical reinjection (RE) approach to improve signal intensity, and wavelength modulation spectroscopy (WMS) to improve the signal-to-noise ratio (SNR) of the system, the experimental study of trace CO2 with high sensitivity was carried out using the setup. The performance was compared and evaluated, and the results show that: Compared with the OA-ICOS, the wavelength modulated reinjection OA-ICOS enhanced the signal intensity by 6.3 times, and the SNR increased 7.2 times from 179 to 1288. The Allan variance results showed that the detection limit of the system is 0.35 ppm when the average system time is 230 s. The setup was used to measure the indoor CO2 concentration for a long time (22 h), and the measured results were in line with the actual concentration change. The proposed method shows good performance enhancement for the OA-ICOS system in trace gas measurements. Full article
(This article belongs to the Special Issue Optical Gas Sensing in Atmosphere)
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