A near-infrared C2H2/CH4 dual-gas sensor system combining off-axis integrated-cavity output spectroscopy and frequency-division-multiplexing-based wavelength modulation spectroscopy

The Analyst ◽  
2019 ◽  
Vol 144 (6) ◽  
pp. 2003-2010 ◽  
Author(s):  
Kaiyuan Zheng ◽  
Chuantao Zheng ◽  
Dan Yao ◽  
Lien Hu ◽  
Zidi Liu ◽  
...  
Keyword(s):  
Near Infrared ◽  
High Sensitivity ◽  
Dynamic Measurement ◽  
Wavelength Modulation Spectroscopy ◽  
Wavelength Modulation ◽  
Frequency Division ◽  
Modulation Spectroscopy ◽  
Cavity Output ◽  
High Finesse ◽  
High Finesse Cavity

A near-infrared C2H2/CH4 sensor was demonstrated utilizing a miniaturized high finesse cavity with high sensitivity and remarkable dynamic measurement performance.

scholarly journals Compact Open-Path Sensor for Fast Measurements of CO2 and H2O using Scanned-Wavelength Modulation Spectroscopy with 1f-Phase Method

Sensors ◽  
2020 ◽  
Vol 20 (7) ◽  
pp. 1910
Author(s):  
Xiang Li ◽  
Feng Yuan ◽  
Mai Hu ◽  
Bin Chen ◽  
Yabai He ◽  
...  
Keyword(s):  
High Sensitivity ◽  
Fast Response ◽  
Wavelength Modulation Spectroscopy ◽  
Phase Method ◽  
High Temporal Resolution ◽  
Wavelength Modulation ◽  
Modulation Spectroscopy ◽  
Open Path ◽  
Averaging Time ◽  
Term Performance

We report here the development of a compact, open-path CO2 and H2O sensor based on the newly introduced scanned-wavelength modulation spectroscopy with the first harmonic phase angle (scanned-WMS-θ1f) method for high-sensitivity, high temporal resolution, ground-based measurements. The considerable advantage of the sensor, compared with existing commercial ones, lies in its fast response of 500 Hz that makes this instrument ideal for resolving details of high-frequency turbulent motion in exceptionally dynamic coastal regions. The good agreement with a commercial nondispersive infrared analyzer supports the utility and accuracy of the sensor. Allan variance analysis shows that the concentration measurement sensitivities can reach 62 ppb CO2 in 0.06 s and 0.89 ppm H2O vapor in 0.26 s averaging time. Autonomous field operation for 15-day continuous measurements of greenhouse gases (CO2/H2O) was performed on a shore-based monitoring tower in Daya Bay, demonstrating the sensor’s long-term performance. The capability for high-quality fast turbulent atmospheric gas observations allow the potential for better characterization of oceanographic processes.

Simultaneous Measurements of CO and CO2 Employing Wavelength Modulation Spectroscopy Using a Signal Averaging Technique at 1.578 μm

2018 ◽  
Vol 72 (9) ◽  
pp. 1380-1387 ◽  
Author(s):  
Chuanliang Li ◽  
Ligang Shao ◽  
Lijun Jiang ◽  
Xuanbing Qiu ◽  
Jilin Wei ◽  
...  
Keyword(s):  
Near Infrared ◽  
Wavelength Modulation Spectroscopy ◽  
Spectral Lines ◽  
Detection Sensitivity ◽  
Line Pair ◽  
Wavelength Modulation ◽  
Modulation Spectroscopy ◽  
Direct Absorption Spectroscopy ◽  
Allan Variation ◽  
Relationship Of

A resolved line pair was selected for simultaneous measurement of carbon monoxide (CO) and carbon dioxide (CO2) in the near-infrared (NIR) region. The spectral lines of CO and CO2 at 1.578 µm were measured by wavelength modulation spectroscopy (WMS)-2 f and the absorption was enhanced with a multipass absorption cell. The white noise was further reduced by averaging technology. The detection sensitivity (1σ) for the system is estimated at 2.63 × 10−7 cm−1 for direct absorption spectroscopy. The ultimate detection limits of CO2 and CO mixed with pure N2 at 75 Torr are 29 parts per million (ppm) and 47 ppm, respectively. It is demonstrated that the signal is highly linear with the concentration in the range of 100–800 ppm. Based on an Allan variation analysis, the minimum detectable limit of CO2 and CO is 7.5 and 14 ppm, respectively. The response time of the system is about 30 s and a relationship of temperature dependence was obtained. As an example, an in situ measurement of exhaust of alkane combustion emission is presented.

scholarly journals Development and Integration of a CO Detection System Based on Wavelength Modulation Spectroscopy Using Near-Infrared DFB Laser

2018 ◽  
Vol 2018 ◽  
pp. 1-8 ◽  
Author(s):  
Bin Li ◽  
Shuo-Cheng Zhang ◽  
Yao-Dan Chi
Keyword(s):  
Near Infrared ◽  
Limit Of Detection ◽  
Detection System ◽  
Wavelength Modulation Spectroscopy ◽  
Detection Accuracy ◽  
Wavelength Modulation ◽  
Modulation Spectroscopy ◽  
Measure Concentration ◽  
Dfb Laser ◽  
Co Detection

A wavelength modulation spectroscopy- (WMS-) based gas sensing system was established to measure concentration of carbon monoxide (CO) in the range 0–100%. The CO absorption line at 1563.06 nm was scanned with a tunable distributed feedback (DFB) laser, and two InGaAs photodiodes were applied to perform optic-electric conversion. Without using commercial instruments, essential electrical circuits were self-developed and integrated, including laser temperature controller, laser current driver, signal generator, and digital lock-in amplifier. The gas cell deployed in the system was fiber coupled with a total effective optical path length of 50 cm. The second-order harmonic signal was extracted, and experiments of gas detection were carried out to investigate the performance of the sensor, including detection repeatability, detection accuracy, response time, and limit of detection (LoD). Experiment results show that the sensor is reliable and has acceptable probing performance. The maximum relative detection error is less than 3.8%, suggesting good detection stability. Benefiting from the self-developed sensor, the whole CO detection system has small size, affordable expense, and application potential.

scholarly journals A Robust Optical Sensor for Remote Multi-Species Detection Combining Frequency-Division Multiplexing and Normalized Wavelength Modulation Spectroscopy

Sensors ◽  
2021 ◽  
Vol 21 (4) ◽  
pp. 1073
Author(s):  
Wenling Jin ◽  
Hui Zhang ◽  
Mai Hu ◽  
Mengpeng Hu ◽  
Yubin Wei ◽  
...  
Keyword(s):  
Optical Sensor ◽  
Laser Intensity ◽  
Spectroscopic Technique ◽  
Wavelength Modulation Spectroscopy ◽  
Laser Source ◽  
Frequency Division Multiplexing ◽  
Wavelength Modulation ◽  
Frequency Division ◽  
Modulation Spectroscopy ◽  
Hazardous Gases

By combining frequency-division multiplexing and normalized wavelength modulation spectroscopy, a robust remote multi-species sensor was developed and demonstrated for practical hydrocarbon monitoring. Independently modulated laser beams are combined to simultaneously interrogate different gas samples using an open-ended centimeter-size multipass cell. Gas species of interest are demodulated with the second harmonics to enhance sensitivity, and high immunity to laser power variation is achieved by normalizing to the corresponding first harmonics. Performance of the optical sensor was experimentally evaluated using methane (CH4) and acetylene (C2H2) samples, which were separated by a 3-km fiber cable from the laser source. Sub-ppm sensitivity with 1-s time resolution was achieved for both gas species. Moreover, even with large laser intensity fluctuations ranging from 0 to 6 dB, the noise can be kept within 1.38 times as much as that of a stable intensity case. The reported spectroscopic technique would provide a promising optical sensor for remote monitoring of multi hazardous gases with high robustness.

scholarly journals Experimental-based comparison between off-axis integrated cavity output spectroscopy and multipass-assisted wavelength modulation spectroscopy at 77 µm

OSA Continuum ◽  
2019 ◽  
Vol 2 (9) ◽  
pp. 2667
Author(s):  
Faisal Nadeem ◽  
Julien Mandon ◽  
Simona M. Cristescu ◽  
Amir Khodabakhsh ◽  
Frans J. M. Harren
Keyword(s):  
Wavelength Modulation Spectroscopy ◽  
Wavelength Modulation ◽  
Modulation Spectroscopy ◽  
Cavity Output
Sign in / Sign up

Export Citation Format

Share Document