A novel methodology to directly pre-determine the relative wavelength response of DFB laser in wavelength modulation spectroscopy

Liu, Jianxin; Zhou, Yueting; Guo, Songjie; Hou, Jiajuan; Gang, Zhao; Ma, Weiguang; Wu, Yirong; Zhang, Lei; Yin, Wen; Liu, Xiao; Axner, Ove; Jia, Suotang

doi:10.1364/oe.27.001249

Cited by 12 publications

(4 citation statements)

References 26 publications

(37 reference statements)

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“…where S(T) is the intensity of the characteristic spectral line of the gas, Φ(]) is the lineshape function of the absorbed spectral line, which is described here by the Voigt function, P is the total pressure of the gas, X is the volume concentration of the gas to be measured, and L is the transmission distance of laser in the gas medium, respectively. When the central laser frequency ] 0 is modulated by a sine wave with an angular frequency ω, the instantaneous laser frequency ](t) can be expressed as follows [25,26]:…”

Section: Correction Methodsmentioning

confidence: 99%

Correcting the light extinction effect of fly ash particles on the measurement of NO by TDLAS

et al. 2022

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The measurement of nitric oxide (NO) concentration in power plant flue gas by tunable diode laser absorption spectroscopy (TDLAS) is susceptible to fly ash particles. The presence of fly ash particles causes laser intensity fluctuations and leads to the second harmonic (2f) signal amplitude changes. In this manuscript, we analyzed the influence of particles on the 2f signal and corrected the measurement error of NO concentration by the wavelength modulation-second harmonic (WMS-2f) technique. Specifically, the 2f signal error caused by quartz sand and fly ash particles were measured, and the exponential function representing the peak-to-peak error of the 2f signal was obtained by fitting. Finally, the peak-to-peak value of the 2f signal and the NO concentration were corrected according to the exponential function. After correction, the NO concentration error under the fly ash influence (the particle size in the range of 10–200 μm and the mass concentration is less than 18.26 g/m3) was no more than 2%. This correction method effectively improves the measurement accuracy of NO concentration by the WMS-2f technique in the fly ash environment.

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Section: Correction Methodsmentioning

confidence: 99%

Correcting the light extinction effect of fly ash particles on the measurement of NO by TDLAS

et al. 2022

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“…The time‐frequency response relationship (

\overset{ν}{true} ((), t)

bold-italica ((), t)

) can be obtained using Fabry–Perot (F–P) interferometer monitoring during the experiments; this is common practice in the TDLAS technique 10–16,23,25 . The absorption harmonic signals can then be simulated accurately.…”

Section: Methodsmentioning

confidence: 99%

“…The time-frequency response relationship (ν t ð Þ, a t ð Þ) can be obtained using Fabry-Perot (F-P) interferometer monitoring during the experiments; this is common practice in the TDLAS technique. [10][11][12][13][14][15][16]23,25 The absorption harmonic signals can then be simulated accurately. The absorption signal includes the integrated absorbance (A) and the line shape derivative ( d kþ2g ϕ dν kþ2g ).…”

Section: Methodsmentioning

confidence: 99%

Linear calibration‐free wavelength modulation spectroscopy

Lin

et al. 2021

Micro & Optical Tech Letters

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This article presents a new linear calibration-free wavelength modulation spectroscopy (LCF-WMS) technique for gas sensing. By combining the natural logarithms of the transmitted intensity and background signals, this technique eliminates the effects of the intensity, intensity modulation, and the modulation phase to obtain integrable harmonic signals along the line-of-sight and thus realize calibration-free measurements. To illustrate the validity of the LCF-WMS technique, it was applied to measurement of the water vapor concentration in air at ambient temperature. Because of its specific features of line-of-sight integrability and baseline independence, this method will be advantageous in absorption tomography and high-pressure applications.

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“…[23,24] In addition, Ma et al have found a method to determine the RWR. [25,26] They have not only considered the linear time-dependent amplitude of the first modulation term but also the constant amplitude of the second modulation term, and this reduced the final scanned-WMS-2 f /1 f fitting residuals significantly. Furthermore, Ma et al proposed a method to pre-determine the RWR, which is based on a second-order polynomial description of the RWR for the ramp-scan current.…”

Section: Introductionmentioning

confidence: 99%

Analysis of relative wavelength response characterization and its effects on scanned-WMS gas sensing*

Zheng¹,

Peng²,

Ding³

et al. 2021

Chinese Phys. B

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Our recently proposed three-step method showed the promising potential to improve the accuracy of relative wavelength response (RWR) characterization in the wavelength-modulation spectroscopy (WMS) over the commonly used summation method. A detailed comparison of the three-step method and the summation method, for the wavelength-scanned WMS gas-sensing, was performed with different laser parameters (modulation indexes and scan indexes) and gas properties (pressures and concentrations). Simulation results show that the accuracy of the predicted gas parameters is strongly limited by the RWR characterization with large modulation index and high gas pressure conditions. Both fitting residuals of RWR and errors of predicted gas parameters from the recently proposed three-step method are nearly 2 orders of magnitude smaller than those from the summation method. In addition, the three-step method is further improved by introducing a coupling term for the 2nd harmonic amplitude. Experiments with CO2 absorption transition at 6976.2026 cm−1 were conducted and validated the simulation analysis. The modified-three-step method presents an improved accuracy in RWR description with at least 5% smaller fitting residual for all conditions compared with the three-step method, although the deviation of the deduced CO2 concentrations between these two methods does not exceed 0.2%.

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A novel methodology to directly pre-determine the relative wavelength response of DFB laser in wavelength modulation spectroscopy

Cited by 12 publications

References 26 publications

Correcting the light extinction effect of fly ash particles on the measurement of NO by TDLAS

Correcting the light extinction effect of fly ash particles on the measurement of NO by TDLAS

Linear calibration‐free wavelength modulation spectroscopy

Analysis of relative wavelength response characterization and its effects on scanned-WMS gas sensing*

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