Photonic Sensors

, Volume 8, Issue 2, pp 127–133 | Cite as

SNR Improvement of QEPAS System by Preamplifier Circuit Optimization and Frequency Locked Technique

  • Qinduan Zhang
  • Jun Chang
  • Zongliang Wang
  • Fupeng Wang
  • Fengting Jiang
  • Mengyao Wang
Open Access


Preamplifier circuit noise is of great importance in quartz enhanced photoacoustic spectroscopy (QEPAS) system. In this paper, several noise sources are evaluated and discussed in detail. Based on the noise characteristics, the corresponding noise reduction method is proposed. In addition, a frequency locked technique is introduced to further optimize the QEPAS system noise and improve signal, which achieves a better performance than the conventional frequency scan method. As a result, the signal-to-noise ratio (SNR) could be increased 14 times by utilizing frequency locked technique and numerical averaging technique in the QEPAS system for water vapor detection.


QEPAS system preamplifier circuit frequency locked method noise optimization 



This work was supported by the National Natural Science Foundation of China (Grant Nos. 61405105 & 61475085), the Shandong Provincial Natural Science Foundation, China (Grant No. ZR2014FQ015), Science and Technology Development Project of Shandong Province (Grant No. 2014GGX101007), and the Fundamental Research Funds of Shandong University (Grant Nos. 2014HW016 & 2014YQ011).


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© The Author(s) 2018

Open Access This article is distributed under the terms of the Creative Commons Attribution 4.0 International License (, which permits unrestricted use, distribution, and reproduction in any medium, provided you give appropriate credit to the original author(s) and the source, provide a link to the Creative Commons license, and indicate if changes were made.

Authors and Affiliations

  • Qinduan Zhang
    • 1
  • Jun Chang
    • 1
  • Zongliang Wang
    • 2
  • Fupeng Wang
    • 1
  • Fengting Jiang
    • 1
  • Mengyao Wang
    • 1
  1. 1.School of Information Science and Engineering and Shandong Provincial Key Laboratory of Laser Technology and ApplicationShandong UniversityJinanChina
  2. 2.School of Physics Science and Information Technology and Shandong Key Laboratory of Optical Communication Science and TechnologyLiaocheng UniversityLiaochengChina

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