Signal demodulation method for fiber grating-based near-infrared absorption type concentration sensor

Abstract

The invention relates to a signal demodulation method for a fiber grating-based near-infrared absorption type concentration sensor, belonging to the fields of sensors and measuring techniques. According to the signal demodulation method for the fiber grating-based near-infrared absorption type concentration sensor, a broadband light source (11), two optical-fiber circulators (12 and 19), a sample absorption cell (13), demodulation fiber gratings (15, 16 and 20), refractive index matching liquid (17), a tuning unit (18), two photodetectors (21 and 22), a signal processing unit (23) and an optical-fiber link are comprised. The method has the characteristics that the Bragg reflection wavelength of the demodulation fiber grating (15) is identical with the near-infrared absorption wavelength of an object to be measured, the Bragg reflection wavelengths of the fiber gratings (16 and 20) are identical but are different form the Bragg reflection wavelength of the fiber grating (15), in this way, the measurement of concentration is realized by utilizing the ingeniously designed optical-fiber link structure and in combination with the differential detection method, and at the same time, the problem that the measurement is affected due to power fluctuation of the light source is solved.

Description

technical field [0001] The invention relates to a signal demodulation method of a near-infrared absorption concentration sensor based on an optical fiber grating, and belongs to the technical field of sensors and detection. Background technique [0002] The mechanism of spectral absorption optical fiber gas sensing is based on the selective absorption characteristics of gas in the near-infrared band, using the absorption peak of gas in the transmission window (0.8μm-1.7μm) of quartz fiber to measure the light intensity attenuation due to gas absorption, and get concentration of the gas. [0003] Foreign research on spectral absorption fiber optic gas sensors originated in the early 1980s. Due to the limitations of the development of light source technology, in the first ten years or so of research, the light source was LED broadband light source. (K.Chan, H.Ito, H.Inaba, et al.An Optical-Fiber-Based Gas Sensor for Remote Absorption Measurement of Low-Level CH 4 Gasin the...

AI Technical Summary

Problems solved by technology

In addition, due to the relatively weak absorption of gas in the near-infrared band, high-sensitivity spectral absorption technology is also the research focus of optical fiber gas detection. The application of cavity absorption spectral analysis technology and ring-down spectral analysis technology to optical fiber gas detection system can improve the test sensitivity, but , the stability of the system needs to be further improved

[0005] Domestic research on fiber optic gas sensors started relatively late, starting in the early 1990s, and they were all theoretical and experimental studies without practical application

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