Optical fiber sensor capable of simultaneously measuring hydrogen concentration and temperature

Abstract

The invention provides an optical fiber sensor capable of simultaneously measuring the hydrogen concentration and the temperature. The optical fiber sensor comprises a wide-spectrum light source 1, a sensing unit 2 and a spectrometer 3. The sensing unit 2 is composed of a single-mode optical fiber 21, a coreless optical fiber 22 and a single-mode fiber grating 23. The outside of the coreless optical fiber 22 is plated with a palladium-based hydrogen sensitive film. The light emitted from the wide-spectrum light source 1 passes through the single-mode optical fiber 21 to enter the coreless optical fiber 22, and is excited at a plurality of higher order modes within a fusion area 24. In the above modes, the lights are propagated inside the coreless optical fiber at different propagation constants and interfere with each other. An interference light signal enters the single-mode fiber grating 23, and will be reflected when meeting the Bragg reflection condition of the single-mode fiber grating 23. When the external hydrogen concentration changes, the interference spectrum will move. When the ambient temperature changes, both the interference spectrum and the Bragg reflection wavelength will move. Therefore, the hydrogen concentration and the temperature can be deduced through observing the movement amount of the interference spectrum and the movement amount of the Bragg wavelength. As a result, the high-precision measurement of the hydrogen concentration can be realized.

Description

technical field [0001] The invention relates to an optical fiber sensor capable of simultaneously measuring hydrogen concentration and temperature, and belongs to the technical field of optical fiber sensing. Background technique [0002] At present, the use of hydrogen has spread in every corner of people's production and life. At the same time, research and development of high-performance hydrogen sensors have become increasingly important [Document 1. T. Hübert, L. Boon-Brett, G. Black , U.Banach. Hydrogen sensors-A review [J], Sensors and Actuators B: Chemical,2011, 157(2): 329-352.]. The measurement principle of the optical fiber hydrogen sensor is to use hydrogen to react with the hydrogen-sensitive material deposited on the optical fiber to change some properties of the hydrogen-sensitive material, so that the wavelength or intensity of the optical signal in the optical fiber changes, and then by detecting the change of the optical signal To reverse the concentration...

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Problems solved by technology

In 2013, A. Hosoki et al [Document 6. A. Hosoki, M. Nishiyama, H. Igawa, A. Seki, Y. Choi, K. Watanabe. Asurface plasmon resonance hydrogen sensor using Au / Ta2O5 / Pd multi-layers onhetero-core optical fiber structures [J], Sensors and Actuators B: Chemical,2013, 185: 53-58.] proposed an optical fiber hydrogen sensing probe based on the principle of surface plasmon resonance, and used a palladium-based composite film to absorb hydrogen. The changed characteristics realize the measurement of hydrogen concentration, but the measurement signal of this sensor is susceptible to interference by ambient temperature, and the preparation process is complicated, which is not suitable for mass production applications; in order to avoid temperature interference, in 2014, M.Wang et al. [Document 7 . M. Wang, D. N. Wang, M. Yang, J. Cheng, J. Li. In-line Mach-Zehnder Interferometer and FBG with Pd film for simultaneous hydrogen and temperature detection [J], Sensors and Actuators B: Chemical, 2014, 202: 893-896.] Coating the Pd film on the surface of the corroded Mach-Zehnder interferometer and fiber grating realized the simultaneous detection of temperature and hydrogen concentration, but the texture of the corroded interferometer sensor probe is fragile , which is not conducive to long-term stable use; in 2015, Y. H. Yang et al. [Document 8. Y. H. Yang, F. L. Yang, H. Wang, W. Yang, W. Jin. interferometer [J], Journal of LightwaveTechnology, 2015, 33(12): 2566-2571.] proposed a polarization-maintaining photonic crystal fiber-optic hydrogen sensor based on Pd and metal-silver composite film. The influence of interference is small, but the price of polarization-maintaining photonic crystal fiber is higher, Increased sensor cost

In summary, optical fiber hydrogen sensing probes based on Pd-based sensitive materials still have varying degrees of problems in terms of complex preparation process, high cost, and unstable structure. The most critical thing is that some current technologies to avoid temperature interference are still not reach the desired level

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