DETERMINATION OF CONCENTRATION AND TEMPERATURE BY A FABRY-PEROT CAVITY FORMED BY TWO FIBER BRAGG GRATINGS |
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| Authors: | Qi Wang Mu-bing Liu Peng Wang Yong Zhao |
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| Affiliation: | 1. College of Information Science and Engineering , Northeastern University , Shenyang , China;2. State Key Laboratory of Synthetical Automation for Process Industries , Northeastern University , Shenyang , China;3. College of Information Science and Engineering , Northeastern University , Shenyang , China |
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| Abstract: | A sensing system based on a Fabry-Perot cavity formed by two fiber Bragg gratings for simultaneous measurements of temperature and liquid concentration is reported. Detailed analysis and discussion of the spectral transmission characteristics of the device are provided based on Coupled-Mode Theory. Through numerical simulation of spectral transmission, reflection spectra are shown to be influenced by the grating and Fabry-Perot cavity lengths, and sensing properties of temperature and liquid concentration are studied. A fast Fourier transform based demodulation method that simultaneously demodulates temperature and liquid concentration signals of the device was studied. The use of the fast Fourier transform provides absolute measurements with high sensitivity. The temperature sensitivity was 0.0104 nm/°C, the resolution was 1°C, the error of repeatability was 4%, the hysteresis was less than 0.010 nm, and the sensitivity of the measurement on liquid reflection was 0.01%. |
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| Keywords: | Fabry-Perot cavity fast Fourier transform fiber Bragg grating liquid concentration sensitivity temperature |
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