Fiber bragg grating type sensing system and method for simultaneous measurement of temperature and strain

Abstract

The invention provides a fiber bragg grating type sensing system and a fiber bragg grating type sensing method for simultaneous measurement of temperature and strain. The fiber bragg grating type sensing system comprises a detection light branch circuit, a feedback detection branch circuit, a polarization-maintaining optical coupler, a modulation unit and a calculation unit, wherein the detection light branch circuit outputs double-sideband intensity-modulated detection light which is input to a sensing grating so as to achieve detection of transmission peak centers on a fast axis and a slow axis of the sensing grating; a reflection signal of the sensing grating is input to the feedback detection branch circuit through the polarization-maintaining optical coupler; the modulation unit outputs a frequency signal to the detection light branch circuit according to a control instruction and reading of the calculation unit; and the calculation unit corrects frequency parameters of the modulation unit according to data provided by the feedback detection branch circuit, so as to lock two sidebands of the detection light on corresponding transmission peaks of the sensing grating and calculates to obtain the temperature and the strain. The fiber bragg grating type sensing system and the fiber bragg grating type sensing method can significantly increase sampling rate and measurement resolution of the temperature and the strain, and achieve higher demodulation precision.

Description

technical field [0001] The invention relates to a technology in the field of optical fiber sensing, in particular to an optical fiber grating sensing system and method for simultaneous measurement of temperature and strain. Background technique [0002] Phase-shifted Fiber Bragg Grating (PS‐FBG) is a variant of traditional Fiber Bragg Grating (FBG). Due to the introduction of phase shift points in the grating with a periodic distribution of refractive index, an extremely narrow transmission window is produced at a certain wavelength in its stop band. The central wavelength of the transmission window is sensitive to both temperature and strain, and its sensitivity is consistent with that of a Bragg grating without phase shift introduced. [0003] Polarization-maintaining fiber is a type of fiber that introduces strong birefringence during design, and its fast axis and slow axis have different refractive indices. The difference between the two refractive indices and the corr...

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Problems solved by technology

[0005] In their paper (12thInternational Conference on Optical Fiber Sensors, OSA Technical Digest Series, Vol.16, 170 / OWC7‐1, 1997), M.Sudo, M.Nakai, etc. proposed that the traditional fiber grating on the polarization maintaining fiber be used for temperature strain Simultaneous measurement scheme, but due to its low demodulation accuracy, the accuracy of the measurement results of the birefringence effect is poor, so it is impossible to achieve a resolution better than 1°C / 10με

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