Fiber bragg grating low-frequency strain sensing demodulation system

Abstract

The invention discloses a fiber bragg grating low-frequency strain sensing demodulation system which comprises a narrow linewidth laser, an electro-optic / acoustic optical modulator, a radio-frequency signal generator, an electro-optic phase modulator, a phase modulation signal generator, a coupler, a first fiber bragg grating sensor, a second fiber bragg grating sensor, a photoelectric detector, a data acquisition card and a strain demodulation module. The narrow linewidth laser provides a narrow linewidth laser source for the whole demodulation system, the electro-optic / acoustic optical modulator modulates the laser source according to a chirp signal generated by the radio-frequency signal generator generating the chirp signal, and the electro-optic phase modulator performs phase modulation on the modulated laser source according to a sinusoidal modulation signal generated by the phase modulation signal generator generating the sinusoidal modulation signal. The coupler divides the laser source subjected to the phase modulation into two paths, the first fiber bragg grating sensor and the second fiber bragg grating sensor generate two paths of fiber bragg grating reflectance spectra under scanning of the two paths of the laser sources, the photoelectric detector performs photovoltaic conversion on the two paths of the fiber bragg grating reflectance spectra, the data acquisition card outputs two paths of optical fiber sensing digital signals, and the strain demodulation module is used for demodulating the two paths of the optical fiber sensing digital signals.

Description

technical field [0001] The invention relates to the field of optical fiber technology, in particular to a high-precision optical fiber grating low-frequency strain sensing demodulation system based on laser linear sweep modulation technology and PDH frequency-locked sensing technology. Background technique [0002] Fiber Bragg Grating (FBG) sensor has been a research hotspot in the field of fiber optic sensing for more than two decades, and has been widely used in strain measurement of smart materials and structures. Fiber Bragg grating sensors have many advantages such as small size, fast response speed, wide range of linear response, and easy reuse. The strain measurement accuracy of FBG strain interrogators widely used in the market is generally 1με, which can meet general application requirements. However, if FBG is to be applied to the observation of terrain deformation, the accuracy of strain observation must be above 10nε, and the system needs to meet the requirements...

AI Technical Summary

Problems solved by technology

[0007] In view of this, the main purpose of the present invention is to provide a high-precision fiber grating low-frequency strain sensing demodulation system based on laser linear frequency sweep modulation technology and sideband interrogation technology, using laser linear frequency sweep modulation technology and optical filtering technology, combined with PDH frequency-locked sensing technology realizes strain measurement with high precision and large dynamic range, and focuses on solving the problem that tunable lasers in frequency-locked sensing are expensive, poor scanning linearity of tunable lasers leads to limited strain measurement accuracy, and the scanning range of tunable lasers Problems such as small dynamic range of limited strain measurement

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