Dynamic strain measurement method and dynamic strain measurement device based on Brillouin phase shift detection

Abstract

The invention discloses a dynamic strain measurement method based on Brillouin phase shift detection. The dynamic strain measurement method comprises the following steps of dividing laser signals into two paths; after one path of signals are subjected to broadband frequency shift, generating optical heterodyne to detect local oscillator light wave and detection signal light wave, and synchronously injecting the local oscillator light wave and the detection signal light wave into a sensor fiber; after spectrum broadening, causing the other path of laser signals and a pulse generator to generate broadband Brillouin pulse pumping light wave, and injecting the broadband Brillouin pulse pumping light wave into the sensor fiber; setting a modulator to drive a voltage waveform to introduce linear chrip so as to obtain broadband laser, which is approximate to a rectangular spectrum, and extending a linear region with the Brillouin phase shift of the sensor fiber; carrying out coherent detection on the local oscillator light wave and the detection signal light wave through coherent demodulation of a beat frequency signal and a radio frequency signal which are generated by photovoltaic conversion so as to obtain the Brillouin phase shift of the detection signal light wave; demodulating information of a strain signal of the sensor fiber. The dynamic strain measurement method has the advantages that the signal to noise ratio is improved, the dynamic strain measurement range is increased and the detection speed is improved. The invention further discloses a dynamic strain measurement device based on the Brillouin phase shift detection.

Description

Technical field [0001] The invention relates to a dynamic strain measuring technology, in particular to a dynamic strain measuring method and measuring device based on Brillouin phase shift detection. Background technique [0002] Distributed sensing based on the Brillouin scattering effect in the optical fiber is a hot research technology in recent years. It can sense the spatial distribution of strain on the entire optical fiber sensing link and the information that changes with time. It is used in bridges, buildings, dams There are important application prospects in the health and safety monitoring of major structures. The Brillouin distributed optical fiber sensor based on the stimulated Brillouin scattering effect of the detection signal light and the oppositely transmitted pump light in the sensing fiber enhances the detection signal, improves the signal-to-noise ratio, and has a longer sensing distance. However, shortening the measurement time and increasing the strain dy...

AI Technical Summary

Problems solved by technology

Traditionally, this technology is based on the detection of the intensity of the detection signal light, which has many shortcomings: it is necessary to sweep the frequency difference between the pump light and the detection signal light to obtain the Brillouin frequency shift of the sensing fiber; in order to improve the detection signal signal-to-noise Ratio, it is necessary to sample, superimpose and average the signal of each sweep point to reduce the influence of intensity noise, etc.

The above process is extremely time-consuming, which limits its application in dynamic strain measurement

At present, this technology is applied to the report of measuring dynamic strain, and the intrinsic Brillouin gain spectrum of the sensing fiber is used, and the corresponding Brillouin phase shift linear region is extremely narrow about ~35MHz (corresponding to ~700με), which greatly limits the Strain dynamic measurement range

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