Pulse pre-pumping single-ended vector botda dynamic strain measurement method and device

Abstract

The invention provides a pulse pre-pumping single-ended vector BOTDA dynamic strain measuring method and measuring device. Stepped pulsed light is utilized to be incident from one end of a sensing fiber, spontaneous Brillouin scattered light generated by a 0-order baseband pre-excited sound wave field of time-limited microwave modulation pre-pumping pulsed light and back Rayleigh scattered light generated by a 1-order sideband serve as probe light, and both generate an excited Brillouin scattering effect with sensing pulsed light; frequency beating of local oscillator light and the probe light carrying Brillouin scattering information is performed in a balance detector, in-phase and orthogonal components in an electrical signal which are obtained after frequency beating are utilized to obtain an excited Brillouin scattering phase shift value, and finally a corresponding dynamic strain value is demodulated according to a corresponding relation curve of phase shifts and dynamic strain which is stored in a computer. The pulse pre-pumping single-ended vector BOTDA dynamic strain measuring device is simple in structure and convenient to use, can effectively reduce a non-local effect, improves a signal to noise ratio of a system, and can realize dynamic strain measurement with wide band, high spatial resolution and measurement accuracy, and good reliability and stability.

Description

technical field [0001] The invention relates to a method and a device for realizing vector BOTDA dynamic strain measurement of a single-end structure by using a pulse pre-pumping technology and an optical fiber Rayleigh scattering principle, and belongs to the field of measurement technology. Background technique [0002] The distributed optical fiber sensor based on Brillouin Optical Time Domain Analysis (BOTDA) technology utilizes the Stimulated Brillouin Scattering (SBS) effect between the probe light and pump light transmitted in opposite directions. , the high-frequency pump light transfers energy to the low-frequency Stokes probe light, and the probe light is amplified by the stimulated Brillouin effect. Therefore, the received signal strength is high, the measurement accuracy is high, and the dynamic range is wide. With its comprehensive performance advantages, BOTDA technology is widely used in submarine optical cable manufacturing and construction maintenance, oil a...

AI Technical Summary

Problems solved by technology

The interferometric dynamic strain measurement technology uses external signals to modulate the phase, wavelength, intensity and polarization state of the light waves transmitted in the optical fiber, and detects the changes of these parameters through the interferometer to realize the measurement of dynamic strain. However, this measurement technology is vulnerable to the surrounding environment. Influenced by noise factors, the stability of the system is poor; Qualitative measurement; BOTDA dynamic strain measurement technology uses the Brillouin gain slope analysis method to realize the measurement of dynamic strain, but it is greatly affected by the frequency drift of the light source, the power fluctuation of the probe light and the pump light, and the system stability is poor. The frequency difference between the pump light and the probe light is used for scanning and data fitting, which takes a long time to measure and cannot respond to high-frequency dynamic strain signals; POTDR dynamic strain measurement technology uses the change of polarization state to realize dynamic strain measurement, but its frequency measurement range Small; 2011,

[0005] A. Zornoza proposed the Brillouin phase shift BOTDA dynamic strain measurement technology, which realized dynamic strain measurement with 1m spatial resolution and 1.66kHz measurement rate at a sensing distance of 160m, and realized dynamic strain by converting phase shift into corresponding frequency shift information The measurement technology is not affected by the power fluctuations of the probe light and the pump light, and has good stability. However, the pump light and the probe light need to be incident from both ends of the fiber separately, and the system structure is complex. In large-scale measurement occasions The application is inconvenient, and the strength of SBS is seriously affected by non-local effects, which will lead to parasitic phase modulation, resulting in phase measurement errors in the system, and when the optical fiber breaks, the system will not be able to detect, and the reliability is low

[0006] In the above-mentioned Brillouin phase shift BOTDA dynamic strain measurement technology, when the sensing pulse width is smaller than the phonon lifetime, the SBS spectrum will be significantly broadened, the measurement accuracy of the system will be greatly reduced, and there will be parasitic phase modulation caused by non-local effects. Due to the large phase measurement error, the measurement with high spatial resolution and high measurement accuracy cannot be realized; since the pump light and the probe light need to be incident from both ends of the optical fiber separately, the system structure is complex, and it is inconvenient to apply in large-scale measurement occasions, and when the optical fiber occurs When it is broken, it will not be detected, and the reliability is low

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