Self-heterodyne single-ended vector BOTDA-based dynamic strain measurement method and apparatus

Abstract

The invention relates to a self-heterodyne single-ended vector BOTDA-based dynamic strain measurement method and apparatus. A laser outputs three paths of light; lower frequency-shift continuous light is generated at the first path; the light at the second path is used as pulse substrate light; and double-sideband-structure-based coding pulse light is generated at the third path. The synthesized light from the three paths enters from one end of a sensing fiber. Back Rayleigh scattering light generated by the light from the first path and the second path in the sensing fiber is used as local oscillator light and detection light respectively; the two kinds of light are led into a photoelectric detector to carry out self-heterodyne detection and quadrature and in-phase components in an obtained electric signal are extracted; according to a function relationship between the quotient of the two kinds of components and a stimulated Brillouin scattering phase shift, a stimulated Brillouin scattering phase shift value is obtained. And then a corresponding dynamic strain value is demodulated based on a corresponding relation curve of the stimulated Brillouin scattering phase shift and the dynamic strain. According to the invention, the structure is simple; the application becomes convenient; the reliability and stability are high; non-destructive high-sensitivity and high-signal-to-noise-ratio dynamic strain measurement can be realized.

Description

technical field [0001] The invention relates to a method and device for realizing distributed measurement of dynamic strain by adopting a self-heterodyne detection single-end vector BOTDA system, and belongs to the field of measurement technology. Background technique [0002] Distributed sensing technology based on Brillouin Optical Time Domain Analysis (BOTDA) technology is widely used in power cables and equipment, Health diagnosis, fault monitoring and positioning of large-scale engineering structures in oil and gas pipelines, construction, water conservancy and other industries. [0003] The traditional BOTDA system needs to inject oppositely transmitted pump light and probe light at both ends of the fiber. When the frequency difference between the pump light and the probe light is the Brillouin frequency shift, stimulated Brillouin will occur in the sensing fiber. Stimulated Brillouin Scattering (Stimulated Brillouin Scattering, SBS) effect, by directly detecting the ...

AI Technical Summary

Problems solved by technology

However, in the traditional Brillouin phase shift BOTDA dynamic strain measurement system, the stimulated Brillouin scattering gain or loss is used, not only the measurement sensitivity and the system signal-to-noise ratio are low, but also the pump light and the probe light need to pass through the optical fiber. Each end is incident separately, and the system structure is complicated. When the optical fiber breaks, it will not be able to detect, and it is inconvenient to apply in a large-scale measurement occasion, and the reliability is low; and the single-ended light that uses Fresnel reflected light and Rayleigh scattered light as the detection light The BOTDA system with the structure has the disadvantages of weak signal and large noise. Therefore, there is an urgent need for a dynamic strain measurement system with simple structure, convenient application, high reliability, high sensitivity, and high signal-to-noise ratio that can simultaneously achieve high frequency and fast measurement. Method and Measuring Device

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