BOTDR system based on Bark sequences and long-distance detection method thereof

Abstract

The invention discloses a BOTDR system based on Bark sequences and a long-distance detection method thereof. The method comprises the steps that continuous light is divided into two paths; a set of bipolar Bark sequences is generated, and the bipolar Bark sequences is divided into two sets of unipolar Bark sequences; the two sets of unipolar Bark sequences are utilized for controlling the electric field to modulate probe light, and light pulse signals of the two sets of unipolar Bark sequences are obtained; the two sets of signals are amplified, optical fibers are injected, and two sets of backward Brillouin scattering light signals are obtained; vibration light signals are in coupling coherence with the two sets of backward Brillouin scattering light signals respectively, and two sets of Brillouin scattering electric signals are collected through photovoltaic conversion, frequency sweeping and filter and amplification; the two sets of Brillouin scattering electric signals are in coherence, Brillouin frequency shift of each point distributed along the optical fiber is obtained, and changes of the temperature or strain around the optical fiber are obtained. An electro-optic modulation module in the system comprises an electro-optic intensity modulation module and a Bark sequence generating module. The self-correlation characteristics of the Bark sequences are utilized for improving the signal to noise ratio and improving the distance detecting distance under the condition that the system space resolution ratio is not reduced.

Description

technical field [0001] The invention relates to a Bark sequence-based BOTDR system and a long-distance detection method thereof, belonging to the technical field of distributed optical fiber sensing. Background technique [0002] As a kind of distributed optical fiber sensor, the Brillouin Optical Time-Domain Reflectometry (BOTDR) based on Brillouin scattering has the advantages of high resolution, small error, simple layout of sensing fiber, low cost, easy to accomplish. Using the relationship between the Brillouin frequency shift in the optical fiber and the strain or temperature at a certain position of the optical fiber, it can be used in the power industry, water conservancy industry and civil construction industry, monitoring of fission of building bridges and other concrete structures, structural health monitoring of large civil engineering, Detection of failure points in traffic highway, subway tunnel industry, oil and gas industry. When there is an axial strain or...

AI Technical Summary

Problems solved by technology

Existing BOTDR systems based on coding technology, such as Gloay and Simplex technology, can solve the contradiction between spatial resolution and dynamic range to a certain extent, but Gloay and Simplex technology do not have a good peak-to-average ratio, due to the self-published Liyuan The existence of the stimulated threshold makes it easier for the system to reach the stimulated threshold, but the dynamic range has not been improved

In actual industrial applications, Gloay and Simplex technologies have large defects in the time and storage space overhead of obtaining a set of data

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