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Distributed fiber strain demodulation method based on subset window length optimization algorithm

A technology of distributed optical fiber and optimization algorithm, which is applied in the direction of testing optical fiber/optical waveguide equipment, detecting backscattered light in the time domain, using optical devices, etc., can solve the problem of strain measurement accuracy decline and strain information To improve the reliability of cross-correlation and the accuracy of strain calculation

Active Publication Date: 2018-11-27
DALIAN UNIV OF TECH
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Problems solved by technology

However, the longer the length of the subset window, the worse the ability to reflect the local potential strain information of the structure, that is, the decrease in the accuracy of strain measurement

Method used

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  • Distributed fiber strain demodulation method based on subset window length optimization algorithm
  • Distributed fiber strain demodulation method based on subset window length optimization algorithm
  • Distributed fiber strain demodulation method based on subset window length optimization algorithm

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Experimental program
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Embodiment

[0039] The first step, using figure 1 The shown optical frequency domain reflectometer OFDR collects a set of reference Rayleigh scattering spectra and measured Rayleigh scattering spectra of a measured fiber length of 22 meters. The scanning wavelength range of the light source is 10nm, the scanning rate is 20nm / s, and the data length is 3000000.

[0040] The second step is to calculate the optimal subset window length of the group of Rayleigh scattering spectra.

[0041] S21: Calculate and obtain the noise variance D(η)=4 of the group of Rayleigh scattering spectrum signals;

[0042] S22: Set the required strain calculation accuracy σ=0.05, and calculate the quality factor Q=1.2×10 through the theoretical model formula 6 , and set as the threshold;

[0043] S23: Set the spatial resolution M=300, and the optical fiber under test contains K=1350 subsets in total. Set the initial value of the subset window length W=300, the expansion step size S=20, and the cut-off subset wi...

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Abstract

The invention discloses a distributed fiber strain demodulation method based on a subset window length optimization algorithm. According to the invention, through two parameters of noise variance andRayleigh scattering spectrum quality, a user is guided to carry out optimal selection on the size of the subset window. By mainly use of the mutual correlation analysis, the offset quantity between areference Rayleigh scattering spectrum and a measurement Rayleigh scattering spectrum is calculated, so strain information in a measured fiber is obtained. The lengths of the two groups of Rayleigh scattering spectrum subsets used for mutual correlation calculation is the subset window defined by the user based on experience. The subset window significantly affects the reliability of the mutual correlation calculation and the precision of strain measurement. By rationally optimizing the subset window, important effects are achieved for improving of the mutual correlation reliability and the strain calculation precision.

Description

technical field [0001] The invention relates to the field of structural health monitoring, in particular to a distributed optical fiber strain demodulation method based on a subset window length optimization algorithm. Background technique [0002] Optical Frequency Domain Reflectometry (OFDR) is an emerging development direction in distributed optical fiber measurement and sensing technology. Compared with the traditional Optical Time Domain Reflectometry (OTDR), OFDR has the characteristics of high signal-to-noise ratio, high spatial resolution, and high sensitivity. The distributed strain measurement based on OFDR mainly calculates the Rayleigh scattering spectrum offset before and after the strain in the measured optical fiber through cross-correlation analysis, so as to obtain the corresponding strain information. [0003] In the actual measurement process, the accuracy of strain measurement is affected by many factors, such as the size of the signal-to-noise ratio, th...

Claims

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Application Information

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IPC IPC(8): G01M11/00G01B11/16
CPCG01B11/16G01M11/3136
Inventor 武湛君锁刘佳赵士元马书义
Owner DALIAN UNIV OF TECH
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