Long-distance optical fiber sensing method based on Hadamard matrix self-correlated characteristic

A technology of long-distance optical fiber and sensing method, which is applied in the direction of using optical devices to transmit sensing components, measuring force by measuring the change of optical properties of materials when they are stressed, thermometers with physical/chemical changes, etc., which can solve the problem of space. Resolution reduction, peak power fiber nonlinear effects, reduced sensor sensitivity, etc.

Inactive Publication Date: 2009-07-08
NANJING UNIV
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Problems solved by technology

Since the spatial resolution of sensing depends on the width of the light pulse, too long pulse width will lead to the reduction of spatial resolution
Therefore, increasing the peak power of the pulse bec

Method used

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  • Long-distance optical fiber sensing method based on Hadamard matrix self-correlated characteristic
  • Long-distance optical fiber sensing method based on Hadamard matrix self-correlated characteristic
  • Long-distance optical fiber sensing method based on Hadamard matrix self-correlated characteristic

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[0027] Specific implementation plan

[0028] reference figure 1 , In the experimental optical path, the sequence encoding pulse using the Hadamard matrix row vector as the code word is generated by the pulse signal generator. Use the Zero-Span mode of the spectrum analyzer to obtain the optical power distribution at each frequency point. Finally, the data processing is carried out on the computer.

[0029] First, use spectrum analysis to measure the approximate frequency position of the Brillouin power spectrum. It is assumed that the center frequency of the finally obtained Brillouin power spectrum is at a ~ bMHz. Then between a ~ bMH, collect the power distribution signal at this frequency point every certain frequency (usually 5 ~ 10MHz). Then perform the following procedures in sequence:

[0030] 1. Fix the center frequency of the spectrum analyzer at a certain frequency, set the spectrum width to Zero-Span, and use a pulse signal generator to provide a trigger signal for it. ...

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Abstract

The invention provides a method for sensing an optical fiber in long distance based on self-correlation characteristics of a Hadamard matrix. The method comprises the following steps that row vectors of matrixes are used as code words for detecting pulse codes; the row vectors of a matrix A and a matrix B are respectively used as train pulse of the code words to be inputted into the optical fiber, and a returned Brillouin signal is correlated with continuous light outputted by a laser; coherent signals are acquired by a spectroanalyzer so as to acquire signal power distribution under a frequency point, and acquired results are subtracted; the row vector Hi of the Hadamard matrix is correlated with a corresponding scattered signal, and then, after the correlated results are summed, the correlated results are divided by n to acquire scattered light power acquired when equivalent individual pulse is inputted into the optical fiber; the steps are repeated on each required frequency point; Brillouin power spectrum consisting of the scattered points corresponding to each moment is acquired; and the method performs sensing by a corresponding relation of center frequency, peak power and full width at half maximum of the power spectrum and temperature and stress.

Description

technical field [0001] The invention is a technique suitable for improving the sensing distance of a Brillouin optical fiber sensor (BOTDR). In particular, it is a technology that utilizes the autocorrelation characteristics of the Hadamard matrix to improve the sensing range of the Brillouin fiber sensor under the condition of low detection optical power, and realize the distributed fiber sensing technology of long-distance temperature and stress. Background technique [0002] The frequency shift of the Brillouin scattering spectrum in the fiber, the change of the peak power and the full width at half maximum are all related to the change of the temperature and stress of the fiber. The distributed optical fiber sensing technology based on spontaneous Brillouin scattering realizes the sensing of temperature and stress by measuring the frequency shift variation and peak power variation of the spontaneous Brillouin scattering spectrum generated by optical pulses in the optical...

Claims

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Application Information

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IPC IPC(8): G01K11/32G01L1/24G01D5/26G01J3/30G01K11/322
Inventor 张旭苹梁浩路元刚
Owner NANJING UNIV
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