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

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...

AI Technical Summary

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 becomes the only way to increase the sensing distance of this type of sensor, but if the peak power is too high, it will cause nonlinear effects in the optical fiber and reduce the sensitivity of the sensor.

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