Brillouin optical time domain reflection measuring method based on quick fourier transform

A technology of Fourier transform and measurement method, which is applied in the field of Brillouin optical time-domain reflectometry, can solve the problems of reduced measurement accuracy and long measurement time, and achieve the effect of simple structure of the measurement device, simplified structure, and improved measurement accuracy

Inactive Publication Date: 2009-06-24
NANJING UNIV
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Problems solved by technology

[0007] The problem to be solved by the present invention is: the existing Brillouin optical time domain reflectance measurement method needs multiple measurements to obtain the required Brillouin scattering spectrum data, and the measurement time is relatively long. Although the bandwidth of each measurement can be increased to Reduces measurement time, but results in reduced measurement accuracy

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  • Brillouin optical time domain reflection measuring method based on quick fourier transform
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  • Brillouin optical time domain reflection measuring method based on quick fourier transform

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[0027] The measuring method of the present invention will be described below in conjunction with specific measuring methods and accompanying drawings.

[0028] Measurement method 1:

[0029] Such as figure 2 As shown, the continuous light of frequency v emitted by the coherent light source laser is divided into two paths by the coupler, and the frequency of one path becomes v-v after passing through the optical frequency shifter S , as a local reference light injected into the heterodyne optical receiver; the other laser light is used as a probe light, which is first modulated into a pulsed light with a pulse width of W by an optical modulator, and then injected into the sensing fiber through an optical amplifier and a circulator. While the pulsed light is propagating forward in the sensing fiber, it generates backward self-Brillouin scattered light on the passing fiber unit. The half-maximum full width of the Brillouin scattering spectrum is tens of megahertz, and the peak ...

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Abstract

In the present invention, the local reference light and the Brillouin scattered light transmitted back by the sensing fiber are coherent, and the generated Brillouin scattered spectrum electric signal completely passes through a broadband low-pass filter, is sampled by a high-speed acquisition and processing circuit, and undergoes fast Fourier transform. Obtain the Brillouin scattering spectrum; then perform Lorentz fitting to finally obtain the Brillouin frequency shift of each unit on the entire fiber; use the relationship between the Brillouin frequency shift and strain and temperature to realize the full distribution of strain or temperature formula measurement. The high-speed acquisition and processing circuit and fast Fourier transform processing method adopted in the present invention can obtain the Brillouin scattering spectrum on the entire sensing fiber within one pulse detection cycle, and the time required for fast Fourier transform processing is short, without reducing the measurement Under the premise of spatial resolution and measurement accuracy, the measurement speed is increased by an order of magnitude compared with the prior art, so that the signal-to-noise ratio can be increased to more than several times, and the measurement accuracy is greatly improved, and the structure of the device of the present invention is simple.

Description

technical field [0001] The invention relates to a distributed optical fiber sensing system for fully distributed measurement of strain and temperature, specifically a fast Fourier transform-based Brillouin sensing system that uses Brillouin scattering in optical fibers to realize fully distributed measurement of strain and temperature Optical Time Domain Reflectometry Method. Background technique [0002] The fully distributed optical fiber sensing technology uses the entire optical fiber as the sensing element, and utilizes the scattering phenomenon in the optical fiber to realize the continuous distribution measurement of the physical quantity to be measured (strain, temperature, etc.) on the sensing optical fiber as a function of time and space. Compared with the quasi-distributed optical fiber sensing technology based on the point sensor array, the fully distributed optical fiber sensing technology has a broader application prospect. Brillouin optical fiber time domain ...

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Application Information

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Patent Type & Authority Patents(China)
IPC IPC(8): G01D5/353G01D5/36G01B11/16G01K11/32G01K11/322
Inventor 路元刚张旭苹窦蓉蓉王峰
Owner NANJING UNIV
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