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

A technology of Fourier transform and optical time domain reflection, which is applied in measurement devices, heat measurement, thermometers with physical/chemical changes, etc., can solve the problems of long measurement time and reduced measurement accuracy, and achieves simplified structure and simple structure of the measurement device. , the effect of improving the measurement speed

Inactive Publication Date: 2008-03-19
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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[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] As shown in Figure 2, 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 of the ...

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Abstract

The invention interferes local reference light with Brillouin diffused light transferred back by a sensing optical fiber, a Brillouin diffused spectrum electrical signal generated completely passes through a broadband low pass wave filter, the sampling is performed by the high speed acquisition and the processing circuit, a quick speed Fourier transformation is performed, a Brillouin diffused spectrum is obtained; then a Lorentz fitting is performed, and a Brillouin frequency shift of each unit on the whole optical fiber is obtained finally; the relation of the Brillouin diffused spectrum, and the strain or the temperature is utilized to realize a full-distribution type measurement of the strain or the temperature. The whole Brillouin diffused spectrum on the whole sensing optical fiber can be obtained in an impulse detecting circle by a processing method of the high speed acquisition, and the processing circuit and the quick speed Fourier transformation adopted by the invention, the measuring speed is improved to an order of magnitude compared with the prior technology on the premise of not decreasing the resolution of a measuring space and the measuring accuracy, thereby improving a speech to noise ratio to more than a plurality of times, the measuring accuracy is improved to a great extent, and the structure of the invention device 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 Applications(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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