System and method for distributed optical fibre sensing measurement based on Brillouin scattering

A technology of Brillouin scattering and distributed optical fiber, which is applied in the direction of measuring devices, instruments, etc., can solve the problems of limiting the practicality of BOTDR, high cost, and low measurement accuracy

Inactive Publication Date: 2012-11-28
GUANGXI NORMAL UNIV
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  • Claims
  • Application Information

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Problems solved by technology

However, because the Brillouin frequency shift in the optical fiber is affected by both temperature and strain, there is a problem of cross sensitivity, that is, it is impossible to distinguish whether the frequency shift is caused by temperature or strain only by the Brillouin frequency shift, and it is difficult to realize multi-parameter Simultaneous sensing of the BOTDR limits the usefulness of
At present, there are three main methods to solve the BOTDR cross-sensitivity problem. The first method is to measure the Brillouin scattered light intensity and Brillouin frequency shift at the same time. The self-published Brillouin scattered power to be measured is weak, and the actual power in the ...

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  • System and method for distributed optical fibre sensing measurement based on Brillouin scattering
  • System and method for distributed optical fibre sensing measurement based on Brillouin scattering
  • System and method for distributed optical fibre sensing measurement based on Brillouin scattering

Examples

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Embodiment 1

[0036] In this example, the structure of the distributed optical fiber sensing measurement system based on Brillouin scattering is as follows: figure 1 As shown, the solid connection lines between the components in the figure indicate the optical path, and the dotted connection lines indicate the circuit. The first narrow linewidth laser 1 and the second narrow linewidth laser 2 are distributed feedback semiconductor lasers with a linewidth of about 1 MHz, and the output wavelengths of the first narrow linewidth laser 1 and the second narrow linewidth laser 2 are λ1 and λ2 respectively The continuous laser, the wavelength difference between λ1 and λ2 is 20nm. The continuous laser λ1 and λ2 are connected to the multiplexer 3 and enter the coupler 4 to be divided into two paths, one path is used as the probe light, and the other path is used as the local oscillator light; the probe light containing λ1 and λ2 first enters the polarization controller 5, and then accesses the pulse...

Embodiment 2

[0048] In this example, the structure of the distributed optical fiber sensing measurement system based on Brillouin scattering is as follows: Figure 4 As shown, the detection optical path is similar to that of Embodiment 1, but an erbium-doped fiber amplifier 14 is connected between the electro-optic modulator 6 and the circulator 7 . The erbium-doped fiber amplifier 14 amplifies the peak power of the optical pulse to be close to the Brillouin threshold of the sensing fiber 8, so as to obtain the maximum sensing distance.

[0049] The local oscillator light from the coupler 4 is first passed through the local oscillator polarization controller 18 and then connected to the local oscillator electro-optic modulator 16, and the microwave signal source 17 is connected to the local oscillator electro-optic modulator 16; the local oscillator optical pulse output by the local oscillator electro-optic modulator 16 The 3dB optical coupler 9 is connected through the polarization scramb...

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Abstract

The invention discloses a system and a method for distributed optical fibre sensing measurement based on Brillouin scattering. According to the invention, the laser of the system outputs two continuous laser lights having a wavelength difference of greater than 15 nm, and the laser lights are split into a detection light and a local oscillation light via a wave combiner and a coupler; the detection light enters sensing optical fibres via an electro-optical modulator and a circulator which are connected with a pulse signal generator, and a self-excited Brillouin scattering light is accessed into the 3 dB coupler via the circulator; and the local oscillation light is accessed into the 3 dB coupler as well, and the output of the 3 dB coupler is connected with a balance detector and a data acquisition and processing unit which stores associated programs and formulas. The measurement method comprises the following steps that: the double-wavelength detection light is modulated into a detection light pulse so as to generate self-excited Brillouin scattering in the sensing optical fibres, and subjected to coherent frequency mixing with the local oscillation light; the data acquisition and processing unit performs a frequency-sweep measurement on the difference-frequency electric signal of the balance detector so as to obtain Brillouin scattering frequency spectrums and Brillouin frequency shifts along different points of the optical fibres, and calculates to obtain the change amounts of a temperature and a strain. Via the system and the method disclosed by the invention, simultaneous measurement for the temperature and the strain is realized, and the measurement accuracy is improved.

Description

technical field [0001] The invention relates to the technical field of optical fiber sensors, in particular to a distributed optical fiber sensing measurement system and measurement method based on Brillouin scattering. Background technique [0002] The safety and health inspection of large-scale infrastructure and the timely detection of hidden failures are of great significance to disaster prevention and mitigation, ensuring the safety of people's lives and national property. Especially with the continuous construction and commissioning of high-speed railways, large-scale bridges and tunnels, oil pipelines, power communication networks, and large-scale nuclear power plants, the demand for safety and health monitoring of large-scale infrastructure continues to increase. [0003] The structural health monitoring of large-scale projects has long-distance, high-precision, and distributed requirements, and traditional detection methods and point sensors are not competent. Dist...

Claims

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Application Information

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IPC IPC(8): G01D21/02
Inventor 阳丽王力虎
Owner GUANGXI NORMAL UNIV
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