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Environmental temperature measurement method based on optical fiber Rayleigh and Brillouin principle

A technology of ambient temperature and measurement method, applied in the field of measurement, can solve the problems of high cost, increase the cost of temperature detection, complex system, etc., and achieve the effect of reducing system cost, reducing the requirements of light source line width, and simplifying the system structure

Active Publication Date: 2012-07-18
NORTH CHINA ELECTRIC POWER UNIV (BAODING)
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Problems solved by technology

[0005] Comprehensive analysis of fiber optic Brillouin temperature distribution sensing systems at home and abroad. The light source uses narrow linewidth lasers and obtains the required optical pulses through external modulation. The system is too complicated and very expensive, which greatly increases the cost of temperature detection.

Method used

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  • Environmental temperature measurement method based on optical fiber Rayleigh and Brillouin principle
  • Environmental temperature measurement method based on optical fiber Rayleigh and Brillouin principle
  • Environmental temperature measurement method based on optical fiber Rayleigh and Brillouin principle

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Embodiment Construction

[0024] The present invention proposes based on the following principles:

[0025] For ordinary LD, its output spectrum is composed of many spectral lines, and the wider the light source spectrum is, the higher the stimulated Brillouin scattering threshold is, the greater the input power allowed by the sensing system is, and the stronger the Brillouin signal is. This common light source can reduce Rayleigh coherent noise, so a better system signal-to-noise ratio can be obtained. LD output spectrum as figure 1 As shown, the output power calculation formula is given by (1), where i is the serial number of the output spectral line.

[0026] (1)

[0027] Let the electric field incident into the fiber be:

[0028]

[0029] The electric field of the Rayleigh scattered light of multiple spectral lines generated at the same position of the fiber can be expressed as

[0030] (2)

[0031] In formula (2) R Indicates the Rayleigh scatteri...

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Abstract

The invention provides an environmental temperature measurement method based on an optical fiber Rayleigh and Brillouin principle. An optical fiber sensing system is composed of a semiconductor laser device, a circulator, a photoelectric detector and a sensing optical cable. In a measurement process, pulse light sent out by the semiconductor laser device is injected into the sensing optical cable through the circulator, back side Rayleigh scattering and Brillouin scattering signals of the sensing optical cable are received from the circulator by the photoelectric detector, so that heterodyne frequency mixing is carried out on the signals in the photoelectric detector; then, an output signal of the photoelectric detector is used for determining a Rayleigh frequency shift of each point on the sensing optical cable; and finally, the temperature of each point on an optical fiber is calculated by utilizing a relation model between the Rayleigh frequency shift and the temperature, so as to realize temperature measurement. Compared with the conventional method, the requirement on a light source line width is reduced, an external modulating unit is saved, the system structure is simplified, the system cost is reduced and the system performance is improved.

Description

technical field [0001] The invention relates to a method for detecting ambient temperature distribution by using an optical fiber, which belongs to the technical field of measurement. Background technique [0002] Optical fiber Brillouin temperature distribution measurement technology is a new type of measurement technology, which has the unique advantages of obtaining distribution information along the entire optical fiber measured field with only one measurement, high measurement accuracy, accurate positioning, and a sensing distance of up to hundreds of kilometers. Advantages, it has broad application prospects in the fields of online monitoring of the health status of large-scale engineering structures in industries such as electric power, petroleum, geology, water conservancy, and construction, and fault location. [0003] The distributed sensing technology based on optical fiber Brillouin scattering has higher measurement accuracy, measurement range and spatial resolut...

Claims

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Application Information

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Patent Type & Authority Applications(China)
IPC IPC(8): G01K11/32G01K11/322
Inventor 李永倩杨志赵丽娟
Owner NORTH CHINA ELECTRIC POWER UNIV (BAODING)
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