Optical Bragg grating sensing system of eliminating sensitiveness

Abstract

The invention relates to a fiber Prague grating sensor system that could remove crossing sensitivity. It is made up of broad band light resource, sensor grating, 2*w coupler, tree optical tapping element, three photo detector, two decoding fiber grating, wavelength adjuster and computer. It has the advantages of low cost, rapid, convenience, and practicality.

Description

technical field [0001] The invention belongs to the technical field of fiber grating sensing and optical testing, in particular to a fiber Bragg grating sensing system that eliminates cross-sensitivity, which is used to measure external strain and temperature, and can also convert changes in other physical quantities into temperature or strain Changes are then measured with this system. Background technique [0002] As a new type of optical device, fiber grating establishes a periodic distribution of spatial refractive index in the optical fiber, so that the propagation characteristics of light can be changed in it. When a broadband light source is incident on a Fiber Bragg Grating (FBG), the central wavelength λ of the reflected light B is given by the Bragg equation: [0003] lambda B =2nΛ [0004] Among them, n is the effective refractive index of the fiber core, and Λ is the grating period. [0005] When the physical quantities such as temperature and strain of the ...

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Problems solved by technology

[0016] Among the above demodulation methods, the interference demodulation technology has high measurement accuracy, but it measures relative values, and the measurement range is limited by the free spectral range of the interferometer; the signal detection of the tunable light source demodulation technology is convenient and the resolution is high , but the light source is difficult to manufacture and the cost is high; the test range of the linear edge filter demodulation technology is inversely proportional to the resolution, and the linearity of the filter is required to be very good, the slope must be very large, and it is difficult to manufacture; the tunable filter demodulation technology demodulation The range is large, but the scan cycle is long, the test speed is slow, and the repeatability is poor

Due to the existence of the above shortcomings, wavelength demodulation technology has become one of the main obstacles to the industrialization of FBG sensing technology

The FBG demodulator currently on the market is mainly based on scanning F-P technology and interferometric scanning technology, which is complicated to manufacture and quite expensive

In addition, fiber gratings are sensitive to both strain and temperature, so it is necessary to distinguish whether the wavelength drift of fiber gratings is caused by temperature or stress. None of the above methods solves the problem of cross-sensitivity of FBG to temperature and strain.

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