The temperature-insensitive optical fiber optical grating displacement transducer of a kind of pair of isosceles triangle simple beam structure
Technical field
The present invention relates to a kind of fiber grating displacement sensor that solves temperature strain cross sensitivity problem, belong to technical field of optical fiber sensing.
Background technology
Fiber-optic grating sensor is a kind of special Fibre Optical Sensor, except the characteristics with Fibre Optical Sensor, also has advantages such as anti-electromagnetic interference (EMI), electrical isolation, corrosion-resistant, highly sensitive, long transmission distance, security are good, simple in structure, light weight.Aspects such as safety monitoring at oil, chemical industry, building, highway, bridge etc. are with a wide range of applications.Yet, in actual applications, the bragg wavelength of fiber grating all is responsive to strain and temperature, and promptly there is temperature-strain cross sensitivity problem in fiber-optic grating sensor, the key that this becomes its development of restriction becomes the problem that must face and solve in the practical application.The present invention adopts a density, thickness is even but asymmetric pair of isosceles triangle simple beam structure design solved the temperature-strain cross sensitivity problem of fiber-optic grating sensor in practice.
Summary of the invention
The invention belongs to technical field of optical fiber sensing.The temperature-insensitive optical fiber optical grating displacement sensor structure that has designed a kind of pair of isosceles triangle simple beam structure is simple, easy operating.
The temperature-insensitive optical fiber optical grating displacement transducer of described a kind of pair of isosceles triangle simple beam structure is characterized in that: be made up of the first isosceles triangular structure beam (1), the second isosceles triangular structure beam (2), fiber grating (3), tail optical fiber (4) and fixed support (5).
The free beam fiber grating displacement sensor of described a kind of pair of isosceles triangular structure is characterized in that: first isosceles triangular structure beam (1) the long 5cm to 5.5cm in the end, high 9cm to 10cm; Second isosceles triangular structure beam (2) the long 4cm to 4.5cm in the end, high 7cm to 8cm; Base (5) is a square structure, and length and width are same with the end appearance of triangular beam respectively, and whole simple beam structure thickness is 4.5mm to 5.0mm, is made by uniform methyl methacrylate of density (PMMA) or the firm material of 65# manganese.
The free beam fiber grating displacement sensor of described a kind of pair of isosceles triangular structure is characterized in that: the crossover sites that fiber grating (3) rigidity is sticked on the first isoceles triangle ellbeam (1) and the second isoceles triangle ellbeam (2) with epoxy resin.
This sensor utilizes the structural design of two isosceles triangles, can solve optical fiber grating temperature-strain cross sensitivity problem, and is simple in structure, easy to operate.
Description of drawings
Fig. 1 is two isosceles triangular structure free beam fiber grating displacement sensor synoptic diagram;
Fig. 2 is a reflectance spectrum broadening lab diagram under the different displacement situations.
Embodiment
Example 1: as shown in Figure 1, the temperature-insensitive optical fiber optical grating displacement transducer of a kind of pair of isosceles triangle simple beam structure is made up of the first isosceles triangular structure beam (1), the second isosceles triangular structure beam (2), fiber grating (3), tail optical fiber (4) and fixed support (5).
First isosceles triangular structure beam (1) end is long to be 5cm, and height is 9cm; Second isosceles triangular structure beam (2) end is long to be 4cm, and height is 7cm; Base (5) is a square structure, and length and width are same with the end appearance of triangular beam respectively, and whole simple beam structure thickness is 4.5mm.
Fiber grating (3) rigidity is sticked on the crossover sites of the first isoceles triangle ellbeam (1) and the second isoceles triangle ellbeam (2) with epoxy resin.The material of the first isoceles triangle ellbeam (1) and the second isoceles triangle ellbeam (2) is the uniform methyl methacrylate of density (PMMA), and fixed support (5) is fixed between the two proper supporting objects, is convenient to measure the size of displacement behind the beam pressurized.
The present invention is based on following principle: fiber grating is under temperature and stress, all can cause the drift of bragg wavelength, when fiber grating was used for sensing measurement, single fiber grating self can't be told the drift value of the Bragg wavelength that strain and temperature cause respectively.
The present invention adopts special two isosceles triangle simple beam structure designs, the fiber grating rigidity is sticked on the axis of two triangle crossover sites, because the two triangle structure is asymmetric, when onesize masterpiece is used for this crossover sites, the two triangle beam can produce two bendings in various degree, thereby the fiber grating that makes rigidity stick on two ends, the cross spider left and right sides is subjected to two strains that vary in size, make the stressed stepped distribution of fiber grating, chirp makes through fiber grating reflectance spectrum broadening.Each position thickness of free beam is identical, and material is even, and temperature variation is identical to the influence at each position of material.As shown in Figure 2, when changing in the scope of displacement at 0mm to 15mm, reflectance spectrum is linear broadening, and integral body moves to long wavelength's direction.Therefore, temperature variation only can make spectrum integral body drift about towards a direction to the not influence of width of output spectrum.Based on the temperature-insensitive characteristic of reflectance spectrum, can realize displacement measurement by the variation that detects spectral width.