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Spiral sapphire fiber bragg grating, preparation method and application thereof

A fiber Bragg and Bragg grating technology, applied in the directions of cladding fiber, grating fiber, optical waveguide light guide, etc., can solve the problems of reflection peak reflectivity change, spectral instability, etc., and achieve easy operation, high coupling efficiency, and good spectral performance. and the effect of spectral stability

Inactive Publication Date: 2021-11-16
JILIN UNIV
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  • Summary
  • Abstract
  • Description
  • Claims
  • Application Information

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Problems solved by technology

This will change the coupling of the refractive index modulation region and the mode field region, making the spectrum unstable, that is, the splitting of the reflection peak or the change of the reflectivity

Method used

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  • Spiral sapphire fiber bragg grating, preparation method and application thereof
  • Spiral sapphire fiber bragg grating, preparation method and application thereof
  • Spiral sapphire fiber bragg grating, preparation method and application thereof

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Effect test

Embodiment 1

[0047] A spiral sapphire fiber Bragg grating, the spiral sapphire fiber Bragg grating is a sapphire fiber comprising a spiral Bragg grating; the spiral Bragg grating is a three-dimensional spring-shaped helical structure as a whole, symmetrically distributed along the axial direction of the sapphire fiber The spiral Bragg grating is obtained by scanning the femtosecond laser point by point along the spring-shaped trajectory inside the sapphire fiber, and the spiral Bragg grating formed after laser modulation is a permanent modulation area of ​​refractive index.

[0048] The modulated refractive index of the spiral Bragg grating is lower than that of the area in the sapphire fiber that is not modulated by the laser, and the difference between the refractive index and the unmodulated area is 0.001-0.1; the grating is modulated by the laser from Single crystals transform into polycrystalline or amorphous states.

[0049] The three-dimensional spiral structure of the spiral Bragg ...

Embodiment 2

[0051] This embodiment provides a method for preparing a helical sapphire fiber Bragg grating. A true three-dimensional helical Bragg grating is prepared inside the sapphire fiber through a femtosecond laser processing system. The helical Bragg grating has good structural symmetry and The large refractive index modulation area can obtain stable spectra with high reflectivity and high quality. The specific steps are as follows:

[0052] (1), optical fiber pretreatment:

[0053] First, take a 30cm-long, 60μm-diameter sapphire fiber, and clean the sapphire fiber as a whole with alcohol cotton;

[0054] (2), optical fiber placement:

[0055] Place the cleaned sapphire fiber in step (1) on the femtosecond laser processing platform (Aerotech, model ABL10050L), adjust the position of the fiber so that the sapphire fiber is immersed in the refraction above the oil immersion objective lens (Olympus, 60× / 1.42) In the ratio matching solution (refractive index value 1.75), and then use ...

Embodiment 3

[0067] The spiral sapphire fiber Bragg grating prepared in embodiment 2 is subjected to a bending test, and the specific test steps are as follows:

[0068] In order to verify the spectral stability of the spiral grating, Figure 7 It is the result of the helical sapphire fiber Bragg grating changing with different bending radii. When the bending radius is gradually reduced to 10mm, the spectral reflectance remains basically unchanged. When continuing to bend the sapphire fiber, when the bending radius reaches 5mm, the spectral reflectance decreases slightly, and the spectrum becomes smoother compared with the unbent, mainly because the bending process will filter out a part of the high-order modes in the sapphire fiber, thus The spectrum is smoothed and the spectral bandwidth is reduced accordingly. The bending test shows that the spiral grating has good spectral stability. When the external disturbance redistributes the mode field intensity in a certain range, it can stil...

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Abstract

The invention discloses a spiral sapphire fiber bragg grating and a preparation method and application thereof, and belongs to the technical field of optical fiber sensing. Preparation of a true three-dimensional spiral bragg grating is realized in a sapphire fiber by using a femtosecond laser processing system; and femtosecond laser has ultrahigh peak power and ultrashort pulse duration, laser additive and subtractive manufacturing is carried out on different materials, and preparation of three-dimensional structures and devices is achieved. When the peak power of the laser exceeds a nonlinear absorption threshold value of the material, a multi-photon absorption nonlinear effect can occur, and permanent refractive index change in the transparent material is induced in a laser focusing area. The femtosecond laser processing technology can realize permanent refractive index modulation inside the sapphire optical fiber, and the optical fiber high-temperature sensor is prepared. The prepared spiral grating has good structural symmetry and a large refractive index modulation area, a high-reflectivity and high-quality spectrum is obtained, the influence of external disturbance on the spectrum is reduced, and the spiral grating has good stability.

Description

technical field [0001] The invention belongs to the technical field of optical fiber sensing, and in particular relates to a spiral sapphire fiber Bragg grating, a preparation method and an application thereof. Background technique [0002] The environment of high temperature strain measurement is relatively harsh and harsh, such as in nuclear reactors, oil and gas wells, steel furnaces, engines, and coal furnaces. In these application scenarios, some test systems cannot work normally or even fail due to the influence of environmental factors, especially in the field of aerospace, where there are inherent high temperature, complex stress and strain, complex electromagnetic environment, strong overload, strong Radiation and other harsh environmental conditions. The use of ultra-high temperatures is increasing, making it difficult for traditional electronic sensors to function effectively. Optical fiber sensors have obvious advantages in high-temperature strain measurement d...

Claims

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Application Information

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Patent Type & Authority Applications(China)
IPC IPC(8): G02B6/02
CPCG02B6/0208G02B6/02147
Inventor 孙洪波国旗于永森
Owner JILIN UNIV
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