Dynamic pressure detection system and method based on fiber grating Stokes parameters

A fiber grating and dynamic pressure technology, applied in the direction of measuring force, measuring the change of optical properties of the material when it is stressed, measuring devices, etc., can solve the problems of difficult detection and poor real-time performance

Active Publication Date: 2016-06-22
PLA UNIV OF SCI & TECH
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Problems solved by technology

In this method, when the pressure is small, it is difficult to detect the difference in the central wavelength of the two eigenmodes in the total amplitude spectrum, and it is difficult to detect
The general measurement method based on polarization parameters mainly detects the maximum value of the polarization parameter spectrum in the wavelength range of the grating stop band, and the real-time performance is poor.

Method used

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  • Dynamic pressure detection system and method based on fiber grating Stokes parameters
  • Dynamic pressure detection system and method based on fiber grating Stokes parameters
  • Dynamic pressure detection system and method based on fiber grating Stokes parameters

Examples

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example 1

[0039] [Example 1] Design grating parameters: period Λ = 535nm, fiber core refractive index n eff =1.448, length L=10mm, refractive index modulation coefficient δn=1×10 -4 . The motorized polarization controller 3 is adjusted by the feedback module 7 so that the polarization state of the incident light is linearly polarized at 45°. Select the tunable laser wavelength λ=1549.3nm. When the sensing fiber grating 4 is affected by external pressure, the birefringence of the line will change, which will lead to the change of the three Stokes parameters of the transmitted light. The transmitted light passes through the online polarization analysis module 5 to detect the change of the polarization parameter, passes through the signal processing module 6, and displays three Stokes parameter values ​​in the display module 8 to monitor the dynamic pressure received in real time. In this example, the theoretical relationship between the three Stokes parameters and the external pressure...

example 2

[0040] [Example 2] Design grating parameters: period Λ = 535nm, fiber core refractive index n eff =1.448, length 20mm, refractive index modulation coefficient δ n =1×10 -4 . Adjust the motorized polarization controller 3 to select multiple incident ray polarization angles, which are 30°, 45° and 60° respectively. In this example, the theoretical relationship between the variation of the three Stokes parameters and the external pressure under different incident polarization states is as follows image 3 As shown, the sensitivity, dynamic range, and linearity of the three Stokes parameters vary with the incident angle.

example 3

[0041] [Example 3] Actual grating parameters: length L=10mm, center wavelength 1550.06nm, maximum insertion loss 9dB. The tunable laser wavelength λ=1549.7nm. Initial incident polarization state (0.541, 0.244, 0.822). In this example, the vibration source pressed on the grating has a vibration period of 4.5ms and a frequency of about 222Hz. In this example, the monitored three Stokes parameters vary with dynamic pressure as Figure 4 As shown, the three Stokes parameters all have good responses to dynamic pressure.

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Abstract

The invention discloses a dynamic pressure detection system and a method based on fiber grating Stokes parameters. The system comprises a tunable laser, an electric polarization controller, a sensing fiber grating, a polarization detection module, a signal processing module, a feedback module and a display unit, wherein the tunable laser emits laser of a certain wavelength and feeds the laser to the electric polarization controller and to the sensing fiber grating; the online polarization detection module acquires laser transmitted from the sensing fiber grating, the laser is outputted to the signal processing module, and three Stokes parameters for the polarization state of the transmitted laser are obtained; and the signal processing module feeds back the parameters to the electric polarization controller to adjust the polarization state of incident laser. Linear birefringence is generated by the fiber grating under effects of external pressure, three parameters for the transmitted laser are caused to change, a single-wavelength source is adopted to realize real-time sensing on the size of the dynamic pressure, the defect that the traditional method is not suitable for small pressure sensing can be overcome, and the defect that the sensing method based on the grating polarization parameter maximum value is not suitable for dynamic pressure sensing can be solved.

Description

technical field [0001] The invention relates to the technical field of optical fiber sensing, in particular to an optical fiber sensing device for real-time monitoring of pressure by using the Stokes parameter of the transmitted light of an optical fiber grating. Background technique [0002] When the optical fiber is affected by the external environment (temperature, stress, magnetic field, pressure, etc.), the parameters such as the intensity, phase, frequency, and polarization state of the transmitted light in the optical fiber will change accordingly. By detecting these parameters of the transmitted light, the change of the corresponding physical quantity can be known. This technology is called fiber optic sensing technology. [0003] As a mature all-fiber device, fiber grating has very important applications in the fields of optical fiber communication and optical fiber sensing due to its small size, low insertion loss, and easy integration with other optical fiber devi...

Claims

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Application Information

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Patent Type & Authority Applications(China)
IPC IPC(8): G01L1/24
CPCG01L1/246
Inventor 苏洋朱勇周华张宝富
Owner PLA UNIV OF SCI & TECH
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