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Research on Fiber Grating Sensing and Key Technology of Sagnac Loop

Author: ZhaoJinZuo
Tutor: TongZuoZuo
School: Tianjin University of Technology
Course: Communication and Information System
Keywords: High birefringence fiber Sagnac loop mirror Long period fiber grating Polarization maintaining fiber Bragg grating
CLC: TN253
Type: Master's thesis
Year: 2011
Downloads: 46
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Abstract


Since the 1970s the advent of fiber grating, it has been widely applied in the field of optical fiber communication and sensing. Long period fiber grating grating period is generally in the tens to hundreds of microns, compared and other passive components, it has the advantages of simple construction techniques, low back reflection, insertion loss, immunity to electromagnetic interference, and is not sensitive to the impact of polarization , thus becoming a research hotspot. Due to the polarization maintaining fiber special cross-sectional structure on inscribing Bragg grating is equivalent to inscribe fiber Bragg grating in the fast and slow axis, respectively, when used for sensing and measuring outside the physical quantity changes will affect the polarization maintaining optical fiber and Bragg grating optic axis optical properties, polarization maintaining fiber Bragg grating resonant wavelength drift, which can achieve the purpose of sensing. Fiber Sagnac loop filter as the field of optical fiber communication and optical fiber sensing device with a simple production, regardless of the state of polarization of the input light. This article focuses on the long period fiber grating and polarization maintaining fiber Bragg grating sensing characteristics, while taking advantage of the fiber Sagnac loop filter to improve the sensitivity of the measurement. The concrete work as follows: 1) Analysis of the various output characteristics when the different media in the fiber Sagnac loop. Jones matrix with uniform fiber Bragg grating, high-birefringent fiber Sagnac ring theory, and its numerical simulation using MATLAB software. Detailed analysis of transmission characteristics with a period of high birefringence fiber and two sections of high birefringence fiber Sagnac ring. In the numerical simulation based on the two with a single segment of high birefringence fiber Sagnac ring directly in series and the two sections of high birefringence fiber length ratio of 1:2 (2:1), experimental verification, obtained from the experiment spectral simulation spectrum is in good agreement. 2) Discussion of the mode coupling characteristics of the long period fiber grating, in this study based on the response characteristic of its temperature, axial strain, lateral loads, and the refractive index of. Using the refractive index of the response characteristics of the long period fiber grating environment, produced a simple structure, low cost, high sensitivity of the liquid level sensor, when the liquid level changes in the range of 0 ~ 17.5mm and the measured liquid is distilled water and ethanol, LPFG transmission power, respectively change the 6.8719dB of 13.4360dB, the sensitivity to 0.3896dB/mm and 0.7678dB/mm. 3) describes the basic characteristics of the polarization maintaining fiber Bragg grating, and theoretical and experimental studies of its temperature, strain sensing mechanism. Simultaneously measuring the temperature and the axial strain sensing structure is designed based on these principles. In this configuration, the polarization maintaining fiber Bragg grating as a sensor head, fiber Sagnac ring as an edge filter member for converting changes in the success rate of change of the optic axis of the polarization maintaining fiber Bragg grating resonance wavelength, the measurement corresponding to the optic axis of the resonance wavelength difference and the power difference to realize the simultaneous measurement of temperature and the axial strain, the sensitivity when the temperature and the axial strain in the range from 30 ° C to 90 ° C and 0 ~ 480με, respectively-0.672pm / ° C-0.0236dB / ° C, 0 pm / με and -0.00361 dB / με.

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CLC: > Industrial Technology > Radio electronics, telecommunications technology > Photonics technology,laser technology > Optical waveguide and integrated optics > Fiber optic components
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