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Studies On Several Key Technologies And Systems In Fiber Sensing Applications

Posted on:2008-01-13Degree:DoctorType:Dissertation
Country:ChinaCandidate:Z G ZhangFull Text:PDF
GTID:1118360215483670Subject:Electromagnetic field and microwave technology
Abstract/Summary:PDF Full Text Request
Fiber-optic sensor, a novel sensor technology that provides measuring and monitoring solutions for temperature, pressure, strain, displacement, force and load, has attracted a considerable amount of interests in the last decades because of their unprecedented properties, such as self-referencing capability, high signal-to-noise ratio, immunity to electromagnetic interference and anti-cauterization. With the development of the fiber sensor applications, much work on the fiber sensor technology was focused on the research of the sensing properties of microstructured optical fiber (MOF) and the wavelength interrogation systems feature high resolution, low cost, low complexity and high utility.This dissertation mainly focuses on theoretical studies on the sensing properties of MOF and experimental studies on sensing systems of fiber Bragg grating (FBG). The works are made up of two parts, one is the relationships between the gas sensing properties and the fiber parameters of MOF, including the fiber length and the operating wavelength, are numerically investigated through a full-vector finite element method (FEM), another is novel schemes of wavelength interrogation of FBG sensing are proposed and demonstrated. Below are the lists of the research.Gas sensing properties of MOFA full-vector finite element mode solver based on the hybrid edge/nodal element is developed to conduct the numerical simulation of MOF. Perfectly matched layer (PML) boundary conditions are incorporated into the mode solver to evaluate the leakage properties of MOF.The gas sensing properties of index-guided photonic crystal fiber (PCF) with air-core are investigated via full-vector FEM. The fraction of the total power located in the holes (including the air-core), which directly affects the sensing sensitivity, is simulated. The relationship between the gas sensing properties and the fiber parameters, as well as the operating wavelength, is discussed. It is predicted that higher relative sensitivity of more than 50% can be achieved by designing the fiber parameters and the operating wavelength properly.The gas sensing properties of high-index-core Bragg fiber are investigated via full-vector FEM. The fraction of the total power located in the holes is simulated. The relationship between the gas sensing properties and the fiber parameters, as well as the operating wavelength, is discussed. It is predicted that the gas sensing sensitivity of the fiber increases with the fiber's radius and refractive index decrease, but increases with the wavelength increase.Wavelength interrogation schemes of FBGA scheme of long-distance FBG sensor system based on linear-cavity fiber Raman laser is firstly proposed and demonstrated. Two schemes of FBG wavelength demodulation based on tunable Er-doped fiber ring laser and linear-cavity Er-doped fiber laser are improved, respectively. In measured experiment, results show that the schemes based on fiber laser feature high Signal-to-Noise ratio (SNR), high sensitivity, and anti-jamming.Two schemes of FBG interrogation system based on matching-FBG are proposed and demonstrated, in which step motor and temperature control equipment are used to adjust the matching-FBG, respectively. In measured experiments, results show that the schemes based on matching-FBG feature low cost, small size, low complexity and high utility.A scheme of FBG sensor interrogation system based on all fiber Mach-Zehnder interferometer (MZI) edge filter and tunable-FBG is firstly proposed and demonstrated. The sensing signal produced by FBG sensor can be interrogated by differing two pairs of power transformed from the wavelengths of FBG sensor and tunable-FBG. In measured experiments, the results show that the precision of the proposed system is 0.02nm in a range of 1nm. Furthermore, the precision can be improved by adjusting the two interference arms of the filter.
Keywords/Search Tags:fiber sensor, full-vector finite element method, microstructured optical fiber, FBG, fiber laser, MZI
PDF Full Text Request
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