Fabrication of Metal-nitride-coated Fiber Bragg Grating Sensor for High Temperature Application

• Main Authors: HSIEH,TSO-SHENG, 謝作生
• Other Authors: CHIANG,CHIA-CHIN
• Format: Others
• Language: en_US
• Published: 2016
• Online Access: http://ndltd.ncl.edu.tw/handle/435b9j

博士 === 國立高雄應用科技大學 === 機械與精密工程研究所 === 104 === This work was devoted to the development of metal-coated optical fiber temperature sensors for harsh environments and critical applications. A significant part of this PhD thesis was dedicated to numerical calculations of a thermo-optical model and temperature sensitivity. In addition, the thermally-induced optical with nitrogen atom behavior of fiber Bragg grating (FBG) sensor are analyzed. The FBG consisted of properly chosen photosensitive fiber materials with a waveguide structure and an optimized thermo-optic coefficient for the core layer. The experimental and optimized thermo-optic coefficient results were consistent in terms of temperature sensitivity. In these experiments, the optical spectrum analyzer obtained an accuracy of 11.9 pm/℃. The second part of this thesis was focused on the performance of a metal-coated FBG used as a high temperature sensor. Specifically, the performance of a transition-metal nitrides (CrN, ZrN, TiN)-coated FBG sensor was evaluated in extreme temperature environments. Using an optical spectrum analyzer, the reflection spectra of the transition-metal nitrides (CrN, ZrN, TiN)-coated FBG sensor were measured and compared with those of bare FBG for temperatures ranging from 100 to 650℃. In this way, the Bragg wavelength shift and temperature sensitivity of both types of FBG were obtained. The results indicated that the CrN-coated FBG sensor exhibited a 14.0 pm/℃ greater temperature sensitivity than the bare FBG.. For experimentation, R-soft software was initially employed to confirm the temperature sensitivity values measured by the TiN-coated FBG and ZrN-coated FBG for the surrounding temperatures by comparing the FBG change results in the Bragg wavelength shifts at various temperatures. The results were then used to analyze the thermal expansion coefficient and the thermo-optic coefficient of metal-coated FBG temperature sensor. The responsivity of the TiN-coated FBG was about 16.4 pm/℃ for the temperatures from 100 to 500℃. TiN film gets oxidized from 350 to 500℃, then the sensitivity of this temperature (20.8 pm/℃) for the experiment measurement is higher than simulation results. The responsivity of the ZrN-coated FBG was about 12.6 pm/℃ for the temperatures from 100 to 650℃, and the gratings of the ZrN-coated FBG demonstrated excellent stability at temperatures as high as 600℃.