From the monitoring of deep ocean conditions to the imaging and exploration of the vast universe, optical sensors are playing a unique, critical role in all areas of scientific research. Optical fiber sensors, in particular, are not only widely used in daily life such as for medical inspection, structural health monitoring, and environmental surveillance, but also in high-tech, high-security applications such as missile guidance or monitoring of aircraft engines and structures. Measurements of physical parameters are required in harsh environments including high pressure, high temperature, highly electromagnetically-active and corrosive conditions. A typical example is fossil fuel-based power plants. Unfortunately, current optical fiber sensors for high-temperature monitoring can work only for single point measurement, as traditional fully-distributed temperature sensing techniques are restricted for temperatures below 800°C due to the limitation of the fragile character of silica fiber under high temperature.
In this research, a first-of-its-kind technology was developed which pushed the limits of fully distributed temperature sensing (DTS) in harsh environments by exploring the feasibility of DTS in optical sapphire waveguides. An all sapphire fiber-based Raman DTS system was demonstrated in a 3-meters long sapphire fiber up to a temperature of 1400°C with a spatial resolution of 16.4cm and a standard deviation of a few degrees Celsius.
In this dissertation, the design, fabrication, and testing of the sapphire fiber-based Raman DTS system are discussed in detail. The plan and direction for future work are also suggested with an aim for commercialization. / Ph. D. / This project studied the temperature dependence of Raman scattering characteristics in the single-crystal sapphire fiber. Based on these results, we designed and implemented a sapphire fiber-based fully distributed temperature sensing system using a high-power pulsed-laser. Our preliminary results show excellent and consistent temperature resolution from room temperature up to 1400 ºC. To our best knowledge, this is the first demonstration of a sapphire fiber-based distributed temperature sensing of any kind. These sensors are suitable for coal gasifiers in which the environment is corrosive, for aerospace engines and turbines requiring compact sensing elements and boilers with high-pressure environments.
| Identifer | oai:union.ndltd.org:VTETD/oai:vtechworks.lib.vt.edu:10919/82741 |
| Date | 13 October 2016 |
| Creators | Liu, Bo |
| Contributors | Electrical and ComputerEngineering, Wang, Anbo, Pickrell, Gary R., Poon, Ting-Chung, Zhu, Yizheng, Xu, Yong |
| Publisher | Virginia Tech |
| Source Sets | Virginia Tech Theses and Dissertation |
| Detected Language | English |
| Type | Dissertation |
| Format | ETD, application/pdf |
| Rights | In Copyright, http://rightsstatements.org/vocab/InC/1.0/ |
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