This dissertation focuses on developing new technologies for ultra-low-cost sapphire fiber-optic high-temperature sensors. The research is divided into three major parts, the souceless sensor, the simple Fabry-Perot (F-P) interrogator, and the sensor system.
Chapter 1 briefly reviews the background of thermal radiation, fiber optic F-P sensors, and F-P signal demodulation. The research goal is highlighted.
In Chapter 2, a temperature sensing system is introduced. The environmental thermal radiation was used as the broadband light source. A sapphire wafer F-P temperature sensor head was fabricated, with an alumina cap designed to generate a stable thermal radiation field. The radiation-induced optical interference pattern was observed. We demodulated the temperature sensor by white-light-interferometry (WLI). Temperature resolution better than 1°C was achieved.
Chapter 3 discusses a novel approach to demodulate an optical F-P cavity at low-cost. A simple interrogator is demonstrated, which is based on the scanning-white-light-interferometry (S-WLI). The interrogator includes a piece of fused silica wafer, and a linear CCD array, to transform the F-P demodulation from the optical frequency domain to the spatial domain. By using the light divergence of an optical fiber, we projected a tunable reference F-P cavity onto an intensity distribution along a CCD array. A model for S-WLI demodulation was established. Performance of the new S-WLI interrogator was investigated. We got a good resolution similar to the well-known traditional WLI.
At last, we were able to combine the above two technologies to a sapphire-wafer-based temperature sensor. The simple silica wafer F-P interrogator was optimized by focusing light to the image sensor. This approach improves the signal to noise ratio, hence allows the new integrator to work with the relatively weak thermal radiation field. We, therefore, proved in the experiment, the feasibility of the low-cost sourceless optical Fabry-Perot temperature sensor with a simple demodulation system. / PHD / Temperature measurements for high temperature harsh environments is a challenge industrial task. In this work, a low-cost sapphire fiber high temperature sensor is introduced which uses single crystal sapphire fiber as the light guiding and a sapphire-wafer-based Fabry-Perot (F-P) interferometer as the temperature sensing element. The research goal is to provide an optical sensing system whose price is competitive to the high temperature thermocouples.
Two technologies were developed to reduce the cost of the sensing system, the sourceless sensor head design and the low-cost wafer-based F-P interrogator.
The sourceless sensor head makes use of the environmental thermal radiation as a broadband light source, together with the white light interferometry signal demodulation method, for temperature measurements. In this case, the system avoids using not only an external light, but also the light driver and the light coupling element.
A low-cost F-P cavity interrogation method was introduced to demodulate the sapphire-wafer-based temperature sensing F-P cavity. The signal demodulation is based on the scanning white light interferometry, but a reliable and low-cost reference F-P cavity is introduced. It includes only a piece of transparent wafer and a CCD array to transfer the interference fringe from the spectra domain to the spatial domain and therefore a low cost CCD can be directly applied to identify the optical path distance of the sensing OPD.
Eventually, the above two technologies were able to put together and an extremely low-cost F-P temperature sensing system was built. It has a good potential for further applications and commercialization.
| Identifer | oai:union.ndltd.org:VTETD/oai:vtechworks.lib.vt.edu:10919/91191 |
| Date | 10 January 2018 |
| Creators | Tian, Zhipeng |
| Contributors | Electrical Engineering, Wang, Anbo, Zhu, Yizheng, Agah, Masoud, Xu, Yong, Pickrell, Gary R. |
| Publisher | Virginia Tech |
| Source Sets | Virginia Tech Theses and Dissertation |
| Detected Language | English |
| Type | Dissertation |
| Format | ETD, application/pdf, application/pdf |
| Rights | In Copyright, http://rightsstatements.org/vocab/InC/1.0/ |
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