Fiber-Optic Sensor with Simultaneous Temperature, Pressure, and Chemical Sensing Capabilities
- MicroMaterials, Inc., Tampa, FL (United States)
This project aimed to develop a multifunctional sensor suitable for process control application in chemical and petrochemical industries. Specifically, the objective was to demonstrate a fiber optic sensing system capable of simultaneous temperature, pressure, and chemical composition determinations based on a single strand of sapphire optical fiber. These capabilities were to be achieved through the incorporation of a phosphor and a Bragg grating into the fiber, as well as the exploitation of the evanescent field interaction of the optical radiation inside the fiber with the surrounding chemical medium. The integration of the three functions into a single probe, compared to having three separate probes, would not only substantially reduce the cost of the combined system, but would also minimize the intrusion into the reactor. Such a device can potentially increase the energy efficiency in the manufacture of chemical and petrochemical products, as well as reduce waste and lead to improved quality. In accordance with the proposed research plan, the individual temperature, pressure and chemical sensors where fabricated and characterized first. Then towards the end of the program, an integrated system was implemented. The sapphire fibers were grown on a laser heated pedestal growth system. The temperature sensor was based on the fluorescence decay principle, which exploits the temperature dependence of the fluorescence decay rate of the selected phosphor. For this project, Cr3+ was chosen as the phosphor, and it was incorporated into the sapphire fiber by coating a short length of the source rod with a thin layer of Cr2O3. After the viability of the technique was established and the growth parameters optimized, the temperature sensor was characterized up to 300 °C and its long term stability was verified. The chemical sensor determined the concentration of chemicals through evanescent field absorption. Techniques to increase the sensitivity of the evanescent field interaction such as tapering and coiling the fiber were successfully demonstrated. It was shown that the sensor is capable of quantitative measurements in both the mid-infrared and the near infrared regions of the spectrum. For the pressure sensor, a novel concept involving a pressure amplifier was investigated. While the basic idea was found to work, technical difficulties prevented the demonstration of a sensor capable of quantitative pressure measurements. As a result, the final combined probe contained only a temperature sensor and a chemical sensor. Under this program not only was the technical feasibility of a dual temperature/chemical sensor demonstrated, so were those of two ancillary devices. The first is a scan-and-dwell fiber optic mid-IR spectrometer specifically designed for process control applications. Also, a versatile high-brightness fiber optic light source with interchangeable emitting elements to cover different spectral regions has been demonstrated. The commercial potentials of the complete system as well as the individual components are being actively explored now.
- Research Organization:
- MicroMaterials, Inc., Tampa, FL (United States)
- Sponsoring Organization:
- USDOE Office of Science (SC)
- DOE Contract Number:
- FG02-05ER86262
- OSTI ID:
- 949037
- Report Number(s):
- DOE-ER86262 Final Report
- Country of Publication:
- United States
- Language:
- English
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