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An Optical Fiber Sensor for the Measurement of Elevated Temperatures
Theodore F. MORSE Yifei HE Fei LUO
IEICE TRANSACTIONS on Electronics
Publication Date: 2000/03/25
Print ISSN: 0916-8516
Type of Manuscript: Special Section PAPER (Special Issue on Optical Fiber Sensors)
Category: Physical and Mechanical Sensors
fiber optics sensors, Bragg reflectors, thin film deposition and fabrication,
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A novel optical technique for the measurement of temperature is proposed. This is accomplished by depositing alternating 1/4 wave layers of silicon nitride and silicon-rich silicon nitride at the end of an optical fiber. These layers of alternating refractive index form the equivalent of a Bragg grating of a high temperature material. When the fiber and the Bragg grating are heated, the Bragg stack expands, and there is a change in the reflective peak wavelength of this wave stack. Thus, the wavelength of peak reflectivity is a function of temperature. Currently, the 15 nm spectral width of the Bragg stacks is achieved in our laboratory, which is conveniently monitored with a CCD solid state spectrometer and the temperature sensor probes can be also multiplexed at separated specific reflection wavelength. In the experiment, the temperatures in excess of 1,100 centigrade have been measured with a resolution of less than 3 centigrade degree.