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Study on Theory and Experiment of Optical Fiber Fluorescence Temperature Sensor

Author: HuChunHai
Tutor: WangYuTian
School: Yanshan University
Course: Measuring Technology and Instruments
Keywords: Fiber Optic Sensors Fluorescence Temperature measurement Rare earths Weak Signal Detection
CLC: TP212
Type: PhD thesis
Year: 2004
Downloads: 959
Quote: 6
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Abstract

Temperature detection, whether in science or engineering technology has been an important area of ??research. Industrial engineering, biomedical monitoring and environmental conditioning systems rely on accurate and reliable temperature information in order to ensure that the system is effective, reliable operation. Especially in inaccessible or harsh environments, such as radio frequency radiation or other electromagnetic noise environment, the need for an optical sensor for temperature measurement, which includes fiber fluorescent temperature sensors, fiber optic fluorescence temperature sensing system topics at the forefront of this field. In this study, as the goal of seeking new fluorescent temperature sensitive materials, to meet different application conditions, improve system reliability and sensitivity. The light-emitting diode as the excitation source, system configuration, control methods, and life has many advantages than the traditional method. Constituted together with the optical fiber technology fiber optic fluorescence temperature sensor, the measurement mode can be a contact type, can also be a non-contact type, the online detection of the temperature. This paper carried the following research: (1) based on the electronic transition theory discussed fluorescent material as the mechanism of temperature-sensitive medium, temperature sensitive characteristics of the solid-state laser crystal, rare earth compounds and rare earth ion doped fiber experimental study The rare earth compound excited fluorescence properties; the visible band excitation light through several light characteristics comparison, it is determined to use the LED as the excitation light source. (2) Since the fluorescence is weak, and the loss of optical fiber, lenses, filters, and the manner and composition of the optical configuration of the system has been studied, designed the form of high fluorescence collection efficiency of the probe. (3) conducted a study of the life of the weak fluorescence signal detected in the time domain and frequency domain. The excitation light and fluorescence, and the temperature dependency of the two embodiments the mathematical model, are given in the frequency domain for the mixed excitation light and fluorescence, it is determined that the modulation frequency of the light source and the system to the sampling frequency selection principle. In the time domain, the fluorescence lifetime of the phase-sensitive detection techniques, based on the Hilbert transform of the phase-sensitive detection methods, the establishment of a mathematical model of the detection method, the method eliminates the need for a low pass filter the inhibition and excitation light leakage. Fluorescence excitation light sine wave drive generated a sinusoidal signal cycle with the same excitation light, but lags behind in phase excitation light excitation light and fluorescence cross-correlation and chaos theory combined approach, in line with the sine law weak fluorescence signal detection, and to improve the system's signal-to-noise ratio. Research portfolio of multi-fluorescence signal detection principle, using PRONY algebraic methods, without iteration the multiple fluorescence lifetime biodegradable composite curves. (4) design a detection system based on the fluorescence temperature of the LED light source, given all aspects of the delivery model and noise model. In order to improve the resolution of the detection circuit, the design of a dual phase locked loop circuit, analysis discusses its principle of operation of the circuit. By the MCU to control the operation of the entire system. (5) on the fiber optic fluorescence temperature sensor system, experimental study, including the absorption spectra and emission spectra of several fluorescent material, LED LT; WP = 5 GT; the spectral characteristics, the dual PLL circuit test, and temperature and fluorescence life of the correspondence relationship experiments.

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