Real-time digital signal processing system for white-light interferometry with application to fiber-optic temperature sensor

A real-time, high-speed digital signal processing (DSP) algorithm for a fiber optic sensor system is designed and implemented. The optical portion of the system utilizes white light interferometry (WLI) for monitoring of a fiber Fabry Perot interferometer (FFPI) sensor head. The WLI scheme utilizes a low coherence light source and a fiber Mach Zehnder reference interferometer to generate a fringe pattern in accordance with the optical length of the FFPl sensor head. The signal processor takes the raw optical signal produced by this system and, using digital signal processing (DSP) techniques, accurately determines that optical path length.; The FFPI sensor, which is formed using two internal mirrors in a continuous length of single mode optical fiber, is a versatile technology for measuring temperature, strain, pressure, magnetic field, and other environmental parameters. The measurand of interest affects the optical length of the interferometer, which therefore must be determined from the raw optical sensor signal by appropriate signal processing. Most applications of the FFPI sensor have utilized a laser light source. The laser provides high sensitivity and rapid response, but does not allow for absolute measurement. An alternative technique, WLI, uses a low coherence light source rather than a laser. WLI does have the capability for absolute parameter measurement, but requires far more signal processing to achieve an accurate result than does a laser-based system.; The primary goal of this research was develop a real time signal processing system for use with an FFPI temperature sensor. The system converts the raw optical data to a temperature reading in real time at a rapid update rate (20 Hz). This dissertation describes the details of hardware and software for implementation of this intensive digital processing system and performance characteristics of the system, and discusses the advantages of the chosen system design.