Research Of PGC Digital Demodulation Realization Of Fiber Optic Sensor

Since the first demonstrations of fiber optic sensors in the late 1970s,the technology has been a considerable amount of development. This development has been driven by principally military applications and has been supported by the enormous advances in optical component technology,which have arisen from the requirements of the telecommunications industry. Now the study has turned into application systems from theories,even some productions have come out in some fields.PGC(phase generated carrier) digital demodulations of optical fiber sensors have become the development trend in practical applications, because they have many advantages, such as the resisting of DC drifting, simple structure, easy processing in array etc.The dissertation reviews and summarizes the development status of fiber optic sensors in foreign courtries,and expatiates the basic theories and phase demodulation schemes of fiber optic interferometer,and discusses the PGC homodyne detection technique of interferometric fiber optic sensors in detail. It is mainly analyzed that the key techniques of PGC digital realization,including the determinations of sampling frequency,and analyzing of quantiziation errors and noises of A/D converter,and the requirement to the speed of DSP in real time algorithms.The hardware system circuits of digital demodulation scheme of fiber optic sensors are designed basing on DSP chip TMS320VC5416,comprising differential input circuit,the interface circuits between A/D,D/A and DSP,FLASH circuit,watchdog circuit and power supply circuitPGC software algorithms are designed on the basis of hardware,involving two frequency doubling algorithms,FIR filter design, differential and integral algorithms. The effects of DC drifting and software algorithms to the demodulation results are researched,and providing a methord of removing DC drifting,and explaining the optimization problems of software programs.The hardware circuit is finished and debugged, and achieving the demodulation function in the subject. Aiming at the problems in practical demodulation system, the paper puts forward some improving suggestions on the hardware design and software programming.