Research On PGC Demodulation Technology Of Fiber-optic Interferometric Sensors

With the development of optical fiber sensor technology, interferometric optic fibersensor has attracted people’s attention for its characters of high sensitivity, strong anti-electromagnetic interference, high dynamic range, structure diversification, easy to reuse andetc.,and is widely used in the fields of military, resource exploration and seismic monitoring.While demodulation methods of interferometric optic fiber sensor directly influences the keyparameters in the sensor systems, such as: dynamic range of detection, detection precision andect. Of the numerous demodulation methods, phase generated carrier (PGC) demodulationtechnique is a kind of passive homodyne demodulation technique, which can eliminate theoutput instability phenomenon caused by the phase drift. For its high sensitivity, large lineardynamic range and good degree, PGC method is widely used.The details are described as follows:First, a brief overview of the current develop status and several commonly usedstructures and demodulation methods of interferometric fiber optic sensor is present. Adetailed analysis in principles of each demodulation method is provided,which laysfoundation for selecting the demodulation method of the interferometric fiber sensor.Second, a detailed analysis of the interference and the basic detection principle ofinterferometric fiber optic sensor is present. And the implementation and significance of PGCmodulation is expounded, and two modulation methods of PGC scheme is introduced. ThePGC demodulation mathematical model is detailed analyzed, and parameters selectingprinciple of PGC demodulation is present. Finally, several typical improved PGC algorithmsare briefly analyzed in principle.Third, we put forward the whole design scheme of interferometric optic fiber sensorsystem. Moreover. We present the scheme of photoelectric conversion pretreatment circuit, webriefly expounds the DSP development environment. At last, software programing realizationscheme of each module of PGC algorithm is proposed.Fourth, an improved PGC algorithm based on frequency mixing is proposed to overcomethe limitations of the traditional frequency mixing algorithm and reduce the minimumsampling frequency. Another improved algorithm is proposed to eliminate the influence of thecompanion amplitude modulation on demodulation result. A detailed analysis of the improvedalgorithm is present, simulation results are given to verify the feasibility and correctness ofthe algorithm.Fifth, Experimental study was carried on the whole design scheme of the system.