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A fiber optic voltage sensor based on intensity modulation

A fiber optic DC voltage sensor based on an intensity modulation scheme is proposed. Fiber optic voltage sensors have the advantage over conventional voltage sensors in that they offer voltage isolation and can easily be incorporated in telecommunication systems. The intensity modulation approach to sensing is a less costly and simpler measurement system compared to other available fiber optic voltage sensor techniques. Intensity modulation is achieved using a piezoelectric ceramic which produces a displacement on application of a voltage varying the transmitted optical power in a fiber to fiber coupling system. A critical analysis was performed on the theory behind the intensity modulation scheme for fiber voltage sensing. Simulations and experimental investigations based on this concept showed good linearity between the applied voltage and optical power in the fiber. The feasibility of obtaining a single valued relationship for voltage sensing purposes was also observed. The constructed voltage sensor produced useful results with the sensor exhibiting good linearity in forward and reverse voltages over a DC voltage of 0V to 100V but exhibited hysteresis. A linearity of 92% and 88.8% was measured for the forward and reverse voltages respectively and a dynamic range of approximately 0.3dB over the 100V range was achieved with a resolution of 1.9V. The hysteresis in the sensor was measured at 20%. Based on the results obtained recommendations have been made on a more linear, lower hysteresis and stable sensor of this type.