Optimization And Implementation Of Temperature Stability Of All Fiber Optic Current Sensor

All fiber-optic current sensor is a novel current detection equipment based on faradayeffect. Contrast to the electromagnetic current transformer，the AFOCS adopt all fiber sensingunit replacement of cumbersome iron core and winding, it is the core primary equipment ofcoming generation smart grid with the advantages of small size, simple insulation structure,no magnetic saturation, digital output interface and so on.At first, the principal of AFOCT is introduced, and then several structures of AFOCT aredescribed. The in line reflective structure is established by comparing advantages of differentstructures. We analyze the modulation and demodulation technique, we migrate the fourstates modulation which is used in fiber optic gyroscope to the all fiber-optic current sensor.The expectable purpose is achieved by relative test.For novel current detection principle, AFOCS remedy many defects of traditionalelectromagnetic current transformer, yet some problems are also induced. For instance, thedetection sensitivity of AFOCS is very low because of linear birefringence, and easilyaffected by environment and system noise. The sensing unit of AFOCS is fixed on theelectrical wire with acutely temperature fluctuation and vibration，so the work environment isvery execrably. Yet the birefringence and verdet constant of sensing fiber change with thetemperature, it will vitally affect the output stability. The restrain of liner birefringence andtemperature compensation of verdet constant are researched and corresponding solutionshave been proposed.(1) Linear birefringence can be optimized by the parameters of fiber-optical-circuit,such as optimizing the azimuth, but this way ignored the factor of Optical Rotatory Angle, sothe optimization of Optical Rotatory Angle is proposed, and the azimuth optimizationalgorithm is improved. The simulation result indicated that the optimization of azimuth andOptical Rotatory Angle can be implemented independently. The combination of the two wayscan restrain the liner birefringence effectively so as to improve the temperature stability ofAFOCS.(2) Verdet constant is one of the parameters which affect the intensity of faraday effect.The verdet constant is not only affected by the optical material, but also the temperature andwavelength. The temperature range of AFOCS is up to100℃, so the temperaturecompensation is essential to AFOCS. By researching the inherent temperature compensationof quarter-wave plate, correct the optimization formula of quarter-wave plate, the temperature stability is further improved.This paper proposed the scheme of AFOCS from circuit and optic. The experimentalfacility is built and the performance of modulate and demodulate circuit are tested.