Philippe Gabus

Temperature and vibration insensitive fiber-optic current sensor

A robust interferometric fiber-optic current sensor with inherent temperature compensation of the Faraday effect is presented. Sensor configurations based on Sagnac and polarization-rotated reflection interferometers are considered. The sensing fiber is residing and thermally annealed in a coiled capillary of fused silica. The capillary is embedded in silicone within a ring-shaped housing. It is theoretically and experimentally shown that the temperature dependence of the birefringent fiber-optic phase retarders of the interferometers can be employed to balance the temperature dependence of the Faraday effect (0.7/spl times/10/sup -4///spl deg/C). Insensitivity of the sensor to temperature within 0.2% is demonstrated between -35/spl deg/C and 85/spl deg/C. The influence of the phase retarders on the linearity of the sensor is also addressed. Furthermore, the sensitivity to vibration of the two configurations at frequencies up to 500 Hz and accelerations up to 10 g is compared. High immunity of the reflective sensor to mechanical perturbations is verified.

Fiber-Optic Current Sensor for Electrowinning of Metals

A highly accurate fiber-optic current sensor for direct currents up to 500 kA is presented. Applications include the control of the electrolysis process for the production of metals such as aluminum, copper, zinc, magnesium, and others. The sensor offers significant advantages with regard to performance and ease of use compared to state-of-the-art Hall-effect-based current transducers. The sensor makes use of the Faraday effect in an optical fiber loop around the current-carrying bus bars. A novel scheme of a polarization-rotated reflection interferometer and fiber gyroscope technology is used to measure the magneto-optic phase shifts. An appropriate technique has been developed for packaging the sensing fiber in a flexible strip of fiber-reinforced epoxy for loop diameters of up to several meters. Sensor accuracy and repeatability are well within 0.1% over a wide range of currents and temperatures. The sensor calibration is valid, regardless of the given magnetic field distribution, and remains stable under repeated manipulation of the flexible sensing strip.

Highly accurate fiber-optic DC current sensor for the electro-winning industry

A fiber-optic current sensor for direct currents up to 500 kA is presented. Applications include current measurement for process control and protection in the electro-winning industry, for example at aluminum smelters. The sensor offers significant advantages with regard to performance and ease of installation compared to state-of-the-art Hall effect based current transducers. The sensor exploits the Faraday effect in an optical fiber and measures the path integral of the magnetic field along a closed loop around the current-carrying bus bars. The differential magneto-optic phase shift of left and right circular light waves propagating in the fiber is detected by means of a novel polarization-rotated reflection interferometer. Fiber gyroscope technology is employed for signal detection and processing. The fiber is packaged in a flexible strip of fiber re-enforced epoxy, which can be installed without opening the current-carrying bus bars. Subsequent re-calibration is not necessary. The sensor achieves accuracy within /spl plusmn/ 0.1% over a wide range of currents and temperatures.

Fiber-optic dc current sensor for the electro-winning industry

A fiber-optic current sensor for direct currents up to 500 kA is presented. Applications include the control of the electrolysis process for the production of metals such as aluminum, copper, magnesium, etc. The sensor offers significant advantages with regard to performance and ease of installation compared to state-of-the-art Hall effect based current transducers. A novel scheme of a polarization-rotated reflection interferometer and fiber gyroscope technology is used to measure the magneto-optic phase shift. A new technique has been developed for packaging the sensing fiber in a flexible strip of fiber re-enforced epoxy for coil diameters up to several meters. The sensor can be installed without opening the current-carrying bus bars. Subsequent re-calibration is not necessary. Accuracy is within ±0.1% over a wide range of currents and temperatures.

Influence of residual fiber birefringence and temperature on the high-current performance of an interferometric fiber-optic current sensor

A highly accurate reflective interferometric fiber-optic current sensor for alternating and direct currents up to 500 kA is investigated. The magnetic field of the current introduces a differential phase shift between right and left essentially circularly polarized light waves in a fiber coil wound around the conductor. Technology adopted from fiber gyroscopes is used to measure the current-induced phase shift. The sensor achieves accuracy to within ±0.1% over at least two orders of magnitude of current and for temperatures from -40 to 80°C with inherent temperature compensation by means of a non-90°-retarder. The paper analyzes the influence of key parameters on the sensor accuracy as well as linearity as a function of magneto-optic phase shift. Particularly, we consider residual birefringence in the sensing fiber and its effect on the high-current performance of the sensor as well as optimum parameters for the temperature compensation scheme. Applications of the sensor are in high-voltage substations and in the electrolytic production of metals such as aluminum.

Experimental and theoretical investigations of the high current regime of an interferometric fiber-optic current sensor

The influence of non-perfect circularity of the left and right circular light waves of a reflective interferometric fiber-optic current sensor is theoretically and experimentally investigated for currents up to several 100 kA and temperatures from -40 to 80degC. By control of crucial parameters and appropriate packaging of the sensing fiber accuracy and repeatability within plusmn0.1% is achieved. Applications of the sensor are in high-voltage substations and in the electrolytic production of metals such as aluminum.

Nonlinearities in the high-current response of interferometric fiber-optic current sensors

The nonlinearities in the response of an interferometric fiber-optic current sensor associated with deviations of the light waves from perfect circular polarization are theoretically and experimentally investigated. The consequences for inherent temperature compensation of the Faraday effect by means of a non-90°-retarder are investigated for currents up to several 100 kA and temperatures between -40°C and 80°C. The results are of particular interest to sensors for high direct currents in the electro-winning industry where measurement accuracy to within ±0.1% is required up to 500 kA.

Towards commercial use of optical fiber current sensors

Summary form only given. Optical fiber current sensors for high-voltage electric power substations have been under investigation in the 1980s and 1990s. So far, however, a number of technical shortcomings such as unacceptable sensitivity to temperature and vibration as well as concerns about their long-term reliability have contributed to prevent extended commercial use. We report a sensor which, we believe, meets all important performance requirements. Two configurations of the sensor have been investigated. In the Sagnac configuration the magnetic field of the current induces a differential optical phase shift, proportional to the current. In the reflection configuration left and right circular polarizations are co-propagating in the coil and are reflected at the coil end.

Nonlinear Phenomena in the Response of Interferometric Fiber-Optic Current Sensors

The nonlinearities in the response of an interferometric fiber-optic current sensor associated with inherent temperature compensation of the Faraday effect are investigated at currents up to several 100 kA and temperatures between -40 and 80degC.

Theoretical and experimental investigations on the calibration stability of fiber-optic current sensors

A fiber-optic current sensor with flexibly packaged sensing fiber for direct currents up to 500kA is presented. Accuracy and calibration stability are well within 0.1%. Applications are in the electro-winning industry such as aluminum smelters.