Abstract: An optical interferometer used to measure the current in a conductor, where the gap between the mirror and the quarter wave plate is minimized, and the gap is shielded magnetically. Additionally, at least the modulator is shielded, and preferably the case containing many of the components, such as the integral number of turns of optical fiber in a coil, is magnetically shielded. By shielding the components, and reducing the gap between the quarter wave plate and the mirror, the error in the current measurement is substantially reduced.

Abstract: An optical interferometer used to measure the current in a conductor, where the gap between the mirror and the quarter wave plate is minimized, and the gap is shielded magnetically. Additionally, at least the modulator is shielded, and preferably the case containing many of the components, such as the integral number of turns of optical fiber in a coil, is magnetically shielded. By shielding the components, and reducing the gap between the quarter wave plate and the mirror, the error in the current measurement is substantially reduced.

Abstract: A non-contact device for measuring current in a conductor. The device includes an interferometer with an optical fiber that extends around the conductor and through which light beams pass. The magnetic field around the conductor, caused by the current conducted through the conductor, causes a phase shift in the light beams, which is measured. The measured current is corrected as a function of the temperature of at least the fiber, and possibly also the temperature of the quarter wave plate and/or the compensation coil in the interferometer. Multiple sensors are evenly spaced and mounted to the fiber in the preferred embodiment, and the signals from the sensors are averaged. The average signal is used to correct the measured current.