Magnetically insensitive fiber optic rotation sensor

Abstract

A fiber optic gyroscope having at least one forty-five degree splice connected to a polarization maintaining sensing coil. The splice is an alignment of forty-five or so degrees between a major axis of a state of polarization of light or an axis of birefringence at a port of a splitter/combiner, which may be an IOC or a coupler, and an axis of birefringence at an end of a fiber of a fiber optic coil loop. The gyroscope is rendered significantly more insensitive to ambient magnetic fields which cause non-rotation errors in the gyroscope's indication of rotation of its sensing loop or coil. The polarization amplitude errors of the present depolarized gyroscope are no greater than those of a similar but non-depolarized gyroscope. The present gyroscope may use an integrated optic circuit or an optical fiber coupler for splitting the light into two beams that counterpropagate in the sensing coil, for combining the beams when they exit the sensing coil. Two forty-five degree splices are placed at each end of the coil thereby resulting in depolarized light beams in the coil. The gyroscope may be either an open loop or a closed loop configuration.