Abstract: A method and apparatus for a fiber optic measuring system is disclosed which works on the speed of propagation principle. The device can be utilized to determine the position of a disturbance or electronic source along the length of an optical path.

Abstract: A fiber optic sensing system detects changes in a material based upon physical deformation of a fiber bonded to the structure in which stress, strain or failure is to be detected. Deformation of the fiber affects propagation of light therethrough, permitting detection based upon detected changes in light throughput.

Abstract: A fiber-optic rotation sensor particularly adapted to be placed adjacent a drill head to measure the orientation of a drill string with respect to the axis of rotation of the earth during or after drilling for minerals such as oil and gas. The analog sensor is based on a Sagnac interferometer and uses light beams counterrotating in one or more oblong circular shaped coils of optical fiber in which dual phase modulators are used to generate an AC signal to enable detection of a rotation rate output. The sensor also includes means to mechanically or electrically flip to sensitive axis of the rotation sensor to null out bias drift. If one coil is used, the flipping is in 90.degree. segments. When two coils at 90.degree. to each other are used, they are flipped 180.degree..

Abstract: There is provided a fiber optic sensor for sensing environmental effects on counterpropagating light beams in an optical loop by comparing the modulation of the light beams in an optical coil exposed to the environmental effects and comparison with a reference fiber shielded from the environmental effects. The counterpropagating light paths contain optical phase modulators for creating nonreciprocal phase shifts and may comprise elongated sections forming a long line array.

Abstract: A fiber-optic rotation sensor particularly adapted to be placed adjacent a drill head to measure the orientation of a drill string with respect to the axis of rotation of the earth during or after drilling for minerals such as oil and gas. The analog sensor is based on a Sagnac interferometer and uses light beams counterrotating in one or more oblong circular shaped coils of optical fiber in which dual phase modulators are used to generate an AC signal to enable detection of a rotation rate output. The sensor also includes means to mechanically or electrically flip the sensitive axis of the rotation sensor to null out bias drift. If one coil is used, the flipping is in 90.degree. segments. When two coils at 90.degree. to each other are used, they are flipped 180.degree..