Abstract: An optical instrument is provided which can be configured as a gyro, spectrometer, or other sensor of effects that can influence the transmission of light through a light conduit wherein a beam of light is split and introduced into both ends of an optical fiber which in the gyro case is a fiber-optic coil. Two fixed frequency shifters and two variable frequency shifters, one each at each end of the coil, which are switched on in alternate pairs, are used to adjust any nonreciprocal phase shift caused by rotation of the coil. The beams are mixed backed together and the resultant beam is detected and analyzed by suitable circuitry to provide an output indicative of the angular position, direction of rotation, and angular rate of the motion of the fiber-optic coil as well as any frequency bias and scale factor changes. When configured as a spectrometer, the coil is made insensitive to rotation so that changes are the result of changes in the light source.

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 by this invention an optical sensing system utilizing a Sagnac interferometer having a frequency shifter within the Sagnac counterpropagating loop that is generally comprised of a plurality of acoustic transducers mounted on acousto-optical material to frequency shift and beamsplit a light beam simultaneously within the material while at the same time having the capability of switching between an upshifted or downshifted frequency in either a Bragg or Raman-Nath mode of operation without realigning the optical beams. The acousto-optical material has a special configuration to eliminate back reflections of the acoustic waves that can interact with the light beam. In addition, special alignment of the transducers with dampening configurations also serves to prevent back reflections of the acoustic wave from interacting with the light beam.

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: There is provided by this invention a fiber optic transducer for accelerometers and gyroscopes that utilize an optical fiber suspended between two points and supported on a vibrating platform such that the optical fiber is deflected to cause light passing through the fiber to be phase modulated. When the device is accelerated, the deflection of the vibrating fiber is assymetrical, and the light passing through the fiber is phase modulated at frequency `f` and odd harmonics of `f`. The first in odd harmonic phase modulation has an amplitude proportional to the acceleration and a phase relative to the driving signal that depends on the direction of acceleration.

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..

Abstract: The demodulator system includes a source of light, and a beamsplitter which produces mutually coherent sensor and reference beams through sensor and reference fibers respectively, the sensor fiber being exposed to the effect to be sensed while the reference fiber is isolated therefrom. A ferrule maintains the output ends of the sensor and reference fibers in fixed positions with respect to a combiner lens which collimates the sensor and reference beams to form an interference pattern on a quad detector through a quad grating. The quad grating has four quadrants lined with the spacing of the interference pattern produced by mixing of the sensor and reference beams but positioned 0.degree., +90.degree., -90.degree., and 180.degree. apart in phase, .phi.. Therefore the quad detector produces outputs which contain +sine .phi., -sine .phi., +cosine .phi., and -cosine .phi.

Abstract: A passive device which allows processing of signals impressed upon a light beam and arranged so that sensitivity is maximized and signal dropout, due to environmental effects such as temperature, do not occur. The passive homodyne demodulator includes a beam combiner, for combining the impressed light beam with a reference beam, beamsplitters, polarizing beamsplitters, and birefringent elements used as polarization shifters, so that ouputs are produced which are the sine and cosine of the phase change between the sensor and reference beams due to changes in the effective optical path length difference of the reference and sensor fibers due to the effect sensed. These signals are then electronically converted into an electrical output which linearly represents the phase of the signal originally impressed on the sensor fiber.

Abstract: An improved compact optical gyro is provided wherein a beam of light is split and introduced into both ends of an optic coil whose rotation is to be sensed. At least one frequency shifter is placed to affect the frequency of the beam to introduce or adjust a nonreciprocal phase shift. The beams are then mixed back together and the resultant beam is detected and analyzed by suitable circuitry to provide an output indicative of the rotation of the light path.

Abstract: A vibration sensor is formed by coupling the vibration to be sensed to change the positional relationship between grating means and light beams so that the resultant variations in light intensity of the beams beyond the grating means vary with a function of the sine and cosine of the positional change. This allows the detection of the vibrationover a wide range of frequencies and amplitudes.

Abstract: A light source is operated near its threshhold and its output is split and sent in opposite direction about a fiber optic coil which is exposed to acoustic energy. The recombined light out of the coil is modulated at acoustic frequency. The modulated light can be fed back to the light source which responds to the modulation with large amplitude variations which are sent to a detector for conversion into an electrical signal representative of the acoustic energy. Alternatively, the light beam may be directed from the fiber coil to the detector directly. The sensors can include components for rejecting noise at frequencies not of interest and a plurality of similar sensors can be formed in an array to obtain directional information or increased sensitivity.

Abstract: A beam of light is split and introduced into different ends of a light path whose rotation is to be sensed. At least one frequency shifter is placed in the light path to affect the frequency difference of the two beams so as to introduce or adjust a nonreciprocal phase shift. The beams are then mixed back together and the resultant beam is detected and analyzed by suitable circuitry to provide an output indicative of rotation of the light path.