Abstract: A fiber optic resonant gyroscope in which the laser beam is coupled to a frequency modulator which produces three spatially separated beams frequency shifted from one another by a predetermined amount equal to the difference between the N.sup.th and N.sup.th +1 traveling wire resonant modes of the fiber optic ring, a portion of the outputs from the laser frequency modulator being applied to travel in one direction around the fiber optic ring, a portion of the other two outputs being applied to travel in the opposite direction around the fiber optic ring. Detectors are employed to detect the N.sup.th and, N.sup.th -1 and N.sup.th +1 resonant modes and the signals from these detectors are fed back to the modulators to cause the respective output beams to track the respective modes. The signal values fed back are used to provide an output signal indicative of the Sagnac shift.

Abstract: A Sagnac interferometer gyroscope including periodic generator driving an optical modulator coupled to one end of the fiber optic loop, the signals from the fiber optic loop being coupled through two feedback loops. The first feedback loop operating on a signal equal to the twice the periodic generator signal frequency which is integrated and supplied, together with the signal from the periodic generator to a summing circuit to drive the optical modulator such that it maintains the measurement of the gyroscope output through specific quad points. The second feedback loop operates on a signal at a frequency equal to the frequency of the periodic generator and provides the integrated value of this signal after demodulation to summing circuit, together with a calibration signal, the output signal from the summing circuit being applied to a line stretcher element in the Sagnac fiber optic loop to maintain the output signal at a constant scale factor.

Abstract: A single-mode optical-fiber directional coupler including at least two optical fibers each having a core surrounded by a cladding material and having a region of reduced cladding diameter contiguous with a reduced-cladding diameter region of the other fiber throughout the length of an optical interaction area. Each reduced-cladding-diameter region is bounded on each end by a tapered region which gradually increases in diameter as it extends away from the reduced-cladding-diameter region toward a full-diameter region of each fiber. There is also a substrate and means for securing the reduced-cladding-diameter region to the substrate, means for supporting the fibers in their full-diameter region beyond each end of the optical interaction area, means for fastening the support means to the substrate and a medium surrounding the reduced-diameter regions and having an index of refraction similar to that of the cladding material.

Abstract: A spliceless optical-fiber resonant-ring laser gyroscopic system is disclosed. The spliceless optical-fiber resonant-ring gyroscopic system includes a cylindrically-shaped monolithic housing fashioned from a material having an ultra-low coefficient of thermal expansion. A selected length of optical-fiber is mounted about the perimeter of the cylindrically-shaped housing and closed on itself to form an optical-fiber ring having at least one turn. The spliceless optical-fiber ring and an evanescant-wave directional coupler are provided by bringing the fiber proximate to the ends of the optical-fiber ring in parallel contiguity. A narrow-band gas-discharge helium-neon optical-frequency tunable laser is formed within the monolithic housing and operatively connected to the ends of the spliceless optical-fiber ring via an integrated-optics chip.

Abstract: A single-coupler guided-wave passive resonant-ring optical gyro system responsive to a coherent light source including: an optical-fiber resonant ring, a single directional coupler that serves as an input for exciting clockwise and counterclockwise traveling wave resonances in the resonant ring and serves as an output for extracting the ouput signals representative of those resonant traveling waves; switching means for selectively alternately applying the light waves from the coherent light source to the clockwise and counterclockwise inputs of the single directional coupler; means for separating the resonant frequencies of orthogonal polarization states of the resonant ring; means for tuning the frequency of the input light waves to the resonant frequencies of the resonant ring; and means for sensing the output signal representative of the clockwise and counterclockwise waves.

Abstract: Apparatus for reflecting an incident laser beam to direct the beam outgoing along a path toward a target, including a stepped array of reflector elements. The array elements have reflective surfaces arranged so that the surfaces are overlapping as seen by the incident beam. In addition, the elements are spaced apart in a direction perpendicular to the path so that light returning from the target passes between the elements.