Abstract: An optical fiber has a dielectric periodic index of refraction phase grating established in its core by intense angled application of several transverse beams of ultraviolet light, enabling the establishment of a distributed, spatially resolving optical fiber strain gauge.

Abstract: A distributed, spatially resolving optical fiber strain gauge in which the core of the optical fiber is written with periodic grating patterns effective for transmitting and reflecting light injected into the core. Spectral shifts in the transmitted and reflected light indicate the intensity of strain or temperature variations at positions of the grating corresponding to the associated wavelengths of injected light.

Abstract: A distributed, spatially resolving optical fiber strain gauge in which the core of the optical fiber is written with periodic grating patterns effective for transmitting and reflecting light injected into the core. Spectral shifts in the transmitted and reflected light indicate the intensity of strain or temperature variations at positions of the grating corresponding to the associated wavelengths of injected light.

Abstract: A method of establishing a dielectric periodic index of refraction phase grating upon the core of an optical waveguide by intense angled application of several transverse beams of ultraviolet light, enabling the establishment of a distributed, spatially resolving optical fiber strain gauge.

Abstract: An optical strain measuring arrangement including an optical waveguide comprising first and second cores fixedly mounted with respect to a mechanical structure to be monitored, and a detection system for relating the contrast in light intensity emerging from said cores to a range of wavelengths to establish an indication of strain along the range of the optical waveguide.

Abstract: An integrated optical pressure transducer having a diaphragm fabricated from a low-loss glass is positioned at the location where pressure changes are to be measured. An optical waveguide loop formed on one surface of the diaphragm acts as a ring cavity in which the difference between the resonating frequencies varies with pressure but not with temperature. Light energy is coupled into the waveguide loop from an optical source through a tangentially located input waveguide. An output waveguide, also tangentially located, couples light energy from the waveguide loop to a broadband detector so that the changes in frequency spectrum of the resonating frequencies within the waveguide loop can be monitored.

Abstract: Acoustic Wave Devices comprise lithium niobate substrates 6, 22 having the principal plane cut at zero degrees and 128.degree., respectively, with respect to the Y crystallographic axis thereof, propagating in the X direction, with amorphous silicon dioxide surface layers of 0.42 and 1.24 wavelengths, respectively.

Abstract: A sensor employs a laser to obtain a collimated light beam for transmission across the gas effluent of a catalytic cracking process. Particulate matter entrained in the gas flow forward scatters light energy to a collecting aperture which, in turn focuses the scattered light on a first photodetector. A second photodetector receives directly transmitted light energy. A ratio between the output signals of the two photodetectors is derived and presented to a threshold level detector. If the magnitude of the scatter exceeds a predetermined level it is concluded that a catalyst load dump has occurred. The optical system is carefully selected to ensure that only light energy scattered from a sample volume within the entrained gas flow reaches the first photodetector. This is important because it prevents particulate matter on the surfaces of the transparent windows from affecting the operating of the sensor.

Abstract: An optical waveguide having a plurality of cores disposed in a common cladding provides an optical fiber with both a wide bandwidth, by minimizing modal dispersion, and a large aperture to enhance light-carrying capacity. Each of the cores is sized to support only the lowest order mode, HE.sub.11, and the intercore spacing is selected to achieve a required bandwidth. At the same time, the multiple cores provide a large aperture allowing a relatively large amount of light energy emitted from a noncoherent light source to be coupled into the optical fiber. An array factor A.sub.f is given which provides design criteria for the intercore spacing by providing an accurate calculation of the pulse spreading with a large number of cores beginning with a simple twin core fiber.

Abstract: A hot spot detector for a power cable, or the like, includes an optical fiber having a plurality of cores including an input core into which light energy is coupled. The core diameters, spacing, and materials of the cores and the cladding are carefully selected so that cross-talk from the input core to the secondary cores occurs only in the vicinity of the point along the fiber where the hot spot is located. Light energy then propagates along the secondary cores and modal interference causes a beat phenomena producing spatial interference that can be analyzed as energy flow between the secondary cores. By measuring the light intensity patterns emerging from the secondary cores at at least two distinct wavelengths, the location of the hot spot along the fiber can be calculated.

Abstract: An optical fiber having at least two cores positioned in a common cladding can be fabricated to be responsive to strain or hydrostatic pressure but not to temperature through the selection of materials, spacing and shape of the cores and cladding in the fiber. Accordingly, the cross-talk between adjacent cores in the optical waveguide can be optimized to respond to a change in hydrostatic pressure or in unidirectional strain along the length of the fiber. The strain or pressure change, can be determined by measuring the relative intensity of light emerging from the different cores of the fiber. A larger unambiguous range for strain or hydrostatic pressure changes can be provided by a multi-core optical fiber embodiment.

Abstract: A multicore optical fiber having a plurality of cores positioned across the diameter of a common cladding can be so optimized to respond to either temperature or strain by the selection of materials, spacing and shape of the cores in the fiber. The cross-talk between adjacent cores in the fiber changes in response to either a change in temperature or a strain along the length of the fiber. The temperature, strain or pressure change, can be determined by measuring the relative intensity of light emerging from the different cores of the fiber. If the fiber is optimized to respond to temperature change, then a high degree of temperature sensitivity can be provided over a large unambiguous range. Alternatively, cross-talk can be made temperature insensitive so that the intensity pattern of light emerging from the various cores in the fiber is only a function of the strain exerted on the fiber.