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: A fiberscope for the viewing of the interior of an operating engine combur is provided with a fused coherent fiber bundle as an image conduit to transmit the image of said interior through the wall of the combustor. Illumination may be provided through the use of a second optical fiber or bundle and a coherent light source aligned with the image conduit.

Abstract: An optical amplifier particularly suitable for use in amplifying signals carried on optical fiber in a select communication band. The amplifier comprises a resonant optical waveguide cavity which has a core containing an active gain material with given absorption and fluorescence spectrums. The gain material is of the type that preferably has at least two different emission bands originating from the same energy level with one of the emission bands encompassing the select communication band. The cavity is structured to resonate wavelengths in both emission bands, but with a higher combination of cavity Q and gain coefficient per excited ion for wavelengths in the emission band not corresponding to the select communication band so that, when pumped, the cavity first lases at this band.

Abstract: An optical fiber laser comprising a gain cavity in the form of a single mode optical fiber with integrally formed reflective end sections for provision of feedback. One end section is an etalon for modifying the gain cavity resonant characteristics and intensity modulation, and the other end section is used to alter gain cavity effective length to tune and frequency modulate. The emission spectrum of the laser gain material, which is preferably neodymium oxide incorporated in a silicate glass core, along with the etalon section reflection, pump energy level, and gain cavity length cooperate so that lasing takes place over just a single line of narrow width or over more than one line within a narrow band. Electro-optic material in the end sections permit output frequency and amplitude to be selectively activated in response to the application of applied voltages.

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: A super-radiant light source having an output with a low temporal coherence well suited, for example, to optical inertial sensor applications, includes a single mode optical waveguide such as an optical fiber having its core doped with an active laser material, such as neodymium. Pump light is coupled into the optical fiber at an intensity sufficient to produce a significant amplification of the spontaneous emission. The reflectivity at the exit end of the fiber is low enough so that even with a high gain for the light in one traverse through the fiber, the fiber is operated well below threshold for laser oscillation. The resulting emission is of high intensity, but has a low temporal coherence. In one form, the pump light is coupled into one end of the fiber and a dichroic filter is interposed in the light path between the pump light and the optical fiber to pass pump light into the core and reflect the spontaneous emission of the active material back into the core and toward the output.

Abstract: A fusible spacer for use in the manufacture of a plasma panel rigidly maintains a preselected spacing between the panel sidewalls. The fusible spacer comprises a core fabricated from a refractory glass, such as R-6 glass, and has a first transverse dimension sized in accordance with the desired spacing between the panel sidewalls. A cladding surrounds the core along and is formed from a material which has a much lower softening point, i.e., 350.degree. C. to 500.degree. C. The separation between the two halves of the panel is set by the first dimension of the core member while the solder glass cladding is fused to rigidly attach to both panel sidewalls bonding the composite structure together. The core and fusible cladding are drawn to size by covering the cladding with a second transitory cladding of the same material as the core material to allow a dimensionally controlled fiber to be drawn even through the fusible cladding has a substantially lower softening point.

Abstract: A method of bonding a plurality of thermally stable high strength graphite fiber reinforced glass matrix composite pieces is described. The process comprises applying to the surfaces to be bonded at least one layer of a metal which is highly adherent to the composite and the solder and is oxidatively stable. A tie layer may be used between the composite bond surface and the metal layer to better bond the metal layer to the composite. Following application of the metal layer, the composite pieces are stacked with the metal layers facing each other and a solder layer in between. The temperature of the assembly is raised to melt the solder and form the bond. The melting temperature of the solder and the metal layers are chosen so as to be higher than the use temperature of the bonded composite. A bonded composite article thus formed is also described.

Abstract: A process of bonding a plurality of thermally stable, high strength graphite fiber reinforced glass matrix composite materials is described. The process comprises applying to the surface of at least one of the composite materials to be bonded, a mixture of low softening point glaze such as high lead oxide containing glaze, a high melting point low coefficient of thermal expansion material such as beta-spodumene and colloidal silica followed by hot pressing the composite materials to be bonded together. The resultant bonded articles and the glass compositions particularly adapted for this bonding process are also described.

Abstract: Organic photochromic materials comprising a photochromic dye and a resinous material can be stabilized with a protective coating which will protect them from deactivation by exposure to moisture, oxygen, various plastic host materials, reactive chemicals or even normal atmospheric conditions. Useful organic photochromic dyes include the spiropyrans, the spirooxazines, the metal dithizonates, the phenazines, the phenothiazines and other known photochromic compositions. Useful resinous materials include vinyl-type thermoplastics, cellulosic materials, polyesters, epoxy resins and aminoplast resins. The encapsulated photochromic materials of the invention comprise an organic photochromic dye in combination with an organic resinous material enclosed within an outer shell of an inorganic material and find use in the preparation of photochromic plastic films, sheets, ophthalmic lenses such as lenses for sunglasses and in camera lenses and filters.

Abstract: A process of bonding a plurality of thermally stable, high strength graphite fiber reinforced glass matrix composite materials is described. The process comprises applying to the surface of at least one of the composite materials to be bonded, a mixture of low softening point glaze such as high lead oxide containing glaze, a high melting point low coefficient of thermal expansion material such as beta-spodumene and colloidal silica followed by hot pressing the composite materials to be bonded together. The resultant bonded articles and the glass compositions particularly adapted for this bonding process are also described.

Abstract: A method of bonding a plurality of thermally stable high strength graphite fiber reinforced glass matrix composite pieces is described. The process comprises applying to the surfaces to be bonded at least one layer of a metal which is highly adherent to the composite and the solder and is oxidatively stable. A tie layer may be used between the composite bond surface and the metal layer to better bond the metal layer to the composite. Following application of the metal layer, the composite pieces are stacked with the metal layers facing each other and a solder layer in between. The temperature of the assembly is raised to melt the solder and form the bond. The melting temperature of the solder and the metal layers are chosen so as to be higher than the use temperature of the bonded composite. A bonded composite article thus formed is also described.

Abstract: A temperature probe formed by an optical fiber having a core fabricated from a glass host doped with a trivalent rare earth is positioned at the location temperature is to be measured. One of the rare earth elements, europium, has low lying energy levels that have significant population changes over certain desirable temperature ranges, i.e., related to the population of this particular energy level transition is monitored to determine the temperature at the location of the temperature probe. A simplified embodiment of a temperature measuring device incorporating the optical temperature probe includes at least one LED, or equivalent, to generate light into the input end of the optical fiber. The preselected wavelength of light that corresponds to the absorption line of interest experiences a change in strength as function of temperature. A detector at the output end measures changes in strength of the absorbed light by normalizing to an unabsorbed wavelength of light.

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: 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.

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 high resolution optical position sensor for measuring the linear displacement of a reciprocating device with a long stroke, includes a code plate having a substrate comprised of a fiber optic faceplate having a plurality of parallel optical waveguides which are fused together and aligned perpendicular to each of two major surfaces of the faceplate, and an optical mask with serial transparent and opaque regions encoded in each of a plurality of bit channels disposed on one of the two major surfaces of the faceplate, a portion of the plurality of optical waveguides being in registration with the transparent regions of each bit channel.

Abstract: A sealing glass composition having a thermal coefficient of expansion (from room temperature to 300.degree. C.) of about 90.times.10 -7/.degree.C. and a softening temperature of about 406.degree. C. is provided and consists essentially of the following ingredients in the following proportions: PbO, 66%; B.sub.2 O.sub.3, 18%; ZnO, 15%; and Fining Agent, 1%.