United Technologies Corporation

USA As Represented by Secretary of the Navy

Electric Power Research Institute Incorporated

William W Morey

Gerald Meltz

William H Glenn

Arnold L Wilson

Leon A Newman

Elias Snitzer

Frederick J Leonberger

Gary A Ball

Walter L Glomb

A fiber laser 26 including a rare-earth doped fiber laser cavity 32 delimited by a pair of reflective elements 28,30, such as Bragg gratings, is tuned by compressing the cavity 32 and the gratings 28,30. Because an optical fiber is a much stronger under compression than in tension, the laser 26 is tunable over a much broader range than conventional tension/stretching techniques.

Compression-tuned fiber laser

A reflective element 26, such as a Bragg grating, impressed in an optical fiber 24, has a reflection wavelength which is tuned by compressing the grating 26. Because an optical fiber is a much stronger under compression than in tension, the grating 26 is tunable over a much broader range than conventional tension/stretching techniques.

Compression-tuned fiber grating

A gas turbine flame diagnostic monitor has been described incorporating a plurality of viewing probes to be positioned in a plurality of combustors of a gas turbine and coupled to a plurality of optical fiber image guides for transferring the image from each viewing probe to a video camera. The video camera is coupled to a monitor for displaying the flame received by each combustor probe. A video analyzer generates flame intensity patterns, centroids and second order moments and compares them with predetermined stored flame intensity patterns, centroids and second order moments, and logic for providing diagnostic interpretations of the operation of the gas turbine which is coupled to a turbine controller for controlling the gas turbine to provide balanced combustor operation for optimum temperature of the exhaust gases at the first blade row and to warn station operators of impending problems and shut down the turbine at times when turbine malfunctions are observed. The flame diagnostic monitor overcomes the problem of diagnosing faults in the combustors of gas turbines, and also helps prevent subsequent duct explosions during start up when ignition does not occur in a combustor.

Gas turbine flame diagnostic monitor

An optical waveguide light redirecting arrangement includes an optical waveguide having a solid portion that guides light in a first path along a longitudinal axis, with at least one grating region being embedded in the solid portion at a location remote from its end portions. The grating region includes a multitude of grating elements extending at such longitudinal spacings and at such oblique angles relative to the longitudinal axis to redirect light reaching the grating elements between the first path and at least one second path extending externally of the waveguide and diverging between a focus situated at a predetermined distance from the waveguide and the grating region. When light is directed in one of the first and second paths toward the grating region, it is redirected by the grating elements into the respectively other of the second and first paths with attendant in-phase combination in the other path of light having a wavelength within a range around a central wavelength. The grating elements are formed in the waveguide by exposing the waveguide to an interference pattern of two ultraviolet radiation beams that are symmetrical with respect to a plane extending at the oblique angle relative to the waveguide axis at the center of the grating region.

Optical waveguide embedded light redirecting and focusing Bragg grating

An optical waveguide mode discrimination light filtering arrangement inclues an optical waveguide having an elongated multimode core, and a cladding that guides at least two modes of light of a given frequency in an elongated path along a longitudinal axis of said core. At least one grating region is embedded in the core at a location remote from the end portions of the core and has a multitude of grating elements extending with a substantially equal longitudinal spacing substantially normal to the longitudinal axis to reflect light propagating in the path and reaching the grating elements back into the path for longitudinal propagation therein opposite to the original propagation direction. The spacing of the grating elements is so related to the axial wavelength of one of the modes that the reflected light of the one mode interferes constructively while the light of any other of the modes passes through the grating region in the original propagation direction substantially without attenuation.

Optical waveguide embedded transverse spatial mode discrimination filter

A temperature compensated embedded grating optical waveguide light filtering device includes an optical fiber having an elongated core in which light is guided toward a core portion of a predetermined limited length that has embedded therein a multitude of grating elements extending with a substantially equal longitudinal spacing substantially normal to the longitudinal axis and collectively constituting a grating that reflects, of the light propagating in the path toward and reaching the grating elements, that of a wavelength within a narrow range about a central wavelength determined by the spacing of the grating elements and by the index of refraction of the material of the core as influenced by the temperature of and longitudinal strains applied to the grating, back into the path for longitudinal propagation therein opposite to the original propagation direction. Each end of the fiber portion is attached to a different one of two compensating members made of materials with such coefficients of thermal expansion relative to one another and to that of the fiber material as to apply to the fiber longitudinal strains the magnitude of which varies with temperature in such a manner that the changes in the central wavelength that are attributable to the changes in the longitudinal strains substantially compensate for those attributable to the changes in the temperature of the grating.

Incorporated Bragg filter temperature compensated optical waveguide

An optical waveguide light redirecting arrangement includes an optical waveguide having at least two solid portions each of which guides light in a path along a longitudinal axis, with at least one grating region being embedded in each solid portion. Each grating region includes a multitude of grating elements extending at such identical longitudinal spacings and at such an identical angle relative to the longitudinal axis as to redirect light reaching the grating elements between the path of one and the path of the other of the waveguiding portions.

Multi-core optical waveguide Bragg grating light redirecting arrangement

A variable light filtering arrangement includes at least one optical fiber section including a waveguiding core, and at least one permanent Bragg grating region in the optical fiber section. The grating region includes a plurality of grating elements constituted by periodic refractive index variations of a predetermined initial periodicity and cumulatively redirecting, of the light launched into the core for guided propagation therein, that having an axial wavelength within a narrow band around a central wavelength that is determined by the periodicity and refractive index variations of the grating elements. At least one of the periodicity and refractive index variations of the grating region is controlledly modified in such a manner as to temporarily change the central wavelength within a predetermined wavelength range.

Variable optical fiber Bragg filter arrangement

An arrangement for determining the magnitudes of selected physical quantities at a multitude of spaced locations includes an elongated optical fiber having a multitude of separate longitudinally spaced Bragg sensing gratings of substantially identical initial periodicity situated at such locations. Light pulses are launched into the core for propagation longitudinally thereof and for return from any of the sensing gratings of a detectable light echo at a central wavelength determined by the instantaneous value of the periodicity of the respective sensing grating that depends on the longitudinal stress applied to such grating as a result of the action of the physical quantity being monitored at the location of such grating. The light echoes are detected and allocated to the respective sensing gratings on the basis of time intervals elapsed between the issuance of the respective light pulses and the arrival of the echoes responsive thereto, and to the respective longitudinal stresses applied to the respective sensing gratings on the basis of the respective wavelengths of the echoes returned from the respective gratings.

Distributed multiplexed optical fiber Bragg grating sensor arrangeement

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.

Combustor fiberscope

A device for responding to the angular orientation of a control handle or other object comprises an electrically passive sensing head connected to a measurement device by an optical cable. In the sensing head, light is emitted from an optical fiber, reflected from a concave mirror mounted on the handle and intercepted by a plurality of optical fibers. The intensity of light intercepted by these fibers provides a measure of the tilt of the handle.

Fiber optic angular sensor

A long rare-gas halide excimer light source excited by a capacitively coupled discharge pumps a dye laser with high efficiency in a configuration matched to the length of the discharge.

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West Hartford, CT, United States of America

William W Morey