United Technologies Corporation

USA As Represented by Secretary of the Navy

William H Glenn

Gerald Meltz

Elias Snitzer

Gary A Ball

Frederick J Leonberger

William W Morey

Richard G Tomlinson

Peter P Chenausky

Carl M Ferrar

Robert A Rubino, Jr

An emedded Bragg grating laser Master-Oscillator and Power-Amplifier (MOPA), includes an optical waveguide which receives and propagates pump light of a predetermined wavelength launched into the optical waveguide; a first master oscillator laser, disposed in the waveguide in the path of the pump light, the laser having a laser cavity disposed between a first pair of reflectors and having a first laser gain medium within the first laser cavity which emits first lasing light in response to the pump light, the first reflectors reflecting a predetermined amount of the first lasing light within the first laser cavity and passing a predetermined amount of the first fusing light as first output laser light from the first laser, the first reflectors passing the pump light through the first laser; at least one of the first reflectors comprises a Bragg grating; and an optical waveguide power amplifier, disposed in the path of the first output laser light and the pump light, and having a first amplifier gain medium therein which emits first amplified laser light in response to the pump light and the first output laser light.

Embedded Bragg grating laser master-oscillator and power-amplifier

A method and apparatus for simultaneously exposing an optical fiber 32, made of a material which has a refractive index that can be permanently changed by exposure to light of a predetermined intensity at a predetermined wavelength, to two writing light beams 268,272 which intersect and interfere in a predetermined region 30 of the fiber 32 so as to create an interference pattern along a longitudinal axis of the fiber 32, for a time long enough to form a permanent refractive index variation in the waveguide. Each of said two writing beams have a predetermined number of wavelengths, each wavelength being sufficiently different from each other so as to cause said refractive index variation to be an aperiodic variation. Also, each wavelength represents a Fourier component of the desired aperiodic refractive index variation.

Method and apparatus for forming aperiodic gratings in optical fibers

A tunable optical waveguide laser arrangement includes a solid optical waveguide capable of guiding light along an axis between axially spaced ends thereof and being at least in part of an excitable material that emits light in response to stimulation by light. Stimulating light is launched into the waveguide for axial propagation therein and attendant emission of light by the excitable material. Two end reflectors are situated in the waveguide, each at one of the axially spaced ends thereof and extending normal to the axis to delimit a laser cavity. Each of the reflectors is constituted by a Bragg grating consisting of a multitude of axially consecutive grating elements constituted by periodic refractive index perturbations with a given periodicity. The length of the cavity, the peak reflectivity of the Bragg gratings and the gain of the excitable material are so coordinated with one another as to enable lasing in only a single longitudinal mode. The length of that portion of the optical waveguide that incorporates the two Bragg gratings and an intervening region of the optical waveguide is uniformly controlledly varied with attendant continuous tuning of the laser output wavelength without longitudinal mode hopping.

Continously tunable single-mode rare-earth doped pumped laser arrangement

An optical waveguide laser arrangement includes a solid optical waveguide having a waveguiding portion that extends along an axis between two spaced regions of the optical waveguide and is of a material capable of emitting stimulated light upon excitation by pumping light that is launched into the optical waveguide for axial propagation through the axially spaced regions of the optical waveguide. Two reflectors are provided, each being disposed at one of the axially spaced regions of the optical waveguide to delimit a laser resonator. At least one of the reflectors is constituted by a Bragg grating consisting of a multitude of axially consecutive periodic perturbations in the refractive index of the respective one of the axially spaced regions that cumulatively reflect the stimulated light at a reflectivity that decreases for adjacent longitudinal modes of the stimulated light with increasing deviation from a central wavelength. The axial length of the laser resonator, the reflectivity of the Bragg grating and the gain of the excitable material are so coordinated with one another as to sustain lasing in only a single longitudinal mode.

Single longitudinal mode pumped optical waveguide laser arrangement

A broadband laser which can be electronically tuned to a narrow line by insertion of a frequency selective element in the laser cavity.

Electronic tuning of a broadband laser

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

An optical waveguide light tapping arrangement includes an optical waveguide having solid portions that guide 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 with a substantially equal longitudinal spacing at an oblique angle 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 at an angle relative to the longitudinal axis that depends on the oblique angle. 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 narrow range around a central wavelength that is in a predetermined relationship to the spacing of the grating elements. The light propagating in the other path can then be captured. The grating elements are formed in the core by exposing the core 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 core axis.

Optical waveguide embedded light redirecting Bragg grating 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 sensing changes in a monitored parameter includes an optical fiber which has at least one sensing fiber length including a sensing portion situated at a monitoring location of a body. Two periodic gratings of the same periodicity are situated in the fiber each at a different end of the sensing fiber length. Such gratings are reflective to a predominant portion of any light that propagates in the fiber and has a wavelength in a stopband range around twice the periodicity. When broadband coherent light including sensing light with wavelengths within the stopband range is launched into a first end of the optical fiber for propagation longitudinally of the fiber toward a first of the gratings, the predominant portion of the sensing light is reflected from the first grating and the remainder of the sensing light passes into the sensing fiber length, where resonant buildup of light at certain wavelengths that are located within the stopband range and depend on the length of the sensing portion as influenced by changes in the monitored parameter takes place, and the gratings are rendered substantially transparent to the sensing light at the plurality of wavelengths following the buildup. The effect of the gratings and of the sensing length on the wavelengths of the light emerging from one of the end portions of the optical fiber is then detected.

Fiber optic sensor arrangement having reflective gratings responsive to

An optical pyrometer makes a temperature measurement of a remote body that is insensitive to spurious radiation by modulating the temperature of the body of optical irradiation in a first optical wavelength range at a low modulation frequency and synchronous detection of emitted optical radiation in a second optical wavelength range, together with modulation in the second optical wavelength range and detection in the first wavelength range. The measurement so made are combined to form a parameter representative of the body temperature that is insensitive to the environment of the body.

Active optical pyrometer

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.

Method for impressing gratings within fiber optics

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.

Distributed, spatially resolving optical fiber strain gauge

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.

A system for sensing pressure features an electrically passive sensing head connected to electrically active components by a fiber optic cable. A preferred embodiment combines a polariscope bracketing a quarter wave plate and a photoelastic medium. The dependence of the intensities of two polarization components of light emerging from the photoelastic medium on the pressure applied to the medium permits the measurement of that pressure in a manner that has quadratic error dependence on optical misalignment.

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Vernon, CT, United States of America

William H Glenn