Abstract: 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 the

Abstract: 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.

Abstract: 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.

Abstract: 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.

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

Abstract: 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.

Abstract: 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.

Abstract: 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.

Abstract: 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.

Abstract: 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.

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: 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.

Abstract: An apparatus for pressure measurement employs fiber optics to transport a broadband beam light to and from a remote electrically passive sensing head. In the sensing head, a linearly polarized beam is phase shifted in a birefringent plate, then passed through a photoelastic pressure sensor and a polarization analyzer. The wavelength for which the output light has an intensity minimum is a measure of the applied pressure.

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 unstable resonator having high magnification and capable of accommodating an active medium having high gain and small dimensions is disclosed. The unstable resonator, formed with a pair of coupled cavities, has a diffraction grating capable of providing high resolution of the bandwidth of radiation from a high gain medium such as a dye medium and is capable of providing a laser beam with a continuous cross-section having far field characteristics of high quality.

Abstract: 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.