Cidra Corporation

Weatherford/lamb, Inc.

Other

Matthew B Miller

Martin A Putnam

Mark R Fernald

Timothy J Bailey

James M Sullivan

Alan D Kersey

Paul Eric Sanders

Robert N Brucato

Michael A Davis

Christopher J Wright

James R Dunphy

Richard Todd Jones

Trevor Wayne MacDougall

James S Sirkis

Thomas Wolfgang Engel

John J Grunbeck

Robert J Maron

Guy A Daigle

Peter C Ogle

Jon T Kringlebotn

A tunable optical filter has a large diameter cane waveguide with 'side-holes' in the cane cross-section that reduce the force required to compress the large diameter optical waveguide without overly compromising the buckling strength thereof. The large diameter optical waveguide has a cross-section of at least about 0.3 millimeters, including at least one inner core, a Bragg grating arranged therein, a cladding surrounding the inner core, and a structural configuration for providing a reduced bulk modulus of compressibility and maintaining the anti-buckling strength of the large diameter optical waveguide. The structural configuration reduces the cross-sectional area of the large diameter optical waveguide. These side holes reduce the amount of glass that needs to be compressed, but retains the large diameter.

Tunable optical filter having large diameter optical waveguide with bragg grating and being configured for reducing the bulk modulus of compressibility thereof

A fiber grating pressure sensor includes an optical sensing element which includes an optical fiber having a Bragg grating impressed therein which is encased within and fused to at least a portion of a glass capillary tube and/or a large diameter waveguide grating having a core and a wide cladding. Light is incident on the grating and light is reflected from the grating at a reflection wavelength &lgr;1. The sensing element may be used by itself as a sensor or located within a housing. When external pressure P increases, the grating is compressed and the reflection wavelength &lgr;1 changes. The shape of the sensing element may have other geometries, e.g., a &ldquo;dogbone&rdquo; shape, so as to enhance the sensitivity of shift in &lgr;1 due to applied external pressure and may be fused to an outer shell.

Optical differential pressure sensor

A pressure-isolated Bragg grating temperature sensor includes an optical element, which includes an optical fiber having at least one Bragg grating disposed therein. The Bragg grating is encased within and fused to at least a portion of an inner glass capillary tube, or comprises a large diameter waveguide grating having a core and a wide cladding and having the grating disposed therein, encased within an outer tube to form a chamber. An extended portion of the sensing element that has the grating therein extends inwardly into the chamber, which allows the grating to sense temperature changes but isolates the grating from external pressure. More than one grating or pair of gratings may be used and more than one fiber or optical core may be used. At least a portion of the sensing element may be doped between a pair of gratings to form a temperature tuned laser, or the grating or gratings may be configured as a tunable DFB laser disposed in the sensing element.

Pressure-isolated bragg grating temperature sensor

A fiber grating pressure sensor for use in an industrial process includes an optical sensing element which includes an optical fiber having a Bragg grating impressed therein which is encased within and fused to at least a portion of a glass capillary tube and/or a large diameter waveguide grating having a core and a wide cladding and which has an outer transverse dimension of at least 0.3 mm. Light is incident on the grating and light is reflected from the grating at a reflection wavelength &lgr; The sensing element may be used by itself as a sensor or located within a housing . When external pressure P increases, the grating is compressed and the reflection wavelength &lgr; changes. The shape of the sensing element may have other geometries, e.g., a &ldquo;dogbone&rdquo; shape, so as to enhance the sensitivity of shift in &lgr; due to applied external pressure and may be fused to an outer shell . A temperature grating may be used to measure temperature and allow for a temperature-corrected pressure measurement. The sensor may be suspended within an outer housing , by a fluid, spacers, or other means. The sensor may also be combined with an instrument, an opto-electronic converter and a controller in an industrial process control system.

Bragg grating pressure sensor for industrial sensing applications

A fiber Bragg grating based sensor is disclosed. The sensor comprises an optical waveguide having a core and a cladding. The core comprises a pressure sensor such as a fiber Bragg grating. In one embodiment, a support is affixed around the cladding which has two first portions each having a first diameter. The pressure sensor is located at a second portion of the support positioned between the two first portions which has a second smaller diameter, thus giving the sensor a &ldquo;dog bone&rdquo; shape. In another embodiment, the dog bone shape is imparted by positioning the pressure sensor at a portion of a waveguide having a reduced cladding diameter.

Optical sensor having differing diameters

A temperature compensated optical device includes a compression-tuned glass element having a Bragg grating therein, a compensating material spacer and an end cap all held within an outer shell The element end cap and shell are made of a material having a low coefficient of thermal expansion (CTE), e.g., silica, quartz, etc. and the spacer is made of a material having a higher CTE, e.g., metal, Pyrex&reg;, ceramic, etc. The material and length L of the spacer is selected to offset the upward grating wavelength shift due to temperature. As temperature rises, the spacer expands faster than the silica structure causing a compressive strain to be exerted on the element which shifts the wavelength of the grating down to balance the intrinsic temperature induces wavelength shift up. As a result, the grating wavelength is substantially unchanged over a wide temperature range. The element includes either an optical fiber having at least one Bragg grating impressed therein encased within and fused to at least a portion of a glass capillary tube or a large diameter waveguide (or cane) with a grating having a core and a wide cladding, which does not buckle over a large range of compressive axial strains. The element may have a &ldquo;dogbone&rdquo; shape to amplify compressive strain on the grating The device may also be placed in an axially tunable system that allows the wavelength to be dynamically tuned while remaining athermal. In addition to a grating, the device may be an athermal laser, DFB laser, etc. Also, the entire device may be all made of monolithic glass materials.

Temperature compensated optical device

A compression-tuned Bragg grating-based laser includes a pair of optical grating elements wherein at least one of the grating elements is tunable by a compression device The grating elements may include either an optical fiber having at least one Bragg grating impressed therein encased within and fused to at least a portion of a glass capillary tube or a large diameter waveguide grating element having a core and a wide cladding. The tunable grating element(s) are axially compressed, which causes a shift in the reflection wavelength of the gratings without buckling the element. The shape of the element may be other geometries (e.g., a &ldquo;dogbone&rdquo; shape) and/or more than one grating or pair of gratings may be used and more than one fiber or core may be used. A gain element, such as Erbium doped fiber, is optical disposed between the grating elements to provide the lasing cavity.

Bragg grating-based laser

A tube-encased fiber grating includes an optical fiber having at least one Bragg grating impressed therein which is embedded within a glass capillary tube . Light is incident on the grating and light is reflected at a reflection wavelength &lgr; . The shape of the tube may be other geometries (e.g., a &ldquo;dogbone&rdquo; shape) and/or more than one concentric tube may be used or more than one grating or pair of gratings may be used. The fiber may be doped at least between a pair of gratings , encased in the tube to form a tube-encased compression-tuned fiber laser or the grating or gratings may be constructed as a tunable DFB fiber laser encased in the tube . Also, the tube may have an inner region which is tapered away from the fiber to provide strain relief for the fiber , or the tube may have tapered (or fluted) sections which have an outer geometry that decreases down to the fiber and provides added fiber pull strength. Also, the tube-encased grating exhibits lower mode coupling from the fiber core to the cladding modes due to the increased diameter of the cladding where the tube is fused to the fiber where the grating is located

Tube-encased fiber grating

A fused tension-based fiber grating pressure sensor includes an optical fiber having a Bragg grating impressed therein. The fiber is fused to tubes on opposite sides of the grating and an outer tube is fused to the tubes to form a chamber. The tubes and fiber may be made of glass. Light is incident on the grating and light is reflected from the grating at a reflection wavelength &lgr; . The grating is initially placed in tension as the pressure P increases, the tension on the grating reduced and the reflection wavelength shifts accordingly. A temperature grating may be used to measure temperature and allow for a temperature-corrected pressure measurement.

Fused tension-based fiber grating pressure sensor

A pressure-isolated Bragg grating temperature sensor includes an optical element which includes an optical fiber having at least one Bragg grating disposed therein. The Bragg grating is encased within and fused to at least a portion of an inner glass capillary tube, or comprises a large diameter waveguide grating having a core and a wide cladding and having the grating disposed therein, encased within an outer tube to form a chamber. An extended portion of the sensing element that has the grating therein extends inwardly into the chamber which allows the grating to sense temperature changes but isolates the grating from external pressure. More than one grating or pair of gratings may be used and more than one fiber or optical core may be used. At least a portion of the sensing element may be doped between a pair of gratings to form a temperature tuned laser, or the grating or gratings may be configured as a tunable DFB laser disposed in the sensing element.

A fiber grating pressure sensor includes an optical sensing element which includes an optical fiber having a Bragg grating impressed therein which is encased within and fused to at least a portion of a glass capillary tube and/or a large diameter waveguide grating having a core and a wide cladding and which has an outer transverse dimension of at least 0.3 mm. Light is incident on the grating and light is reflected from the grating at a reflection wavelength &lgr; The sensing element may be used by itself as a sensor or located within a housing When external pressure P increases, the grating is compressed and the reflection wavelength &lgr; changes. The shape of the sensing element may have other geometries, e.g., a &ldquo;dogbone&rdquo; shape, so as to enhance the sensitivity of shift in &lgr; due to applied external pressure and may be fused to an outer shell At least a portion of the sensing element may be doped between a pair of gratings to form a compression-tuned laser or the grating or gratings may be constructed as a tunable DFB laser. Also, the axial ends of element where the fiber exits the tube may have an inner tapered region and/or a protruding tapered (or fluted) axial section to provide strain relief or improved pull strength for the fiber A temperature grating may be used to measure temperature and allow for a temperature-corrected pressure measurement. The sensor may be suspended within an outer housing by a fluid, spacers, or other means. The invention may also be used as a force transducer.

Bragg grating pressure sensor

A compression-tuned bragg grating includes a tunable optical element which includes either an optical fiber having at least one Bragg grating impressed therein encased within and fused to at least a portion of a glass capillary tube or a large diameter waveguide grating having a core and a wide cladding. Light is incident on the grating and light is reflected at a reflection wavelength &lgr;1. The tunable element is axially compressed which causes a shift in the reflection wavelength of the grating without buckling the element. The shape of the element may be other geometries (e.g., a &ldquo;dogbone&rdquo; shape) and/or more than one grating or pair of gratings may be used and more than one fiber or core may be used. At least a portion of the element may be doped between a pair of gratings , to form a compression-tuned laser or the grating or gratings may be constructed as a tunable DFB laser. Also, the element may have an inner tapered region or tapered (or fluted) sections . The compression may be done by a PZT, stepper motor or other actuator or fluid pressure.

Compression-tuned Bragg grating and laser

A method and apparatus for forming a tube-encased fiber grating includes an optical fiber,which is encased within and fused to at least a portion of a glass capillary tube,and a substantially transparent index-matching medium,, such as an optically flat window, having an optically flat surface,adjacent to the tube,. A substantially transparent index-matching intermediate material (e.g., UV transparent oil),is used between the window,and the tube,to substantially eliminate the interface between the tube,and the medium,. A pair of writing beams,are incident on and pass through the medium,, the tube,and intersect and interfere in a region,on the fiber,. Also, the width Wb of the writing beams,may be set to be less than the width Woil of the intermediate material,to eliminate surface damage (ablations) of the tube,. Attentively, the medium,may have a geometry to eliminate surface ablations (e.g., a collar shape) and/or to match the shape of the tube,. More than one grating or pair of gratings may be written in the tube-encased fiber or one or more gratings may be formed in multiple fibers,encased in the tube,. Further, high intensity writing beams,on the fiber,may be achieved by having the medium,have a predetermined thickness T.

Method and apparatus for forming a tube-encased bragg grating

A compression-tuned bragg grating includes a tunable optical element,which includes either an optical fiber,having at least one Bragg grating,impressed therein encased within and fused to at least a portion of a glass capillary tube,or a large diameter waveguide grating,having a core and a wide cladding. Light,is incident on the grating,and light,is reflected at a reflection wavelength &lgr;1. The tunable element,is axially compressed which causes a shift in the reflection wavelength of the grating,without buckling the element. The shape of the element may be other geometries (e.g., a &ldquo;dogbone&rdquo; shape) and/or more than one grating or pair of gratings may be used and more than one fiber,or core,may be used. At least a portion of the element may be doped between a pair of gratings,, to form a compression-tuned laser or the grating,orgratings,may be constructed as a tunable DFB laser. Also, the element,may have an inner tapered region,or tapered (or fluted) sections,. The compression may be done by a PZT, stepper motor or other actuator or fluid pressure.

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Glastonbury, CT, United States of America

Matthew B Miller