摘要:
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.
摘要:
A compression-tuned bragg grating includes a tunable optical element 20,600 which includes either an optical fiber 10 having at least one Bragg grating 12 impressed therein encased within and fused to at least a portion of a glass capillary tube 20or a large diameter waveguide grating 600 having a core and a wide cladding. Light 14 is incident on the grating 12 and light 16 is reflected at a reflection wavelength &lgr;1. The tunable element 20,600 is axially compressed which causes a shift in the reflection wavelength of the grating 12 without buckling the element. The shape of the element may be other geometries (e.g., a “dogbone” shape) and/or more than one grating or pair of gratings may be used and more than one fiber 10 or core 612 may be used. At least a portion of the element may be doped between a pair of gratings 150,152, to form a compression-tuned laser or the grating 12 or gratings 150,152 may be constructed as a tunable DFB laser. Also, the element 20 may have an inner tapered region 22 or tapered (or fluted) sections 27. The compression may be done by a PZT, stepper motor or other actuator or fluid pressure.
摘要:
A compression-tuned bragg grating includes a tunable optical element 20,600 which includes either an optical fiber 10 having at least one Bragg grating 12 impressed therein encased within and fused to at least a portion of a glass capillary tube 20 or a large diameter waveguide grating 600 having a core and a wide cladding. Light 14 is incident on the grating 12 and light 16 is reflected at a reflection wavelength &lgr;1. The tunable element 20,600 is axially compressed which causes a shift in the reflection wavelength of the grating 12 without buckling the element. The shape of the element may be other geometries (e.g., a “dogbone” shape) and/or more than one grating or pair of gratings may be used and more than one fiber 10 or core 612 may be used. At least a portion of the element may be doped between a pair of gratings 150,152, to form a compression-tuned laser or the grating 12 orgratings 150,152 may be constructed as a tunable DFB laser. Also, the element 20 may have an inner tapered region 22 or tapered (or fluted) sections 27. The compression may be done by a PZT, stepper motor or other actuator or fluid pressure.
摘要:
A fiber grating pressure sensor for use in an industrial process includes an optical sensing element 20,600 which includes an optical fiber 10 having a Bragg grating 12 impressed therein which is encased within and fused to at least a portion of a glass capillary tube 20 and/or a large diameter waveguide grating 600 having a core and a wide cladding and which has an outer transverse dimension of at least 0.3 mm. Light 14 is incident on the grating 12 and light 16 is reflected from the grating 12 at a reflection wavelength &lgr;1. The sensing element 20,600 may be used by itself as a sensor or located within a housing 48,60,90,270,300. When external pressure P increases, the grating 12 is compressed and the reflection wavelength &lgr;1 changes. The shape of the sensing element 20,600 may have other geometries, e.g., a “dogbone” 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 50. A temperature grating 270 may be used to measure temperature and allow for a temperature-corrected pressure measurement. The sensor may be suspended within an outer housing 112, 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.
摘要:
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 “dog bone” 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.
摘要:
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;1. 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.
摘要:
A method and apparatus for forming a tube-encased fiber grating includes an optical fiber 28 which is encased within and fused to at least a portion of a glass capillary tube 120 and a substantially transparent index-matching medium 122, such as an optically flat window, having an optically flat surface 126 adjacent to the tube 120. A substantially transparent index-matching intermediate material (e.g., UV transparent oil) 124 is used between the window 22 and the tube 120 to substantially eliminate the interface between the tube 120 and the medium 122. A pair of writing beams 26,34 are incident on and pass through the medium 122, the tube 120 and intersect and interfere in a region 30 on the fiber 28. Also, the width Wb of the writing beams 26,34 may be set to be less than the width Woil of the intermediate material 124 to eliminate surface damage (ablations) of the tube 120. Attentively, the medium 122 may have a geometry to eliminate surface ablations (e.g., a collar shape) and/or to match the shape of the tube 120. 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 28,250 encased in the tube 120. Further, high intensity writing beams 26,34 on the fiber 28 may be achieved by having the medium 122 have a predetermined thickness T.
摘要:
A method for monitoring wall thickness of an industrial piping component or pump/fluid machinery, including a pump casing for a pump used for pumping an abrasive fluid or slurry, comprising providing a signal containing information about a ultrasonic-based transducer pulse from a discrete ultrasonic-based transducer attached directly on an industrial piping component or pump/fluid machinery at a local point of interest and configured to inject the ultrasonic-based transducer pulse into the industrial piping component or pump/fluid machinery at the local point of interest and sense the ultrasonic-based transducer pulse reflected off a wall of the industrial piping component or pump/fluid machinery at the local point of interest; and determining with an electronic monitoring system the thickness of the wall of the industrial piping component or pump/fluid machinery at the local point of interest based at least partly on the signal received containing information about the discrete ultrasonic-based transducer pulse sensed. The discrete ultrasonic-based transducer may include a discrete ultrasonic-based piezoelectric transducer.
摘要:
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.
摘要:
A strain-isolated bragg grating temperature sensor includes an optical sensing element 20,600 which includes an optical fiber 10 having at least one Bragg grating 12 disposed therein which is encased within and fused to at least a portion of a glass capillary tube 20 and/or a large diameter waveguide grating 600 having a core and a wide cladding and having the grating 12 disposed therein, which senses temperature changes but is substantially not sensitive to strains on the element caused by the fiber or other effects. Light 14 is incident on the grating 12 and light 16 is reflected at a reflection wavelength λ1. The shape of the sensing element 20,600 may be other geometries and/or more than one concentric tube may be used or more than one grating or pair of gratings may be used or more than one fiber or optical core may be used. At least a portion of the element 20,600 may be doped between a pair of gratings 150,152, disposed therein to form a temperature tunable laser or the grating 12 or gratings 150,152 may be constructed as a temperature tunable DFB laser disposed in the element. Also, the element may have an inner or outer tapered regions 22,27, respectively, to provide strain relief and/or added pull strength for the fiber 10. Further, the fiber 10 and the tube 20 may be made of different coefficients of thermal expansion for increased sensitivity.