摘要:
A fiber optic Bragg grating pressure sensor particularly suited for measuring ambient pressure of a fluid includes a pressuring detecting device 12 such as a glass element whose elastic deformation is proportional to applied pressure. An optical fiber 28 with an integral first grating 33 is wrapped at least once around the device and has at least a portion of its length fused to the device 12 such that elastic deformation of the device 12 generates a corresponding axial strain in the fiber 28 and/or the grating 33 and thus a corresponding change of the fiber length and/or characteristic reflectance wavelength of the grating 33. A second grating 35 may be formed near the pressure detecting device 12 so as to sense ambient temperature but not be affected by deformation of the device 12 for temperature compensation. Also, the fiber 28 may have more than one grating or be doped at least between a pair of gratings 160,162, to form a fiber laser or a DFB fiber laser which lasing wavelength changes with changing pressure.
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:
An apparatus and method for interrogating fiber optic sensors non-intrusively sensing fluid flow within a pipe is provided. The apparatus includes a two-beam interferometer which comprises an optical circuit for generating a series of discrete light pulses that are directed at sensors positioned between pairs of low reflectivity fiber Bragg gratings. The successive light pulses are split into first light pulses and second light pulses, and the second light pulses are delayed a known time period relative to the first pulses. The first and second light pulses are combined onto a single optical fiber and directed through the low reflectivity gratings and the sensors positioned between the gratings. Reflected pulses from the series of pulses impinge on a photo receiver and interrogator, wherein the phase shift between the reflected first light pulses from a particular grating and the reflected second light pulses from the preceding grating, for each sensor are determined. Phase shifts from successive pulses for each sensor are compared, and a change in a measured parameter of the fluid is determined.
摘要:
The invention provides a signal processor that receives a signal containing information about an acoustic signal that is generated by at least one acoustic transmitter, that travels through an aerated fluid in a container, and that is received by at least one acoustic receiver arranged in relation to the container, including inside the container; and determines the gas volume fraction of the aerated fluid based at least partly on the speed of sound measurement of the acoustic signal that travels through the aerated fluid in the container. The signal processor also sends an output signal containing information about the gas volume fraction of the aerated fluid. The signal processor may be configured together with at least one acoustic transmitter, the at least one acoustic receiver, or both.
摘要:
A tube-encased fiber grating includes an optical fiber 10 having at least one Bragg grating 12 impressed therein which is embedded within a glass capillary tube 20. Light 14 is incident on the grating 12 and light 16 is reflected at a reflection wavelength &lgr;1. The shape of the tube 20 may be other geometries (e.g., a “dogbone” 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 10 may be doped at least between a pair of gratings 150,152, encased in the tube 20 to form a tube-encased compression-tuned fiber laser or the grating 12 or gratings 150,152 may be constructed as a tunable DFB fiber laser encased in the tube 20. Also, the tube 20 may have an inner region 22 which is tapered away from the fiber 10 to provide strain relief for the fiber 10, or the tube 20 may have tapered (or fluted) sections 27 which have an outer geometry that decreases down to the fiber 10 and provides added fiber pull strength. Also, the tube-encased grating 12 exhibits lower mode coupling from the fiber core to the cladding modes due to the increased diameter of the cladding where the tube 20 is fused to the fiber 10 where the grating is located 12.
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 apparatus 10,110,170 is provided that measures the speed of sound and/or vortical disturbances propagating in a single phase fluid flow and/or multiphase mixture to determine parameters, such as mixture quality, particle size, vapor/mass ratio, liquid/vapor ratio, mass flow rate, enthalpy and volumetric flow rate of the flow in a pipe, by measuring acoustic and/or dynamic pressures. The apparatus includes a spatial array of unsteady pressure sensors 15-18 placed at predetermined axial locations x1-xN disposed axially along the pipe 14. The pressure sensors 15-18 provide acoustic pressure signals P1(t)-PN(t) to a signal processing unit 30 which determines the speed of sound amix propagating through of the process flow 12 flowing in the pipe 14. The pressure sensors are piezoelectric film sensors that are mounted or clamped onto the outer surface of the pipe at the respective axial location.
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.
摘要:
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 “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.