Abstract: The present invention provides a sensor system for sensing a parameter, comprising an optical source, coupler and signal processor system in combination with multiple structured fiber Bragg gratings. The optical source, coupler and signal processor system provide an optical source signal to the multiple structured fiber Bragg gratings. The optical source, coupler and signal processor system also responds to multiple structured fiber Bragg grating signals, for providing an optical source, coupler and signal processor system signal containing information about a sensed parameter. The multiple structured fiber Bragg gratings respond to the optical source signal, and further respond to the sensed parameter, for providing the multiple structured fiber Bragg grating signals containing information about a complex superposition of spectral responses or codes related to the sensed parameter.

Abstract: A tunable external cavity semiconductor laser incorporating a tunable Bragg grating, including: a semiconductor gain medium; an elongated tuner housing having a tuner housing head and having a tuner housing foot, the tuner housing head and tuner housing foot being rigidly connected; a span of waveguide having a Bragg grating, for receiving the source light and for providing in turn the reflected light, and having a waveguide head and a waveguide foot, the waveguide head abutting the tuner housing head and the waveguide foot disposed toward the tuner housing foot; a piezoelectric crystal or other device or arrangement for providing a compressive force, disposed so as to abut the waveguide foot and also to abut the tuner housing foot, the means for applying a compressive force for exerting a compressive force on the span of waveguide along the direction of the axis of the span of waveguide, the compressive force being sufficient to alter the grating so as to affect the wavelength of light reflected by the grati

Abstract: An athermal packaging for a span of optical fiber having a Bragg grating to counteract a shift in the wavelength reflected light caused by a change in temperature of the span. The packaging is made from a resin system reinforced by a layer of contrahelically wound (and in some applications braided) reinforcing fibers and further reinforced by reinforcing fibers disposed substantially parallel to the axis of the span of the optical fiber. The reinforcing fibers are typically KEVLAR fibers. In some applications, a bulge is provided in the optical fiber on both sides of the span of the optical fiber having the Bragg grating and the athermal packaging is molded over at least a portion of both bulges as well as over the intervening span having the Bragg grating, thus creating mechanical interference against slippage of the athermal packaging during expansion of the optical fiber in response to an increase in temperature.

Abstract: A fiber Bragg grating reference module provides a precise temperature reference for a temperature probe, including a thermistor, located in close proximity thereto, and includes an optical fiber having a fiber Bragg grating therein, a glass element and a reference housing. The fiber Bragg grating has two ends and with a coefficient of thermal expansion. The glass element anchors the two ends of the fiber Bragg grating, and has a substantially similar coefficient of thermal expansion as the coefficient of thermal expansion of the fiber Bragg grating to ensure that the glass element does not substantially induce strain on the fiber Bragg grating as the ambient temperature changes. The reference housing has a cavity and also has a means for receiving and affixing one end of the fiber Bragg grating and for suspending the fiber Bragg grating in the cavity leaving the other end of the fiber Bragg grating free to move as the ambient temperature changes without inducing strain in the fiber Bragg grating.

Abstract: A process for adapting a length of optical fiber with a pure silica core to enable imprinting a Bragg grating in the core without doping the core, the process using an optical fiber having some fluorine in its cladding, and besides the process, a pure silica core optical fiber having a Bragg grating. The process causes fluorine to diffuse from the cladding into the core for a selected length, and then by one of several alternative methods, creates defects in the core within the length. The alternatives include heating and reducing or oxidizing the length; performing flame brushing; or irradiating the length using ionizing radiation, such as gamma radiation. Next, the process uses hydrogenation to load the core with hydrogen, and then exposes the length to a pattern of UV light as is normally done in imprinting a Bragg grating. Finally, the process heats the length, causing hydrogen fluoride to form in the regions exposed to appreciable UV light.

Abstract: An athermal grating design has a Bragg grating unit and a lever arrangement. In operation, the Bragg grating unit responds to an optical signal, a change of temperature and a lever force for offsetting thermally-induced changes in the Bragg grating unit, for providing a grating signal that does not change in relation to change of temperature. The lever arrangement responds to a change of temperature, for providing the level force to the grating to compensate for the change in the temperature. The Bragg grating unit includes a large diameter waveguide cane structure. The lever arrangement may include a top plate, a bottom plate, a lever arm pivotally coupled between the top plate and the bottom plate, and a rod coupled between the top plate and the bottom plate on one side of the lever arm. The Bragg grating unit is arranged between the top plate and the bottom plate on another side of the lever arm. The level arm and the rod have different coefficients of expansion.

Abstract: Non-intrusive pressure sensors 14-18 for measuring unsteady pressures within a pipe 12 include an optical fiber 10 wrapped in coils 20-24 around the circumference of the pipe 12. The length or change in length of the coils 20-24 is indicative of the unsteady pressure in the pipe. Bragg gratings 310-324 impressed in the fiber 10 may be used having reflection wavelengths &lgr; that relate to the unsteady pressure in the pipe. One or more of sensors 14-18 may be axially distributed along the fiber 10 using wavelength division multiplexing and/or time division multiplexing.

Abstract: A method and apparatus for compensating for systematic error in a wavelength measuring device that provides values for the wavelengths reflected from one or more optical fibers in which fiber Bragg gratings (FBGs) serve as sensors. A high-precision temperature sensing and measuring circuit is used to measure the temperature of a reference FBG that also provides light at some wavelength to the wavelength measuring device. The wavelength reflected by the reference FBG changes with temperature in a way that is known. The (value of) the wavelength being reflected from the reference FBG is then provided to a dynamic compensator, which also receives the wavelengths of light reflected from the sensor FBGs, and the dynamic compensator adjusts the wavelengths of the sensor FBGs using a correction based on the correction required to adjust the value of the wavelength of the reference FBG as measured by the wavelength measuring device.

Abstract: 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.

Abstract: At least one parameter of at least one fluid in a pipe 12 is measured using a spatial array of acoustic pressure sensors 14,16,18 placed at predetermined axial locations x1,x2,x3 along the pipe 12. The pressure sensors 14,16,18 provide acoustic pressure signals P1(t), P2(t), P3(t) on lines 20,22,24 which are provided to signal processing logic 60 which determines the speed of sound amix of the fluid (or mixture) in the pipe 12 using acoustic spatial array signal processing techniques with the direction of propagation of the acoustic signals along the longitudinal axis of the pipe 12. Numerous spatial array processing techniques may be employed to determined the speed of sound amix. The speed of sound amix is provided to logic 48 which calculates the percent composition of the mixture, e.g., water fraction, or any other parameter of the mixture or fluid which is related to the sound speed amix. The logic 60 may also determine the Mach number Mx of the fluid.

Abstract: A DC pressure and temperature sensor system for sensing and measuring the DC pressure and temperature of a production fluid (such as oil, gas and water mixtures) in tubing, such as tubing used to extract production fluid from a drilled site. The sensor system includes at least one fluid sensor, but sometimes two. Only one is needed if either the DC pressure or temperature of the production fluid (but not both) is provided by an independent measurement. In general, though, the sensor system includes: a first and second fluid sensor, the first using a first sensing material, and the second using a second sensing material in which sound travels at a rate that depends on the DC pressure and temperature of the second sensing material in a measurably different way than for the first sensing material. Each sensing material is coupled to the production fluid, preferably via a thin-walled membrane, so as to be at a DC pressure and temperature that is, preferably, the same as for the production fluid.

Abstract: A fiber Bragg grating peak detection system has a broadband source that provides a broadband optical signal, a fiber Bragg grating and a variable threshold and/or grating profile peak detection unit. The fiber Bragg grating responds to the broadband optical signal, and further responds to a physical parameter, for providing a fiber Bragg grating optical signal containing information about the physical parameter. The variable threshold or grating profile peak detection unit responds to the fiber Bragg grating optical signal, for providing a variable threshold or grating profile peak detection unit signal containing information about a peak detected in the fiber Bragg grating optical signal that is used to determine the physical parameter. The variable threshold or grating profile peak detection unit detects the peak using either a variable threshold peak detection or a grating profile peak detection, or a combination thereof.

Abstract: A method and device for tuning an optical device including an optical fiber having a core, a cladding and a Bragg grating imparted in the core to partially reflect an optical signal at a reflection wavelength characteristic of the spacing of the Bragg grating. The cladding has two variation regions located on opposite sides of the Bragg grating to allow attachment mechanisms to be disposed against the optical fiber. The attachment mechanisms are mounted to a frame so as to allow the spacing of the Bragg grating to be changed by an actuator which tunes the reflection wavelength. In particular, the variation region has a diameter different from the cladding diameter, and the attachment mechanism comprises a ferrule including a front portion having a profile substantially corresponding to diameter of the variation region and a butting mechanism butting the ferrule against the optical fiber.

Abstract: A method and device for pressure sensing using an optical fiber having a core, a cladding and a Bragg grating imparted in the core for at least partially reflecting an optical signal at a characteristic wavelength. The cladding has two variation regions located on opposite sides of the Bragg grating to allow attachment mechanisms to be disposed against the optical fiber. The attachment mechanisms are mounted to a pressure sensitive structure so as to allow the characteristic wavelength to change according to pressure in an environment. In particular, the variation region has a diameter different from the cladding diameter, and the attachment mechanism comprises a ferrule including a front portion having a profile substantially corresponding to at least a portion of the diameter of the variation region and a butting mechanism which holds the ferrule against the optical fiber.

Abstract: A single mode optical fiber, having a pure silica core and a cladding, and having a Bragg grating in along a length of some of the cladding, providing reflectivity in some of the cladding but not in the core, and a method for making same. Because the core is pure silica, it is unaffected by exposure to ultraviolet light, and so the process of imprinting a Bragg grating does not affect the refractive index of the core. The portion of the cladding in which the Bragg grating is to be imprinted is a glass containing an index-lowering dopant, such as fluorine, as well as a photosensitizing dopant, such as germanium. Exposure to ultraviolet light therefore forms a Bragg grating in a portion of the cladding, but not in the core, providing reflectivity in the cladding, but not in the core. A second portion of cladding can also be provided, surrounding the portion doped with the photosensitizing dopant. The second portion of cladding is an outer cladding, surrounding the doped portion, which abuts the core.

Abstract: A creep-resistant optical fiber attachment includes an optical fiber 10, having a cladding 12 and a core 14, having a variation region 16 (expanded or recessed) of an outer dimension on of the cladding and a structure, such as a ferrule 30, disposed against least a portion of the variation region 16. The fiber 10 is held in tension against the ferrule and the ferrule 30 has a size and shape that mechanically locks the ferrule 30 to the variation 16, thereby holding the fiber 10 in tension against the ferrule 30 with minimal relative movement (or creep) in at least one axail direction between the fiber 10 and the ferrule 30. The ferrule 30 may be attached to or part of a larger structure, such as a housing. The variation 16 and the ferrule 30 may have various different shapes and sizes. There may also be a buffer layer 18 between the cladding 12 and the ferrule 30 to protect the fiber 10 and/or to help secure the ferrule 30 to the fiber 10 to minimize creep.

Abstract: A tunable optical device has a compression tuned optical structure and a displacement sensor. The compression tuned optical structure responds to an optical signal, and further responds to a displacement sensor signal, for providing a compression tuned optical structure signal containing information about a change in an optical characteristic of the compression tuned optical structure, and for also further providing an excitation caused by a change in a displacement of the compression tuned optical structure. The displacement sensor responds to the excitation, for providing a displacement sensor signal containing information about the change in the displacement of the compression tuned optical structure. The compression tuned optical structure may be in the form of a dogbone structure that is an all-glass compression unit having wider end portions separated by a narrower intermediate portion.

Abstract: A quartz sensing system includes a quartz sensor, an electromechanical converter, an optical source, an optical fiber and a signal processor. The quartz sensor responds to a pressure, and further responds to an electrical power signal, for providing a quartz sensor electrical signal containing information about the pressure. The electromechanical converter responds to the quartz sensor signal, for providing an electromechanical converter force containing information about the sensed voltage or current signal. The optical source for provides an optical source signal. The optical fiber responds to the electromechanical converter force, for changing an optical parameter or characteristic of the optical source signal depending on the change in length of the optical fiber and providing an electromechanical converter optical signal containing information about the electromechanical converter force.

Abstract: 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.

Abstract: A well assembly for extracting production fluids from at least one production zone of at least one well includes a production pipe for transporting fluid downstream to a surface, a packer for defining the production zone, and a fiber optic sensor package disposed substantially adjacent to a downstream side of the packer. The fiber optic sensor package measures parameters of the production fluid and communicates these parameters to the surface to determine composition of the production fluid entering the production pipe through each production zone. The production pipe has a zone opening for allowing the production fluid to enter the production pipe and a control valve for controlling the amount of production fluid flowing downstream from each production zone. The production pipe control valve is adjusted to optimize fluid production from the particular production zone of the well based on fluid parameters measured by the fiber optic sensor package.