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 fiber grating pressure sensor 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.

Abstract: 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.

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 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.

Abstract: A fiber grating pressure sensor 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.

Abstract: A gas turbine engine includes a variable area nozzle having a plurality of flaps. The flaps are actuated by a plurality of actuating mechanisms driven by shape memory alloy (SMA) actuators to vary fan exist nozzle area. The SMA actuator has a deformed shape in its martensitic state and a parent shape in its austenitic state. The SMA actuator is heated to transform from martensitic state to austenitic state generating a force output to actuate the flaps. The variable area nozzle also includes a plurality of return mechanisms deforming the SMA actuator when the SMA actuator is in its martensitic state.

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 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 gas turbine engine includes a variable area nozzle having a plurality of flaps. The flaps are actuated by a plurality of actuating mechanisms driven by shape memory alloy (SMA) actuators to vary fan exist nozzle area. The SMA actuator has a deformed shape in its martensitic state and a parent shape in its austenitic state. The SMA actuator is heated to transform from martensitic state to austenitic state generating a force output to actuate the flaps. The variable area nozzle also includes a plurality of return mechanisms deforming the SMA actuator when the SMA actuator is in its martensitic state.

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: The invention provides a select trigger or detonation system featuring an optical source, an optical fiber, one or more optical couplers and one or more light trigger or detonation devices. The an optical source provides an optical signal containing information about triggering or detonating a respective device. The optical fiber has one or more fiber Bragg Gratings for providing one or more fiber Bragg Grating optical trigger or detonation signals, each having a respective optical trigger or detonation wavelength. The one or more optical couplers each respond to the one or more fiber Bragg Grating optical trigger or detonation signals depending on the respective optical trigger or detonation wavelength, for providing a respective coupled fiber Bragg Grating optical trigger or detonation signal.

Abstract: A device for providing optical reference signals includes an optical fiber having a reference array formed therein, the array including at least one reference fiber Bragg grating. The array is mounted on a mounting fixture having a low coefficient of thermal expansion. The mounting fixture is in thermal contact with a thermoelectric (TE) element, and a controller controls the temperature of the TE element. A temperature sensor is in thermal contact with the mounting fixture and provides feedback to the controller to control to the temperature of the TE element to thereby maintain the temperature of the mounting fixture at a selected temperature. The other side of the temperature control element is mounting to a heat sink element. The optical fiber is attached to the mounting fixture in a configuration that minimizes any stress or strain in the optical fiber.

Abstract: A Bourdon tube pressure gauge is mounted for sensing the pressure of a system. The Bourdon tube is connected to at least one optical strain sensor mounted to be strained by movement of the Bourdon tube such that when the Bourdon tube is exposed to the pressure of the system, movement of the tube in response to system pressure causes a strain in the optical sensor. The optical sensor is responsive to the strain and to an input optical signal for providing a strain optical signal which is directly proportional to the pressure. A reference or temperature compensation optical sensor is isolated from the strain associated with the pressure of the system and is responsive to temperature of the system for causing a temperature-induced strain. The reference optical sensor is responsive to the temperature induced strain and the input optical signal for providing a temperature optical signal which is directly proportional to the temperature of the system.

Abstract: Resin curing of a composite laminated structure is monitored using an optical fiber 20 having a grating sensor 28 embedded therein. The fiber 20 is surrounded by upper and lower buffer regions 12,14 having a predetermined minimum number of layers 30 (or thickness) with uni-directional reinforcing filaments 32 and resin 34 therebetween. When the filaments 32 are oriented perpendicular to the longitudinal axis of the fiber 20, the buffer regions 12,14 allow the sensor 28 to exhibit maximum sensitivity to detection of the minimum resin viscosity and the gelation point (i.e., the onset of a rapid crosslinking rate) of the resin 34. The buffer regions 12,14 also have a minimum thickness which serve to isolate the sensor 28 from interfering stresses from arbitrarily angled filaments 32 in layers 30 of outer regions 10,16 which surround the buffer regions 12,14.

Abstract: An optical fiber entry strain relief interface includes a composite structure (lay-up) 10 having an optical fiber 20 embedded therein. The optical fiber 20 enters (or exits) the lay-up 10 at at least one point 24 and passes through transition layers 47 comprising an adhesive film 42, a thin rubber sealing layer 44, and a thick rubber strain relief layer 46, and through a polymer plug 48 located above the layer 46. The lay-up is consolidated by heating the lay-up over a temperature profile and applying pressure through mostly closed compression molding tools 30,32.

Abstract: A system based on integrated optical technologies for the measurement and diagnostics of physical parameters on whatever structure, by the use of optical sensors, made by the fiber embedded Bragg grating method and by the use of a planar integrated optics device for the analysis of the optical signal. The sensors may be embedded or bonded to the structure, allowing the measurement of parameters like strain and temperature, in either a static or dynamic regime. The system pertains to the technical field of the diagnostics and measurements of mechanical or thermal parameters and to the application field of ground, water and aerospace transportation and also to the application field of construction.

Abstract: A highly sensitive optical fiber cavity coating removal detector employs an optical fiber 18 having a pair of Bragg gratings 20,30 embedded therein and separated by a section of fiber making up an optical cavity 26. The optical path length of the cavity 26 is sized with the central reflection wavelength of the fiber gratings 20,30 so as to create an optical resonator. The cavity 26 is coated with a material 40 which corrodes or is otherwise removable, such as aluminum. The coating 40 exerts forces 46 radially inward on the cavity 26 so as to cause the refractive index of the cavity and thus its optical path length to change, thereby causing the resonator to come out of resonance. The forces 46 on the cavity 26 are reduced when the coating 40 corrodes, thereby causing the resonator to re-enter resonance. Additionally, the coating causes optical losses to exist due to non-uniform variations in refractive index caused by non-uniform forces from coating irregularities.

Abstract: A measurement system for fiber sensors includes a broadband light source 11 providing continuous light which is launched into a fiber 20 having a plurality (or string) of Bragg grating sensors 24, 28, 34. Each sensor has a predetermined central reflection wavelength which shifts as a function of applied strain. Reflected light 40 from the sensors 24, 28, 34 are fed to a plurality of optical bandbass filters 50, 64, 78, each having a monotonic region in a passband corresponding to one of the sensors. Each monotonic region transmits the reflected wavelength from a corresponding sensor. Light 52, 66, 80 is passed from the filters 50, 64, 78 to optical detectors 54, 68, 82 each providing an electrical signal having a magnitude related to transmission of the filter at the reflection wavelength of the sensor. Optional demodulators 58, 72, 86 are connected to each of the detectors 54, 68, 82 if the light source 10 is modulated.

Abstract: An optical sensor diagnostic system includes a tunable narrow wavelength-band source 9 which provides a variable wavelength light 44 into an optical fiber 32,52. Reflective sensors 54,58, such as Bragg gratings, are disposed along the fiber 52 in the path of the variable light 44. The sensors 54,58 transmit light 56,60 having a minimum transmission wavelength which varies due to a perturbation, such as strain, imposed thereon. A tuner control circuit 42 drives the tunable light source 9 to cause the source light 44 to scan across a predetermined wavelength range to illuminate each sensor at its minimum transmission wavelength. The power of the transmitted light is converted to an electrical signal by a detector 64 and monitored by a signal processor 68 which detects drops in transmitted power level and provides output signals on lines 71 indicative of the perturbation for each sensor.