Abstract: A window can be used for object detection and/or identification. The window can have a first side and a second side. An optical grating can be operatively positioned with respect to the first side of the window. A light source can be configured to emit light toward the optical grating. A detector can be operatively positioned to acquire spectroscopic data of the light emitted from the light source after the light has interacted with the optical grating. Using the optical grating, a temperature at or near the first side can be determined. Based on the temperature, it can be determined whether an object is located on the first side of the window.

Abstract: A window can comprise a first side and a second side substantially parallel to the first side. The window can comprise an optical grating operatively positioned with respect to one of the first side and the second side. The optical grating can be used to determine a temperature at or near the respective one of the first side and the second side.

Abstract: The present application provides an optical fibre grating sensor and a strain monitoring method and system for a surrounding rock of a deep roadway, which are used for monitoring deformation of the surrounding rock of the deep roadway and are provided with a weak optical fibre grating array large-range strain sensor, which can accurately monitor the strain of the surrounding rock of the deep roadway. The optical fibre grating sensor comprises an optical fibre, the optical fibre comprises an optical fibre core and a plurality of optical fibre gratings inscribed on the optical fibre core, the optical fibre grating is a weak optical fibre grating with a peak reflectivity lower than 1%, and the plurality of optical fibre gratings perform unit discretization on the whole piece of the optical fibre so as to realize quasi-distributed sensing.

Abstract: A multicore optical fiber includes a cladding and multiple cores disposed in the cladding. Each core has a light-guiding path and follows a helical trajectory about a fiber axis. The multicore fiber also includes a set of discrete lateral coupling zones, which are longitudinally distributed and azimuthally aligned with respect to the fiber axis. Each lateral coupling zone forms an optical coupling path, which enables at least one of lateral in-coupling and out-coupling of light between a corresponding one of the cores and an exterior of the multicore fiber. An optical probing system for light delivery to and/or light collection from a probed region includes a multicore optical fiber to enable coupling of guided light out of the cores for delivery to the probed region and/or collection of light from the probed region for coupling into one of the cores.

Abstract: Overheat and fire detection for aircraft systems includes an optical controller and a fiber optic loop extending from the optical controller. The fiber optic loop extends through one or more zones of the aircraft. An optical signal is transmitted through the fiber optic loop from the optical controller and is also received back at the optical controller. The optical controller analyzes the optical signal to determine the temperature, strain, or both experienced within the zones.

Abstract: An apparatus for performing a measurement of a downhole property includes an optical fiber having a first section that has a first set of fiber Bragg gratings with a first resonant wavelength inscribed therein and a second section that has a second set of fiber Bragg gratings with a second resonant wavelength different from the first resonant wavelength inscribed therein. The second section is in series with the first section. An optical interrogator emits a swept-wavelength frequency domain light signal having varying wavelength amplitude modulation into the optical fiber, receives a frequency domain return light signal, and transforms the frequency domain return signal into a time domain to determine a resonant wavelength shift of each fiber Bragg grating and the corresponding location of each interrogated fiber Bragg grating. A processor converts the resonant wavelength shift of each interrogated fiber Bragg grating into the downhole property measurement.

Abstract: A sensing cable has a sensing fiber assembly, which includes a pair of sensing fibers joined by a turnaround section with a modal filter, at a terminating end of the sensing fibers. The sensing cable also includes an inner sleeve that surrounds the sensing fiber assembly and an armored casing that caps the terminating end of the inner sleeve. The sensing cable has a low profile and its components are each made of high temperature and hydrogen tolerant materials and are capable of prolonged operation at high temperatures, such as up to 300° C., in hydrogen environments over long lengths of fiber. A distributed thermal sensing (DTS) interrogator is connected to the sensing cable and performs DTS measuring according to protocols and algorithms that leverage the modal filter of the turnaround section to calculate temperature readings along the sensing fiber assembly.

Abstract: A combustion turbine flashback sensing system with a sensor cable that includes an optical fiber having at least one and preferably multiple fiber Bragg grating (FBG) temperature sensors along the fiber. The sensor cable is oriented in a combustor turbine upstream a combustion zone, so that it is capable of sensing temperature at multiple sensing points within the combustor. A protective conduit having a first thermal conductivity circumscribes the optical fiber. A sensor shield is oriented in circumferential proximity to the FBG temperature sensor. It is preferable that each such sensor has an associated sensor shield. The sensor shield has a thermal conductivity greater than the conduit thermal conductivity. The sensor shield facilitates FBG sensor rapid thermal response, with sufficient thermal and mechanical shielding to isolate the sensor from harsh operating conditions within the combustor, while the less thermally conductive conduit provides greater isolation protection for the cable structure.

Abstract: A method is presented for detecting an alarm condition with an optical fiber sensing system. An interrogator with a light source, a spectrometer, and a data processor is used to conduct a fast scan of a plurality of fiber optic sensing elements. First environmental parameter values are calculated for each fiber optic sensing element from spectrographic data collected by the interrogator during the first scan, and compared with a first threshold value. If the first environmental parameter value exceeds the first threshold value for any fiber optic sensing element, the fast scan is interrupted to perform a high resolution slow scan of that fiber optic sensing element. The optical fiber sensing system reports an alert if this high resolution slow scan indicates the alarm condition.

Abstract: A method of estimating temperature includes selecting a plurality of known calibration temperature values; determining a bulk wavelength for each of the calibration temperature values; formulating a calibration data set that includes the plurality of known temperature values and the corresponding plurality of bulk wavelengths; and using the calibration data set to determine an estimated current temperature value based upon a current bulk wavelength, wherein the current temperature value is estimated based upon one or more data points in the calibration data set.

Abstract: This invention teaches the fiber optic sensors temperature sensors for cryogenic temperature range with improved sensitivity and resolution, and method of making said sensors. In more detail, the present invention is related to enhancement of temperature sensitivity of fiber optic temperature sensors at cryogenic temperatures by utilizing nanomaterials with a thermal expansion coefficient that is smaller than the thermal expansion coefficient of the optical fiber but larger in absolute value than the thermal expansion coefficient of the optical fiber at least over a range of temperatures.

Abstract: A temperature sensor array comprises an optical fiber (16) on which are a plurality of Bragg gratings (18) on respective spaced apart portions of the fiber. Each portion is in a housing (14) which freely houses the said portion substantially without axial strain on the fiber within the housing and which also isolates the grating from strain imposed on the fiber outside the housing. Thus substantially only changes in temperature affect the Bragg grating of that portion. The array may be used to detect and control the temperature of a tool (12) for forming a composite component amongst other uses.

Abstract: A mount (20) for a temperature-compensated fiber optic strain gauge (10), the mount (20) comprising: a void (19) located at a middle portion of the mount (20) to separate the mount (20) into a first section (17) and a second section (18); and removable bridges (24) to connect the first section (17) to the second section (18); wherein after the mount (20) has been operatively attached to a host structure (5), the removable bridges (24) are removed.

Abstract: A twin core fiber for sensor applications is developed. It is particularly useful in de-coupling the strain and temperature and thus obtaining both measurement parameters at the same time and location. It is also particularly useful for measuring the temperature in a high humidity environment. The twin core fiber has two cores and each of the cores having a different dopant regime. Also, each of the cores includes a grating having substantially the same grating period.

Abstract: A temperature monitoring system for a medical device comprises an optical transmit/receive unit, an elongate optical fiber having a proximal end, a distal end, and an inner core extending between the proximal end and the distal end, and one or more fiber Bragg grating elements formed in the inner core of the optical fiber. The optical fiber is operably coupled to the transmit/receive unit at the proximal end. At least a portion of the optical fiber is also operably coupled to a medical device and is structured to measure temperature at one or more temperature sensing locations on the medical device.

Abstract: A bridge intelligent cable system with a built-in fiber grating sensor is provided, which is applied in a cable bearing structure such as a cable-stayed bridge, a suspension bridge, and an arch bridge. The system includes an anchor cup (1), a wire dividing plate (5), a connecting cylinder (4), a fiber grating sensor, and a cable body (11), in which the fiber grating sensor includes a fiber grating strain sensor (9) and a fiber grating temperature sensor (10), tail fibers of the fiber grating strain sensor (9) and the fiber grating temperature sensor (10) are led out, the packaged fiber grating strain sensor (9) is fixedly connected to an outer-layer steel wire (3) of the connecting cylinder (4), the packaged fiber grating temperature sensor (10) is suspended on the steel wire (3) of the connecting cylinder (4), holes (5-1) are punched in the wire dividing plate (5), and a preserved steel pipe (7) is buried in advance in the connecting cylinder (4) and the anchor cup (1).

Abstract: A mount (20) for a temperature-compensated fibre optic strain gauge (10), the mount (20) comprising: a void (19) located at a middle portion of the mount (20) to separate the mount (20) into a first section (17) and a second section (18); and removable bridges (24) to connect the first section (17) to the second section (18); wherein after the mount (20) has been operatively attached to a host structure (5), the removable bridges (24) are removed.

Abstract: An apparatus and method for increasing the resolution of a linear array of fiber Bragg gratings by applying a plastic coating having a high CTE over the optical fiber. Apparatus and method for determining the temperature of each of a succession of points along a tissue portion during hyperthermia treatment includes an optical fiber with a succession of closely spaced fiber Bragg gratings. Each grating is responsive to a different wavelength and is sensitive to ambient temperature to change that wavelength as a function of temperature. A tunable laser operative continuously over a range of wavelengths including those to which the gratings respond is used to interrogate the gratings. Sensitivity-enhancing coatings are used on the fibers and the lasers are tuned over very short time cycles.

Abstract: The invention provides an optical measurement system and method for monitoring the condition of a sail, the system comprising: an optical interrogation unit that produces and receives an optical signal; and an optical fibre network that interconnects the interrogation unit with a plurality of optical sensors in communication with the sail, wherein the sensors are mounted onto the sail. The optical system measures parameters of the sail, from which shape, integrity and overall conditions of the sail can be calculated in real-time.

Abstract: A physical quantity measuring apparatus utilizing optical frequency domain reflectometry of the invention includes a tunable laser; a first polarization-maintaining fiber; a polarization-maintaining coupler; a second polarization-maintaining fiber; a third polarization-maintaining fiber; a sensor consists of fiber Bragg gratings formed at a core of the third polarization-maintaining fiber; a fourth polarization-maintaining fiber; a photodiode detects Bragg reflected light from the sensor and reference light from the referential reflecting end; a controller detects a modulation of an interference intensity between the Bragg reflected light and the reference light, based on an intensity change of multiplexed light of the Bragg reflected light and the reference light; an incidence part inputs the measuring light; and an optical path-length adjuster arranged on the third polarization-maintaining fiber; the incidence part provided on the first polarization-maintaining fiber, or on both the second and third polariz

Abstract: A physical quantity measuring apparatus utilizing optical frequency domain reflectometry includes a tunable laser; a first polarization maintaining fiber; a polarization maintaining coupler; a second polarization maintaining fiber; a third polarization maintaining fiber; a sensor consists of a fiber Bragg grating formed in a core of the third polarization maintaining fiber; a fourth polarization maintaining fiber; a photodiode detects Bragg reflected light from the sensor and reference light from the referential reflecting end; a controller that detects modulation of an interference intensity between the Bragg reflected light and the reference light; and an incidence part that inputs the measuring light, wherein the incidence part being provided on the first polarization maintaining fiber or on both the second polarization maintaining fiber and the third polarization maintaining fiber.

Abstract: A temperature sensor array comprises an optical fibre (16) on which are a plurality of Bragg gratings (18) on respective spaced apart portions of the fibre. Each portion is in a housing (14) which freely houses the said portion substantially without axial strain on the fibre within the housing and which also isolates the grating from strain imposed on the fibre outside the housing. Thus substantially only changes in temperature affect the Bragg grating of that portion. The array may be used to detect and control the temperature of a tool (12) for forming a composite component amongst other uses.

Abstract: The present invention relates to a measuring method and a sensor unit of measuring temperature distribution of an object by using an optical fiber sensing technology of BOCDA system. In the measuring method, an optical fiber that functions as a BOCDA-type optical fiber sensor is disposed two-dimensionally or three-dimensionally with respect to a predetermined measurement region of the object, and thereby the temperature distribution of the object can be measured at a high speed and a high accuracy, in the predetermined measurement region configuring a surface or space where the optical fiber is disposed.

Abstract: A twin core fiber for sensor applications is developed. It is particularly useful in de-coupling the strain and temperature and thus obtaining both measurement parameters at the same time and location. It is also particularly useful for measuring the temperature in a high humidity environment. The twin core fiber has two cores and each of the cores having a different dopant regime. Also, each of the cores includes a grating having substantially the same grating period.

Abstract: An optical measuring device for determining temperature in a cryogenic environment includes at least one optical waveguide provided with at least one fiber Bragg grating sensor that is interrogated by a light signal. The device includes a light injector that injects light into the at least one fiber Bragg grating sensor, and an evaluation unit that determines a temperature value from the modulated light signal emanating from the at least one fiber Bragg grating sensor. The device includes at least one jacket that non-rigidly encloses the optical waveguide, at least in the region of the at least one fiber Bragg grating sensor. The jacket has a larger coefficient of thermal expansion, at least at cryogenic temperatures, than the optical waveguide. A winding arrangement for use in a cryogenic environment is provided with such a device for temperature monitoring of a conductor of the winding arrangement.