Abstract: An optical phase detector comprising coupling means for receiving two optical inputs and for producing two combined optical outputs, means for detecting the two combined optical outputs and producing two corresponding electrical signals, and means for measuring the difference between the two electrical signals and generating an output difference signal which may be used to provide an indication of the phase difference between the two optical inputs. The optical phase detector comprises a voltage-tuneable electro-optic phase modulator for modulating the phase of an optical input to the optical phase detector to provide a linearized response. In this arrangement the output difference signal may be maintained at a constant level by varying the voltage applied to the electro-optic phase modulator, the applied voltage providing an indication of the phase difference between the two optical inputs. Applications include frequency discriminators, various sensors, and a laser stabilization apparatus.

Abstract: There is provided a process and apparatus for measuring and monitoring motor systems, which includes providing a motor system having at least one component selected from a stator and an armature, which at least one component is connected to at least one electrical wire incorporating at least one means for data measurement, collecting data with the means for data measurement, and transferring the collected data to a data collection station.

Abstract: A sensor measures temperature in stationary components of electrical machines using fiber optics. An optical fiber is embedded in a non-metallic ribbon. Notches are cut in the ribbon to effect bends that accommodate a shape of a stationary component. The ribbon and optical fiber are attached to the stationary component. A series of laser pulses can be injected from at least one end of the optical fiber, and the stationary component temperature can be monitored by interrogation of reflections from the series of laser pulses.

Abstract: A fiber optic cable forms a temperature sensor arranged along an object or space to monitor the temperature thereof and detect overheating or fire conditions. An end of the sensor is connected through an interface to a laser emitter and an optical receiver, which are further connected to a computer. The computer controls the laser emitter to emit a laser pulse into the sensor. The optical receiver receives the resulting reflection signal from the sensor, and provides a corresponding signal to the computer to be evaluated in connection with a nominal comparison signal. If any location of the sensor is subjected to an unacceptable temperature increase, the sensor's refractive characteristics are changed, to cause an additional reflection pulse in the reflection signal. By evaluating the amplitude and the return time of the additional reflection pulse, the temperature level and the location of the overheating condition are determined by the computer.

Abstract: A differential measurement system using pairs of Bragg gratings including at least one optical sensor having two Bragg gratings in two optical waveguides and having sensitivities adjusted so that respective spectra of the two gratings have a relative spectral shift dependent on a parameter or parameters to be measured. The system also includes an optical source to supply light to the two optical waveguides to interrogate them, a mechanism enabling light to pass successively through the two Bragg gratings of the same sensor, photodetectors to measure the power level of light having passed only through one of the two optical waveguides and the power level of light having passed successively through the two optical waveguides, and a processor to process the power levels and supply values of the parameter or parameters measured. The system is applicable in particular to measurements of temperatures, stresses, and pressures.

Abstract: An optical fiber sensor system comprising of an optical fiber including plurality of sensitive elements, each sensitive element has characteristic spectral band which in normal undisturbed condition lies in a first wavelength range and, under an influence of some specified condition to be detected, shifts to a second wavelength range; first and second wavelength ranges do not overlap. Means for probing an optical transmission or reflection of the fiber operate within second wavelength range to monitor the changes of the transparency or reflectivity of the fiber caused by the shift of characteristic spectral band into the second wavelength range. The invention provides means for distributed monitoring of equipment or construction structures and detection of specified conditions and can provide alarm signal when the specified conditions become effective.

Abstract: The deformation sensor does not require a supplementary sensor to check functionality. This deformation sensor includes an optical transmission medium, multiple transmission elements, which couple the light of various wavelengths into the transmission medium, and multiple reception elements, which selectively couple the transmitted light out of the transmission medium according to wavelength. An evaluation unit detects deviations between the output signals of the reception elements and signals a malfunction of the sensor if the deviations exceed a preset measure.

Abstract: The present invention provides a method and apparatus, such as an integrated circuit, to control the extinction ratio of a semiconductor laser and maintain the extinction ratio substantially constant at a predetermined level. Apparatus embodiments include a semiconductor laser, a modulator, a photodetector, and an extinction ratio controller. The semiconductor laser is capable of transmitting an optical signal in response to a modulation current. The modulator is capable of providing the modulation current to the semiconductor laser, with the modulation current corresponding to an input data signal. The photodetector, which is optically coupled to the semiconductor laser, is capable of converting the optical signal into a photodetector current. The extinction ratio controller, in response to the photodetector current, is capable of adjusting the modulation current provided by the modulator to the semiconductor laser to generate the optical signal having substantially a predetermined extinction ratio.

Abstract: A portion of at least one fiber is moved into an exterior annulus of a well between a tubular structure in the well and the wall of the borehole of the well such that the portion is placed to conduct a signal responsive to at least one parameter in the exterior annulus. One particular implementation uses fiber optic cable with a cementing process whereby flowing cementing fluid pulls the portion of the cable into the exterior annulus.

Abstract: In a preferred embodiment, the invention provides a fiber optic pressure sensor apparatus which includes a light source, a reflective sensor diaphragm movable in accordance with pressure in a medium and an optical fiber coupled to the light source for delivering a first wavefront of light to the reflective sensor diaphragm. The optical fiber has an endface which is separated from the reflective sensor diaphragm by a gap, the endface receiving a second wavefront of light reflected from the reflective sensor diaphragm. The first and second wavefronts constructively and destructively interfere to create a modulated optical signal. A spectrometer is coupled to the optical fiber for converting the optical signal into a series of digital values, and means for analyzing the digital values is provided for obtaining a measurement of the pressure in the medium. An optical coupler is preferably provided for coupling the light source, the optical fiber, and the spectrometer.

Abstract: A pressure-sensitive sensor which is a load detecting device of the present invention is structured to include: an optical fiber of a predetermined length; a light-emitting element, disposed at a longitudinal direction one end side of the optical fiber, for emitting light and making the light incident from one end of the optical fiber; a light-receiving element, disposed at a longitudinal direction other end side of the optical fiber, for receiving light which has passed through the optical fiber and outputting a signal corresponding to an amount of received light; and a power source wire for light-emission and a ground wire for light-emission which are wound around an outer periphery of the optical fiber, and are formed in spiral forms along the outer periphery, and are connected to the light-emitting element.

Abstract: In the present invention an optical waveguide grating sensing device for a dual-parameter optical waveguide grating sensor includes a first optical waveguide grating of a first resonant wavelength provided in a first section of an optical waveguide and a second optical waveguide grating of a second resonant wavelength provided in a second of an optical waveguide. The first and second gratings have different coefficients of rate of change of wavelength as a function of temperature and have substantially the same coefficient of rate of change of wavelength as a function of stain.

Abstract: Using an array of optical sensors affixed to measure interactions on a surface of an object, in combination with a specially configured personal computer, dynamic mapping of interaction is provided. One application maps washover of an object towed in a large body of water. Data are collected on optical characteristics of the interaction such as reflectivity at a boundary. For example, in one embodiment the reflectivity at an optical fiber/seawater boundary is compared to that of an optical fiber/air boundary and dynamic measurements made using an optical time domain reflectometer (OTDR). These data are then processed using specialized software to yield representation of the dynamics (spatial and temporal) of selected washover events on a surface of interest. The system specifically provides a real-time representation of washover, including two and three-dimensional visualization of washover, as well as recording selected data for future use. Methods of employment of the system are also provided.

Abstract: A preferred embodiment of a system for measuring a level of a fluid comprises a light source adapted to generate light having a predetermined wavelength, an optical waveguide slab at least partially filled with a material adapted to fluoresce when illuminated by the light having a predetermined wavelength, and a light pipe. The light pipe is adapted to transmit the light having a predetermined wavelength to the optical waveguide slab at an angle that causes the light to be internally reflected only within a portion of the optical waveguide slab located above the fluid thereby illuminating the fluorescent material within the portion of the optical waveguide slab located above the fluid. The preferred embodiment also comprises a photo-multiplier tube adapted to generate an electrical output in response to the fluorescence of the fluorescent material.

Abstract: An optical transducer includes a base member, a light source carried on a face of the base member, a light detector carried on the face of the base member, a displaceable member overlying and spaced from the light source and light detector and effective to reflect light from the light source to the light detector, and light shielding means effective to shield the light detector from exposure to the light source except for the light reflected by the displaceable member from the light source to the light detector. The light detector is configured to substantially surround the light source such as to receive light emitted in substantially all directions from the light source for reflection to the light detector by the displaceable member.

Abstract: An apparatus and method for determining a physical parameter affecting an optical sensor or a number of sensors in a network. The apparatus uses a narrow linewidth source at an emission wavelength &lgr;e and an arrangement for varying the emission wavelength &lgr;e of the radiation. An analysis module with curve fitting is used to generate a fit to the response signal obtained from the optical sensor. The physical parameter is determined form the fit rather than from the response signal. The apparatus can be employed with Bragg gratings, etalons, Fabry Perot elements or other optical sensors.

Abstract: This invention provides a method for controlling production operations using fiber optic devices. An optical fiber carrying fiber-optic sensors is deployed downhole to provide information about downhole conditions. Parameters related to the chemicals being used for surface treatments are measured in real time and on-line, and these measured parameters are used to control the dosage of chemicals into the surface treatment system. The information is also used to control downhole devices that may be a packer, choke, sliding sleeve, perforating device, flow control valve, completion device, an anchor or any other device. Provision is also made for control of secondary recovery operations online using the downhole sensors to monitor the reservoir conditions. The present invention also provides a method of generating motive power in a wellbore utilizing optical energy. This can be done directly or indirectly, e.g., by first producing electrical energy that is then converted to another form of energy.

Abstract: An optical spectrum analyzer (10), receiving a multi-channel optical signal (12). The optical signal (12) is passed through an optical isolator (14) and a fiber coupler (16) to a tunable optical filter. The tunable optical filter comprises one or more fiber Bragg gratings (18) inscribed in a length of optical fiber. The optical fiber is mounted on a means operable to apply a variable strain to the fiber, to they tune the peak wavelength of the Bragg grating (18) over a desired wavelength range, the tunable optical filter thereby reflecting each channel of the input signal (12) in turn. The detector (20) therefore detects a signal only if the input signal (12) contains wavelengths corresponding to the reflection wavelength of a grating (18).

Abstract: An optoelectronic sensor, which is based on optodes and with which, thanks to optode material that has been rendered reflective, virtually any angle for injecting the light into the optode material is feasible, is proposed. Thus, advantageously, a longer optical path is achieved than would be feasible in the case of total reflection. Thus greater measuring precision can be achieved. In the present case the optode material is a polymer, reflectivity being provided by introducing metal particles into the polymer. The light emitter and the light-sensitive sensors are an LED and photodiodes respectively. A plurality of optoelectronic sensors can be combined to form a gas sensor array.

Abstract: A misalignment detection system for checking the coupling of a component and a medium via a receptacle of a connectorized arrangement. Power coupling measurements between an optical component and a fiber are presented as illustrative examples of the invention. A ferrule of a fiber is inserted into a bore of a receptacle that has the component attached to the end of the receptacle opposite of the bore. The ferrule of the fiber is attached to a support structure having an absorber spring between the structure and ferrule. A first force is applied pressing the ferrule into the bore. Also, a rotating force orthogonal to the first force is applied to the structure causing the ferrule to wiggle in the bore. Power measurements are taken while the first force is applied and then also while the rotating force is applied.

Abstract: Methods, and corresponding apparatus, for detecting the occurrence of cracks or fractures are described and claimed. The methods utilize Bragg gratings, and the occurrence of a crack is detected by detecting a change in the reflectance and/or transmittance characteristics of the Bragg grating when the crack is transmitted to it. In addition to merely detecting that a crack has occurred, the methods may also provide information on the position of the fracture along the length of the Bragg grating. This may be achieved by comparing the peak intensities and/or widths of the optical reflectance spectra of the unbroken and broken grating. In certain preferred embodiments the Bragg gratings are interrogated using the combination of a broad band source and an optical spectrum analyser, or a tunable laser source and a broad band detector.

Abstract: A strain sensor comprises an optical waveguide having a plurality of reflecting structure (Bragg grating) along its length. Each structure reflects light at a different characteristic wavelength (&lgr;1 to &lgr;n+1) which changes in dependence on a change of physical length of at least part of the reflecting structure. The reflectivity of reflecting structures which reflect at characteristic wavelengths which are adjacent to each other (&lgr;1 and &lgr;2 or &lgr;n and &lgr;n+1) are configured to be different such that the intensity of light reflected from adjacent structures can be used to discriminate between them.

Abstract: A fiber optic cable is used as a distributed temperature sensing (DTS) transducer for temperature profile measurements in a protective underground duct in which a high voltage (HV) cable has already been laid. The sensing cable is not incorporated into the power cable itself, and in some installations does not have direct physical contact with the HV cable. The sensing cable is installed externally (along side) of the HV power cable, either in direct surface contact with the HV cable, or alternatively, the fiber optic sensing cable is installed in a small diameter guide tube that is placed in the upper annulus between the HV cable and the protective duct. The sensing fiber and one or more guide tubes are installed in a loose bundle at least in part by fluid drag forces (blowing with pressurized air) using conventional cable launching equipment.

Abstract: Brillouin scattering spectrum analysis is used to measure strain, displacement, temperature or other physical quantities at any location along an optical fiber attached to a structure. The fiber can be interrogated with different pulse widths for coarse and fine scans. The fiber can also have multiple sensors, either formed in a single fiber or branching off from a backbone fiber, in which case other segments of the fiber can be used for temperature compensation.

Abstract: This system comprises at least one optical sensor (C1, C2, C3) comprising two Bragg gratings (B11, B12; B21, B22; B31, B32) written in two optical waveguides and having sensitivities adjusted so that the respective spectra of the two gratings have a relative spectral shift which depends on the parameter or parameters to be measured. The system also comprises an optical source (6) provided in order to supply light to the two optical waveguides so as to interrogate the latter, means enabling the light to pass successively through the two Bragg gratings of the same sensor, photodetectors in order to measure, on the one hand, the power level of light (R1) having passed only through one of the two optical waveguides and, on the other hand, the power level of light (R′1) having passed successively through the two optical waveguides, and means to process these power levels and supply the values of the parameter or parameters measured.

Abstract: A bond separation inspection method using an optical fiber sensor. The method includes a step of embedding a sensor part of an optical fiber sensor in an adhesive joining a plurality of members together. The sensor part is embedded in the adhesive in such a way that the sensor part undergoes a compressive strain. Separation of the bond is detected on the basis of an optical characteristic of the sensor part when light from a light source is directed into the optical fiber sensor.

Abstract: A fiber optic liquid level detector uses optical fibers to detect the presence or absence of liquids. The waveguide properties of optical fibers tends to deviate from the normal dielectric interfaces so that a fiber immersed in a liquid has a reflection coefficient smaller than when surrounded by air. This is caused by the differences in refractive indices of liquid and air and is used to measure the amount of light transmitted or reflected by the fiber in the preserve or absence of a liquid.

Abstract: A detection system is used during irradiation of an interaction region of a structure with laser light. The structure includes embedded material. The detection system includes a focusing lens positioned to receive light emitted from the interaction region. The detection system further includes an optical fiber optically coupled to the focusing lens to receive light from the focusing lens. The detection system further includes a spectrometer optically coupled to the optical fiber to receive light from the optical fiber. The spectrometer is adapted for analysis of the light for indications of the embedded material within the interaction region.

Abstract: An optical component mount with beam deviation monitoring and beam guiding system using such optical component mounts. The optical component mount has a location for mounting an optical element thereon for operating on the beam and at least one sensor attached to the optical mount at a predetermined position. The predetermined position is selected depending on the state of the optical component mount. The state can be, e.g., a vibrational state or a thermal expansion state. The predetermined position is chosen near or at an anti-node of at least one mode contributing to the state but not at a node of any mode expected to contribute to the state of the optical mount. The state of the optical mount is determined based on the signals obtained from the at least one sensor, which can be an accelerometer in the case of monitoring a vibrational state or a temperature sensor in the case of monitoring a thermal expansion state.

Abstract: A detection system is used during irradiation of an interaction region of a structure including embedded material with laser light. The detection system includes a collimating lens positioned to receive light emitted from the interaction region. The detection system further includes an optical fiber optically coupled to the collimating lens and a spectrometer optically coupled to the optical fiber. The spectrometer is adapted for analysis of the light for indications of the embedded material within the interaction region. The spectrometer includes an input slit adapted to receive light from the optical fiber. The input slit has a width selected to provide sufficient light transmittance and sufficient resolution. The spectrometer further includes an optical grating adapted to receive light from the input slit and to separate the light into a spectrum of wavelengths.

Abstract: A highly sensitive accelerometer for determining the acceleration of a structure includes a mass within a housing suspended by opposing support members. The support members are alternately wound around a pair of fixed mandrels and the mass in a push pull arrangement. At least a portion of one of the support members comprises a transducer capable measuring the displacement of the mass within the housing. An embodiment of the invention employs optical fiber coils as the support members for use in interferometric sensing processes. Arrays of such interferometer based accelerometers may be multiplexed using known techniques.

Abstract: This invention provides a method for controlling production operations using fiber optic devices. An optical fiber carrying fiber-optic sensors is deployed downhole to provide information about downhole conditions. Parameters related to the chemicals being used for surface treatments are measured in real time and on-line, and these measured parameters are used to control the dosage of chemicals into the surface treatment system. The information is also used to control downhole devices that may be a packer, choke, sliding sleeve, perforating device, flow control valve, completion device, an anchor or any other device. Provision is also made for control of secondary recovery operations online using the downhole sensors to monitor the reservoir conditions. The present invention also provides a method of generating motive power in a wellbore utilizing optical energy. This can be done directly or indirectly, e.g., by first producing electrical energy that is then converted to another form of energy.

Abstract: A fiber optic sensor comprises two independent fibers having Bragg gratings which are coupled to commutating broadband optical sources through splitters and wavelength discriminators. The ratio of detected optical energy in each of two detectors examining the wave intensity returned to a wavelength discriminator coupled with the characteristic of the wavelength discriminator determines the wavelength returned by the grating. In another embodiment, tunable filters are utilized to detect minimum returned wave energy to extract a sensor wavelength Reference to the original grating wavelength indicates the application of either temperature or strain to the grating. In another embodiment, a plurality of Bragg grating sensor elements is coupled to sources and controllers wherein a dimensional change in a fiber having a Bragg grating is detected using a measurement system comprising broad-band sources, optical power splitters, a high-sensitivity wavelength discriminator, optical detectors, and a controller.

Abstract: A touch pad for controlling electronic equipment includes a deformable touch surface and a compressible pad body in contact with the touch surface. The compressible body is formed from a material which scatters or diffuses light within the material. Multiple sources of light or other wave energy are directed into the interior of the substrate to form multiple illuminated cells inside the pad body. Each illuminated cell forms an integrated cavity within the pad body. A detector in communication with the compressible material detects light intensity within the integrated cavity. A processor receives signals from the detector and converts the signals into useable information relating to the position of regions of compression of the pad.

Abstract: Disclosed herein is a photonic silicon filter capable of binding and detecting biological and chemical target molecules in liquid or gas samples. A photonic waveguiding silicon filter with chemical and/or biological anchors covalently attached to the pore walls selectively bind target molecules. The system uses transmission curve engineering principles to allow measurements to be made in situ and in real time to detect the presence of various target molecules and determine the concentration of bound target.

Abstract: A strain sensor has a fiber Bragg grating fastened in a one-quarter circular arc to the strain sensing section of a strain sensor member. One end of the fiber Bragg grating is aligned in the longitudinal direction of the strain sensing section, while the other end is aligned at a right angle to the longitudinal direction. When longitudinal stress is applied, the fiber Bragg grating is elongated at one end and compressed at the other end, creating a high degree of chirp, thereby enabling strain to be measured with high sensitivity. The sensitivity is determined partly by Poisson's ratio, and thus is not limited by geometrical constraints on the strain sensing section.

Abstract: A device and a method for detecting the edge of a recording material, in particular, a printing plate, in an exposer for recording printing originals includes an exposer having an exposure drum holding the plate, and an exposure head moved axially along the drum and focusing exposure beams onto the plate. An optical fiber is let into the drum surface and an illuminating device, moved axially along the drum, radiates light radially into the fiber. A photodetector at the fiber receives the light radiated therein. Covering the light radiated in with the plate is used to detect the plate edge. Counting cycles of a feed drive moving the illuminating device determines an axial position of the edge. Alternatively, light of a light source is radiated axially into the fiber and the light emitted radially by the fiber is received using an optical detector moved by the feed drive.

Abstract: The present invention relates to a fiber optic sensing device having utility as a roll sensor and/or a pitch sensor. The sensing device comprises at least one optical fiber supported in a structure, a movable mass supported within the structure, and at least one detector for detecting changes in tension in the at least one optical fiber due to movement of the movable mass. In the sensor of the present invention, the optical fiber(s) are the only deformable structures, thus maximizing sensitivity.

Abstract: A structure analysis and defect detection system in which a laser light source provides light via optical fiber to fiber Bragg gratings that change resonant frequency as stresses change in the structure. Light at the resonant frequencies of the fiber Bragg gratings is reflected and light of other frequencies is passed. The respective reflected light is directed through a Fabry-Perot interference filter or a fiber interferometer and detected by a photodetector. If the Fabry-Perot interference filter is used, the intensity of the reflected light indicates current stress at a fiber Bragg grating. If the fiber interferometer is used, a beat frequency due to heterodyne interference in the light indicates current stress at the respective fiber Bragg grating. Comparison data for the respective characteristic in the detected light over time permits stress analysis, and comparison of such data with pre-determined limit values permits defect or failure detection.

Abstract: A method of monitoring a temperature condition includes inputting a light pulse into a fiber optic cable and receiving a reflection signal that arises from said input light pulse in said fiber optic cable. A temperature condition along the fiber optic cable and a location of the temperature condition along the fiber optic cable is determined based on said reflection signal.

Abstract: A small,compact optical scanning system with small aperture size requirements, wide field-of-regard and minimal color dispersion characteristics. The inventive scanning system and method provides for optical beam steering over a broad spectral band and over a wide field-of-regard. The inventive system includes a novel device for receiving an input wavefront of electromagnetic energy along a first axis and refracting the wavefront as an output wavefront along a second axis. The device is a unique form of a liquid crystal array which can be electrically manipulated to change the effective refractive index of each pixel. The index of refraction of the device varies in response to an applied voltage. The voltage is supplied by a microprocessor and/or a servo-control system. By changing the index, the incident phase front can be steered at an angle with respect to the first axis and otherwise manipulated according to the index variant pattern induced in the array.

Abstract: Disclosed is an apparatus for use in the measurement of the heat generated in a chemical or biochemical reaction, by detecting and measuring a change in the conformation of a polymer transducer responsive to a heat change, the transducer being bound to the surface of the waveguides of an interferometer. The conformational change is detected by optical means and is compared with a control. The polymer transducer may be selected from an organic polymer or a biological macromolecule.

Abstract: The invention is directed to an apparatus and a method for reducing noise, in particular RIN noise, in optical sensors, in particular fiber-optic sensors. The optical sensor produces a sensor output signal representing a physical quantity to be measured and also contains a first noise component, which is detected by a first detector. A separate detector detects an input light noise component of the input light source of the optical sensor and produces a second noise component. The second noise component is electronically processed and time-delayed by a filter by a time delay which substantially corresponds to the time delay experienced by the sensor input light traversing the optical sensor. The time-delayed processed signal is then subtracted from the sensor output signal to produce a reduced noise optical sensor signal corresponding to the measured physical quantity.

Abstract: The present invention relates to a torque sensor apparatus and method using variations in the microstructure of an optical waveguide affixed to the surface of a stress bearing member to measure the deflective force applied to the stress bearing member. A signal propagating through the optical waveguide is modified as a result of forces applied to the stress bearing member and to the optical waveguide. Induced changes in the index of refraction and alterations in the critical bending radius value of the optical waveguide result in modulation of the transmitted signal.

Abstract: An apparatus for measuring pressure in a medium comprises a laser for emitting light; a dichroic beam splitter that reflects the light from the laser; a first lens that receives and focuses the light from the beam splitter; a first optical fiber for receiving the light from the first lens; a crystal having fluorescence properties and having a hemispherical shape, the crystal being attached to an end of the first optical fiber; a second lens that receives and focuses fluorescence generated by the crystal and reflected by the dichroic beam splitter; a second optical fiber for receiving the fluorescence from the second lens; a spectrometer that receives the fluorescence from the second optical fiber; a streak camera connected to the spectrometer; a charge-coupled device connected to the spectrometer; and a delay generator connected to the charge-coupled device, the streak camera and the laser.

Abstract: Fiber grating environmental measurement systems are comprised of sensors that are configured to respond to changes in moisture or chemical content of the surrounding medium through the action of coatings and plates inducing strain that is measured. These sensors can also be used to monitor the interior of bonds for degradation due to aging, cracking, or chemical attack. Means to multiplex these sensors at high speed and with high sensitivity can be accomplished by using spectral filters placed to correspond to each fiber grating environmental sensor. By forming networks of spectral elements and using wavelength division multiplexing arrays of fiber grating sensors may be processed in a single fiber line allowing distributed high sensitivity, high bandwidth fiber optic grating environmental sensor systems to be realized.

Abstract: An apparatus for measurement of strain in a material. The apparatus comprises a passive fiber optic ring; at least one sensor having a predetermined shape and in line with the fiber optic ring, the at least one sensor coupled to the substrate; coupling means for i) introducing a portion of radiation emitted by the coherent source to the passive fiber optic ring and ii) receiving a portion of the radiation resonant in the passive fiber optic ring; a detector for detecting a level of the radiation received by the coupling means and generating a signal responsive thereto; and a processor coupled to the detector for determining a level of the strain inducing into the substrate based on a rate of decay of the signal generated by the detector.

Abstract: Optical isolation device (10) optically couples and electrically isolates various components on a local source circuit (36) from components on a remote isolated circuit (30). Light source (12) is coupled to opto-electrical detector (16) and opto-electrical sensor (20) is coupled to optical signal generator (18) by optical channel (14). The opto-electrical detector (16) is electrically coupled to remote isolated circuit (30) which is powered by the electricity generated by opto-electrical detector (16) in response to being impinged upon by light (22). Remote isolated circuit (30) is also electrically coupled to optical signal generator (18) which generates optical signals (32) in response to electrical signals received from remote isolated circuit (30). Opto-electrical sensor (20) produces electrical signals in response to being impinged upon by optical signals (32). Thus, remote isolated circuit (30) is completely electrically isolated from, but in communication with and powered by, local source circuit (36).

Abstract: A fiber optic sensor comprises two independent fibers having Bragg gratings which are coupled to commutating broadband optical sources through splitters and wavelength discriminators. The ratio of detected optical energy in each of two detectors examining the wave intensity returned to a wavelength discriminator coupled with the characteristic of the wavelength discriminator determines the wavelength returned by the grating. In another embodiment, tunable filters are utilized to detect minimum returned wave energy to extract a sensor wavelength Reference to the original grating wavelength indicates the application of either temperature or strain to the grating. In another embodiment, a plurality of Bragg grating sensor elements is coupled to sources and controllers wherein a dimensional change in a fiber having a Bragg grating is detected using a measurement system comprising broad-band sources, optical power splitters, a high-sensitivity wavelength discriminator, optical detectors, and a controller.

Abstract: The invention relates to an arrangement for detecting an optical signal which enables the light emitted from a curved optical fibre (40) on the long side thereof to be detected. Said arrangement comprises a device (10) for curving the optical fibre (40), a first retaining device (20, 30) for maintaining the optic fibre (40) in its curved state, and a second retaining device (60) for maintaining at least one photodetector (70). The curving device (10) and the second retaining device (60) are displaceable in relation to each other, whereby the photodetector (70) is placed directly on to a predetermined section of the curved optical fibre (40) in an operating state. As a result, the optical path between the fibre section, where the light is emitted from, and the photodetector (70) is minimal.