Abstract: A perimeter barrier system and method of monitoring a perimeter barrier are disclosed which comprise a perimeter barrier element in the form of a picket or fence panel which is mounted for limited movement by spring loading the barrier element by means of springs. An optical fiber is coupled to the barrier elements so that upon an attempt to breach the perimeter barrier system the barrier element is moved to in turn cause movement of the waveguide. A light source and detector is provided for launching light into the fiber and for detecting light which is passed through the fiber so that when the fiber is moved a parameter of the light is changed and that change in parameter is detected by detector to provide an indication of an attempt to breach the perimeter barrier system.

Abstract: A channel detection system includes an interferometer coupled to a spectrum analyzer to differentiate additive spontaneous emission (ASE) noise from optical channels in a dense wave-division multiplex (DWDM) signal. It is assumed that channels, if present, are centered at frequencies corresponding to a standardized channel grid. The relative delay of the interferometer is chosen to be greater than the coherence time of the ASE noise but less than the coherence time of the channels with the interferometer's free spectral range set to an integer divisor of the channel-to-channel frequency spacing of the grid such that active channels experience a high degree of interference. The phase delay of the interferometer is then adjusted to maximize the interference at each grid-aligned frequency. The spectrum-analyzed outputs are compared (e.g., subtracted from one another and then thresholded) to determine the channels present in the DWDM signal.

Abstract: An optical medium having a cavity that defines a variable gap is provided. The optical medium is used in an optical sensor, laser, and variable frequency resonator, by way of example. The cavity is physically altered in response to changes in a measurable parameter like pressure, temperature, force, flow rate, and material composition. The optical medium is characterized in some embodiments by having a cavity disposed near or within a high Q optical resonator. The optical resonator can be formed by various structures of which Bragg reflector cavities, ring resonators, microdiscs, and microspheres are examples. The optical resonator is preferably coupled to a laser source. The altering of the cavity affects the resonance condition within the optical resonator and thereby the laser signal of the system. If the laser source is a mode locked laser, the repetition rate of the pulse train changes in response to changes in the measurable parameter.

Abstract: An integrated optical chip device for molecular diagnostics comprising a tunable laser cavity sensor chip using heterodyned detection at the juncture of a sensor laser and a reference laser, and including a microfluid chip to which the sensor chip is flip-chip bonded to form a sample chamber that includes exposed evanescent field material of the tunable laser cavity to which fluid to be diagnosed is directed.

Abstract: An optical coupler 13, a reflection attenuation amount measurement photodetector 14, and an APC photodetector 15 are provided in a variable-wavelength light source apparatus 1 and the reflection attenuation amount can be measured simply by connecting a device under test without using any external optical power meter, etc, and when wavelength calibration is executed, an external wavelength calibration gas cell 18 and a total reflection termination 20 are connected, whereby the wavelength of an optical signal output from a variable-wavelength light source 11 can be measured and controlled with higher accuracy.

Abstract: A source and/or method of generating quantum-correlated and/or entangled photon pairs using parametric fluorescence in a fiber Sagnac loop. The photon pairs are generated in the 1550 nm fiber-optic communication band and detected by a detection system including InGaAs/InP avalanche photodiodes operating in a gated Geiger mode. A generation rate>103 pairs/s is observed, a rate limited only by available detection electronics. The nonclassical nature of the photon correlations in the pairs is demonstrated. This source, given its spectral properties and robustness, is well suited for use in fiber-optic quantum communication and cryptography networks. The detection system also provides high rate of photon counting with negligible after pulsing and associated high quantum efficiency and also low dark count rate.

Abstract: A fiber optic sensor system comprises at least one measuring sensor 1 providing an optical output dependent upon one or more parameters to be measured, e.g. temperature, and at least one reference sensor 2 providing a reference output for comparison with the measuring sensor output. The reference sensor is provided in a birefringent fiber. The system includes a detecting means 13,14 whereby a reference beat signal f2 is derived by measuring the optical frequency splitting between frequency components in different polarization planes of the reference sensor output. A further beat signal f3 is generated between the measuring and reference sensor outputs, such beat signals being used to derive a measurement of one or more parameters.

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: 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: The present invention relates to a method for determining crystallization in a very small amount of a material of interest (eg a chemical or biological material of interest).

Abstract: A phase difference calculation method, a device (34), and a system (38) are disclosed. In an optical fiber ring interference sensor (37) using a 3×3 optical splitting coupler (30) and an optical splitting coupler (12), linear sections are determined in advance, where a relationship between a phase difference &thgr; of propagation lights and an intensity Ppdn (n=1, 2, 3) outputted from each photo detector (15-1, 15-2, 15-3) becomes approximately linear. The intensity Ppdn of an interference light, between propagation lights in CW and CCW directions in an optical fiber loop (13), having a difference non-reciprocal phase bias is measured not less than two times. A phase difference &thgr; is then calculated based on the intensity Ppdn in the linear sections.

Abstract: A fiber optic grating sensor (10) comprising an optical fiber (12) in which a grating portion (14) is provided, the refractive index (16) of the fiber (12) varying periodically along the grating portion (14). The periodic variation of the refractive index (16) has an amplitude envelope which includes, in this example, two regions (24) in which the amplitude of the envelope is substantially reduced, and in this example is substantially nulled. The null regions (24) give the grating portion a spectral profile (20) within which there are, in this example two pass bands (18).

Abstract: The device serves for changing the length of a running path of an electromagnetic wave. It comprises a wave guide which is wound onto a core. The core is formed in two parts, wherein the distance of the core parts to one another is changeable in order to extend the wave length in a defined manner.

Abstract: A passive, temperature compensated tunable filter calibration device in a Bragg-grating interrogation system. The invention comprises two systems: 1) a dual substrate Bragg grating calibration system, the temperature of an array of gratings is estimated using an array of gratings bonded to a common host substrate and a single grating bonded to a material with a different coefficient of thermal expansion; 2) a hydrogen cyanide wavelength reference absorption cell that absorbs light at discrete wavelengths corresponding to the molecular vibration mode frequencies of the gas. A first photodetector sees the transmission spectrum and a second sees the reflections from Bragg gratings in a sensing array. In this system there is no temperature compensation step as the absorption lines are not sensitive to temperature.

Abstract: The invention relates to a DFB fiber laser sensor (1). A measurement quantity makes it possible to induce a linear birefringence between mode pairs of the laser-amplifying fiber (2) and to measure an associated beat frequency (&Dgr;&ngr;1, &Dgr;&ngr;2, &Dgr;&ngr;3). According to the invention, the laser-amplifying fiber (2) has a nonrotationally symmetrical structure, so that it is possible to detect isotropic pressures p, acoustic waves or chemical substances that can be added radially to the laser-amplifying fiber (2). In a second aspect of the invention, an emission wavelength range and parameters (a, b, &Dgr;N) of the laser-amplifying fiber (2) and also a grating period L of the fiber Bragg grating resonator (3) are coordinated with one another such that at least two different spatial modes (LP01, LP11even, LP11odd, LP21even) are propagatable and it is possible to measure beat frequencies (&Dgr;&ngr;1, &Dgr;&ngr;2, &Dgr;&ngr;3) between oscillatory longitudinal laser modes assigned to them.

Abstract: A device having an electromagnetic actuator for actuating a control element, in particular a charge cycle valve of an internal combustion engine. The actuator includes at least one elastic element, for example, a valve spring, provided for the purpose of elastic deformation. The elastic element is connected to a deformation sensor providing a signal making it possible to determine the deformation of the elastic element, and to determine the position of the control element.

Abstract: A system for measuring changes in an environmental parameter, such as velocity or pressure, includes an optical signal source for providing a coherent light signal, and an interferometer having a first and second optical legs of unequal optical path lengths. The signal is split into first and second beams that are respectively directed into the first and second optical legs of the interferometer. A fixed mirror reflects the first beam received at the end of the first optical leg. An optical pick-off includes a movable mirror, positioned to reflect the second beam received from the end of the second optical leg. The movable mirror is movable in response to changes in the-value of the parameter to be measured. An optical coupler combines the first and second beams after they have been reflected back into their respective optical legs, producing an interference signal, which is detected by an optical detector.

Abstract: A gyro apparatus has a ring laser in which laser beams of different oscillation frequencies coexist and propagate in mutually opposite circulation directions in an optical resonator, a power source of driving for the ring laser, a device for measuring a difference between the oscillation frequencies of the laser beams, and a device for controlling the power source of driving according to the frequency difference.

Abstract: A method and system for stabilizing and demodulating an interferometer at quadrature are described. In response to receipt of a signal indicative of optical power of the interferometer, an interferometer control system determines an optical path length correction required to stabilize the interferometer at quadrature utilizing signal amplitudes appearing at multiple harmonics of the signal. In a particularly preferred embodiment, the signal amplitudes are calculated utilizing the Goertzel algorithm, a computationally efficient discrete Fourier transform. The interferometer control system then outputs an error signal indicative of the optical path length correction. In a preferred embodiment, the error signal forms the DC component of a composite stabilization signal, whose AC component is the reference modulation signal utilized to excite a transducer to modulate the optical path length of the interferometer.

Abstract: The present invention provides a method and devices for time division multiplexing of a fiber optic serial Bragg grating sensor array containing more than one Bragg grating. The device provides a pulse read-out system that allows for a reduction in system noise and an increase in sensor resolution and flexibility. In one aspect the optical signals reflected from the Bragg grating sensor array are gated by an electronically controlled optical modulator before any wavelength measurement is performed to determine the sensor information. This offers significant advantages since the sensor information is encoded into the wavelength of the optical signal and not its intensity. Therefore the sensor signal information is not distorted by the gating.

Abstract: An apparatus and method for measuring strain of gratings written into an optical fiber. Optical radiation is transmitted over one or more contiguous predetermined wavelength ranges into a reference optical fiber network and an optical fiber network under test to produce a plurality of reference interference fringes and measurement interference fringes, respectively. The reference and measurement fringes are detected, and the reference fringes trigger the sampling of the measurement fringes. This results in the measurement fringes being sampled at 2&pgr; increments of the reference fringes. Each sampled measurement fringe of each wavelength sweep is transformed into a spatial domain waveform. The spatial domain waveforms are summed to form a summation spatial domain waveform that is used to determine location of each grating with respect to a reference reflector.

Abstract: A fiber optic displacement sensor includes a flexural disk assembly affixed to a mounting post that extends from a support base that is enclosed by a housing. Spiral wound optical fiber coils are mounted on opposite sides of the flexural disk with optical fiber leads extending from both the inner and outer diameters of the optical fiber coils and being optically coupled together to form an interferometer. An inertia ring connected to the periphery of the flexural disk has a plurality of peripheral slots therein for routing the optical fiber leads from the optical fiber coils to other components in the housing. The slots in the inertia ring are arranged to allow differing lengths of fiber to be wound circumferentially in different depth slots to accommodate mismatches in optical fiber lead lengths.

Abstract: The method and system serve to optically detecting an electric current with an extended measurement range. To that end, two light signals having different wavelengths pass through a Faraday element, the polarization of the two light signals being rotated in each case by at least 0.0014°/A as a function of the electric current. By taking account of both wavelength-dependent polarization rotations, at least one of which lies beyond an unambiguity range, the measurement range is extended distinctly beyond the unambiguity range of each of the two light signals.

Abstract: A coherent optical spectrum analyzer is provided in which an optical balancing tone having a specific signature is injected into a signal path of a balanced optical receiver. A measuring unit is provided to analyze the balancing tone component in the signal output from the balanced optical receiver and determine characteristics of the optical receiver. A compensation unit is provided for providing compensation to counter, or negate any imbalances determined via the measuring unit. The balanced optical receiver is preferably a polarization state independent optical receiver.

Abstract: A method of two interferometric configurations to measure bending of an extended element. The measurement arm of each configuration is a long optical fiber. A first interferometric configuration has a segment of its measurement arm attached to one side of the element. The second interferometric configuration has a segment of its measurement arm attached to one side of the element and another segment of its measurement arm attached to an opposing side of the element. The two configurations are used to obtain two sets of interference fringe measurement values. If one set is subtracted from the other, the result is intensity differential values that indicate only the effects of bending and not of temperature or pressure. Variations of the method can be used for irregularly shaped elements.

Abstract: A Sagnac or loop type interferometer is disclosed which uses a single broadband Erbium-doped fibre source (10) and a single IngaAs detector (150) together with a 40 km long sensor loop (90). A wavelength division multiplexer (50) spectrally slices the broadband light from the source (10) into two sub-bands, with different optical paths being defined between the source (10) and detector (150) for the light in the different spectrally sliced sub-bands. The two optical paths include separate phase modulators (70, 130) which modulate the two signals at different frequencies, and also separate delay loops (60, 130) at different places relative to the sensor loop (90). Effectively, two separate Sagnac loops are provided with a single sensor loop (90), source (10) and detector (150). Standard phase locked loop techniques can be used to extract information from signals that have passed through the two loops and to determine the location of a mechanical or thermal perturbation applied to the sensor loop (90).

Abstract: A dynamic light scattering apparatus comprises at least two lasers (11) of different wavelengths which illuminate the same volume (SV) of a fluid containing scattering or fluorescent centres. The scattered or fluoresced radiation is detected at each discrete wavelength and properties, such as the concentration of different particle sizes, of the volume (SV) are derived. The detection at multiple wavelengths allows the effects of multiple scattering to be overcome. Multiple volumes (SV) may be illuminated and detected simultaneously so as to measure the spatial variation of particle size concentration. The rotational diffusion constants of the particles may be measured from the depolarized component of scattered light.

Abstract: A coherent optical spectrum analyzer is provided in which an optical balancing tone having a specific signature is injected into a signal path of a balanced optical receiver. A measuring unit is provided to analyze the balancing tone component in the signal output from the balanced optical receiver and determine characteristics of the optical receiver. A compensation unit is provided for providing compensation to counter, or negate any imbalances determined via the measuring unit. The balanced optical receiver is preferably a polarization state independent optical receiver.

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 shutting off a source of optical power to an optical fiber in the event of a cut in the fiber are disclosed. Embodiments of the invention are particularly suited in fiber optic communications systems that use Raman pumps for signal amplification. Optical power from the pump to a fiber is shut off in response to a change in a supervisor signal provided to a first end of the fiber. The supervisor signal is generally operated in an “always-on” mode to provide for fail-safe operation. The apparatus generally comprises a controller coupled to the source of optical power and means for coupling a supervisor signal, which has been provided to a first end of the fiber, to the controller. The method and/or apparatus may be incorporated into an optical communications system having an optical fiber and two or more hubs coupled to the fiber.

Abstract: The present invention significantly improves the signal to noise ratio (SNR) in a passive optical array comprising sensors located in rungs between a distribution bus and a return bus. Erbium-doped optical fiber amplifiers are included in the buses proximate to each rung coupling to offset the coupler splitting losses. The gains of the amplifiers are selected to offset losses due to the couplings. The overall SNR can be maintained without significant degradation even for large numbers of sensors. In one aspect of the present invention, the amplifiers are located along the distribution and return buses directly after the couplers, except for the last coupler. In a second aspect, the amplifiers are located directly before each coupler. The optical amplifiers preferably are made of short lengths of erbium-doped fiber spliced into the distribution and return buses. Improvements can be made to the SNR when the distribution bus coupling ratios are set at optimal values.

Abstract: Disclosed is a Fizeau interference system for causing interference between reflection lights from a reflection surface and a semi-transmission surface, respectively, disposed along one and the same optical axis.

Abstract: An article and method including an optical fiber coupled to a microstructure which is easily manufactured. The microstructure is comprised of a plurality of layers including a receptacle layer and a movable layer. The optical fiber has a high reflectivity terminal end forming the non-movable layer. The receptacle layer has an opening aligned with the movable layer for receiving the terminal end of the optical fiber. The optical fiber is inserted into the opening and the receptacle layer and fixed in relation to the microstructure, so as to form cavity between the terminal end of the fiber and the movable layer of the microstructure. The movable layer is physically adapted for moving relative to the non-movable layer under the influence of an actuating force.

Abstract: An acoustic array includes amplifiers and sensor subarrays, both of which are placed along rungs that connect a return distribution bus with both a signal distribution bus and a pump distribution bus. By placing the amplifiers along the rungs, separate buses can be used for distributing the optical signal and the pump energy for the amplifiers, thereby facilitating the use of standardized couplers. Time division multiplexed sensor subarrays are advantageously connected to unique combinations of laser signal sources and signal return buses, in which the laser signal sources generate different optical wavelengths that are multiplexed on the signal return buses. Optical sources include intensity modulators on either side of an amplifier to eliminate extraneous noise between optical pulses. In addition, amplified spontaneous emission (ASE) filters may be advantageously used to reduce optical noise at wavelengths other than those of interest.

Abstract: A seismic sensing device has a light source, detection measuring and processing device in combination with an optical seismic sensor reconfigurable array. The light source, detection measuring and processing device provides a selective optical signal to the optical seismic sensor reconfigurable array, and responds to an optical seismic sensor reconfigurable array signal, for providing information about a seismic force to be sensed. The optical seismic sensor reconfigurable array responds to the selective optical signal, and responds to the seismic force, for providing an optical seismic sensor reconfigurable array signal containing information about the seismic force over at least one selective length of the optical seismic sensor reconfigurable array. The optical seismic sensor reconfigurable array includes an optical fiber having optical seismic sensors, each having at least one sensor coil arranged between a respective adjacent Fiber Bragg Grating partial reflector pair having a selectable wavelength.

Abstract: A sensor for facilitating the measurement of temperature and magnetic field is described. The sensor comprises an optical cable having a distal end encompassed in a sheath of giant magnetoresistive material. Temperature changes alter the spectrum emissivity of the giant magnetoresistive material. Magnetic field changes alter the spectrum changes that occur from distorting the optical fiber that occur when the giant magnetoresistive material distorts the optical fiber.

Abstract: A gyroscope which utilizes light waves to sense motion in the plane of the substrate. The gyroscope has a primary optical waveguide which is adapted to pass light from a single light source through the primary optical waveguide in both directions. The light exiting from each end of the primary optical waveguide is withdrawn and passed through two dedicated waveguides (one dedicated waveguide for each end of the primary optical waveguide). Preferably, these two dedicated waveguides have differing times for light travel such that one of the dedicated waveguides emits its light one-quarter wavelength behind the other dedicated waveguide. The light being emitted from each dedicated waveguide is then combined permitting a sensor to monitor any shifts between the two light signals as a monitor to motion of the primary optical waveguide.

Abstract: The present invention provides a method and device for to implement time division multiplexing of a fiber optic serial Bragg grating sensor array containing more than one Bragg grating. The device provides a pulse read-out system that allows for a reduction in system noise and an increase in sensor resolution and flexibility. The optical signals reflected from the Bragg grating sensors are gated by an electronically controlled optical modulator before any wavelength measurement is performed to determine the sensor information. This offers significant advantages since the sensor information is encoded into the wavelength of the optical signal and not its intensity. Therefore the sensor signal information is not distorted by the gating.

Abstract: An interferometric sensor includes a broadband optical source, a depolarizer for depolarizing optical radiation emitted by the broadband optical source, a matched interferometer, a sensing interferometer, and a detector. The matched interferometer contains a phase modulator. The sensor is configured so that the optical path length difference in the sensing interferometer is approximately equal to the optical path length difference in the matched interferometer.