Abstract: Temperature sensing apparatus comprises a source of electromagnetic radiation (1), a wavelength-selective element (3) which interacts with radiation emitted from the source (1) and a detection system (6) which monitors radiation from the wavelength-selective element (3). The wavelength-selective element (3) is fixedly mounted on a substantially rigid substrate (not shown). The apparatus can be used for temperature sensing in aquatic environments.

Abstract: A wavelength detector configuration for detecting the Bragg wavelength of at least one Bragg grating in at least one FBG sensor, in which light reflected by each Bragg grating is conducted by fiber couplers into two detector channels, each containing a detector, whereby an evaluator device is provided to detect the signals of the detectors and to determine the Bragg wavelength from a quotient of the detector signals, the detectors of each pair of detector channels having narrowband spectral sensitivities that overlap with one another and who central wavelengths of maximum sensitivity span a wavelength range containing the Bragg wavelength of the corresponding Bragg grating.

Abstract: Systems and methods of measuring optical pulses are described. In one aspect, an optical pulse measurement system includes an optical signal divider and an optical signal conversion system. The optical signal divider has an optical input for receiving an input optical signal, multiple optical outputs, and a set of multiple optical channels. The optical channels are coupled between the optical input and respective optical outputs and are operable to delay propagation of optical signals, which are divided from the input optical signal, from the optical input to respective optical outputs by different respective amounts of time. The optical signal conversion system is coupled to the optical signal divider optical outputs and is operable to convert temporal intensity distributions of light received from the optical signal divider optical outputs into respective spatial intensity distributions in parallel.

Abstract: A distributed fiberoptic radiation sensor is described which may employ one or more radiation sensor elements distributed in a single optical fiber. Such optical fibers may be placed on surfaces, or even within parts, to unobtrusively measure radiation in precise and even difficult to reach locations. Different sensor elements may respond to different radiation types and wavelength ranges, with each sensor element causing a different wavelength of light to be emitted or absorbed within the fiber. By employing an appropriate combination of detection methods at the ends of the fiber, the distributed sensor may provide type and calorimetric discrimination of radiation incident on one or more distinguishable locations. The radiation information thus detected may be integrated, if desired, to obtain corresponding real-time dose information. With such integration, the device becomes a distributed real-time dosimeter.

Abstract: A temperature-compensated optical grating is fed an optical probe signal of a predetermined wavelength. An optical detector having a plurality of apertures for receiving an optical signal is positioned to detect a probe light signal from the grating and to detect the deflection of the probe light signal from a preferred location. The detector provides an indication of the deflection to a controller which operates a temperature adjustment device, such as a fan or thermoelectric cooler to adjust the temperature of the grating in a direction which reduces the deflection.

Abstract: There are provided an optical transfer characteristic measuring method and apparatus capable of measuring an optical transfer characteristic of an optical device on optical frequency axis in wide optical frequency bandwidth with high resolution. There are provided a variable wavelength sweep type light source capable of switching the wavelength of an optical signal generated therefrom stepwise and sweeping the optical frequency of the optical signal in a predetermined frequency range, and a variable wavelength reference light source capable of switching the wavelength of an optical signal generated therefrom stepwise and not capable of sweeping the optical frequency of the optical signal.

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 system and method for resolving polarization mode dispersion (PMD) in a span of optical fiber is described. The method involves three main stages: (1) launch two co-polarized optical signals to generate respective four-wave mixing product fields at the Stokes wavelength &lgr;S or the anti-Stokes wavelength &lgr;A sequentially in each part of the fiber to calculate chromatic dispersion; (2) repeatedly launch two optical signals at various states of polarization (SOP) using methods of stage (1) to calculate overall dispersion (i.e., a combination of chromatic dispersion and PMD); and (3) resolve from the overall dispersion calculated at stage (2) the PMD based on the known chromatic dispersion calculated at stage (1). In an ideal case, the PMD can be calculated from two separate measurements at different co-polarized states of polarization, where group velocity is calculated from a measured dispersion map, as a function of wavelength, at the SOPs and the difference is calculated to resolve PMD.

Abstract: A micromonochromator is formed on a substrate and includes a diffraction device (6) associated with an entry that includes at least one entry point and an exit that includes at least one exit point. A mobile arrangement of light guidance (2-20, 4-26) is associated with the entry or the exit or both, and a recovery device (23) is provided by the exit. The mobile arrangement includes at least one mobile beam integrated in the substrate and equipped with at least one light guide. The mobile beam is able to sweep the entry and/or exit in a continuous manner.

Abstract: Light under measurement whose wavelength is continuously swept is incident on fiber-optic Etalon. The fiber-optic Etalon transmits the light under measurement each time the wavelength of the light under measurement satisfies specific conditions. A PD detects the transmitted light of the fiber-optic Etalon and outputs the intensity of the light under measurement. A counter counts the number of peaks of the output of the PD. A CPU calculates the wavelength of the light under measurement based on the count value of the counter.

Abstract: A method and apparatus for hyper-dense communications provides a photonic signal, such as an optical or radio frequency signal produced with substantially reduced sidebands. Signals may be filtered photonically, such as by a photonic transistor or photonic drop filter, to remove such frequency components. The resulting bandwidth of the photonic output signal is narrower in the photonic domain than the bandwidth of the information it carries in the original domain of the information. This hyper-dense signal is then transmitted and received. Such signals retain their reduced spectral distributions while in the photonic domain. Upon reception and conversion into electronic form, the full spectrum of the original information may be restored, including the sidebands, by passing the transmitted signal through a non-linear device.

Abstract: A solid-state apparatus for tracking the wavelength of a laser emission has a power splitter that divides the laser emission into at least three equal components. Differing phase shifts are detected and processed to track variations of the laser emission.

Abstract: An optical amplitude modulator for modulating signals for transmission by a fibre optic link. The modulator comprises of a plurality of optical transmitters, whereby each transmitter is driven by an electronic circuit. Generally, each optical transmitter provides a light output, and the light outputs of the plurality of optical transmitters are combined optically for transmission as an optical output signal. Additionally, each of the plurality of optical transmitters has an associated optical filter, whereby each filter has a different level of opaqueness. Each filter, filters light output from the associated optical transmitter.

Abstract: An apparatus for measuring the optical-signal-to-noise ratio (OSNR) of an optical system is adapted to function in single channel or in multi-channel wavelength division multiplexed optical communication systems. An optical signal spectrum and a center frequency characterize the optical signals. A narrow-band notch filter, realized by an in-fiber Bragg grating, is utilized to remove a component of the signal so the remaining signal can be measured. When multiple channels are present, a bandpass filter is used to select the part of the multiplexed signal to be measured. Both the narrow-band notch filter and the bandpass filter can be tunable to further extend the capabilities of the system. Two detectors are utilized with the power in the channel being measured by a low-gain detector and the power in the noise being measured by a high-gain detector. A processor receives the detector outputs, calculates OSNR, and controls the tunable components.

Abstract: Apparatus for modifying the optical characteristics of an optical fiber by controlled stretching of a length of the fiber, comprising a first fiber holder fixedly carried by a base and capable of firmly holding a first portion of the optical fiber, a lever part attached to the base at a fulcrum, and second fiber holder movably connected to the lever part and capable of firmly holding a second portion of the fiber, so that an intermediate length of fiber may be held taut between said first and second holding means. An electromagnetic circuit moves the lever part between first and second predetermined positions, so that the intermediate length of fiber is stretched as the lever part moves between first and second positions. Preferably, the intermediate length of fiber includes a Bragg grating.

Abstract: An isolation system is provided for generating a control voltage in a low voltage control system that is representative of the input voltage in a high voltage power system of an excitation system, such as in a rotating electrical apparatus. The control voltage isolation system includes a voltage-controlled oscillator for converting the input voltage into a first frequency signal corresponding to the input voltage. Fiber optic conversion and receiving devices are employed in conjunction with a fiber optic cable to transmit the first frequency signal from the high voltage power system to the low voltage control system. Utilizing a fiber optic device provides voltage isolation between the power system and the control system. The use of a fiber optic device for voltage isolation also resists the damaging effects of relatively high transient currents and voltages from affecting sensitive semiconductor components and the like in the control system.

Abstract: A device is provided for measuring a bending load in mechanical constructions, which device enables measurement over a broad range of stresses with high precision and which simultaneously compensates for deviations caused by temperature fluctuations.

Abstract: The invention was originally developed to determine the strain-relief capability of a fusion splice protector as well as the compressive stress imparted to a fusion splice by the splice protector. The invention also permits performance and comparative analyses of splice protectors as well as any package in which the optical fiber is at least partially disposed. To those ends a fiber Bragg grating (FBG) is axially arranged relative to the package such that a free or reference section of the FBG protrudes from the package while a shielded section lies within the package. Broadband light is supplied to the FBG which reflects certain wavelengths that are measured by an optical spectrum analyzer. The FBG reflected spectra will be split into two peaks as the reference and shielded sections experience different amounts or types of stress thereby providing a powerful analysis tool.

Abstract: Fiber optic grating sensor demodulation systems are described that offer high speed and multiplexing options for both single and multiple parameter fiber optic grating sensors. To attain very high speeds for single parameter fiber grating sensors ratio techniques are used that allow a series of sensors to be placed in a single fiber while retaining high speed capability. These methods can be extended to multiparameter fiber grating sensors. Optimization of speeds can be obtained by minimizing the number of spectral peaks that must be processed and it is shown that two or three spectral peak measurements may in specific multiparameter applications offer comparable or better performance than processing four spectral peaks. Combining the ratio methods with minimization of peak measurements allows very high speed measurement of such important environmental effects as transverse strain and pressure.

Abstract: In a detection section using a fiber grating (FBG), both ends of the FBG are protected with resin coating and a coated part is adhered or mechanically clamped to fixed parts. A spring or a lever or both of these are connected to one end of this fixed part. This is used as a detection section to convert a variation of a physical quantity such as displacement, weight, pressure or acceleration applied to between the fixed parts to a variation of a reflected wavelength or a transmitted wavelength from a fiber grating and to output the variation of the reflected wavelength and transmitted wavelength.

Abstract: A robust fiber optic sensor and sensing method for reliable, long-term measurement of analytes is disclosed. The sensor comprises an optical interrogation region comprising an indicator dye confined at a distal end of an optical fiber and an analyte permeable membrane enclosing the interrogation region at the distal fiber end. In a preferred embodiment, a reservoir member is provided with excess dye for continuous replenishment of the interrogation region with dye over the lifetime of the sensor. In another preferred embodiment, the reservoir member comprises an indicator support for containment of excess dye. In one preferred embodiment, a ratiometric dye is used for monitoring optical signal-to-noise and signal drift caused by sensor aging. The sensor may be configured with a variety of alternative indicator dyes and membrane materials as a specific ion sensor for analyzing dissolved analytes such as gases, cations, and anions.

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: An electric-current sensing device comprises an input ultrasonic transducer assembly, an output ultrasonic transducer assembly and an ultrasonic fiber between the two assembly. The input ultrasonic transducer assembly consists of an input piezoelectric vibrator, a driving electrode, an input ground electrode and an input vibrating plate. The output ultrasonic transducer assembly consists of an output piezoelectric vibrator, a detecting electrode, an output ground electrode and an output vibrating plate. When an input electric signal is applied to the input piezoelectric vibrator through the driving electrode and the input ground electrode, the input piezoelectric vibrator is acoustically vibrated. An acoustic vibration in the input piezoelectric vibrator is transmitted to the output piezoelectric vibrator, and detected between the detecting electrode and the output ground electrode, as a delayed electric signal.

Abstract: An optical fiber is provided with a Bragg grating formed along a portion of its core and a mechanical structure arranged adjacent to the Bragg grating for amplifying longitudinal strain on the fiber in the vicinity of the grating. The mechanical structure is designed to convert ambient pressure into longitudinal strain on the fiber in the vicinity of the grating and to allow the fiber to pass through the structure so that several pressure measuring apparatus may be arranged along a single optical fiber. An intermediate structure is provided between the fiber and the mechanical structure for minimizing buckling of the fiber. The methods of the invention include converting pressure into longitudinal strain on an optical fiber, amplifying the effect of pressure on the longitudinal strain, measuring pressure by determining the spectral location related to peaks (or minimums) of light reflected from an optical grating subjected to longitudinal strain.

Abstract: A dynamic pressure sensor with measures for its operation in high temperature and high pressure environments. The sensor uses at least one winding about a deformable mandrel of an optical fiber inscribed by a Bragg grating at its beginning and another at the end of the winding. To counter the effects of high ambient static pressure and temperature, various steps are taken: the mandrel is filled with a high-viscosity low bulk modulus fluid, such as a silicone fluid, and is provided with a baffle system that regulates the flow of the fluid between spans around which the optical fiber is wound. The baffle system is based either on protuberances on a core rod inserted into the mandrel and a system of pinhole size passageways through the protuberances, or based on an open cell foam or fibrous material located on a core rod within a span covered by a stiff jacket. In addition, in high pressure gradient applications, the mandrel is pinched off at different locations along its length.

Abstract: A system such as for sensing strain or temperature of an aircraft and for transmitting information in communication systems. A sensor array includes a first light responsive Bragg grating sensor having a first operating bandwidth and a second light responsive Bragg grating sensor having a second operating bandwidth. Each sensor modifies light provided to it at a wavelength indicative of changes in strain or temperature. The second sensor operates within a bandwidth which is different from the operating bandwidth of the first sensor. A tunable light source such as an LED and tunable etalon provides light for illuminating the first and second sensors, the provided light having a wavelength which varies within a band including the first and second bandwidths. A detecting circuit provides signals representative of light modified by the first and second sensors. A processor processes the representative signals to determine the strain and/or temperature.

Abstract: A current sensor having an optmized optical fiber coil for sensing the magnetic field of a current of wire passing by or through the coil. The coil is optimally spun such that a particular ratio of the spin rate to the intrinsic polarization beat length is such for best maintenance of the circular polarization state of the light in the coil. The coil fiber may also be Terbium doped for greater sensitivity. The phase or birefringence modulation of the light may be piezoelectric or electro-optic. A Faraday rotator may be used in place of those modulators. The system may be open loop or closed loop. The feedback scheme may be via the modulator or the phase nulling current affecting the sensing coil.

Abstract: An accelerometer has a main body in combination with one or more Bragg grating sensors respectively arranged along one or more axes. The main body has a mass that responds to an acceleration, for providing a force having a component in one or more axes. The Bragg grating sensor means responds to the force, and further responds to an optical signal, for providing a Bragg grating sensor signal containing information about the acceleration respectively in one or more axes. The one or more axes may include orthogonal axes such as the X, Y and Z Euclidian axes. In one embodiment, the main body includes a proof mass and a pair of flexure disks, each having an inner ring, an outer ring, and radial splines connecting the inner ring and the outer ring. The proof mass is slidably arranged between the flexure disks. The Bragg grating means has an optical fiber and a Bragg grating sensor arranged therein. A first end of the Bragg grating sensor is fixedly coupled by a first ferrule to the proof mass.