Abb Research Ltd.

Abb Schweiz Ag

Asea Brown Boveri Inc.

Abb Power Grids Switzerland Ag

Vetco Gray Controls Limited

Asea Brown Boveri Ag

Hitachi Energy Switzerland Ag

Bbc Brown Boveri Ag

Abb T&d Technology Ltd.

Klaus Bohnert

Andreas Frank

Philippe Gabus

Xun Gu

Hubert Braendle

Hubert Brandle

Sergio Vincenzo Marchese

Hubert Brändle

Georg Müller

Hubert Br&auml;ndle

Jurgen Nehring

Stephan Wildermuth

Lin Yang

Frank Kassubek

Axel Kramer

Robert Wueest

Georg Mueller

Yang Lin

Karim Haroud

Lutz Niemeyer

Meinolph Kaufmann

Jan Czyzewski

Göran Eriksson

Costante Piazza

Jiri Talir

Michael Stanimirov

Werner Buser

Olivier Steiger

Tobias Erford

Jadran Kostovic

Roland Stierlin

Roberto Cameroni

Rolf Kirchhofer

Norbert Koch

Lars Andersson

Juergen Nehring

Georg Muller

Georg Müeller

J&uuml;rgen Nehring

Emiliano Centenaro

Patrick Bodor

Robert Wüest

Mathias Fauth

Tone Schanke

Pascal Pequignot

Juergen Haefner

Moritz Hochlehnert

Thomas Lorek

Burak Büyükkavir

Ahmed Zekhnini

Sergio Vincenzo Machese

Georg MÜLLER

Pascal Joris

Robert WÜEST

In order to measure a voltage, an electro-optic element is placed in an electrical field generated by the voltage, and light is passed from a light source through a Faraday rotator and the electro-optic element onto a reflector and from there back through the electro-optic element and the Faraday rotator, thereby generating a voltage-dependent phase shift between two polarizations of the light. The interference contrast as well as a principal value of the total phase shift between said polarizations are measured and converted to a complex value having an absolute value equal to the contrast and a phase equal to the principal value. This complex value is offset and scaled using calibration values in order to calculate a compensated complex value. The voltage is derived from the compensated complex value.

Interferometric voltage sensor with error compensation

In order to carry out the polarimetric detection of a measurand, light of two polarization states is passed through a sensing element, where the two states suffer a differential phase shift depending on the value of the measurand. In order to compensate for only imperfections of the device, a method is proposed that is based on calibration values obtained in a low-value regime of the measurand only. Yet the method can still be used for accurately determining higher values of the measurand.

Polarization optical detection with enhanced accuracy in the high-signal regime

The optical interferometric sensor device comprises an integrated beam splitter having a first facet and a second facet with optical ports arranged therein. On the beam splitter, the beam splitting junctions as well as the optoelectronics-side ports and the sensing-side port are arranged with a mutual displacement along the direction of the first facet. This displacement reduces undesired interference effects caused by stray light. Also, a quarter-wave retarder is provided in a recess of the beam splitter with layers of soft adhesive adjacent to it in order to reduce stress.

Sensor device having an integrated beam splitter

A fiber-optic current sensor includes an opto-electronics module, a sensor head and a connecting fiber connecting the opto-electronics module to the sensor head. The sensor includes a first and a second beam splitter, between which the measuring light runs in two branches. One fiber connector is arranged in each branch, for connecting a cable assembly to the opto-electronics module. The optical path lengths between the two connectors and the second beam splitter are different, such that light waves cross-coupled into an orthogonal polarization mode due to angular misalignment of the connectors become incoherent with the non-cross-coupled waves returning from the sensor head.

Fiber-optic current sensor with tolerance to connector misalignment

A fiber optic sensor and related method are described, with the sensor including a cross-coupling element in the optical path between a polarizing element and a sensing element, but separated from the sensing element itself; with the cross-coupling element generating a defined cross-coupling between the two orthogonal polarization states of the fundamental mode of a polarization maintaining fiber guiding light from the light source to the sensing element thus introducing a wavelength-dependent or temperature-dependent sensor signal shift to balance wavelength-dependent or temperature-dependent signal shifts due to other elements of the sensor, particularly signal shifts due to the wavelength dependence of the Faraday effect or the electro-optic effect constant.

Fiber-optic sensor and method

An interferometric sensor and related methods are provided, with a sensing element whereby a measurand induces a relative phase shift between two waves, at least one detector measuring an interference signal between the two waves, and further including a phase shift detection unit having as input the interference signal and determining a first measure representative of the principal value of the relative phase shift, and a contrast detection unit having as input the interference signal for determining a second measure representative of the cross-correlation between the two waves, and a further a processing unit for converting the first and second measures to a measurand value.

Interferometric sensor

There is described an optical fiber current sensor having an opto-electronic module part for detecting an optical phase shift induced by the measurand field in a sensing fiber, a sensor head including the sensing fiber, wherein the sensing fiber is a spun highly-birefringent fiber having a length L=&#x222b; ds defined by the line integral along the space curve given by the sensing fiber coil such that the length L of the sensing fiber is sufficiently long to suppress thermal signal instabilities due to the spun character of the sensing fiber while the effective number of fiber windings is low enough to maintain a maximum sensitivity over the full measurement range of the fiber-optical sensor.

Optical sensor with spun birefringent sensing fiber

It is proposed to use a spun birefringent fiber for a current sensor or magnetic field sensor. The fiber has a birefringence that increases with temperature. In this case, the temperature dependence of the fiber's sensitivity to magnetic fields counteracts the temperature dependence of the fiber's Verdet constant, which allows to design current and field sensors that have reduced temperature dependence.

Spun highly-birefringent fiber for current sensing with inherent insensitivity to temperature

The invention relates to an assembly of a gas-tight compartment and an optical voltage sensor that further comprises a module. The module comprises an electro-optic crystal and electrodes, wherein the electro-optic crystal is the only element of the module to mechanically connect the two electrodes and to bridge the potentials of the two electrodes. The assembly is particuarly suited to measure direct current voltages.

Gas-tight compartment and optical voltage sensor with coated electro-optic crystal

A fiber-optic current sensor uses a highly-birefringent spun fiber as sensing fiber. The light is fed through a retarder, which is a detuned quarter-wave or half-wave retarder. It is shown that such detuning can be used to compensate for temperature dependencies of the sensing head.

Fiber-optic current sensor with spun fiber and temperature compensation

In order to measure the contrast of interference in an interference-based, closed-loop, phase-modulating optical sensor device, the gain of the feedback loop in a feedback controller is evaluated. This gain is found to be a measure for the contrast. The contrast evaluated in this way can e.g. be used for period-disambiguation when determining the measurand of the sensor device. The sensor device can e.g. be a high-voltage sensor or a current sensor.

Closed-loop interferometric sensor using loop gain for determining interference contrast

A method of increasing accuracy of optical sensors based on generating two sets of light waves having different velocities in the presence of a non-vanishing measurand field within a sensing element of the sensor is described. A defined static bias phase shift is introduced between the two sets of light waves. The sensor converts a total optical phase shift including static bias optical phase shifts and measurand-induced optical phase shifts into anti-phase optical power changes in at least two detector channels. The method includes steps of normalizing the optical power changes after their conversion into electrical detector signals in the two detector channels to reduce effects of uneven intensity or power of the light source and different loss or gain in the detector channels. Further methods, sensors and apparatus for temperature stabilizing such optical sensors and novel sensors are also presented.

Optical sensor

In a fiber-optic current sensor, a 22.5&#xb0; Faraday rotator, which is part of the sensing fiber coil, determines the working point of the sensor. The coil is operated with substantially linearly polarized light or incoherent substantially left and right circularly polarized light waves. In one arrangement, a polarization beam splitter generates two optical signals that vary in anti-phase with changing current. A signal processor determines the current from the two anti-phase signals. Appropriately detuned and oriented fiber-optic half-wave or quarter-wave retarders before the fiber coil are used to reduce or cancel the adverse effects of temperature and bend-induced birefringence on the measurement signal. Moreover, the temperature may be derived from the difference in the bias of the anti-phase signals and may be used to cancel temperature effects in the signal processor.

Temperature compensated fiber-optic current sensor

A fiber-optic current sensor includes a measuring unit having a light source and a light detector, and a sensing head having a sensing fiber wound around a conductor and a retarder connected to the sensing fiber. The scale factor as a function of current of the fiber-optic current sensor is described by the product of two scaling functions fe' and fs&#x2032; for the measuring unit and the sensing head, respectively. The data describing the scaling functions fe&#x2032;, fs&#x2032; is stored in a memory of the measuring unit, while the data describing the scaling function fs&#x2032; is also stored in a memory of the sensing head. Providing two such memory devices allows to store the scaling functions fe&#x2032; and fs&#x2032; separately, thereby turning the control unit as well as the sensor head into easily replaceable modules.

Fiber-optic current sensing using a sensor with exchangeable sub-modules

Growing community of inventors

Oberrohrdorf, Switzerland

Klaus Bohnert