Abb Schweiz Ag

Abb Power Grids Switzerland Ag

Georg Müller

Klaus Bohnert

Andreas Frank

Philippe Gabus

Xun Gu

Lin Yang

Yang Lin

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

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

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.

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Glattpark, Switzerland

Georg Müller