Fiber optic system for measuring electric fields
First Claim
1. A system for measuring an electric field, comprising:
- a source of coherent light having a narrow optical frequency;
means optically connected to said source for splitting the coherent light into a pair of substantially equal beams;
first fiber-optic means optically connected to said beam splitting means for propagating one of said beams through an isolated environment via a first optical path length;
second fiber-optic means optically connected to said beam splitting means for propagating the other of said beams through the electric field via a second optical path length modulated piezoelectrically;
shield means rotatably disposed adjacent to said second fiber-optic means for periodically reducing the electric field to near-zero in the immediate proximity thereof; and
interferometric detector means optically connected to receive said beams from said first and second fiber-optic means for combining said beams while maintaining a quadrature relaionship therebetween;
whereby deviations from the quadrature relationship are indicative of the phase change, relative to said first fiber-optic means, in said second fiber-optics means induced piezoelectrically by and determinative of the value of the electric field.
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Accused Products
Abstract
A fiber optic sensor system and associated technique is disclosed for measuring an electric field wherein a sensor arm of optical fiber cable is wound about a core member of piezoelectric material. A reference arm of optical fiber cable substantially equal in optical path length to the sensor arm is isolated and connected in parallel to the sensor arm so that coherent light generated by a single mode laser source may be split through the fiber-optic arms and recombined after passage therethrough for phase comparison. When subjected to a local electric field, the core member of piezoelectric material varies in dimensions and thereby causes a change in the strain in the optical fiber cable of the sensor arm. Relative phase changes in the coherent light caused by the resulting optical path length change of the strained sensor arm are detected by a passive homodyne demodulator and determinative of the value of the local electric field. A vane-type shield is adapted to be rotated about the core member for periodically reducing the local electric field to near zero thereby providing a reference level for field measurement.
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Citations
14 Claims
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1. A system for measuring an electric field, comprising:
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a source of coherent light having a narrow optical frequency; means optically connected to said source for splitting the coherent light into a pair of substantially equal beams; first fiber-optic means optically connected to said beam splitting means for propagating one of said beams through an isolated environment via a first optical path length; second fiber-optic means optically connected to said beam splitting means for propagating the other of said beams through the electric field via a second optical path length modulated piezoelectrically; shield means rotatably disposed adjacent to said second fiber-optic means for periodically reducing the electric field to near-zero in the immediate proximity thereof; and interferometric detector means optically connected to receive said beams from said first and second fiber-optic means for combining said beams while maintaining a quadrature relaionship therebetween; whereby deviations from the quadrature relationship are indicative of the phase change, relative to said first fiber-optic means, in said second fiber-optics means induced piezoelectrically by and determinative of the value of the electric field. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14)
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Specification