Fiber optic system for electromagnetic surveying
First Claim
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1. An electromagnetic survey sensing device, comprising:
- at least two electrodes disposed at spaced apart locations;
an electrical to optical converter electrically coupled to the at least two electrodes, the electrical to optical converter configured to change a property of light from a source in response to voltage imparted across the at least two electrodes; and
an optical fiber optically coupled to an output of the electrical to optical converter, the optical fiber in optical communication with a detector,wherein the electrical to optical converter comprises a means for changing an optical path length in response to the voltage imparted across the at least two electrodes, andwherein the means for changing the optical path length comprises a first piezoelectric element electrically coupled to the at least two electrodes, a first mirror functionally associated with the first piezoelectric element and disposed proximate a first end of an optical path associated with the optical fiber, such that electrical actuation of the first piezoelectric element by the voltage causes corresponding change in distance between the end of the first optical path and the first mirror.
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Abstract
An electromagnetic survey sensing device includes at least two electrodes disposed at spaced apart locations. An electrical to optical converter is electrically coupled to the at least two electrodes. The converter is configured to change a property of light from a source in response to voltage imparted across the at least two electrodes. The device includes an optical fiber optically coupled to an output of the electrical to optical converter, the optical fiber in optical communication with a detector.
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Citations
15 Claims
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1. An electromagnetic survey sensing device, comprising:
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at least two electrodes disposed at spaced apart locations; an electrical to optical converter electrically coupled to the at least two electrodes, the electrical to optical converter configured to change a property of light from a source in response to voltage imparted across the at least two electrodes; and an optical fiber optically coupled to an output of the electrical to optical converter, the optical fiber in optical communication with a detector, wherein the electrical to optical converter comprises a means for changing an optical path length in response to the voltage imparted across the at least two electrodes, and wherein the means for changing the optical path length comprises a first piezoelectric element electrically coupled to the at least two electrodes, a first mirror functionally associated with the first piezoelectric element and disposed proximate a first end of an optical path associated with the optical fiber, such that electrical actuation of the first piezoelectric element by the voltage causes corresponding change in distance between the end of the first optical path and the first mirror. - View Dependent Claims (2, 3)
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4. An electromagnetic survey system, comprising:
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a receiver cable having an optical fiber associated therewith and coupled at one end to a recording device and at another end to at least one electrical to optical converter, the recording device including a light source and a photodetector therein in optical communication with the associated fiber; at least two electrodes disposed at spaced apart locations along the receiver cable; the electrical to optical converter electrically coupled to the at least two electrodes, the electrical to optical converter configured to change a property of light from the source in response to voltage imparted across the at least two electrodes; and the optical fiber optically coupled to an output of the electrical to optical converter, the optical fiber in optical communication with the detector in the recording device, wherein the at least one electrical to optical converter comprises a means for changing an optical path length in response to the voltage imparted across the at least two electrodes, and wherein the means for changing the optical path length comprises a first piezoelectric element electrically coupled to the at least two electrodes, a first mirror functionally associated with the first piezoelectric element and disposed proximate a first end of an optical path associated with the optical fiber, such that electrical actuation of the first piezoelectric element by the voltage causes corresponding change in distance between the end of the first optical path and the first mirror. - View Dependent Claims (5, 6, 7)
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8. A method for sensing an electromagnetic field, comprising:
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exposing an electric dipole antenna to the electromagnetic field; conducting voltage imparted to the antenna to an electrical to a device that changes a property of light imparted thereto in response to the voltage; changing a property of light conducted from a light source to the device and from the device to a photodetector along an optical fiber, so that a signal corresponding to the voltage is optically communicated to the photodetector, wherein the changing the property of light comprises causing a phase change therein by changing a length of an optical path between the light source and the photodetector. wherein the changing the optical path length comprises moving a mirror by changing a dimension of a piezoelectric element, the piezoelectric element configured to change shape in response to voltage applied thereto from the antenna. - View Dependent Claims (9, 10)
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11. An electromagnetic survey system, comprising:
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a survey vessel configured to tow a receiver cable through a body of water; a receiver cable having an optical fiber associated therewith and coupled at one end to a recording device on the survey vessel and at another end to a plurality of optical magnetic field sensors disposed at spaced apart positions along the receiver cable, each magnetic field sensor configured to change a property of light from a source associated with the recording device; and a signal detector associated with the recording device configured to convert each changed property of light into a signal corresponding to a property of a magnetic field proximate the associated magnetic field sensor. - View Dependent Claims (12, 13)
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14. A method for electromagnetic surveying of formations in the Earth'"'"'s subsurface, comprising:
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imparting an electromagnetic field into the formations; exposing a magnetostrictive material to an electromagnetic field produced in response to the imparted electromagnetic field; transferring a change in dimension of the magnetostrictive material to an optical fiber to cause a change in a property of light conducted from a light source to a photodetector along the optical fiber, so that a signal corresponding to the responsively produced electromagnetic field is optically communicated to the photodetector. - View Dependent Claims (15)
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Specification