Fiber optic current sensor
AssigneeThe Texas A&M Universtiy System
InventorJames N. Blake
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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.
Claims43
A fiber optic current sensor comprising:
- a light source;
- a polarizer coupled to said light source;
- a first polarization converter coupled to said polarizer;
- a sensing fiber coil connected to said polarization converter, wherein fiber of said sensing fiber coil is spun with a spin rate for a predetermined maintenance of circular polarization;
- a terminating reflector connected to said sensing fiber;
- and
- a detector coupled to said polarizer.
A fiber optic current sensor comprising
- a light source;
- a polarizer coupled to said light source;
- an optical splitter connected to said polarizer;
- a fiber loop connected at each end to said optical splitter;
- a sensing fiber coil, situated within said fiber loop and having sensing fiber, wherein the sensing fiber of said sensing fiber coil is spun and contains linear birefringence, and has a spin rate for a predetermined maintenance of circular polarization;
- and
- a detector coupled to said polarizer and having an output.
A fiber optic current sensor comprising:
- a light source;
- a polarizer coupled to said light source;
- a Faraday rotator coupled to said polarizer;
- a first quarter waveplate coupled to said Faraday rotator;
- a polarization maintaining fiber coupled to said first quarter waveplate;
- a second quarter waveplate coupled to said polarization maintaining fiber;
- and
- a sensing fiber, that substantially preserves circular states of polarization, coupled to said second quarter waveplate;
- a reflective termination coupled to said sensing fiber;
- and
- a photodetector coupled to said polarizer and having an output.
Dependencies are inferred from the claim text.