Method of operating a fiber-optic acoustical sensor, apparatus for practicing the method, and in-line fiber-optic polarizer usable in such apparatus
First Claim
1. A method of operating a fiber-optic acoustical sensor, said method comprising steps of:
- providing into one end of an elongate fiber-optic conductor a pair of orthogonally-polarized light beams;
providing a polarizer receiving said pair of orthogonally-polarized light beams from a second opposite end of said elongate fiber-optic conductor and responsively providing a polarized output light beam;
providing an optical acoustical transducer receiving said polarized output light beam and also receiving acoustical energy ambient to said transducer, andutilizing said optical acoustical transducer to responsively providing a modulated optical output light beam signal analogous to a characteristic of said acoustical energy;
further including the step of providing said pair of orthogonally-polarized light beams in the form of a train of time-interleaved pulses of light.
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Accused Products
Abstract
A fiber-optic acoustical sensor system includes a light source, an elongate optical cable conducting light from the light source to an optical acoustical transducer located at a distance from the light source along this cable, and a polarizer at the acoustical transducer. The sensor system includes a polarizer providing orthogonally-polarized light along the optical cable to the polarizer located adjacent to the transducer. Because of the polarizer adjacent to the transducer, disturbances of the optical cable and resulting polarization perturbations of the light transmitted along this cable do not affect the optical acoustical transducer. The acoustic transducer is responsive to sound energy to provide an optical return signal indicative of this sound energy. An in-line fiber-optic polarizer suitable for use in this acoustical transducer includes a pair of confronting optical fiber portions aligned along an optical axis and which each define end surfaces disposed at a Brewster polarizer angle with respect to light transmitted along this optical axis. The end surface of one of these optical fibers carries plural alternating sub-layers of high-index and low-index dielectric material, which are effective to p-polarize the transmitted light and substantially eliminate s-polarized light transmission to the optical acoustical transducer.
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Citations
18 Claims
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1. A method of operating a fiber-optic acoustical sensor, said method comprising steps of:
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providing into one end of an elongate fiber-optic conductor a pair of orthogonally-polarized light beams; providing a polarizer receiving said pair of orthogonally-polarized light beams from a second opposite end of said elongate fiber-optic conductor and responsively providing a polarized output light beam; providing an optical acoustical transducer receiving said polarized output light beam and also receiving acoustical energy ambient to said transducer, and utilizing said optical acoustical transducer to responsively providing a modulated optical output light beam signal analogous to a characteristic of said acoustical energy; further including the step of providing said pair of orthogonally-polarized light beams in the form of a train of time-interleaved pulses of light. - View Dependent Claims (2)
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3. A fiber-optic acoustical sensor comprising:
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a light source providing a polarized light beam; an elongate optical fiber at a proximal end receiving said light beam and having a distal end from which issues said light beam in an indeterminate state of polarization; a polarizer receiving said light beam in an unknown state of polarization from said distal end of said optical fiber, and responsively providing light having substantially a stable state of polarization; and an optical acoustical transducer receiving said light having substantially a stable state of polarization from said polarizer and also receiving acoustical energy ambient to said transducer, said transducer responsively providing a phase modulated light beam signal analogous to a characteristic of said acoustical energy; wherein said light source further includes means for providing two orthogonally polarized light beams into said proximal end of said elongate optical fiber; wherein said means for providing said pair of orthogonally-polarized light beams further includes means for time-intcrleaving orthogonally polarized pulses of said pair of light beams. - View Dependent Claims (4, 5)
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6. A fiber-optic acoustical sensor comprising:
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a light source providing a polarized light beam; an elongate optical fiber at a proximal end receiving said light beam and having a distal end; a polarizer receiving said light beam in an unknown state of polarization from said distal end of said optical fiber, and responsively providing light having substantially a stable state of polarization; said polarizer including a pair of optical fiber portions aligning along an optical axis, each one of said pair of optical fiber portions defining a respective one of a confronting pair of end surfaces angulated with respect to said optical axis at substantially a Brewster angle;
a dielectric layer disposed between said pair of end surfaces, said dielectric layer including plural sub-layers including at least a pair of high-index sub-layers each adjacent to a respective one of said pair of end surfaces, and at least one low-index sub-layer disposed between said pair of high-index sub-layers, and each of said high-index and low-index sub-layers having a respective index of refraction determining said Brewster angle; andan optical acoustical transducer receiving said light having substantially a stable state of polarization from said polarizer and also receiving acoustical energy ambient to said transducer and responsively providing a modulated light beam signal analogous to a characteristic of said acoustical energy. - View Dependent Claims (7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18)
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Specification