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US 5,402,231 AGranted
Distributed sagnac sensor systems
AssigneeMcDonnell Douglas Corporation
InventorEric Udd
Life of this patent
Estimating the term…
Abstract
Wavelength division multiplexed Sagnac distributed sensor systems that allow the determination of the position and amplitude of a frequency dependent environmental effect acting on the optical path of Sagnac loops. The sensor includes two Sagnac interferometers operating at different wavelengths and having optically spaced combining couplers and optical loops which include as portions thereof, the optical path. The outputs of the Sagnac interferometers are summed to determine the relative amplitude of the sensed effect and compared to determine its position on the optical path.
Claims52
A distributed fiber optic sensor system for sensing environmental effects having:
- a first optical fiber having:
- a first end;
- and
- a second end;
- a second optical fiber having:
- a first end;
- and
- a second end;
- light source means that produce light in a first band and a second band;
- a first beamsplitter that splits said light in said first band into first and second light beams and connects said first and second light beams into said first ends of said first and second optical fibers respectively;
- first light transmission means connecting said first light beam from said first optical fiber second end to said second optical fiber second end and connecting said second light beam from said second optical fiber second end to said first optical fiber second end so that said second and first light beams traverse said first and second optical fibers respectively and recombine at said first beamsplitter to form a first recombined light beam;
- a second beamsplitter that splits said light in said second band into third and fourth light beams and connects said third and fourth light beams into said second ends of said first and second optical fibers respectively;
- second light transmission means connecting said third light beam from said first optical fiber first end to said second optical fiber first end and connecting said fourth light beam from said second optical fiber first end to said first optical fiber first end so that said fourth and third light beams traverse said first and second optical fibers respectively and recombine at said second beamsplitter to form a second recombined light beam;
- a first detector connected to receive said first recombined light beam and to produce therefrom a first sensor output;
- a second detector connected to receive said second recombined light beam and to produce therefrom a second sensor output;
- and
- signal processor means connected to said first and second sensor outputs to calculate the amplitude and position of any environmental effect on said first optical fiber.
14 more elements
A sensor system including:
- first optical fiber means having:
- a first end;
- and
- a second end;
- second optical fiber means having:
- a first end;
- and
- a second end;
- a first Sagnac interferometer sensor having:
- a first Sagnac loop that includes said first and second optical fiber means, said first Sagnac interferometer sensor producing a first interferometric output representative of any disturbance effecting at least said first optical fiber means;
- a second Sagnac interferometer sensor spaced from said first Sagnac interferometer sensor and having:
- a second Sagnac loop that includes said first and second fiber means, said second Sagnac interferometer sensor producing a second interferometric output representative of any disturbance effecting at least said first optical fiber means;
- and
- signal processor means connected to said first and second Sagnac interferometer sensors to calculate the amplitude and position of a disturbance that occurs on at least said first optical fiber means from said first and second interferometric outputs.
11 more elements
A distributed sensor system including:
- a first optical fiber;
- a first Sagnac interferometer including:
- a first Sagnac loop in which said first optical fiber is located;
- a second Sagnac interferometer including:
- a second Sagnac loop in which said first optical fiber is located, said first and second Sagnac loops being positioned to sense from opposite directions along said first optical fiber, the position and amplitude of environmental effects indicative of a disturbance of said first optical fiber.
2 more elements
A sensor system including:
- a sensing element exposed to environmental effects over a predetermined distance;
- a first Sagnac interferometer including:
- a first Sagnac loop in which said sensing element is located;
- a second Sagnac interferometer having:
- a second Sagnac loop having at least said sensing element in common with said first Sagnac loop, said first and second Sagnac interferometers being differently located with respect to said sensing element to sense the position along said predetermined distance and the amplitude of environmental effects affecting said sensing element.
2 more elements
A sensor system including:
- an elongate sensing element exposed to effects capable of at least momentarily changing the light transmission characteristics of said elongate sensing element;
- a first Sagnac interferometer producing a first output representative of effects to which said elongate sensing element is exposed and including:
- a first Sagnac loop in which said elongate sensing element is located;
- a second Sagnac interferometer producing a second output representative of effects to which said elongate sensing element is exposed and including:
- a second Sagnac loop different than said first Sagnac loop in which at least said elongate sensing element of said first Sagnac loop is also located;
- and
- means to receive said first and second outputs and produce therefrom at least a third output indicative of effects changing the light transmission characteristics of said elongate sensing element.
4 more elements
A sensor system including:
- an elongate sensing element exposed to a periodic environmental effect;
- a first interferometer including:
- a first Sagnac loop in which said elongate sensing element is located, said first interferometer producing a first output representative of the periodic environmental effect;
- a second interferometer including:
- a second Sagnac loop in which said elongate sensing element is also located, said second interferometer producing a second output representative of the periodic environmental effect;
- and
- means to receive said first and second outputs and produce therefrom at least a third output indicative of the position of the periodic environmental effect along said elongate sensing element.
4 more elements
Dependencies are inferred from the claim text.