Fiber optic strain sensor
AssigneeSystems Planning & Analysis, Inc.
InventorsPeter C. Chen, Shiping Chen
Life of this patent
Estimating the term…
Abstract
A fiber optic sensor flatpack capable of extremely sensitive strain measurements, without the complexity, high installation costs, and sensitivity to extraneous effects associated with conventional strain gage technologies, such as resistance foil strain gages. The “flatpack” strain sensor houses two individual sensors to allow for accurate temperature compensated strain measurements. The packaging method incorporates plastic materials and laminate manufacturing techniques, which results in a fully hermetic package that is resistant to harsh environmental conditions. Multiple flatpacks can be connected in series and interrogated along a single optical fiber cable when the flatpacks are constructed with fiber optic sensors that can be serially multiplexed, such as with Bragg grating sensors.
Claims29
A strain sensor comprising:
- first and second fiber ends, a first fiber grating and a second fiber grating being proximately located and optically coupled to each other, said first and second gratings being coupled between the first and second fiber ends, wherein when said strain sensor is mechanically strained, said first fiber grating realizes corresponding axial strain and said second fiber grating does not realize corresponding axial strain, said second fiber grating has a first end and a second end, said strain sensor further comprising a plate for constraining movement of said first end and said second end.
A strain sensor system comprising:
- one or more strain sensors including first and second fiber end, a first fiber grating and a second fiber grating being proximately located and optically coupled to each other, said first and second gratings being coupled between the first and second fiber ends;
- a light source;
- a scanning Fabry-Perot device in optical communication with said light source;
- each of said sensors having an input end and an output end, said input end being in optical communication with said scanning Fabry-Perot device;
- a detector exclusively dedicated to and in optical communication with the output end of each strain sensor;
- and
- a microprocessor responsive to said detectors,
- wherein when said strain sensor is mechanically strained, said first fiber grating realizes corresponding axial strain and said second fiber grating does not realize corresponding axial strain, said second fiber grating has first and second ends, said strain sensor further comprising a plate for constraining movement of said first and second ends.
A strain sensor system comprising:
- one or more strain sensors including first and second fiber end, a first fiber grating and a second fiber grating being proximately located and optically coupled to each other, said first and second fiber gratings being coupled between the first and second fiber ends;
- a light source;
- each strain sensor having an input end and an output end, said input end being in optical communication with said light source;
- an interferometer exclusively dedicated to and in optical communication with the output end of each strain sensor;
- a wavelength division multiplexer dedicated to and in optical communication with each of said interferometers;
- and
- a set of demodulation circuits dedicated to and in optical communication with each of said wavelength division multiplexers, wherein a number of demodulation circuits in each of said sets corresponds to a number of gratings a fiber in optical communication with said wavelength division multiplexer, and wherein when said strain sensor is mechanically strained, said first fiber grating realizes corresponding axial strain and said second fiber grating does not realize corresponding axial strain, said second fiber grating has first and second ends, said strain sensor further comprising a plate for constraining movement of said first and second ends.
A strain sensor comprising:
- a carrier;
- a pair of fiber ends coupled to the carrier;
- a first fiber grating fixedly mounted on said carrier;
- and
- a second fiber grating optically coupled to the first fiber grating, being independently mounted on the carrier such that said first fiber grating realizes corresponding axial strain and said second fiber grading does not realize corresponding axial strain, said first and second fiber gratings being coupled between the pair of fiber ends, wherein said second fiber grating has first and second ends, said strain sensor further comprising a plate for constraining movement of said first and second ends.
A method of measuring strain, said method comprising:
- locating first and second fiber gratings in close proximity and coupling the first and second fiber gratings between fiber ends;
- transferring strain to the first fiber grating;
- isolating a second fiber grating from the strain;
- and
- deriving a strain value from the first fiber grating;
- deriving a modification value from the second fiber grating;
- and
- modifying the strain value derived from the first fiber grating by the modification value derived from the second fiber grating,
- wherein said second fiber grating has first and second ends, said strain sensor further comprising a plate for constraining movement of said first and second ends.
Dependencies are inferred from the claim text.