Microbending of optical fibers for remote force measurement
First Claim
1. A system for monitoring forces acting upon a structure, comprising:
- a plurality of optical fibers extending along the structure;
a plurality of sets of force transducers wherein each of said sets is operatively associated with a respective one of said fibers and wherein each of said transducers is mounted on the structure for movement in response to a localized force acting upon the structure to induce microbending of its associated fiber wherein light passing through each of said fibers is abruptly attenuated at each microbend therein;
means for launching a pulsed optical signal into said fibers for passage therethrough and for substantially continuous reflection along the lengths of said fibers of a portion of said signal back through said fibers as backscattered light; and
means for detecting the intensity of said backscattered light from each of said fibers as a function of time of reflection whereby each microbend along each fiber is indicated by an abrupt attenuation in said detected intensity and the time of detection is indicative of the location of the microbend along said fiber;
said signal launching means and said detecting means being positioned at a common monitoring station, said signal launching means comprising a light source and said detecting means comprising a photodetector, and including optical means positioned generally adjacent one end of said fibers for direction of said pulsed optical signal into said fibers and for direction of said backscattered light to said photodetector.
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Accused Products
Abstract
A system for remote measurement of structural forces includes a plurality of microbend transducers mounted along the length of the structure for microbending an optical fiber in response to structural forces, such as stress acting upon an oil or gas pipeline or the like. An optical time domain reflectometer (OTDR) has a light source for launching a pulsed optical signal for passage through the fiber and a photodetector for sensing as a function of time the intensity of backscattered light reflected back through the fiber, wherein this sensed time function is correlated directly with discrete longitudinal positions along the length of the fiber and the structure. When one or more of the microbend transducers is activated to induce a microbend in the fiber in response to localized forces acting upon the structure, a portion of the backscattered light is lost at the microbend. This attenuation in backscattered light intensity is sensed quantitatively and positionally identified by the photodetector. Specific preferred constructions for microbend transducers and system arrangements particularly adapted for detecting structural strain in an oil or gas pipeline are disclosed.
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Citations
27 Claims
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1. A system for monitoring forces acting upon a structure, comprising:
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a plurality of optical fibers extending along the structure; a plurality of sets of force transducers wherein each of said sets is operatively associated with a respective one of said fibers and wherein each of said transducers is mounted on the structure for movement in response to a localized force acting upon the structure to induce microbending of its associated fiber wherein light passing through each of said fibers is abruptly attenuated at each microbend therein; means for launching a pulsed optical signal into said fibers for passage therethrough and for substantially continuous reflection along the lengths of said fibers of a portion of said signal back through said fibers as backscattered light; and means for detecting the intensity of said backscattered light from each of said fibers as a function of time of reflection whereby each microbend along each fiber is indicated by an abrupt attenuation in said detected intensity and the time of detection is indicative of the location of the microbend along said fiber; said signal launching means and said detecting means being positioned at a common monitoring station, said signal launching means comprising a light source and said detecting means comprising a photodetector, and including optical means positioned generally adjacent one end of said fibers for direction of said pulsed optical signal into said fibers and for direction of said backscattered light to said photodetector. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8)
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9. A method of monitoring stress acting upon a pipeline, comprising the steps of:
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providing a plurality of optical fibers to extend from a monitoring station along the pipeline; mounting a plurality of sets of strain transducers wherein each of said sets is in operative association with a respective one of the fibers and wherein each of the transducers is mounted on the pipeline for movement in response to a localized stress acting upon the pipeline to induce microbending of its associated fiber wherein light passing through each of the fibers is abruptly attenuated at each microbend therein; launching a pulsed optical signal from the monitoring station into the fibers for passage therethrough and for substantially continuous reflection along the lengths of said fibers of a portion of the signal back through the fibers as backscattered light; and detecting at the monitoring station the intensity of the backscattered light from each of the fibers as a function of time of reflection whereby each microbend along each fiber is indicated by an abrupt attenuation in the detected intensity and the time of detection is indicative of the location of the microbend along the fiber.
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10. A system for monitoring stress acting upon a structure, comprising:
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a plurality of optical fibers extending along the structure; a plurality of sets of strain transducers wherein each of said sets is operatively associated with a respective one of said fibers and wherein each of said transducers is mounted on the structure for movement in response to a localized stress acting upon the structure to induce microbending of its associated fiber wherein light passing through each of said fibers is abruptly attenuated at each microbend therein; means for launching a pulsed optical signal into said fibers for passage therethrough and for substantially continuous reflection along the lengths of said fibers of a portion of said signal back through said fibers as backscattered light; and means for detecting the intensity of said backscattered light from each of said fibers as a function of time of reflection whereby each microbend along each fiber is indicated by an abrupt attenuation in said detected intensity and the time of detection is indicative of the location of the microbend along said fiber; said signal launching means and said detecting means being positioned at a common monitoring station, said signal launching means comprising a light source and said detecting means comprising a photodetector, and including optical means positioned generally adjacent one end of said fibers for direction of said pulsed optical signal into said fibers and for direction of said backscattered light to said photodetector. - View Dependent Claims (11, 12, 13)
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14. A system for monitoring stress acting upon a pipeline, comprising:
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a plurality of optical fibers extending along the pipeline; a plurality of sets of strain transducers wherein each of said sets is operatively associated with a respective one of said fibers and wherein each of said transducers is mounted on the pipeline for movement in response to localized stress acting upon the pipeline to induce microbending of its associated fiber wherein light passing through each of said fibers is abruptly attenuated at each microbending therein; means for launching a pulsed optical signal into said fibers for passage therethrough and for substantially continuous reflection along the lengths of said fibers of a portion of said signal back through said fibers as backscattered light; and means for detecting the intensity of said backscattered light from each of said fibers as a function of time of reflection whereby each microbend along each fiber is indicated by an abrupt attenuation in said detected intensity and the time of detection is indicative of the location of the microbend along said fiber; said signal launching means and said detecting means being positioned at a common monitoring station, said signal launching means comprising a photodetector, and including optical means positioned generally adjacent one end of said fibers for direction of said pulsed optical signal into said fibers and for direction of said backscattered light to said photodetector. - View Dependent Claims (15, 16, 17, 18, 19)
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20. A method of monitoring forces acting upon a structure, comprising the steps of:
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providing a plurality of optical fibers to extend from a monitoring station along the structure; mounting a plurality of sets of force transducers wherein each of said sets is in operative association with a respective one of said fibers and wherein each of the transducers is mounted on the structure for movement in response to a localized force acting upon the structure to induce microbending of its associated fiber wherein light passing through each of the fibers is abruptly attenuated at each microbend; launching a pulsed optical signal from the monitoring station into the fibers for passage therethrough and for substantially continuous reflection along the lengths of said fibers of a portion of the signal back through the fibers as backscattered light; and detecting at the monitoring station the intensity of the backscattered light from each of the fibers as a function of time of reflection whereby each microbend along each fiber is indicated by an abrupt attenuation in the detected intensity and the time of detection is indicative of the location of the microbend along the fiber. - View Dependent Claims (21, 22, 23, 24, 25, 26, 27)
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Specification