Abstract: Mechanical parameters of an object subjected to a force or condition are measured. A curved portion of a multicore optical fiber is attached to the object, and the multicore optical fiber includes a center core and plural off-center cores. A distributed, optically-based sensing technique is used to obtain information at each of multiple points along the curved portion from multiple ones of the cores of the multicore optical fiber. A curvature associated with the fiber attached to the object is determined using the information obtained from multiple ones of the cores. Strain information is obtained for the center core without having to obtain strain information for the off-center cores. Mechanical parameters are determined based on the strain information obtained for the center core and the curvature information obtained from the multiple ones of the cores.

Abstract: Mechanical parameters of an object subjected to a force or condition are measured. A curved portion of a multicore optical fiber is attached to the object, and the multicore optical fiber includes a center core and plural off-center cores. A distributed, optically-based sensing technique is used to obtain information at each of multiple points along the curved portion from multiple ones of the cores of the multicore optical fiber. A curvature associated with the fiber attached to the object is determined using the information obtained from multiple ones of the cores. Strain information is obtained for the center core without having to obtain strain information for the off-center cores. Mechanical parameters are determined based on the strain information obtained for the center core and the curvature information obtained from the multiple ones of the cores.

Abstract: Mechanical parameters of an object subjected to a force or condition are measured. A curved portion of a multicore optical fiber is attached to the object, and the multicore optical fiber includes a center core and plural off-center cores. A distributed, optically-based sensing technique is used to obtain information at each of multiple points along the curved portion from multiple ones of the cores of the multicore optical fiber. A curvature associated with the fiber attached to the object is determined using the information obtained from multiple ones of the cores. Strain information is obtained for the center core without having to obtain strain information for the off-center cores. Mechanical parameters are determined based on the strain information obtained for the center core and the curvature information obtained from the multiple ones of the cores.

Abstract: An optical interrogation system, e.g., an OFDR-based system, measures local changes, of index of refraction of a sensing light guide subjected to a time-varying disturbance. Interferometric measurement signals detected for a length of the sensing light guide are transformed into the spectral domain. A time varying signal is determined from the transformed interferometric measurement data set. A compensating signal is determined from the time varying signal which is used to compensate the interferometric measurement data set for the time-varying disturbance. Further robustness is achieved using averaging and strain compensation. The compensation technique may be applied along the length of the light guide.

Abstract: An accurate measurement method and apparatus using an optical fiber are disclosed. A total change in optical length in an optical core in the optical fiber is determined that reflects an accumulation of all of the changes in optical length for multiple segment lengths of the optical core up to a point on the optical fiber. The total change in optical length in the optical core is provided for calculation of an average strain over a length of the optical core based on the detected total change in optical length.

Abstract: Mechanical parameters of an object subjected to a force or condition are measured. A curved portion of a multicore optical fiber is attached to the object, and the multicore optical fiber includes a center core and plural off-center cores. A distributed, optically-based sensing technique is used to obtain information at each of multiple points along the curved portion from multiple ones of the cores of the multicore optical fiber. A curvature associated with the fiber attached to the object is determined using the information obtained from multiple ones of the cores. Strain information is obtained for the center core without having to obtain strain information for the off-center cores. Mechanical parameters are determined based on the strain information obtained for the center core and the curvature information obtained from the multiple ones of the cores.

Abstract: An accurate measurement method and apparatus are disclosed for shape sensing with a multi-core fiber. A change in optical length is detected in ones of the cores in the multi-core fiber up to a point on the multi-core fiber. A location and/or a pointing direction are/is determined at the point on the multi-core fiber based on the detected changes in optical length. The accuracy of the determination is better than 0.5% of the optical length of the multi-core fiber up to the point on the multi-core fiber. In a preferred example embodiment, the determining includes determining a shape of at least a portion of the multi-core fiber based on the detected changes in optical length.

Abstract: One or more mechanical parameters of a structure subjected to a force or condition are measured using distributed, optical fiber sensing technology. At least a curved portion an optical fiber having is attached to an object. A distributed, optically-based, strain sensing technique is used to determine strain information associated with multiple points along the curved portion of the fiber. The determined strain information is processed to generate one or more representations of one or more of the following: an expansion of the object, a thermal gradient associated with the object, or a stress-induced strain at multiple locations on the object corresponding to ones of the multiple points. An output is generated corresponding to the representation.

Abstract: An interferometric measurement system includes a spun optical fiber including multiple optical waveguides configured in the fiber. Interferometric detection circuitry detects measurement interferometric pattern data associated with each of the multiple optical waveguides when the optical fiber is placed into a bend. Data processing circuitry determines compensation parameters that compensate for variations between an optimal configuration of the multiple optical waveguides in the fiber and an actual configuration of multiple optical waveguides in the fiber. The compensation parameters are stored in memory for compensating subsequently-obtained measurement interferometric pattern data for the fiber.

Abstract: An interferometric measurement system measures a parameter using at least one optical waveguide. A memory stores reference interferometric pattern data associated with a segment of the optical waveguide. Interferometric detection circuitry detects and stores measurement interferometric pattern data associated with the segment of the optical waveguide during a measurement operation. A spectral range of the reference interferometric pattern of the optical waveguide is greater than a spectral range of the measurement interferometric pattern of the optical waveguide. A processor shifts one or both of the measurement interferometric pattern data and the reference interferometric pattern data relative to the other to obtain a match and to use the match to measure the parameter. An example parameter is strain.

Abstract: An interferometric measurement system includes a spun optical fiber including multiple optical waveguides configured in the fiber. Interferometric detection circuitry detects measurement interferometric pattern data associated with each of the multiple optical waveguides when the optical fiber is placed into a bend. Data processing circuitry determines compensation parameters that compensate for variations between an optimal configuration of the multiple optical waveguides in the fiber and an actual configuration of multiple optical waveguides in the fiber. The compensation parameters are stored in memory for compensating subsequently-obtained measurement interferometric pattern data for the fiber.

Abstract: An interferometric measurement system measures a parameter using at least one optical waveguide. A memory stores reference interferometric pattern data associated with a segment of the optical waveguide. Interferometric detection circuitry detects and stores measurement interferometric pattern data associated with the segment of the optical waveguide during a measurement operation. A spectral range of the reference interferometric pattern of the optical waveguide is greater than a spectral range of the measurement interferometric pattern of the optical waveguide. A processor shifts one or both of the measurement interferometric pattern data and the reference interferometric pattern data relative to the other to obtain a match and to use the match to measure the parameter. An example parameter is strain.

Abstract: One or more mechanical parameters of a structure subjected to a force or condition are measured using distributed, optical fiber sensing technology. At least a curved portion an optical fiber having is attached to an object. A distributed, optically-based, strain sensing technique is used to determine strain information associated with multiple points along the curved portion of the fiber. The determined strain information is processed to generate one or more representations of one or more of the following: an expansion of the object, a thermal gradient associated with the object, or a stress-induced strain at multiple locations on the object corresponding to ones of the multiple points. An output is generated corresponding to the representation.

Abstract: An optical device under test (DUT) is interferometrically measured. The DUT can include one or more of an optical fiber, an optical component, or an optical system. First interference pattern data for the DUT is obtained for a first path to the DUT, and second interference pattern data for the DUT is obtained for a second somewhat longer path to the DUT. Because of that longer length, the second interference pattern data is delayed in time from the first interference pattern data. A time varying component of the DUT interference pattern data is then identified from the first and second interference pattern data. The identified time varying component is used to modify the first or the second interference pattern data to compensate for the time-varying phase caused by vibrations, etc. One or more optical characteristics of the DUT may then be determined based on the modified interference pattern data.

Abstract: An optical device under test (DUT) is interferometrically measured. The DUT can include one or more of an optical fiber, an optical component, or an optical system. First interference pattern data for the DUT is obtained for a first path to the DUT, and second interference pattern data for the DUT is obtained for a second somewhat longer path to the DUT. Because of that longer length, the second interference pattern data is delayed in time from the first interference pattern data. A time varying component of the DUT interference pattern data is then identified from the first and second interference pattern data. The identified time varying component is used to modify the first or the second interference pattern data to compensate for the time-varying phase caused by vibrations, etc. One or more optical characteristics of the DUT may then be determined based on the modified interference pattern data.

Abstract: An accurate measurement method and apparatus are disclosed for shape sensing with a multi-core fiber. A change in optical length is detected in ones of the cores in the multi-core fiber up to a point on the multi-core fiber. A location and/or a pointing direction are/is determined at the point on the multi-core fiber based on the detected changes in optical length. The accuracy of the determination is better than 0.5% of the optical length of the multi-core fiber up to the point on the multi-core fiber. In a preferred example embodiment, the determining includes determining a shape of at least a portion of the multi-core fiber based on the detected changes in optical length.

Abstract: An optical device under test (DUT) is interferometrically measured. The DUT can include one or more of an optical fiber, an optical component, or an optical system. First interference pattern data for the DUT is obtained for a first path to the DUT, and second interference pattern data for the DUT is obtained for a second somewhat longer path to the DUT. Because of that longer length, the second interference pattern data is delayed in time from the first interference pattern data. A time varying component of the DUT interference pattern data is then identified from the first and second interference pattern data. The identified time varying component is used to modify the first or the second interference pattern data to compensate for the time-varying phase caused by vibrations, etc. One or more optical characteristics of the DUT may then be determined based on the modified interference pattern data.

Abstract: The present invention is directed toward a fiber optic position and shape sensing device and the method of use. The device comprises an optical fiber means. The optical fiber means comprises either at least two single core optical fibers or a multicore optical fiber having at least two fiber cores. In either case, the fiber cores are spaced apart such that mode coupling between the fiber cores is minimized. An array of fiber Bragg gratings are disposed within each fiber core and a frequency domain reflectometer is positioned in an operable relationship to the optical fiber means. In use, the device is affixed to an object. Strain on the optical fiber is measured and the strain measurements correlated to local bend measurements. Local bend measurements are integrated to determine position and/or shape of the object.

Abstract: An optical device under test (DUT) is interferometrically measured. The DUT can include one or more of an optical fiber, an optical component, or an optical system. First interference pattern data for the DUT is obtained for a first path to the DUT, and second interference pattern data for the DUT is obtained for a second somewhat longer path to the DUT. Because of that longer length, the second interference pattern data is delayed in time from the first interference pattern data. A time varying component of the DUT interference pattern data is then identified from the first and second interference pattern data. The identified time varying component is used to modify the first or the second interference pattern data to compensate for the time-varying phase caused by vibrations, etc. One or more optical characteristics of the DUT may then be determined based on the modified interference pattern data.

Abstract: The technology described here enables the use of an inexpensive laser to measure an interferometric response of an optical device under test (DUT) at reflection lengths significantly greater than the coherence length of the laser. This is particularly beneficial in practical interferometric applications where cost is a concern. In other words, inexpensive lasers having shorter coherence lengths may be used to achieve very high interferometric measurements at longer DUT reflection lengths. The technology also enables the use of such inexpensive lasers to measure Rayleigh scatter in commercial-grade, single-mode optical fiber.