# US 12,000,691 B2 · One or more fiber optic sensors locally bonded with a flexible filament structure > Agents: this data is available as JSON from the patentgrep API and MCP server — see https://patentgrep.com/llms.txt - Number: US 12,000,691 B2 - Document ID: US12000691B2 - Status: Granted - Kind: B2 - Application number: 17/638,458 - Filed: 2020-08-27 - Published: 2022-10-06 - Granted: 2024-06-04 - Earliest claimed: 2019-08-30 - Assignees: Luna Innovations Incorporated - Applicants: Luna Innovations Incorporated - Inventors: Osgar John Ohanian, III; Matthew Anthony Davis - Web page: https://patentgrep.com/patent/US12000691B2 ## CPC - G01B 11/18: {using photoelastic elements} - G01D 5/35374: {Particular layout of the fiber} - G01L 1/246: {using integrated gratings, e.g. Bragg gratings} - G01M 5/0091: {by using electromagnetic excitation or detection} - G02B 6/4298: {coupling with non-coherent light sources and/or radiation detectors, e.g. lamps, incandescent bulbs, scintillation chambers} - G02B 6/02395: {Glass optical fibre with a protective coating, e.g. two layer polymer coating deposited directly on a silica cladding surface during fibre manufacture (G02B6/02052, G02B6/02057, G02B6/024, G02B6/032, G02B6/105, G02B6/14 take precedence; coating on fibre gratings G02B6/02104; multilayer core or cladding G02B6/036; reinforcing splice joints G02B6/2558; optical cables, i.e. comprising protective structures external to the protective coating such as a jacket or plural coated optical fibres G02B6/44; coating of glass to obtain optical fibres C03C25/104)} - G02B 6/3628: {for mounting fibres to supporting carriers (G02B6/3608, G02B6/3616 take precedence)} - G02B 2006/12138: {Sensor} - G01B: MEASURING LENGTH, THICKNESS OR SIMILAR LINEAR DIMENSIONS; MEASURING ANGLES; MEASURING AREAS; MEASURING IRREGULARITIES OF SURFACES OR CONTOURS - G01D: MEASURING NOT SPECIALLY ADAPTED FOR A SPECIFIC VARIABLE; ARRANGEMENTS FOR MEASURING TWO OR MORE VARIABLES NOT COVERED IN A SINGLE OTHER SUBCLASS; TARIFF METERING APPARATUS; MEASURING OR TESTING NOT OTHERWISE PROVIDED FOR - G01L: MEASURING FORCE, STRESS, TORQUE, WORK, MECHANICAL POWER, MECHANICAL EFFICIENCY, OR FLUID PRESSURE (weighing G01G) - G01M: TESTING STATIC OR DYNAMIC BALANCE OF MACHINES OR STRUCTURES; TESTING OF STRUCTURES OR APPARATUS, NOT OTHERWISE PROVIDED FOR - G02B: OPTICAL ELEMENTS, SYSTEMS OR APPARATUS ## Abstract An apparatus comprises a flexible filament structure, and a fiber optic sensor with a buffer material that locally bonds the fiber optic sensor to the flexible filament structure to create a bond between the fiber optic sensor and the flexible filament structure to transfer strain from the flexible filament structure to the fiber optic sensor to allow the fiber optic sensor to detect strain on the flexible filament structure while maintaining flexibility in the flexible filament structure. A fiber optic interrogator may be optically coupled to the fiber optic sensor and configured to measure strain. A method comprises embedding a fiber optic sensor with a buffer material in or on a flexible filament structure. Thereafter, the buffer material is activated via heating or curing to locally adhere the fiber optic sensor to the flexible filament structure to create a local bond. The local bond transfers strain from the flexible filament structure to the fiber optic sensor. ## Claims ### Claim 1 An apparatus comprising: a woven structure to be monitored, and a fiber optic sensor with a curable or meltable material woven into the woven structure to produce a woven assembly that has an initial flexibility, wherein activation of the curable or meltable material after the woven assembly is produced locally bonds the fiber optic sensor to just one or more portions of the woven structure adjacent to the fiber optic sensor to create a local bond between the fiber optic sensor and the woven structure that transfers strain from the woven structure to the fiber optic sensor to allow the fiber optic sensor to detect strain on the woven structure, and wherein after the local bonding between the fiber optic sensor and the one or more portions of the woven structure, the woven assembly retains a high degree of the initial flexibility that is greater than a flexibility of the woven structure if more or all of the woven structure were infused with curable or meltable material. ### Claim 2 (depends on 1) The apparatus in claim 1, wherein the local bond provides a uniform strain coupling between the fiber optic sensor to detect strain on the woven structure and the fiber optic sensor. ### Claim 3 (depends on 1) The apparatus in claim 1, wherein the curable or meltable material includes one or more of: a thermoplastic, a thermoset resin, an adhesive, and a flexible polymer. ### Claim 4 (depends on 1) The apparatus in claim 1, wherein the curable or meltable material is arranged to maximize strain coupling between the fiber optic sensor and the woven structure through bonding. ### Claim 5 (depends on 1) The apparatus in claim 1, wherein the curable or meltable material is arranged to maximize frictional coupling between the fiber optic sensor and the woven structure. ### Claim 6 (depends on 1) The apparatus in claim 1, wherein the fiber optic sensor includes an optical fiber with a fiber coating and the curable or meltable material is on top of the fiber coating. ### Claim 7 (depends on 1) The apparatus in claim 1, wherein the fiber optic sensor includes an optical fiber with the curable or meltable material on top of the fiber. ### Claim 8 (depends on 1) The apparatus in claim 1, wherein the fiber optic sensor includes an optical fiber embedded within the woven structure along a longitudinal neutral plane of the woven structure. ### Claim 9 (depends on 1) The apparatus in claim 1, wherein the fiber optic sensor includes an optical fiber embedded within the woven structure along two or more longitudinal parallel axes of the woven structure with one end of the optical fiber being a fiber termination and the other end of the optical fiber coupled to a connector. ### Claim 10 (depends on 1) The apparatus in claim 1, wherein the fiber optic sensor includes two or more optical fibers embedded within the woven structure along two or more longitudinal parallel axes of the woven structure with one end of each optical fiber being a fiber termination and the other end of each optical fiber coupled to a connector. ### Claim 11 (depends on 1) The apparatus in claim 1, wherein the fiber optic sensor is bendable with the woven structure to detect one or more of: (i) bending of the woven structure in a plane that contains a longitudinal axis of the woven structure, (ii) bending out of the plane, and (iii) axial strain along a longitudinal axis of the filament structure. ### Claim 12 (depends on 1) The apparatus in claim 1, wherein the woven structure includes one or more of: Kevlar, Vectran, Nylon, Polyester, cotton, other synthetic, and organic-based fibers. ### Claim 13 (depends on 1) The apparatus in claim 1, wherein the woven structure includes one or more of: axial filaments, lateral filaments, and vertical filaments. ### Claim 14 (depends on 13) The apparatus in claim 13, wherein the woven structure includes a first layer of axial filaments and lateral filaments and a second layer of axial filaments and lateral filaments, wherein the vertical filaments extend to couple the first layer and the second layer, and wherein one or more fiber optic sensors are embedded between the first layer and the second layer. ### Claim 15 A system comprising: a woven structure to be monitored, and a fiber optic sensor with a curable or meltable material woven into the woven structure to produce a woven assembly that has an initial flexibility, wherein activation of the curable or meltable material after the woven assembly is produced locally bonds the fiber optic sensor to just one or more portions of the woven structure adjacent to the fiber optic sensor to create a local bond between the fiber optic sensor and the woven structure that transfers strain from the woven structure to the fiber optic sensor to allow the fiber optic sensor to detect strain on the woven structure, and wherein after the local bonding between the fiber optic sensor and the one or more portions of the woven structure, the woven assembly retains a high degree of the initial flexibility that is greater than a flexibility of the woven structure if more or all of the woven structure were infused with curable or meltable material; and a fiber optic interrogator optically coupled to the fiber optic sensor and configured to measure strain. ### Claim 16 (depends on 15) The system in claim 15, wherein the fiber optic interrogator is configured to use one or more of: Raman scatter, Brillouin scatter, FBG point sensors, distributed FBG sensors to measure strain in the fiber optic sensor. ### Claim 17 (depends on 15) The system in claim 15, wherein the fiber optic interrogator is an optical frequency domain reflectometry (OFDR)-based interrogator to measure strain in a continuous fashion with high spatial resolution based on light reflections from Rayleigh scatter in the fiber optic sensor. ### Claim 18 (depends on 15) The system in claim 15, wherein the fiber optic interrogator is an optical frequency domain reflectometry (OFDR)-based interrogator to measure strain based on light reflections from fiber Bragg gratings (FBG) in the fiber optic sensor. ### Claim 19 (depends on 15) The system in claim 15, wherein the fiber optic interrogator is configured to localize strain information associated with the fiber optic sensor using time optical time domain reflectometry (OTDR) or wavelength division multiplexing (WDM). ### Claim 20 (depends on 15) The system in claim 15, wherein the fiber optic interrogator is configured to determine distributed strain along a longitudinal axis of the woven structure and to determine from the distributed strain one or more of the following: an applied load to the woven structure, damage to the woven structure, pressure on the woven structure, a material creep of the woven structure, in-plane and/or out-of-plane bending or curvature of the woven structure, and a direction of damage to the woven structure. ### Claim 21 A method comprising: weaving a fiber optic sensor with a curable or meltable material woven into the woven structure to produce a woven assembly that has an initial flexibility; after the woven assembly is produced, activating the curable or meltable material via heating or curing to locally adhere the fiber optic sensor to just one or more portions of the woven structure to create a local bond, where the local bond transfers strain from the woven structure to the fiber optic sensor to allow the fiber optic sensor to detect strain on the woven structure, wherein after the local bond between the fiber optic sensor and the one or more portions of the woven structure, the woven assembly retains a high degree of the initial flexibility that is greater than a flexibility of the woven structure if more or all of the woven structure were infused with curable or meltable material. ### Claim 22 (depends on 21) The method in claim 21, wherein the heating uses one or more of conduction, convection, radiation, and induction. ### Claim 23 (depends on 21) The method in claim 21, wherein the fiber optic sensor includes an optical fiber, the method further comprising: forming the curable or meltable material on the optical fiber or on a coating of the optical fiber. ### Claim 24 (depends on 21) The method in claim 21, further comprising: generating the woven structure using axial filaments, lateral filaments, and vertical filaments, where the woven structure includes a first layer of axial filaments and lateral filaments and a second layer of axial filaments and lateral filaments and the vertical filaments extend to couple the first layer and the second layer, and embedding one or more fiber optic sensors between the first layer and the second layer. ### Claim 25 A method comprising: embedding a fiber optic sensor with a buffer material in or on a flexible filament structure; thereafter, activating the buffer material via heating or curing to locally adhere the fiber optic sensor to the flexible filament structure to create a local bond, where the local bond transfers strain from the flexible filament structure to the fiber optic sensor to allow the fiber optic sensor to detect strain on the flexible filament structure while maintaining flexibility in the flexible filament structure. ### Claim 26 (depends on 25) The method in claim 25, wherein the heating uses one or more of conduction, convection, radiation, and induction, and wherein the fiber optic sensor includes an optical fiber, the method further comprising: forming the buffer material on the optical fiber or on a coating of the optical fiber. ### Claim 27 (depends on 25) The method in claim 25, further comprising: generating the flexible filament structure using axial filaments, lateral filaments, and vertical filaments, where the woven structure includes a first layer of axial filaments and lateral filaments and a second layer of axial filaments and lateral filaments and the vertical filaments extend to couple the first layer and the second layer, and embedding one or more fiber optic sensors between the first layer and the second layer. ### Claim 28 An apparatus comprising: a flexible filament structure, and a fiber optic sensor with a buffer material that locally bonds the fiber optic sensor to the flexible filament structure to create a bond between the fiber optic sensor and the flexible filament structure to transfer strain from the flexible filament structure to the fiber optic sensor to allow the fiber optic sensor to detect strain on the flexible filament structure while maintaining flexibility in the flexible filament structure, wherein the buffer material is arranged to maximize one or both of: strain coupling between the fiber optic sensor and the flexible filament structure through bonding, and frictional coupling between the fiber optic sensor and the flexible filament structure. ### Claim 29 An apparatus comprising: a flexible filament structure, and a fiber optic sensor with a buffer material that locally bonds the fiber optic sensor to the flexible filament structure to create a bond between the fiber optic sensor and the flexible filament structure to transfer strain from the flexible filament structure to the fiber optic sensor to allow the fiber optic sensor to detect strain on the flexible filament structure while maintaining flexibility in the flexible filament structure, wherein the woven structure includes a first layer of axial filaments and lateral filaments and a second layer of axial filaments and lateral filaments, wherein the vertical filaments extend to couple the first layer and the second layer, and wherein one or more fiber optic sensors are embedded between the first layer and the second layer.