# US 9,435,702 B2 · Method and apparatus for optical strain sensing > Agents: this data is available as JSON from the patentgrep API and MCP server — see https://patentgrep.com/llms.txt - Number: US 9,435,702 B2 - Document ID: US9435702B2 - Status: Granted - Kind: B2 - Application number: 14/932,023 - Filed: 2015-11-04 - Published: 2016-02-25 - Granted: 2016-09-06 - Earliest claimed: 2010-04-09 - Assignees: Intuitive Surgial Operations, Inc. - Applicants: Intuitive Surgical Operations, Inc. - Inventors: Mark E. Froggatt; Dawn K. Gifford - Web page: https://patentgrep.com/patent/US9435702B2 ## CPC - G01L 1/246: {using integrated gratings, e.g. Bragg gratings} - G01D 5/35306: {using an interferometer arrangement} - G01K 11/3206: at discrete locations in the fibre, e.g. using Bragg scattering - G01L: MEASURING FORCE, STRESS, TORQUE, WORK, MECHANICAL POWER, MECHANICAL EFFICIENCY, OR FLUID PRESSURE (weighing G01G) - 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 - G01K: MEASURING TEMPERATURE; MEASURING QUANTITY OF HEAT; THERMALLY-SENSITIVE ELEMENTS NOT OTHERWISE PROVIDED FOR (radiation pyrometry G01J5/00) ## 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. ## Claims ### Claim 1 Apparatus for measuring one or more mechanical parameters of an object subjected to a force and a temperature, where at least a curved portion of an optical fiber is attached to the object, the apparatus comprising electronic circuitry configured to: use a distributed, optically-based, strain sensing technique to determine distributed strain information at each of multiple points along the curved portion of the optical fiber while the object is subjected to the force and the temperature; process the determined distributed strain information to distinguish between temperature-induced strain and stress-induced strain on the object; and generate an output corresponding to one or both of the temperature-induced strain and stress-induced strain on the object. ### Claim 2 (depends on 1) The apparatus in claim 1, wherein the electronic circuitry is configured to process the determined distributed strain information to calculate a 3rd order or 4th order harmonic value of the strain measured over a loop of optical fiber. ### Claim 3 (depends on 2) The apparatus in claim 2, wherein the calculation of a 3rd order or 4th order harmonic strain value includes a frequency transform of the determined distributed strain information. ### Claim 4 (depends on 1) The apparatus in claim 1, wherein the electronic circuitry is configured to process the determined distributed strain information to calculate a temperature at one or more points along the curved portion of the fiber. ### Claim 5 (depends on 4) The apparatus in claim 4, wherein the electronic circuitry is configured to process the determined distributed strain information to calculate a temperature gradient at multiple loops along the optical fiber. ### Claim 6 (depends on 1) The apparatus in claim 1, wherein the electronic circuitry is configured to process the determined distributed strain information to calculate first and second temperature gradients at multiple loops along the optical fiber. ### Claim 7 (depends on 1) The apparatus in claim 1, wherein the electronic circuitry is configured to process the determined distributed strain information to generate a strain-related parameter compensated for temperature-induced strain. ### Claim 8 (depends on 1) The apparatus in claim 1, wherein the electronic circuitry includes an optical frequency domain reflectometer. ### Claim 9 (depends on 1) The apparatus in claim 1, wherein the curved portion of the optical fiber includes multiple periodic circular arcs, each arc covering 90 degrees, and wherein the electronic circuitry is configured to decompose the determined strain information at each of the multiple points using a Fourier transform. ### Claim 10 A method for measuring one or more mechanical parameters of an object subjected to a force and a temperature, where at least a curved portion of an optical fiber is attached to the object, the method comprising: using a distributed, optically-based, strain sensing technique to determine distributed strain information at each of multiple points along the curved portion of the optical fiber while the object is subjected to the force and the temperature; processing, using electronic circuitry, the determined distributed strain information to distinguish between temperature-induced strain and stress-induced strain on the object; and generating an output corresponding to one or both of the temperature-induced strain and stress-induced strain on the object. ### Claim 11 (depends on 10) The method in claim 10, further comprising processing the determined distributed strain information to calculate a 3rd order or 4th order harmonic value of the strain measured over a loop of optical fiber. ### Claim 12 (depends on 11) The method in claim 11, wherein the calculation of a 3rd order or 4th order harmonic strain value includes a frequency transform of the determined distributed strain information. ### Claim 13 (depends on 10) The method in claim 10, further comprising processing the determined distributed strain information to calculate a temperature at one or more points along the curved portion of the fiber. ### Claim 14 (depends on 13) The method in claim 13, further comprising processing the determined distributed strain information to calculate a temperature gradient at multiple loops along the optical fiber. ### Claim 15 (depends on 10) The method in claim 10, further comprising processing the determined distributed strain information to calculate first and second temperature gradients at multiple loops along the optical fiber. ### Claim 16 (depends on 10) The method in claim 10, further comprising processing the determined distributed strain information to generate a strain-related parameter compensated for temperature-induced strain. ### Claim 17 (depends on 10) The method in claim 10, wherein the distributed, optically-based, strain sensing technique is based on optical frequency domain reflectometry. ### Claim 18 (depends on 10) The method in claim 10, wherein the curved portion of the optical fiber includes multiple periodic circular arcs, each arc covering 90 degrees, the method further comprising decomposing the determined strain information at each of the multiple points using a Fourier transform.