Methods and apparatus for determining shape parameter(s) using a sensing fiber having a single core with multiple light propagating modes

Patent metadata

Field	Value
Publication number	US-11940305-B2
Application number	US-202217899463-A
Country	US
Kind code	B2
Filing date	Aug 30, 2022
Priority date	Dec 29, 2016
Publication date	Mar 26, 2024
Grant date	Mar 26, 2024

Abstract

Example embodiments include an optical interrogation system with a sensing fiber having a single core, the single core having multiple light propagating modes. Interferometric apparatus probes the single core multimode sensing fiber over a range of predetermined wavelengths and detects measurement interferometric data associated with the multiple light propagating modes of the single core for each predetermined wavelength in the range. Data processing circuitry processes the measurement interferometric data associated with the multiple light propagating modes of the single core to determine one or more shape-sensing parameters of the sensing fiber from which the shape of the fiber in three dimensions can be determined.

First claim

We claim:

1. A system for interrogating an optical sensing fiber comprising a multimode core, the system comprising:
multiple reference branches and multiple measurement branches, the multiple measurement branches comprising an array of single-core, single-mode optical fibers, each optical fiber of the array of single-core, single-mode optical fibers having a different optical delay;
a tunable laser configured to generate laser light over a range of wavelengths, the laser light configured to be coupled into the multiple reference branches and the multiple measurement branches for interferometrically probing the multimode core; and
a micro lens array and collimator lens configured to optically couple the laser light from the array of single-core, single-mode optical fibers into the multimode core, and configured to image backward traveling multimode light from the multimode core onto the array of single-core, single-mode optical fibers, wherein light from each mode of the backward traveling multimode light is directed into a corresponding fiber of the single-core, single-mode optical fibers.

2. The system of claim 1 , wherein the micro lens array has a numerical aperture between 0.1 and 0.25.

3. The system of claim 1 , further comprising acquisition circuitry, the acquisition circuitry comprising multiple detectors configured to detect measurement interferometric data at an output of the multiple interferometers, the measurement interferometric data corresponding to reference light combined with the backward traveling multimode light directed into the array of single-core, single-mode optical fibers.

4. The system of claim 3 , further comprising data processing circuitry configured to:
determine coupling coefficients from the measurement interferometric data, the coupling coefficients being between light input from the array of single-core, single-mode optical fibers into the multimode core and light output from the multimode core to the array of single-core, single-mode optical fibers; and
determine, from the coupling coefficients, cross-coupling coefficients between forward traveling modes in the multimode core and backward traveling modes in the multimode core.

5. The system of claim 3 , further comprising:
the optical sensing fiber, wherein the multimode core includes a grating pattern that varies with bend, strain, and twist applied to the optical sensing fiber; and
data processing circuitry configured to process the measurement interferometric data to determine a variation in the grating pattern, and to determine the bend, strain, and twist applied to the optical sensing fiber based at least in part on the variation in the grating pattern.

6. The system of claim 5 , wherein the grating pattern comprises overlapping tilted grating written in the multimode core.

7. The system of claim 5 , wherein the grating pattern is associated with a cross-sectional index perturbation of the optical sensing fiber, and wherein the cross-sectional index perturbation is associated with cross-coupling coefficients between forward traveling modes in the multimode core and backward traveling modes in the multimode core.

8. The system of claim 7 , wherein the data processing circuitry is further configured to process the measurement interferometric data to determine the cross-coupling coefficients, and to determine the variation in the grating pattern based at least in part on the cross-coupling coefficients.

9. The system of claim 1 , further comprising the optical sensing fiber, wherein the multimode core has a shape that limits a number of modes in the backward traveling multimode light in the multimode core below a predetermined number while providing a predetermined sensitivity to twist applied to the optical sensing fiber.

10. The system of claim 9 , wherein the multimode core is ring-shaped in cross-section.

11. A method for interrogating an optical sensing fiber comprising a multimode core, the method comprising:
generating laser light over a range of wavelengths;
coupling the laser light into multiple interferometers, the multiple interferometers including multiple reference branches and multiple measurement branches, the multiple measurement branches comprising an array of single-core, single-mode optical fibers, each fiber of the array of single-core, single-mode optical fibers having a different optical delay; and
using a micro lens array and a collimator lens to couple the laser light from the array of single-core, single-mode optical fibers into the multimode core, and to image backward traveling multimode light from the multimode core onto the array of single-core, single-mode optical fibers, wherein light from each mode of the backward traveling multimode light is directed into a corresponding fiber of the single-core, single-mode optical fibers.

12. The method of claim 11 , further comprising:
detecting, at an output of the multiple interferometers, measurement interferometric data corresponding to reference light combined with the backward traveling multimode light directed into the array of single-core, single-mode optical fibers.

13. The method of claim 12 , further comprising:
determining coupling coefficients from the measurement interferometric data, the coupling coefficients being between light input from the array of single-core, single-mode optical fibers into the multimode core and light output from the multimode core to the array of single-core, single-mode optical fibers.

14. The method of claim 13 , further comprising:
determining, from the coupling coefficients, cross-coupling coefficients between forward traveling modes in the multimode core and backward traveling modes in the multimode core.

15. The method of claim 12 , wherein the multimode core includes a grating pattern that varies with bend, strain, and twist applied to the optical sensing fiber, the method further comprising:
determining a variation in the grating pattern based at least in part on the measurement interferometric data; and
determining, based at least in part on the variation in the grating pattern, the bend, strain, and twist applied to the optical sensing fiber.

16. The method of claim 15 , wherein the grating pattern comprises overlapping tilted grating written in the multimode core.

17. The method of claim 15 , wherein the grating pattern is associated with a cross-sectional index perturbation of the optical sensing fiber and the cross-sectional index perturbation is associated with cross-coupling coefficients between forward traveling modes in the multimode core and backward traveling modes in the multimode core, and wherein determining the variation in the grating pattern comprises:
processing the measurement interferometric data to determine the cross-coupling coefficients, and
determining the variation in the grating pattern based at least in part on the cross-coupling coefficients.

18. The method of claim 11 , wherein the multimode core has a shape that limits a number of modes in the backward traveling multimode light in the multimode core below a predetermined number while providing a predetermined sensitivity to twist applied to the optical sensing fiber.

19. The method of claim 18 , wherein the multimode core is ring-shaped in cross-section.

20. The method of claim 11 , wherein the micro lens array has a numerical aperture between 0.1 and 0.25.

Assignees

• Intuitive Surgical Operations

Inventors

• Froggatt Mark E
• Gifford Dawn K
• Sanborn Eric E
• Sang Alexander K

Classifications

• G01D5/35316 Primary

  using a Bragg gratings · CPC title

• G01J1/0425

  using optical fibers · CPC title

• G02B6/02042

  Multicore optical fibres · CPC title

• G02B6/02085

  characterised by the grating profile, e.g. chirped, apodised, tilted, helical · CPC title

• G02B6/02142

  based on illuminating or irradiating an amplitude mask, i.e. a mask having a repetitive intensity modulating pattern · CPC title