OPTICAL FIBER GRATING SENSORS AND METHODS OF MANUFACTURE

• US 20090123111A1
• Filed: 09/23/2008
• Published: 05/14/2009
• Est. Priority Date: 02/22/2006
• Status: Active Grant

• Current Assignee: Auris Health, Inc. (Johnson & Johnson)
• Original Assignee: Hansen Medical Incorporated (Johnson & Johnson)
• Inventors: Udd, Eric
• Granted Patent: US 8,989,528 B2
• Time in Patent Office: Days
• US Class Current: 385/13
• CPC Class Codes: A61B 2034/2061 using shape-sensors, e.g. fiber shape sensors with Bragg gratings
• CPC Class Codes: A61B 2034/301 for introducing or steering flexible instruments inserted into the body, e.g. catheters or endoscopes
• CPC Class Codes: A61B 2034/305 Details of wrist mechanisms at distal ends of robotic arms
• CPC Class Codes: A61B 2090/064 for measuring force, pressure or mechanical tension
• CPC Class Codes: A61B 34/77 Manipulators with motion or force scaling
• CPC Class Codes: A61B 5/06 Devices, other than using radiation, for detecting or locating foreign bodies for removing same A61B17/50 ; determining position of probes within or on the body of the patient
• CPC Class Codes: A61B 5/065 Determining position of the probe employing exclusively positioning means located on or in the probe, e.g. using position sensors arranged on the probe
• CPC Class Codes: A61B 5/066 Superposing sensor position on an image of the patient, e.g. obtained by ultrasound or x-ray imaging
• CPC Class Codes: G01D 5/35303 using a reference fibre, e.g. interferometric devices
• CPC Class Codes: G01D 5/35316 using a Bragg gratings
• CPC Class Codes: G01D 5/35354 Sensor working in reflection

Abstract

Systems and methods comprise or involve optical fibers having Bragg gratings. The optical fibers can be assembled in a parallel manner into a fiber sensor configuration. Bragg gratings can be written onto different cores of optical fibers. Bragg gratings may be written at a same or nearly same axial position for all optical fibers in the configuration and may be written at the same time and may have a substantially equal index of refraction variation and unequal lengths. Spaced Bragg gratings may also have characteristic sidelobe spectrums for tagging the respective gratings. Gratings can also be written at different wavelengths and over another grating at the same location.

Claims

1. A method of manufacturing a Bragg sensor system comprising a plurality of optical fibers, each optical fiber having a single fiber core, the method comprising:

assembling the plurality of optical fibers into a configuration in which their respective cores are aligned substantially parallel to one another; and

writing Bragg gratings onto the respective fiber cores at a same or nearly same axial position for all optical fibers in the configuration.

2. The method of claim 1, wherein a single interference pattern is used to write the Bragg gratings.

3. The method of claim 1, wherein the plurality of optical fibers comprises three optical fibers, and the configuration has a triangular geometry.

4. The method of claim 3, wherein the Bragg gratings on the respective fiber cores are written at the same time.

5. The method of claim 3, wherein the fibers are small diameter fibers having lengths suitable to support bending measurements.

6. The method of claim 1, wherein the fibers are maintained in the configuration by mechanically securing together respective ends of the fibers in a holding fixture.

7. The method of claim 1, wherein the fibers are maintained in the configuration by bonding the fibers together.

8. The method of claim 7, wherein the fibers are bonded together by heat fusing edges of the fibers together.

9. The method of claim 1, wherein writing Bragg gratings onto the respective fiber cores at a same or nearly same axial position is repeated at axially spaced apart locations along a grating region of the optical fiber configuration.

10. The method of claim 9, further comprising coating the grating region to facilitate transfer of strain between fibers during bending of the fibers.

11. The method of claim 10, wherein coating is performed before writing the Bragg gratings.

12. The method of claim 10, wherein the coating is performed after writing of the Bragg gratings.

13. The method of claim 10, wherein the grating region is coated with polyimide or glass frit.

14. The method of claim 9, wherein ends of the respective fibers of the configuration are mechanically constrained together prior to writing the Bragg gratings and/or applying the coating material.

15. The method of claim 9, wherein axially spaced apart Bragg gratings are written at a same or substantially same wavelength with low reflectivity.

16. The method of claim 9, wherein axially spaced apart Bragg gratings are written at differing wavelengths, and wherein the Bragg sensor system is for use with a wavelength division multiplexing output unit.

17. The method of claim 9, further comprising separating the fibers at a first end of the optical fiber configuration after writing the Bragg gratings and coating the grating region.

18. The method of claim 17, further comprising coupling connectors configured for interfacing with a fiber grating output unit to the respective separated ends of the fibers.

19. The method of claim 18, wherein the separated ends of the fibers are fusion spliced to respective larger diameter fibers that in turn are secured to the respective grating output unit connectors.

20. The method of claim 19, wherein the optical fibers of the configuration have a relatively small diameter in order to decrease the spectral dynamic range associated with a tightly bent optical fiber.

21. The method of claim 1, wherein the optical fibers of the configuration are single mode optical fibers.

22. An amplitude and spectral shape Bragg sensor optical fiber comprising a fiber core having an array of axially spaced Bragg gratings, the gratings being written with a substantially equal index of refraction variation and unequal lengths.

23. The optical fiber of claim 22, where a center to center distance between adjacent gratings of the array is maintained substantially uniform by sequencing the gratings of the array so that gratings having relatively short lengths are located adjacent to gratings having relatively long lengths.

24. A multiplexed amplitude and spectral shape Bragg sensor optical fiber, comprising:

a plurality of axially spaced arrays of Bragg gratings provided on a single optical fiber core, each array comprising a plurality of axially spaced gratings written on the optical fiber core with a substantially equal index of refraction variation and unequal lengths.

25. The optical fiber of claim 24, including

a first grating array corresponding to a first wavelength, and

a second grating array corresponding to a second wavelength and axially spaced from the first grating array, the first and second grating arrays having an identical number of individual Bragg gratings, wherein corresponding gratings of the respective first and second grating arrays have substantially equal lengths.

26. The optical fiber of claim 24, wherein a center to center distance between adjacent gratings of each array is maintained substantially uniform by sequencing the gratings of the array such that gratings having relatively short lengths are located adjacent to gratings having relatively long lengths.

27. The optical fiber of claim 24, wherein an overall spectral position of a respective Bragg grating of each array is uniquely determined by processing spectral profiles of each of the Bragg gratings to measure an overall amplitude of the respective gratings operating over a common spectral region.

28. A Bragg sensor optical fiber comprising an array of axially spaced Bragg gratings written on a single optical fiber core with non uniform spacing between refractive index periods that are unique to each grating resulting in unique characteristic sidelobe spectrums tagging the respective gratings.

29. The optical fiber of claim 28, wherein sidelobe structures of the respective gratings have different numbers of peaks.

30. The optical fiber of claim 28, wherein sidelobe structures of the respective gratings have different amplitudes.

31. A Bragg sensor system, comprising:

a plurality of single core optical fibers assembled into a fiber sensor configuration in which the respective fiber cores are aligned substantially parallel to one another, each fiber core having written thereon one or more Bragg grating arrays.

32. The system of claim 31, the plurality of optical fibers comprising three optical fibers bonded together in a triangular geometry and having lengths suitable to support bending measurements.

33. The system of claim 32, wherein the optical fibers have a relative small diameter in order to decrease the spectral dynamic range associated with a tightly bent optical fiber.

34. The system of claim 32, further comprising a hard coating material applied over a grating region of the bonded optical fibers to facilitate transfer of strain between fibers during subsequent bending.

35. The system of claim 34, wherein respective ends of the optical fibers are separated from one another extending out of one end of the coated grated region.

36. A system of claim 35, wherein the separated fiber ends of the sensor configuration are coupled to respective coupling connectors configured for interfacing with a grating output unit.

37. The system of claim 35, wherein the separated fiber ends are fusion spliced to respective larger diameter fibers that in turn are secured to the respective coupling connectors.

38. The system of claim 37, further comprising a multi-port tunable light source system having at least three ports configured for coupling to the respective coupling connectors, the one or more Bragg grating arrays comprising respective multiplexed Bragg grating arrays on the respective fiber cores of the fiber sensor configuration, the tunable light source system further comprising respective beamsplitter and detector assemblies used to read out the respective multiplexed grating arrays.

39. The system of claim 38, the tunable light source system further comprising an array of Bragg gratings on a fourth port to measure temperature.

40. The system of claim 38, further comprising a spectrally broadband light source including a dispersive output unit coupled to the bonded optical fibers via the respective connectors.

41. The system of claim 40, wherein the dispersive output unit comprises one or more bulk gratings and a detector array.

42. A system, comprising:

an elongate catheter instrument having a distal portion and a proximal portion that is more rigid than the distal portion; and

a Bragg sensor optical fiber coupled to the catheter instrument and comprising at least one optical fiber core having a distribution of Bragg gratings in which a number of gratings in a portion of the fiber core coupled to the proximal portion of the catheter instrument is lower than a number of gratings in a portion of the fiber core coupled to the distal portion of the catheter.

43. The system of claim 42, comprising a plurality of single core optical fibers assembled in a configuration in which the respective fiber cores are aligned substantially parallel to one another, each fiber core having written thereon respective multiplexed Bragg grating arrays.

44. The system of claim 42, wherein the multiplexed fiber gratings are supported by each of amplitude, spectrum and wavelength measurements.

45. An optical fiber including multiplexed Bragg gratings using a substantially same spectral space, comprising:

a first grating written at a wavelength λ

₁, and

a second spatially displaced set of dual overlaid gratings written at λ

₁+ε and

λ

₁−

ε

.

46. An optical fiber including multiplexed Bragg gratings using a substantially same spectral space, comprising:

a first grating at a wavelength λ

₁;

a second spatially displaced set of dual overlaid gratings at λ

₁+ε and

λ

₁−

ε

;

a third spatially displaced set of dual overlaid gratings at λ

₁+2ε and

λ

₁−

2ε

; and

an nth spatially displaced set of dual overlaid gratings at λ

₁+nε and

λ

₁−

nε

.

47. An optical fiber including multiplexed Bragg gratings using a substantially same spectral space, comprising:

a first grating at a wavelength λ

₁;

a second spatially displaced set of dual overlaid gratings at λ

₁+α

₁ and λ

₁−

β

₁, where α

₁ is not equal to β

₁;

a third spatially displaced set of dual overlaid gratings at λ

₁+α

₂ and λ

₁−

β

₂, where α

₂ is not equal to β

₂, and

an nth spatially displaced set of dual overlaid gratings at λ

₁+α

_n, and λ

₁−

β

_n, where α

_n is not equal to β

_n.

48. An optical fiber including multiplexed Bragg gratings using a substantially same spectral space, comprising:

a first grating at a wavelength λ

₁;

a second spatially displaced set of dual overlaid gratings at λ

₁+α

₁ and λ

₁−

β

₁, where α

₁ is not equal to β

₁;

a third spatially displaced set of three overlaid gratings at λ

₁+α

₂, λ

₁−

β

₂ and λ

₁−

ω

₂, where α

₂, β

₂, and ω

₂ are not equal; and

an nth spatially displaced set of n overlaid gratings λ

₁+α

_n, λ

₁−

β

_n, λ

₁−

ω

_n . . . λ

₁−

ζ

_n, where the spectral displacements of the overlaid gratings from λ

₁ are not equal.