Optical catheter with double-clad fiber

1. A catheter comprising:

a double-clad fiber extending along an axis of the catheter, the double-clad fiber having a core a first annular cladding surrounding the core; and a second annular cladding integral with the first annular cladding; and

a lens assembly having a first sub-aperture in optical communication with the core and a second sub-aperture in optical communication with the first annular cladding.

2. The catheter of claim 1 , further comprising a beam re-director in optical communication with the lens assembly.

3. The catheter of claim 2 , wherein the beam re-director is selected from the group consisting of a mirror and a prism.

4. The catheter of claim 1 , wherein the lens assembly comprises an annular wedge prism.

5. The catheter of claim 4 , wherein the annular wedge prism comprises walls forming a hole that defines the first sub-aperture.

6. The catheter of claim 4 , wherein the annular wedge prism comprises a central zone having planar proximal and distal faces, the central zone defining the first sub-aperture.

7. The catheter of claim 4 , wherein the annular wedge prism comprises an annular zone having a frusto-conical face.

8. The catheter of claim 1 , wherein the lens assembly is configured to cause a first beam entering the first sub-aperture and a second beam entering the second sub-aperture to diverge from each other.

9. The catheter of claim 1 , wherein the lens assembly comprises a GRIN (“graduated index of refraction”) lens.

10. The catheter of claim 9 , wherein the GRIN (“graduated index of refraction”) lens comprises a central sub-aperture that is index-matched to the core of the double-clad fiber.

11. The catheter of claim 10 , wherein the GRIN (“graduated index of refraction”) lens further comprises an annular sub-aperture having a radially varying index of refraction.

12. The catheter of claim 9 , wherein the GRIN (“graduated index of refraction”) lens is an annular lens.

13. The catheter of claim 4 , wherein the annular wedge prism comprises a proximal face that is in contact with a distal face of the double-clad fiber.

14. The catheter of claim 1 , wherein the lens assembly is in contact with the double-clad fiber.

15. The catheter of claim 1 , wherein the lens assembly is integral with the double-clad fiber.

16. The catheter of claim 15 , wherein a distal face of the double-clad fiber is shaped to form a portion of the lens assembly.

17. The catheter of claim 16 , wherein the distal face of the double-clad fiber comprises sloped walls forming a recess.

18. The catheter of claim 1 , wherein the lens assembly comprises a beam-redirector, the beam-redirector having a central sub-aperture oriented to re-direct a beam in a first direction and an annular sub-aperture oriented to re-direct a beam in a second direction different from the first direction.

19. A distal tip assembly for a catheter, the distal tip assembly comprising:

a lens assembly for optically coupling to a multi-channel fiber having at least

a first channel for transmitting light carrying a first signal,

a second channel for transmitting light carrying a second signal, the second channel confining light carrying the first signal in the first channel, and

a cladding layer to confine light carrying the second signal in the second channel,

the lens assembly having

a first sub-aperture for optically coupling to the first channel of the multi-channel fiber, and

a second sub-aperture surrounding the first sub-aperture for optically coupling to the second channel of the multi-channel fiber.

20. The distal tip assembly of claim 19 , wherein the lens assembly comprises a prism having a first sub-aperture and a second sub-aperture, the first and second sub-aperture being in optical communication with first and second channels of the multi-channel fiber.

21. The distal tip assembly of claim 19 , wherein the first and second sub-apertures are disposed to optically couple a double-clad fiber having a core and an annular cladding layer surrounding the core.

22. The distal tip assembly of claim 20 , wherein the prism comprises an annular wedge prism.

23. The distal tip assembly of claim 21 , wherein the lens assembly comprises an annular wedge prism having a central sub-aperture disposed for optical coupling with the core of the double-clad fiber and an annular sub-aperture disposed for optical coupling with the annular cladding layer of the double-clad fiber.

24. A method for coupling light into and out of an optical catheter, the method comprising:

providing a multi-channel optical fiber extending along the catheter, the multi-channel optical fiber having at least

a first channel for transmitting light carrying a first signal, and

a second channel for transmitting light carrying a second signal, the second channel confining light carrying the first signal in the first channel;

directing a delivery beam from the first channel in a direction away from the optical catheter; and

directing light incident on the optical catheter into the second channel.

25. The method of claim 24 , wherein providing a multi-channel optical fiber comprises providing a double-clad fiber having a core and an annular cladding layer.

26. The method of claim 24 , wherein directing a delivery beam from the first channel in a direction away from the optical catheter comprises:

providing a lens element having first and second sub-apertures; and

optically coupling the first sub-aperture to the first channel.

27. The method of claim 24 , wherein directing light incident on the optical catheter into the second channel comprises:

providing a lens element having first and second sub-apertures; and optically coupling the second sub-aperture to the second channel.