Multi-function beam delivery fibers and related system and method

1. An optical fiber comprising:

multiple cores, at least one of the multiple cores forming an optical waveguide and having an elongated cross-section with a narrower dimension in a fast-axis direction and a wider dimension in a slow-axis direction, wherein an aspect ratio of the wider dimension to the narrower dimension exceeds about 30 to 1; and

a cladding surrounding the multiple cores, the cladding having a refractive index that differs from at least one refractive index of the multiple cores.

2. The optical fiber of claim 1 , wherein:

the multiple cores comprise first and second cores; and

the multiple cores are stacked such that the first core is located at least partially over the second core in the fast-axis direction.

3. The optical fiber of claim 1 , wherein:

the multiple cores comprise first and second cores; and

the optical fiber further comprises an additional core within the cladding and separated from the first and second cores, the additional core having a substantially circular cross-section.

4. The optical fiber of claim 3 , wherein:

the first core is configured to transport a high-power laser beam;

the second core is configured to transport an illumination laser beam; and

the additional core is configured to transport an alignment laser beam.

5. The optical fiber of claim 4 , wherein:

the first core is configured to transport the high-power laser beam having an average power of at least about 50 kW;

the second core is configured to transport the illumination laser beam having an average power of at least about 1 kW; and

the additional core is configured to transport the alignment laser beam having an average power of around 1 W.

6. The optical fiber of claim 1 , wherein:

the multiple cores comprise first and second cores; and

the first and second cores are coaxial.

7. The optical fiber of claim 1 , wherein the optical fiber is mechanically flexible more in the fast-axis direction and less in the slow-axis direction.

8. The optical fiber of claim 1 , wherein one or more of the multiple cores has a substantially rectangular cross-section.

9. An optical fiber comprising:

multiple cores, at least one of the multiple cores forming an optical waveguide and having an elongated cross-section with a narrower dimension in a fast-axis direction and a wider dimension in a slow-axis direction; and

a cladding surrounding the multiple cores, the cladding having a refractive index that differs from at least one refractive index of the multiple cores;

wherein the optical fiber has a length of at least two meters.

10. The optical fiber of claim 1 , wherein the optical fiber is configured to suppress stimulated Brillouin scattering (SBS) using at least one of:

transport of at least one laser beam having a frequency selected so that a ratio δv/δv B of signal bandwidth δv to SBS gain bandwidth δv B in the optical fiber increases SBS threshold power of the optical fiber;

longitudinal variations in acoustic velocity where different portions of the optical fiber contain different specific concentrations of one or more dopants;

longitudinal variations in acoustic velocity where different portions of the optical fiber operate at different temperatures; and

transverse variations in acoustic velocity having a transverse gradient in dopant concentrations in the optical fiber.

11. The optical fiber of claim 1 , further comprising:

an optical coupler configured to launch multiple laser beams into the optical fiber.

12. An optical fiber comprising:

multiple cores, at least one of the multiple cores forming an optical waveguide and having an elongated cross-section with a narrower dimension in a fast-axis direction and a wider dimension in a slow-axis direction;

a cladding surrounding the multiple cores, the cladding having a refractive index that differs from at least one refractive index of the multiple cores; and

an optical coupler configured to launch multiple laser beams into the optical fiber, wherein the optical coupler comprises a fused, all-glass coupler that is physically attached to an end of the optical fiber.

13. A method comprising:

generating multiple laser beams;

arranging the laser beams for entry into multiple cores of an optical fiber, at least one of the multiple cores forming an optical waveguide and having an elongated cross-section with a narrower dimension in a fast-axis direction and a wider dimension in a slow-axis direction, wherein an aspect ratio of the wider dimension to the narrower dimension exceeds about 30 to 1; and

transporting the laser beams using the optical fiber;

wherein a cladding surrounds the multiple cores, the cladding having a refractive index that differs from at least one refractive index of the multiple cores.

14. The method of claim 13 , wherein:

the multiple cores comprise first and second cores;

the multiple cores are stacked such that the first core is located at least partially over the second core in the fast-axis direction; and

arranging the laser beams comprises arranging the laser beams to enter the stacked cores.

15. A method comprising:

generating multiple laser beams;

arranging the laser beams for entry into first and second cores of an optical fiber, at least one of the first and second cores forming an optical waveguide and having an elongated cross-section with a narrower dimension in a fast-axis direction and a wider dimension in a slow-axis direction; and

transporting the laser beams using the optical fiber;

wherein:

a cladding surrounds the first and second cores, the cladding having a refractive index that differs from at least one refractive index of the first and second cores;

the optical fiber further comprises an additional core within the cladding and separated from the first and second cores, the additional core having a substantially circular cross-section; and

the method further comprises generating an additional laser beam and arranging the additional laser beam for entry into the additional core.

16. The method of claim 15 , wherein:

the first core transports a high-power laser beam;

the second core transports an illumination laser beam; and

the additional core transports an alignment laser beam.

17. The method of claim 13 , wherein:

the multiple cores comprise first and second cores;

the first and second cores are coaxial; and

arranging the laser beams comprises arranging the laser beams to enter the coaxial cores.

18. The method of claim 13 , further comprising:

mechanically moving the optical fiber more in the fast-axis direction and less in the slow-axis direction.

19. The method of claim 13 , further comprising suppressing stimulated Brillouin scattering (SBS) by at least one of:

selecting a frequency of at least one laser beam to be transported over the optical fiber so that a ratio δv/δv B of signal bandwidth δv to SBS gain bandwidth δv B in the optical fiber increases SBS threshold power of the optical fiber;

using longitudinal variations in acoustic velocity where different portions of the optical fiber contain different specific concentrations of one or more dopants;

using longitudinal variations in acoustic velocity where different portions of the optical fiber operate at different temperatures; and

using transverse variations in acoustic velocity having a transverse gradient in dopant concentrations in the optical fiber.

20. The method of claim 13 , further comprising:

launching multiple laser beams into the optical fiber using an optical coupler.

21. A system comprising:

multiple lasers configured to generate multiple laser beams; and

an optical fiber configured to transport the multiple beams, the optical fiber comprising:

one or more cores configured to transport the multiple beams, at least one of the one or more cores forming an optical waveguide and having an elongated cross-section with a narrower dimension in a fast-axis direction and a wider dimension in a slow-axis direction, wherein an aspect ratio of the wider dimension to the narrower dimension exceeds about 30 to 1; and

a cladding surrounding the one or more cores, the cladding having a refractive index that differs from at least one refractive index of the one or more cores.

22. The system of claim 21 , wherein the one or more cores comprise a single core configured to transport at least two of the laser beams.

23. The system of claim 21 , wherein:

the one or more cores comprise first and second cores; and

the first and second cores are stacked such that the first core is located at least partially over the second core in the fast-axis direction.

24. The system of claim 21 , wherein:

the one or more cores comprise first and second cores; and

the first and second cores are coaxial.

25. The system of claim 21 , wherein:

the one or more cores comprise first and second cores; and

the optical fiber further comprises an additional core within the cladding and separated from the first and second cores, the additional core having a substantially circular cross-section.

26. The system of claim 21 , wherein the optical fiber is configured to suppress stimulated Brillouin scattering (SBS) using at least one of:

transport of at least one laser beam having a frequency selected so that a ratio δv/δv B of signal bandwidth δv to SBS gain bandwidth δv B in the optical fiber increases SBS threshold power of the optical fiber;

longitudinal variations in acoustic velocity where different portions of the optical fiber contain different specific concentrations of one or more dopants;

longitudinal variations in acoustic velocity where different portions of the optical fiber operate at different temperatures; and

transverse variations in acoustic velocity having a transverse gradient in dopant concentrations in the optical fiber.

27. The system of claim 21 , further comprising:

an optical coupler configured to launch the laser beams into the optical fiber.

28. The system of claim 27 , wherein the optical coupler comprises one of:

at least one free space lens or mirror; and

a fused, all-glass coupler that is physically attached to an end of the optical fiber.