Archimedean-lattice microstructured optical fiber

1. A microstructured optical fiber, comprising:

a light-guiding core; and

a primary cladding surrounding said core, wherein said primary cladding comprises a plurality of holes extending parallelly to said light-guiding core, arranged in hexagonal unit cells and defining an Archimedean-like lattice transverse to said light-guiding core, each of said holes being fully enclosed within one of said hexagonal unit cells.

2. The microstructured optical fiber according to claim 1 , wherein said core is defined by a break in a center of said Archimedean-like lattice, said break being characterised by an absence of at least one of said unit cells.

3. The microstructured optical fiber according to claim 1 , wherein said Archimedean-like lattice comprises at least one complete ring of said unit cells arranged circumferentially around said core.

4. The microstructured optical fiber according to claim 3 , wherein said Archimedean-like lattice comprises one incomplete outer ring of said unit cells arranged circumferentially around said at least one complete ring.

5. The microstructured optical fiber according to claim 1 , wherein each of said unit cells comprise seven of said holes arranged in a centred hexagon.

6. The microstructured optical fiber according to claim 1 , wherein each of said unit cells comprises six of said holes of said plurality of holes arranged in a hexagon.

7. The microstructured fiber according to claim 1 , wherein each of said unit cells comprises nineteen of said holes.

8. The microstructured optical fiber according to claim 1 , wherein each of said unit cells comprises eighteen of said holes.

9. The microstructured optical fiber according to claim 1 , wherein said core is substantially solid.

10. The microstructured optical fiber according to claim 1 , wherein said core is made of a vacuum or air.

11. The microstructured optical fiber according to claim 1 , wherein said holes are substantially circular in shape.

12. The microstructured optical fiber according to claim 1 , wherein said holes have a refractive index which is less than a refractive index of the primary cladding.

13. The microstructured optical fiber according to claim 1 , wherein said holes are defined by vacuum or air.

14. The microstructured optical fiber according to claim 1 , wherein said optical fiber further comprises an overcladding surrounding the primary cladding.

15. A method for making a microstructured optical fiber comprising the step of:

(I) fabricating a fiber preform comprising the steps of:

(a) providing a rod for defining a light-guiding core;

(b) fabricating a plurality of canes, each of said plurality of canes having a substantially hexagonal cross-section and comprising a number of holes arranged in a unit cell and defining an Archimedean-like lattice, each of said holes being fully enclosed within said unit cell; and

(c) stacking said plurality of canes concentrically around said rod.

16. The method according to claim 15 , wherein said fabricating a plurality of canes of step (I)(b) comprises the substeps of:

(i) providing a rod;

(ii) drilling said number of holes longitudinally through said rod and milling said rod to give said rod the hexagonal cross-section;

(iii) drawing said rod into an elongated cane;

(iv) cutting said elongated cane to obtain one of said plurality of canes; and

(v) repeating steps (iii) to (iv) to obtain said plurality of canes.

17. The method according to claim 15 , wherein said fabricating a plurality of canes of step (I)(b) comprises the substeps of:

(i) fabricating a cane preform by stacking rods to form said number of holes arranged in a unit cell and defining an Archimedean-like lattice;

(ii) drawing said cane preform into an elongated cane;

(iii) cutting said elongated cane to obtain one of said plurality of canes; and

(iv) repeating steps (ii) to (iii) to obtain said plurality of canes.

18. The method according to claim 17 , wherein said stacking rods of step (I)(b)(i) comprises assembling rods and solid filler rods.

19. The method according to claim 18 , comprising an additional step before step (ii) of overcladding said cane preform.

20. The method according to claim 19 , comprising an additional step of etching said elongated cane.

21. The method according to claim 15 , wherein said fabricating a plurality of canes of step (I)(b) comprises a substep of filling said holes with a solid material capable of being drawn.

22. The method according to claim 15 , wherein said fabricating a fiber preform further comprises an additional step of overcladding said fiber preform.

23. The method according to claim 22 , further comprising an additional step, after said step of overcladding, of partially filling spaces by inserting solid filler rods.

24. The method according to claim 15 , further comprising an additional step (II) of drawing said fiber preform into said microstructured optical fiber.

25. The method according to claim 24 , wherein said rod of step (I)(a) has a substantially hexagonal cross-section and comprises a number of holes arranged in said unit cell and defining said Archimedean-like lattice, each of said holes being fully enclosed within one of said hexagonal unit cells, and wherein step (II) comprises a substep of regulating pressure in said number of holes of said rod during said drawing to collapse said number of holes of said rod and create a solid core in said microstructured optical fiber.