Microstructured optical fibers and methods

• US 20070104437A1
• Filed: 10/18/2006
• Published: 05/10/2007
• Est. Priority Date: 11/08/2005
• Status: Active Grant

• Current Assignee: Corning Incorporated
• Original Assignee: Corning Incorporated
• Inventors: Li, Ming-Jun, Tandon, Pushkar, Bookbinder, Dana, Fiacco, Richard, Murtagh, Michael
• Granted Patent: US 7,450,806 B2
• Time in Patent Office: Days
• US Class Current: 385/125
• CPC Class Codes: C03B 2201/02 Pure silica glass, e.g. pure fused quartz
• CPC Class Codes: C03B 2201/31 doped with germanium
• CPC Class Codes: C03B 2203/14 Non-solid, i.e. hollow products, e.g. hollow clad or with core-clad interface
• CPC Class Codes: C03B 2203/42 Photonic crystal fibres, e.g. fibres using the photonic bandgap PBG effect, microstructured or holey optical fibres
• CPC Class Codes: C03B 37/01446 Thermal after-treatment of preforms, e.g. dehydrating, consolidating, sintering C03B37/01853 takes precedence
• CPC Class Codes: C03B 37/02781 Hollow fibres, e.g. holey fibres
• CPC Class Codes: C03C 13/00 Fibre or filament compositions manufacture of fibres or filaments C03B37/00
• CPC Class Codes: C03C 13/04 Fibre optics, e.g. core and clad fibre compositions light guides G02B6/00
• CPC Class Codes: G02B 1/048 characterised by the cladding material
• CPC Class Codes: G02B 6/02333 Core having higher refractive index than cladding, e.g. solid core, effective index guiding
• CPC Class Codes: G02B 6/02357 Property of longitudinal structures or background material varies radially and/or azimuthally in the cladding, e.g. size, spacing, periodicity, shape, refractive index, graded index, quasiperiodic, quasicrystals

Abstract

Microstructured optical fiber and method of making. Glass soot is deposited and then consolidated under conditions which are effective to trap a portion of the consolidation gases in the glass to thereby produce a non-periodic array of voids which may then be used to form a void containing cladding region in an optical fiber. Preferred void producing consolidation gases include nitrogen, argon, CO₂, oxygen, chlorine, CF₄, CO, SO₂ and mixtures thereof.

Claims

1. A microstructured optical fiber comprising:

a core region having a first refractive index and a cladding region having a second refractive index which is lower than that of the core region such that the light which is to be transmitted through the fiber is retained generally within the core, wherein the cladding comprises at least one region in the cladding which is comprised of a plurality of non-periodically located voids, greater than 95 percent of the voids having a maximum diameter of 1550 nm or less, said fiber exhibiting an attenuation at least one wavelength between 600 and 1550 nm which is less than 500 dB/km.

2. The microstructured optical fiber of claim 1, wherein greater than 95 percent of the voids in said fiber have a maximum diameter of 775 nm or less.

3. The optical fiber of claim 1, wherein said fiber exhibits an attenuation of less than 200 dB/km at 1550.

4. The optical fiber of claim 3, wherein the entire void containing region in the cladding of said fiber exhibits a regional void area percent of greater than about 0.5 percent and less than about 20 percent.

5. The optical fiber of claim 1, wherein said region containing non-periodically distributed holes is not immediately adjacent to the core.

6. The optical fiber of claim 3, wherein at least a portion of the cladding of said fiber within a 10 micron distance from said core exhibits a regional void area percent greater than about 1.0 percent.

7. The optical fiber of claim 1, wherein said core comprises germanium.

8. The optical fiber of claim 3, wherein said core comprises germanium.

9. The microstructured optical fiber of claim 7, wherein said fiber exhibits an increase in attenuation at 1550 nm when bent around a 10 mm diameter mandrel, which is less than 20 dB/turn.

10. The microstructured optical fiber of claim 1, wherein the maximum diameter of each one of said voids is less than 375 nm.

11. A microstructured optical fiber comprising:

a core region having a first refractive index and a cladding region having a second refractive index which is lower than that of the core region such that the light which is to be transmitted through the fiber is retained generally within the core region, wherein said cladding comprises a void containing region in the cladding which is comprised of a plurality of non-periodically located voids, wherein at least 95% of the voids in said void containing region have a maximum diameter of 1550 nm or less, wherein the fiber exhibits a total fiber void area percent which is greater than 0.01 percent

12. The microstructured optical fiber of claim 11, wherein said fiber exhibits a total fiber void area percent which is less than 10 percent.

13. The microstructured optical fiber of claim 11, wherein said fiber exhibits a mean fiber diameter of less than 1550 nm, and a standard deviation of said holes is less than 1 micron.

14. The microstructured optical fiber of claim 11, wherein said fiber exhibits an increase in attenuation at 1550 nm when bent around a 10 mm diameter mandrel, which is less than 20 dB/turn.

15. The microstructured optical fiber of claim 12, wherein said void containing region is spaced apart from said core.

16. The microstructured optical fiber of claim 11, wherein said void containing region comprises at least 25 holes, and the mean diameter of the holes in said void containing region is less than 2000 nm.

17. The microstructured optical fiber of claim 11, wherein said void containing region comprises at least 25 holes, and the mean diameter of the holes in said void containing region is less than 775 nm.

18. A microstructured optical fiber comprising:

a core region having a first refractive index and a cladding region having a second refractive index which is lower than that of the core region such that the light which is to be transmitted through the fiber is retained generally within the core region, wherein said cladding comprises a region in the cladding which surrounds the core region and is comprised of voids having a mean diameter less than about 2000 nm and a standard deviation less than about 750 nm, wherein said void containing region is spaced apart from the core region of said fiber.

19. The microstructured optical fiber of claim 18, wherein said hole containing region comprises between about 25 and 200 holes.

20. The microstructured optical fiber of claim 18, wherein the mean diameter of the holes in said hole containing region is less than 775 nm.

21. The microstructured optical fiber of claim 18, wherein said fiber exhibits an increase in attenuation at 1550 nm when bent around a 10 mm diameter mandrel, which is less than 20 dB/turn.

22. The microstructured optical fiber of claim 18, wherein said fiber exhibits an increase in attenuation at 1550 nm when bent around a 10 mm diameter mandrel, which is less than 15 dB/turn.

23. A method of making an optical fiber comprising forming via a CVD operation a soot containing optical fiber preform;

consolidating the soot in said soot containing preform in a gaseous atmosphere under conditions which are effective to trap a portion of said gaseous atmosphere in said preform during said consolidation step, thereby forming a consolidated preform having voids in said preform, and

using said preform in a manufacturing process to make an optical fiber having a core region having a first refractive index and a cladding region having a second refractive index lower than that of the core, said cladding comprising a region of non-periodically located voids surrounding said core having a total fiber void area percent, when the fiber is viewed in cross-section, that is greater than 0.05 percent.

24. The method of claim 23, wherein said consolidating step comprises consolidating said soot containing perform in a furnace a temperature greater than 1500 C and heating said perform at least a first temperature ramp rate grater than 10 C, and said gaseous atmosphere comprises at least one gas selected from the group consisting of nitrogen, argon, CO₂, oxygen, chlorine, CF4, CO, SO2 and mixtures thereof, and wherein said using said perform in a manufacturing process step comprises drawing an optical fiber from said perform such that said voids formed in consolidating step are retained in said fiber.

25. The method of claim 23, wherein said soot containing perform in said consolidating step comprises at least a void free core region onto which additional soot has been deposited via said CVD operation, and said consolidating step results in said perform having voids in the cladding region of said consolidated preform.

26. The method of claim 23, wherein the maximum cross sectional diameter of each of said voids is less than 1550 nm.

27. The method of claim 24, wherein said soot preform comprises a tubular preform, and said consolidated preform comprises a tubular preform.

28. The method of claim 23, wherein said forming step comprises depositing soot via CVD onto the outside of a glass core rod and said consolidating step takes place after said forming step.

29. The method of claim 23, wherein said using said perform step further comprises drawing said consolidated preform into an optical fiber, wherein said voids which were formed during said consolidation step are retained and deformed during said drawing step and remain in the fiber after said drawing step.

30. The method of claim 23, wherein said gaseous atmosphere comprises at least one gas selected from the group consisting of argon, nitrogen, carbon monoxide, carbon dioxide, oxygen, CF4, C2F6, Kr, and mixtures thereof.

31. A method of making an optical fiber comprising forming via a CVD operation a soot containing optical fiber preform;

consolidating the soot preform in a gaseous atmosphere which comprises at least one gas selected from the group consisting of nitrogen, argon, CO₂, oxygen, chlorine, CF4, CO, SO2 and mixtures thereof under conditions which are effective to trap a portion of said gaseous atmosphere in said preform during said consolidation step, thereby resulting in the formation of voids in said consolidated preform, and

using said consolidated preform in a manufacturing process to form an optical fiber having a core region having a first refractive index and a cladding region having a second refractive index lower than that of the core such that light which is transmitted through the fiber is retained generally within the core, whereby said voids are located at least substantially in the cladding of said optical fiber.

32. The method of claim 31, wherein said consolidating step comprises first exposing said preform to a temperature greater than about 1500 C and a feed rate into a consolidation furnace sufficient to result in at least a portion of said preform increasing in temperature at a rate greater than about 12°

C./min.

33. The method of claim 31, wherein said consolidating step comprises first exposing said preform to a temperature and feed rate into a consolidation furnace sufficient to result in said preform increasing in temperature at a rate greater than about 14°

C./min.

34. The method of claim 33, wherein said consolidating step comprises exposing the preform in a furnace which is maintained at a temperature of equal to or greater than 1390°

C.

35. The method of claim 32, wherein said consolidating step further comprises, subsequent to said first exposing step, exposing said preform to a temperature and feed rate into a consolidation furnace sufficient to result in said preform increasing in temperature at a rate which is at least 2°

C./min less than in said first exposing step.

36. The method of claim 32, wherein said consolidating step further comprises, subsequent to said first exposing step, exposing said preform to a temperature and feed rate into a consolidation furnace sufficient to result in said preform increasing in temperature at a rate which is at least 2°

C./min less than in said first exposing step.

37. The method of claim 35, wherein said atmosphere comprises at least one gas selected from the group consisting of nitrogen, argon and combinations thereof in an amount greater than 85 percent by volume, the remainder of said atmosphere at least substantially made up of helium.

38. The method of claim 31, wherein said atmosphere comprises nitrogen and/or argon in an amount greater than 65 percent by volume.

39. The method of claim 31, said method further comprising either (1) forming said soot containing preform by depositing said soot onto a core cane doped with germanium or (2) inserting a germanium doped core cane into a void containing cladding region formed via said consolidating step.

40. The method of claim 31, wherein said region containing non-periodically distributed holes is not immediately adjacent to the core.

41. A microstructured optical fiber which is multimoded at 1550 nm, said fiber comprising;

a core region having a first refractive index and a cladding region having a second refractive index which is lower than that of the core region such that the light which is to be transmitted through the fiber is retained generally within the core, wherein the cladding comprises at least one region in the cladding which is comprised of a plurality of non-periodically located voids, said fiber is multimoded at 1550 nm and exhibits an increase in attenuation at 1550 nm, when said fiber is wrapped once around a mandrel having a radius of 5 mm, which is less than 1 dB/turn.