Low diameter optical fiber

1. An optical fiber comprising:

a core, said core having an outer radius r 1 ;

a cladding surrounding said core, said cladding having an outer radius r 4 ;

a primary coating surrounding said cladding, said primary coating having an outer radius r 5 , said primary coating having an in situ modulus of 0.50 MPa or less; and

a secondary coating surrounding said primary coating, said secondary coating having an outer radius r 6 , said secondary coating having an in situ modulus of 1500 MPa or greater;

wherein said outer radius r 6 is 110 μm or less, said fiber has a mode field diameter of greater than 9 μm at 1310 nm, a cable cutoff wavelength of 1260 nm or less, a zero dispersion wavelength λ 0 in the range 1300 nm≦λ 0 ≦1324 nm, and said fiber exhibits a bend loss at a wavelength of 1550 nm, when turned about a mandrel having a diameter of 20 mm, of less than 0.5 dB/turn.

2. The fiber of claim 1 ,

wherein said cladding includes an inner cladding region having an outer radius r 3 and an outer cladding region surrounding said inner cladding region and having said outer radius r 4 , said inner cladding region having a refractive index Δ 3 with a minimum value Δ 3MIN , said outer cladding region having a refractive index Δ 4 with a minimum value Δ 4MIN >Δ 3MIN .

3. The fiber of claim 2 , wherein said inner cladding region is directly adjacent to said core and said refractive index Δ 3 is substantially constant between said outer radius r 1 and said outer radius r 3 .

4. The fiber of claim 2 , wherein said inner cladding region is directly adjacent to said core, said refractive index Δ 3 decreasing linearly between said outer radius r 1 and said outer radius r 3 .

5. The fiber of claim 4 , wherein said outer cladding region is directly adjacent said inner cladding region and said refractive index Δ 4 is substantially constant between said outer radius r 3 and said outer radius r 4 .

6. The fiber of claim 1 , wherein said cladding includes a first inner cladding region having an outer radius r 2 , a second inner cladding region surrounding said first inner cladding region and having an outer radius r 3 , and an outer cladding region surrounding said second inner cladding region and having said outer radius r 4 , said first inner cladding region having a refractive index Δ 2 with a minimum value Δ 2MIN , said second inner cladding region having a refractive index Δ 3 with a minimum value Δ 3MIN <Δ 2MIN , said outer cladding region having a refractive index Δ 4 with a minimum value Δ 4MIN >Δ 3MIN .

7. The fiber of claim 6 , wherein second inner cladding region is directly adjacent said first inner cladding region and said refractive index Δ 3 is substantially constant between said outer radius r 2 and said outer radius r 3 .

8. The fiber of claim 6 , wherein second inner cladding region is directly adjacent said first inner cladding region and said refractive index Δ 3 decreases linearly between said outer radius r 2 and said outer radius r 3 .

9. The fiber of claim 1 , wherein said outer radius r 4 is at least 60 μm.

10. The fiber of claim 1 , wherein said outer radius r 5 is 85 μm or less.

11. The fiber of claim 1 , wherein said outer radius r 6 is 100 μm or less.

12. The fiber of claim 1 , wherein said fiber exhibits a bend loss at a wavelength of 1550 nm, when turned about a mandrel having a diameter of 20 mm, of less than 0.25 dB/turn.

13. The fiber of claim 1 , wherein said cladding includes a depressed index region, said depressed index region having a moat volume with a magnitude between 30% μm 2 and 80% μm 2 .

14. The fiber of claim 1 , wherein said primary coating has an in situ modulus of 0.20 MPa or less.

15. The fiber of claim 1 , wherein said secondary coating has an in situ modulus of 1800 MPa or greater.

16. The fiber of claim 1 , wherein said primary coating has a glass transition temperature of less than −15° C.

17. The fiber of claim 1 , wherein said primary coating has a glass transition temperature higher than −50° C.

18. The fiber of claim 1 , wherein said primary coating has a glass transition temperature higher than −60° C.

19. The fiber of claim 1 , wherein said primary coating is the cured product of a primary composition that includes a urethane acrylate oligomer and a monomer selected from the group consisting of (meth)acrylates, N-vinyl amides, and epoxy acrylates.

20. The fiber of claim 19 , wherein said primary composition comprises one or more monofunctional (meth)acrylate monomers in an amount of from about 5 to 95% by weight; an N-vinyl amide monomer in an amount of from about 0.1 to 40% by weight; and one or more difunctional urethane acrylate oligomers which comprise a polyol and an isocyanate, said oligomer present in an amount of from about 5 to 95% by weight, wherein the polyol in said oligomer is a polypropylene glycol and the isocyanate in said oligomer is an aliphatic diisocyanate.

21. The fiber of claim 19 , wherein said primary composition comprises one or more monofunctional (meth)acrylate monomers in an amount of from about 40 to 65% by weight; an N-vinyl amide monomer in an amount of from about 2 to 10% by weight; and one or more polypropylene glycol-based difunctional urethane acrylate oligomers in an amount of from about 35 to 60% by weight.

22. The fiber of claim 1 , wherein said secondary coating is the cured product of a secondary composition that lacks urethane-containing oligomers.

23. The fiber of claim 22 , wherein said secondary composition comprises a monomer selected from the group consisting of alkoxylated bisphenol-A diacrylate, alkylene glycol acrylate, and epoxy diacrylate.

24. The fiber of claim 23 , wherein said secondary composition comprises:

about 40 to 80% by weight of ethoxylated (4) bisphenol A monomer;

from about 0 to about 30% by weight of ethoxylated (10) bisphenol A monomer;

from about 0 to about 25% by weight of ethoxylated (30) bisphenol A monomer; and

from about 5 to 18% by weight of epoxy acrylate.