Low diameter optical fiber
Small-radius coated optical fibers having large mode field diameter and low bending losses. The coated fiber may have an outer radius of 110 μm or less, while providing a mode field diameter of 9.0 μm or greater and a bending loss when wrapped about a 15 mm mandrel of 0.5 dB/km or less at wavelength of 1550 nm. The coated fiber may have a mode field diameter of 9.2 μm or greater and may have a bending loss at 1550 nm of 0.25 dB/km or less when wrapped about a 20 mm mandrel or a bending loss at 1550 nm of 0.02 dB/km or less when wrapped about a 30 mm mandrel.
1. A single-mode optical fiber comprising:
a core, said core having an outer radius r 1 and a refractive index profile selected from the group consisting of a Gaussian profile, a super-Gaussian profile, and an α-profile with α=2;
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 1.0 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 1200 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 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 0.10 dB/turn.
14. 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 0.05 dB/turn.
15. 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 15 mm, of less than 0.5 dB/turn.
16. 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 15 mm, of less than 0.25 dB/turn.
17. The fiber of claim 1 , wherein said primary coating has an in situ modulus of 0.50 MPa or less.
18. The fiber of claim 1 , wherein said primary coating has an in situ modulus of 0.20 MPa or less.
19. The fiber of claim 1 , wherein said secondary coating has an in situ modulus of 1500 MPa or greater.
20. The fiber of claim 1 , wherein said secondary coating has an in situ modulus of 1800 MPa or greater.
21. A cable comprising the fiber of claim 1 .
22. The fiber of claim 7 , wherein r 2 <8 μm.
23. The single-mode optical fiber of claim 1 , wherein said primary coating has an in situ modulus of 0.50 MPa or less, said secondary coating has an in situ modulus of 1500 MPa or greater, and said fiber exhibits a bend loss at a wavelength of 1550 nm, when turned about a mandrel having a diameter of 15 mm, of less than 0.5 dB/turn.
24. The single-mode optical fiber of claim 23 , wherein said fiber exhibits a bend loss at a wavelength of 1550 nm, when turned about a mandrel having a diameter of 15 mm, of less than 0.25 dB/turn.
25. The single-mode optical fiber of claim 1 , wherein said primary coating has an in situ modulus of 0.50 MPa or less, said secondary coating has an in situ modulus of 1500 MPa or greater, 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 0.25 dB/turn.