Small diameter low attenuation optical fiber

1. An optical fiber comprising:

a core, said core having an outer radius r 1 , wherein r 1 is 3.6 microns to 5.4 microns;

a cladding surrounding said core, said cladding having an outer radius r 4 , wherein r 4 is less than 45 microns;

a primary coating surrounding said cladding, said primary coating having an outer radius r 5 and a thickness t P >8 microns, an in situ modulus E P , wherein E P is 0.35 MPa or less, and a spring constant χ P <1.6 MPa, where χ P =2E P r 4 /t P ; and

a secondary coating surrounding said primary coating, said secondary coating having an outer radius r 6 and a thickness t S =r 6 −r 5 , and an in situ modulus E S of 1200 MPa or greater,

wherein t S is greater than 10 microns, said outer radius r 6 is 85 microns or less, and said fiber has a mode field diameter MFD greater than 8.2 microns at 1310 nm, a fiber cutoff wavelength of less than 1310 nm, and

said fiber exhibits a bend loss when wrapped around a mandrel having a diameter of 10 mm, of less than 1.0 dB/turn at a wavelength of 1550 nm, and

said fiber exhibits a puncture resistance load greater than 30 grams and a wire mesh drum microbending attenuation of less than 0.5 dB/turn at a wavelength of 1550 nm.

2. The fiber of claim 1 , wherein t S >12 microns.

3. The fiber of claim 1 , wherein 24 microns≤r 4 ≤45 microns.

4. The fiber of claim 1 , wherein 38 microns≤r 4 ≤42 microns.

5. The fiber of claim 1 , wherein 30 microns≤r 4 ≤35 microns.

6. The fiber of claim 3 , wherein r 6 ≤75 microns.

7. The fiber of claim 4 , wherein 75 microns≤r 6 ≤85 microns.

8. The fiber of claim 5 , wherein 60 microns≤r 6 ≤65 microns.

9. The fiber according to claim 2 , wherein 39 microns≤r 4 ≤41 microns and 75 microns≤r 6 ≤85 microns.

10. The fiber according to claim 5 , wherein 30 microns≤r 4 ≤32.5 microns and 60 microns≤r 6 ≤75 microns.

11. The fiber according to claim 1 , wherein χ P ≤1.3 MPa.

12. The fiber according to claim 1 , wherein χ P ≤1.0 MPa.

13. The fiber according to claim 1 , wherein 0.5≤t P /t S ≤1.5.

14. The fiber according to claim 1 , wherein MFD is greater than 8.6 microns at 1310 nm.

15. The fiber of claim 1 , wherein said cladding includes a first inner cladding region having an outer radius r 2 and a relative refractive index Δ 2 , and a second inner cladding region surrounding said first inner cladding region and having an outer radius r 3 , said second inner cladding region having a relative refractive index Δ 3 with a minimum value Δ 3MIN , wherein Δ 3MIN <−0.2%.

16. The fiber of claim 15 , wherein said first inner cladding region is directly adjacent to said core and said relative refractive index Δ 2 is substantially constant between said outer core radius r 1 and said outer radius r 2 .

17. The fiber of claim 15 , wherein −0.05≤Δ 2 ≤0.5.

18. The fiber of claim 1 , wherein said fiber exhibits a bend loss, when turned about a mandrel having a diameter of 10 mm, of less than 0.5 dB/turn at a wavelength of 1550 nm.

19. The fiber of claim 1 , wherein said primary coating has an in situ modulus of 0.3 MPa or less.

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

21. The fiber of claim 1 , wherein r 4 is 38 to 42 microns, r 5 is 60 microns to 65 microns, and r 6 is 77.5 microns to 82.5 microns.

22. The fiber of claim 1 , wherein r 4 is 38 microns to 42 microns, r 5 is 45 microns to 55 microns, r 6 is 60 microns to 65 microns.