Low bend loss single mode optical fiber with chlorine updoped cladding
An optical fiber having both low macrobend loss and low microbend loss. The fiber has a central core region, a first (inner) cladding region surrounding the central core region and having an outer radius r 2 >16 microns and relative refractive index Δ 2 , and a second (outer) cladding region surrounding the first cladding region having relative refractive index, Δ 3 , wherein Δ 1 >Δ 3 >Δ 2 . The difference between Δ 3 and Δ 2 is greater than 0.12 percent. The fiber exhibits a 22 m cable cutoff less than or equal to 1260 nm, and r 1 /r 2 is greater or equal to 0.24 and bend loss at 1550 nm for a 15 mm diameter mandrel of less than 0.5 dB/turn.
1. An optical fiber comprising:
(i) a central core region having outer radius r 1 and refractive index Δ 1
(ii) a cladding surrounding the central core region, the cladding comprising:
(a) a first cladding region having an outer radius 25 microns>r 2 >16 microns and relative refractive index Δ 2 , wherein the ratio of r 1 /r 2 is larger than 0.24 and
(b) a second cladding region surrounding the first cladding region and having a relative refractive index Δ 3 and an outer radius r 3 , wherein the second cladding region comprises at least 1.25 wt % chlorine (Cl), and wherein Δ 1 >Δ 3 >Δ 2 , and wherein the difference between Δ 3 and Δ 2 is greater than 0.12%, and Δ 3 >0.12%;
and said fiber exhibits a bend loss at 1550 nm for a 15 mm diameter mandrel of less than 0.5 dB/turn.
2. The optical fiber of claim 1 , wherein the difference between Δ 3 and Δ 2 is greater than 0.13%.
3. The optical fiber of claim 1 , wherein the difference between Δ 3 and Δ 2 is between 0.12% and 0.25%.
4. The optical fiber of claim 1 , wherein said fiber exhibits a 22 m cable cutoff less than or equal to 1260 nm.
5. The optical fiber of claim 1 , wherein the central core region of said fiber exhibits an alpha less than 10.
6. The optical fiber of claim 1 , said fiber further exhibiting a wire mesh covered drum microbend loss at 1550 nm which is less than or equal to 0.07 dB/km.
7. The optical fiber of claim 1 , wherein the first cladding region contains less than 0.02 wt % fluorine.
8. The optical fiber of claim 1 , wherein the first cladding region is essentially free of fluorine and germania.
9. The optical fiber of claim 1 , wherein Δ 3 >Δ 2 for a length extending from r 2 to a radius of at least 30 microns.
10. The optical fiber of claim 1 , wherein the volume of the first cladding region is |V 2 |>30% □micron 2 .
11. The fiber of claim 1 , wherein said fiber exhibits an attenuation at 1550 nm which is less than or equal to 0.186 dB/km.
12. The optical fiber of claim 1 , wherein said central core region comprises a maximum relative refractive index (Δ 1 ) of greater than or equal to 0.70%.
13. The optical fiber of claim 1 , wherein the central core region of said fiber exhibits an alpha greater than or equal to 0.5 and less than or equal to 10.
14. The fiber of claim 1 , wherein the optical fiber exhibits:
1200 nm ≤cable cutoff wavelength ≤1260 nm;
1300 nm ≤zero dispersion wavelength ≤1324 nm;
0.7 dB/turn <macrobend loss at 10 mm bend diameter <1.3 dB/turn;
0.1 dB/turn <macrobend loss at 15 mm bend diameter<0.5 dB/turn;
0.05 dB/turn <macrobend loss at bend 20 mm diameter <0.20 dB/turn;
0.1 dB/turn <macrobend loss at 30 mm bend diameter <0.2 dB/turn;
wherein the macrobend loss is measured at 1550 nm wavelength.
15. The optical fiber of claim 1 , wherein the volume of the first cladding region is |V 2 |>60% Δ micron 2 .
16. The optical fiber comprising:
(i) a central core region having outer radius r 1 and refractive index Δ 1
(ii) a cladding surrounding the central core region, the cladding comprising:
(a) a first cladding region having an outer radius 25 microns>r 2 >16 microns and relative refractive index Δ 2 , wherein the ratio of r 1 /r 2 is larger than 0.24 and
(b) a second cladding region surrounding the first cladding region and having a relative refractive index Δ 3 and an outer radius r 3 , wherein the second cladding region comprises at least 1.25 wt % chlorine (Cl), and wherein Δ 1 >Δ 3 >Δ 2 , and wherein the difference between Δ 3 and Δ 2 is greater than 0.12%, and Δ 3 >0.12%;
and said fiber exhibits a bend loss at 1550 nm for a 15 mm diameter mandrel of less than 0.5 dB/turn, said fiber having a coating thereon and exhibiting a basketweave microbend loss at −60° C. at 1550 nm which is less than or equal to 0.05 dB/km.
17. The optical fiber of claim 16 , wherein said fiber exhibits a 22 m cable cutoff less than or equal to 1260 nm.
18. An optical fiber comprising:
(i) a central core region having outer radius r 1 and refractive index Δ 1 ;
(ii) a cladding surrounding the central core region, the cladding comprising:
(a) a first cladding region having an outer radius 25 microns>r 2 >16 microns and relative refractive index Δ 2 , wherein the ratio of r 1 /r 2 is larger than 0.24, and
(b) a second cladding region surrounding the first cladding region and having a relative refractive index Δ 3 and an outer radius r 3 , wherein the second cladding region comprises at least 1.2 wt % chlorine (Cl), and wherein Δ 1 >Δ 3 >Δ 2 , and wherein the difference between Δ 3 and Δ 2 is greater than 0.12%, and Δ 3 >0.12%;
said fiber exhibits a bend loss at 1550 nm for a 15 mm diameter mandrel of less than 0.5 dB/turn said fiber further comprising a third cladding region surrounding the second cladding region, the third region having a refractive index Δ 4 , wherein Δ 3 >Δ 4 , and wherein the difference between Δ 3 and Δ 4 is greater than 0.1%, and −0.02<Δ4 <0.02.
19. The optical fiber of claim 18 , wherein the third cladding region includes less chlorine than the second cladding region, or no chlorine.
20. The optical fiber of claim 19 wherein, the third cladding region has viscosity that is larger than the viscosity of the second cladding region by at least 0.1×107 Poise.
21. The optical fiber of claim 18 , wherein the third cladding region includes less than 1 wt % of chlorine.
22. The optical fiber of claim 18 , wherein said fiber exhibits a 22 m cable cutoff less than or equal to 1260 nm.
23. The optical fiber of claim 22 , wherein the second cladding region comprises at least 1.3 wt % chlorine (Cl).
24. The optical fiber of claim 22 , said fiber further exhibiting a basketweave microbend loss at −60° C. at 1550 nm which is less than or equal to 0.01 dB/km.
25. The optical fiber of claim 22 , said fiber further exhibiting a basketweave microbend loss at −60° C. at 1625 nm which is less than or equal to 0.05 dB/km.
26. The optical fiber of claim 22 , said fiber further exhibiting a basketweave microbend loss at −60° C. at 1625 nm which is less than or equal to 0.01 dB/km.
27. The optical fiber of claim 22 , wherein said coating comprises: a primary coating P having a Young's modulus 0.1 to 1 MPa; and a secondary coating S having a Young's modulus of 1400 MPa to 2500 MPa, wherein the secondary coating has an outer coating diameter of not greater than 242 microns.
28. The fiber of claim 1 , wherein the optical fiber exhibits:
MFD at 1310 nm >9 microns;
cable cutoff wavelength ≤1260 nm;
zero dispersion wavelength, □0, of 1300 nm ≤□0 ≤1324 nm;
bend loss at 10 mm diameter <1.5 dB/turn;
bend loss at 15 mm diameter <0.5 dB/turn
wherein the bend loss is macrobend loss and is measured at 1550 nm wavelength.
29. The fiber of claim 28 , wherein said fiber exhibits a wire mesh covered drum macrobend loss at 1550 nm which is less than or equal to 0.07 dB/km.
30. The fiber of claim 28 , wherein said fiber exhibits an attenuation at 1550 nm which is less than or equal to 0.18 dB/km.