Coated optical fibers

1. A coated optical fiber comprising:

(i) an optical fiber;

(ii) a primary coating; and

(iii) a secondary coating;

wherein

(a) said coated optical fiber has an attenuation increase of less than 0.650 dB/km at 1550 nm;

(b) said primary coating has a modulus retention ratio after hydrolytic aging of at least 0.5 and/or a glass transition temperature (Tg) below −35° C.; and

(c) said primary coating is obtained by curing a primary coating composition having a cure dose to attain 95% of the maximum attainable modulus of less than 0.65 J/cm 2 .

2. The coated optical fiber of claim 1 , wherein said primary coating has an in-situ modulus of less than 0.60 MPa.

3. The coated optical fiber of claim 1 , wherein said primary coating has an in-situ modulus of less than 0.56 MPa.

4. The coated optical fiber of claim 1 , wherein said attenuation increase is less than 0.5 dB/km.

5. The coated optical fiber of claim 1 , wherein said primary coating composition comprises an ethylenically unsaturated oligomer.

6. The coated optical fiber of claim 5 , wherein said oligomer is prepared by reacting the following components:

(1) one or more polyisocyanates;

(2) one or more polyols; and

(3) one or more hydroxyfunctional (meth)acrylates.

7. The coated optical fiber of claim 6 , wherein said one or more polyols includes polypropylene glycol.

8. The coated optical fiber of claim 6 , wherein said one or more polyols consists essentially of polypropylene glycol.

9. The coated optical fiber of claim 6 , wherein said one or more polyols includes a polyester polyol.

10. The coated optical fiber of claim 6 , wherein said one or more polyols each have a molecular weight of at least 3,000 g/mol.

11. The coated optical fiber of claim 6 , wherein said one or more hydroxyfunctional (meth)acrylates includes hydroxyethyl acrylate.

12. The coated optical fiber of claim 1 , wherein said primary coating composition comprises one or more monomers.

13. The coated optical fiber of claim 12 , wherein said one or more monomers includes an alkoxylated acrylate monomer.

14. The coated optical fiber of claim 12 , wherein said one or more monomers includes an alkoxylated aliphatic polyacrylate monomer.

15. The coated optical fiber of claim 1 , wherein said cure dose is below 0.55 J/cm 2 .

16. The coated optical fiber of claim 1 , wherein said primary coating has a Tg below −35° C.

17. The coated optical fiber of claim 1 , wherein said primary coating has a Tg below −45° C.

18. The coated optical fiber of claim 1 , wherein said secondary coating has:

(a) a Tg of at least 40° C.;

(b) a secant modulus of at least 400 MPa; and

(c) an elongation at break of at least 10%.

19. The coated optical fiber of claim 1 , wherein said an optical fiber is an optical glass fiber.

20. An inner primary coating composition having:

(a) an in-situ modulus (after cure) of less than 0.6 MPa;

(b) a cure dose to attain 95% of the maximum attainable modulus of less than 0.65 J/cm 2 ; and

(c) a modulus retention ratio (after cure) of at least 0.6 after hydrolytic aging.

21. The composition of claim 20 , wherein said composition comprises a radiation-curable oligomer selected from the group consisting of:

(i) radiation-curable oligomers having a backbone derived from one or more polyether polyols; and

(ii) radiation-curable oligomers having a backbone derived from one or more polyether polyols in combination with one or more polyester polyols.

22. An inner primary coating composition having:

(i) an in-situ modulus (after cure) of less than 0.56 MPa;

(ii) a cure dose to attain 95% of the maximum attainable modulus of less than 0.65 J/cm 2 ; and

(iii) a modulus retention ratio (after cure) of at least 0.5 after hydrolytic aging.