Coated optical fibers
View Patent ↗A coated optical fiber can have a primary coating and a secondary coating, where the primary coating can have good microbending resistance and is obtained by curing a composition having a high cure speed. In one example, a coated optical fiber can include as optical fiber, a primary coating and a secondary coating. The optical fiber can have an attenuation increase of less than 0.650 dB/km at 1550 nm, with the primary coating having a modulus retention ratio of at least 0.5, a glass transition temperature of −35° C., and where the 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 .
1. 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; wherein said composition comprises:
(i) 20–98 wt. % relative to the total weight of the composition of a radiation curable urethane (meth)acrylate oligomer having polyether polyol backbone;
(ii) 0–80% wt. % relative to the total weight of the composition of one or more reactive diluents;
(iii) 0.1–20 wt. % relative to the total weight of the composition of one or more photoinitiators; and
(iv) 0–5 wt. % relative to the total weight of the composition of additives.
2. The composition according to claim 1 , wherein the number average molecular weight of said urethane (meth)acrylate is from about 1,200 g/mol to about 20,000 g/mol.
3. The composition according to claim 1 , wherein the number average molecular weight of said urethane (meth)acrylate is from about 2,200 g/mol to about 10,000 g/mol.
4. The composition according to claim 1 , wherein the number average molecular weight of said polyether polyol is from about 500 g/mol to about 15,000 g/mol.
5. The composition according to claim 1 , wherein the number average molecular weight of said polyether polyol is from about 1,500 g/mol to about 6,000 g/mol.
6. The composition according to claim 5 , wherein said polyether polyol is polypropylene glycol.
7. The composition according to claim 1 , wherein said one or more reactive diluents are selected from the group consisting of alkoxylated alkyl substituted phenol acrylates, alkoxylated aliphatic polyacrylates, and alkoxylated bisphenol A diacrylates.
8. The composition according to claim 1 , wherein said one or more reactive diluents comprise one or more aromatic rings.
9. The composition according to claim 1 , wherein said one or more photoinitiators contain a phosphorous, sulfur or nitrogen atom.
10. The composition according to claim 1 , wherein said one of said additives is a silane coupling agent.
11. The composition according to claim 1 , wherein said composition, when cured, has a glass transition temperature of below −35° C.
12. The composition according to claim 1 , wherein said composition, when cured, has a glass transition temperature of below −45° C.
13. The composition according to claim 1 , wherein said composition has an in-situ modulus (after cure) of less than 0.56 MPa.
14. The composition according to claim 1 , wherein said composition has an in-situ modulus (after cure) of less than 0.54 MPa.
15. The composition according to claim 1 , wherein said composition has an in-situ modulus (after cure) of less than 0.52 MPa.
16. A coated optical fiber comprising:
(a) an optical fiber;
(b) a primary coating obtained by curing the coating composition according to claim 1 ;
(c) a secondary coating, wherein said secondary coating has:
(i) a Tg of about 60° C. or higher;
(ii) an elongation at break of at least 20%; and
(iii) a tensile modulus of at least 500 MPa.
17. The coated optical fiber according to claim 16 , wherein said primary coating has an elongation at break of at least 75%.
18. The coated optical fiber according to claim 16 , wherein said primary coating has an elongation at break of at least 120%.