Method for producing an optical fiber and optical fiber
In the known method for producing an optical fiber, a coaxial arrangement comprising a core rod and an outer jacket tube is elongated, the coaxial arrangement being supplied in a vertical orientation to a heating zone and being softened therein zonewise, starting with the lower end thereof, and the optical fiber being withdraw downwards from the softened portion, whereby an annular gap existing between core rod and jacket tube is collapsed. Starting therefrom, in order to provided a method which makes it possible to produce optical fibers with a minimum curl and at low costs, the invention suggests that a quartz glass cylinder treated mechanically to its final dimension and having an outer diameter of at least 100 mm should be used as the jacket tube. An optical fiber obtained according to the method is characterized in that without the action of external forces it assumes a radius of curvature of at least 6 mm.
1. A method for producing an optical fiber by elongating a coaxial arrangement comprising a core rod and an outer jacket tube, said method comprising: supplying said coaxial arrangement being in a vertical orientation to a heating zone, said coaxial arrangement being softened therein zonewise, starting with a lower end thereof, to form a softened portion, and withdrawing said optical fiber being downwards from the softened portion, whereby an annular gap defined between the core rod and the outer jacket tube is collapsed, wherein the outer jacket tube comprises a quartz glass cylinder treated mechanically to give said cylinder a final dimension with an outer diameter of at least 100 mm.
2. The method according to claim 1 , wherein the annular gap has a width that is larger than 2 mm.
3. The method according to claim 2 , wherein the width of the annular gap is larger than 5 mm.
4. The method according to claim 2 , wherein the width of the annular gap is larger than 10 mm.
5. The method according to claim 1 , wherein the outer diameter of the quartz glass cylinder is at least 150 mm.
6. The method according to claim 5 , wherein the quartz glass cylinder has an inner diameter of not more than 70 mm.
7. The method according to claim 1 , wherein the annular gap has a width that is smaller than 0.6 mm.
8. The method according to claim 7 , wherein the width of the annular gap is smaller than 0.3 mm.
9. The method according to claim 1 , wherein the quartz glass cylinder is used with an ovality of not more than 0.3 mm.
10. The method according to claim 1 , wherein the quartz glass cylinder is produced according to the OVD method.
11. The method according to claim 1 , wherein the quartz glass cylinder has an inner diameter of not more than 70 mm.
12. The method according to claim 1 , wherein the quartz glass cylinder has an inner diameter of not more than 40 mm.
13. The method according to claim 1 , wherein the quartz glass cylinder has a radial cross-sectional area CSA (C) and the core rod has a radial cross-sectional area CSA (R) , wherein a ratio CSA (C) /CSA (R) of the radial cross-sectional area CSA (C) of the quartz glass cylinder and the radial cross-sectional area CSA (R) of the core rod is in a range between 5 and 100.
14. The method according to claim 1 , wherein the quartz glass cylinder has a length of at least 2 m.
15. The method according to claim 1 , wherein the quartz glass cylinder has a bow of not more than 0.3 mm per length meter.
16. The method according to claim 1 , wherein the quartz glass cylinder has a wall thickness deviation of not more than 0.3 mm.
17. The method according to claim 1 , wherein the outer diameter of the quartz glass cylinder is at least 200 mm.
18. The method according to claim 1 , wherein the quartz glass cylinder is used with an ovality of not more than 0.05 mm.
19. The method according to claim 1 , wherein the quartz glass cylinder has an inner diameter of not more than 50 mm.
20. The method according to claim 1 , wherein the quartz glass cylinder has an inner diameter of not more than 30 mm.
21. The method according to claim 1 , wherein the quartz glass cylinder has a radial cross-sectional area CSA (C) and the core rod has a radial cross-sectional area CSA (R) , wherein a ratio CSA (C) /CSA (R) of the radial cross-sectional area CSA (C) of the quartz glass cylinder and the radial cross-sectional area CSA (R) of the core rod is in a range between 10 and 80.
22. The method according to claim 1 , wherein the quartz glass cylinder has a length of at least 3 m.
23. The method according to claim 1 , wherein the quartz glass cylinder has a bow of not more than 0.1 mm per length meter.
24. The method according to claim 1 , wherein the quartz glass cylinder has a bow of not more than 0.05 mm per length meter.
25. The method according to claim 1 , wherein the quartz glass cylinder has a wall thickness deviation of not more than 0.1 mm.
26. The method according to claim 1 , wherein the quartz glass cylinder has a wall thickness deviation of not more than 0.05 mm.
27. The method according to claim 1 , wherein the quartz glass cylinder is used with an ovality of not more than 0.1 mm.