Method of making a jacketed preform for optical fibers using OVD
View Patent ↗On the basis of a known process for the production of a preform for an optical fiber for optical data transmission technology, the productivity of the process for the production of complex refractive index profiles is to be improved by providing a quartz glass substrate tube which exhibits different doping in radial direction, introducing a core glass made of synthetic quartz glass into the substrate tube and covering the substrate tube with a jacket tube. A substrate tube suitable therefor is also being provided which tube requires less core glass material for the production of the preform, whether during the internal deposition or for the core glass rod in the rod-in-tube technique. Regarding the process it is proposed according to the invention that a substrate tube be used which was obtained by vitrification of a porous tube-shaped SiO 2 blank, the substrate tube being provided with a core glass layer which is produced in that to the first radial portion of the SiO 2 blank there is added before the vitrification a first dopant which increases the refractive index of quartz glass. The substrate tube according to the invention has in the radial direction regions of different doping whereby it incorporates a core glass layer which has a refractive index of at least 1.459.
1. A process for the production of an optical fiber preform for optical data communications, said process comprising:
providing a tubular porous SiO 2 blank having a first radial portion containing a first dopant that increases the refractive index of quartz glass, said providing including forming said porous SiO 2 blank by an outside vapor deposition (OVD) process, which includes forming the first radial portion by outside vapor deposition;
vitrifying the tubular porous SiO 2 blank so as to form a substrate tube which has in the radial direction different dopants and such that the fist radial portion is formed into an inner glass layer of the substrate tube, said inner glass layer containing said first dopant and having a refraction index of at least 1.459;
introducing in the substrate tube a core of synthetic quartz glass and collapsing the substrate tube so as to form a collapsed substrate tube containing said core; and
placing a jacket tube around the collapsed substrate tube, and collapsing the jacket tube so as to form the optical fiber preform.
2. A process according to claim 1 , wherein the inner glass layer is configured so as to adjoin the core.
3. A process according to claim 2 , wherein the inner glass layer contains germanium.
4. A process according to claim 3 , wherein the inner glass layer additionally contains fluorine.
5. A process according to claim 2 , wherein the substrate tube comprises a cladding layer made of fluorine-doped quartz glass.
6. A process according to claim 5 , wherein the inner glass layer contains germanium.
7. A process according to claim 6 , wherein the inner glass layer additionally contains fluorine.
8. A process according to claim 7 , wherein the inner glass layer has an index of refraction in the range from 1.4593 to 1.490.
9. A process according to claim 8 , wherein the hydroxyl ion content in the inner glass layer is max. 1 ppm by weight.
10. A process according to claim 9 wherein a diffusion-blocking layer is provided adjacent to the inner glass layer.
11. A process according to claim 5 , wherein the inner glass layer additionally contains fluorine.
12. A process according to claim 2 , wherein the inner glass layer additionally contains fluorine.
13. A process according to claim 1 , wherein the substrate tube comprises a cladding layer made of fluorine-doped quartz glass.
14. A process according to claim 13 , wherein the inner glass layer contains germanium.
15. A process according to claim 14 , wherein the inner glass layer additionally contains fluorine.
16. A process according to claim 13 , wherein the inner glass layer additionally contains fluorine.
17. A process according to claim 1 , wherein the inner glass layer contains germanium.
18. A process according to claim 17 , wherein the inner glass layer additionally contains fluorine.
19. A process according to claim 1 , wherein the inner glass layer contains fluorine.
20. A process according to claim 1 , wherein the inner glass layer has an index of refraction in the range from 1.4593 to 1.490.
21. A process according to claim 1 , wherein the hydroxyl ion content in the inner glass layer is max. 1 ppm by weight.
22. A process according to claim 1 , wherein a diffusion-blocking layer is provided adjacent to the inner glass layer.
23. A process for the production of an optical fiber preform for optical data communications, said process comprising:
providing a tubular porous SiO 2 blank having a first radial portion containing a first dopant that increases the refractive index of quartz glass, said providing including forming said porous SiO 2 blank by an outside vapor deposition (OVD) process, which includes forming the first radial portion by outside vapor deposition;
vitrifying the tubular porous SiO 2 blank so as to form a substrate tube which has in the radial direction different dopants and such that the first radial portion of the substrate tube is formed into an inner glass layer of the substrate tube, said inner glass layer containing said first dopant and having a refraction index of at least 1.459;
depositing on the inner layer of the substrate tube a core glass of synthetic quartz glass and collapsing the substrate tube so as to form a collapsed substrate tube containing said core glass; and
placing a jacket tube around the collapsed substrate tube and collapsing the jacket tube so as to form the optical fiber preform.
24. A process according to claim 23 , wherein the inner glass layer is configured so as to adjoin the core glass.
25. A process according to claim 23 , wherein the substrate tube comprises a cladding layer made of fluorine-doped quartz glass.
26. A process according to claim 25 , wherein the inner glass layer contains germanium.
27. A process according to claim 26 , wherein the inner glass layer contains fluorine.
28. A process according to claim 27 , wherein the hydroxyl ion content in the inner glass layer is max. 1 ppm by weight.
29. A process according to claim 28 , wherein a diffusion-blocking layer is provided adjacent to the inner glass layer.
30. A process according to claim 27 , wherein a diffusion-blocking layer is provided adjacent to the inner glass layer.
31. A process according to claim 25 , wherein the inner glass layer contains fluorine.
32. A process according to claim 25 , wherein a diffusion-blocking layer is provided adjacent to the inner glass layer.
33. A process according to claim 23 , wherein the inner glass layer contains germanium.
34. A process according to claim 33 , wherein the inner glass layer contains fluorine.
35. A process according to claim 33 , wherein the hydroxyl ion content in the inner glass layer is max. 1 ppm by weight.
36. A process according to claim 33 , wherein a diffusion-blocking layer is provided adjacent to the inner glass layer.
37. A process according to claim 23 , wherein the inner glass layer contains fluorine.
38. A process according to claim 37 , wherein the hydroxyl ion content in the inner glass layer is max. 1 ppm by weight.
39. A process according to claim 37 , wherein a diffusion-blocking layer is provided adjacent to the inner glass layer.
40. A process according to claim 23 , wherein the inner glass layer has an index of refraction in the range from 1.4593 to 1.490.
41. A process according to claim 23 , wherein the hydroxyl ion content in the inner glass layer is max. 1 ppm by weight.
42. A process according to claim 41 , wherein a diffusion-blocking layer is provided adjacent to the inner glass layer.
43. A process according to claim 23 , wherein a diffusion-blocking layer is provided adjacent to the inner glass layer.