EP0850431A1 - Fibre optique a chemisage dope au tantale - Google Patents

Fibre optique a chemisage dope au tantale

Info

Publication number
EP0850431A1
EP0850431A1 EP97932380A EP97932380A EP0850431A1 EP 0850431 A1 EP0850431 A1 EP 0850431A1 EP 97932380 A EP97932380 A EP 97932380A EP 97932380 A EP97932380 A EP 97932380A EP 0850431 A1 EP0850431 A1 EP 0850431A1
Authority
EP
European Patent Office
Prior art keywords
optical fiber
index
annular region
tantalum
core
Prior art date
Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
Withdrawn
Application number
EP97932380A
Other languages
German (de)
English (en)
Other versions
EP0850431A4 (fr
Inventor
James P. Murphy
David K. Smith
Current Assignee (The listed assignees may be inaccurate. Google has not performed a legal analysis and makes no representation or warranty as to the accuracy of the list.)
Corning Inc
Original Assignee
Corning Inc
Priority date (The priority date is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the date listed.)
Filing date
Publication date
Application filed by Corning Inc filed Critical Corning Inc
Priority claimed from PCT/US1997/011347 external-priority patent/WO1998000739A1/fr
Publication of EP0850431A1 publication Critical patent/EP0850431A1/fr
Publication of EP0850431A4 publication Critical patent/EP0850431A4/fr
Withdrawn legal-status Critical Current

Links

Definitions

  • U.S. Patent No. 4,715,679 describes an optical fiber with little or no dispersion over a wide band of wavelengths.
  • the optical fiber has a central core surrounded by an inner clad that is in turn surrounded by an outer clad.
  • the core and clad have one or more regions with a depressed index of refraction compared to the adjacent regions.
  • the core has a maximum refractive index and that index that may decrease with the distance from the center.
  • Adjacent the core is a first annular region of the inner clad that has a depressed index of refraction.
  • Adjacent the depressed region is a second annular region having an index of refraction greater than the depressed, first annular region.
  • the index depression modifies the light energy propagation characteristics of a fiber to provide a desired relationship between waveguide dispersion and wavelength. So, dispersion is controlled by depressing the index of refraction of an inner clad region that is adjacent the central core.
  • the index depression is created by adding a suitable depressant dopant such as fluorine or boron.
  • depressed regions made with fluorine and boron dopants have undesired limitations.
  • Depressed regions made with fluorine have a maximum amount of index depression of about 0.5 percent delta, but 0.3 percent delta is a more common result.
  • Fluorine presents manufacturing problems because it is corrosive and a commercial source of dry fluorine for a common outside vapor deposition (OVD) process is not currently available.
  • OLED outside vapor deposition
  • Boron has a large adverse effect on propagation of light with wavelengths above 1200 n . As such, boron is not useable for single mode optical fibers which generally transmit light at about 1500 nm.
  • germanium is not suitable for raising the index of the clad. Germanium reacts with chlorine during drying and consolidation to form a germanium monoxide. The monoxide is relatively volitile and migrates out of the clad during chlorine drying and consolidation steps. So, it is difficult to keep germanium in the clad and thereby raise the index of the clad with respect to an adjacent region of depressed index, such as fused silica.
  • an optical fiber structure that is compatible with fused silica glass, increases the index of refraction of a clad region with a dopant that does not migrate from its initial location and does not absorb light at the wavelength transmitted through the optical fiber.
  • Tantalum has a number of technical advantages. For one, tantalum does not migrate from its initial position. Tantalum has low volitivity so it resists migration even when the fiber is subjected to high temperatures during drying and consolidation. By resisting migration, the doping profile of the tantalum doped region remains sharply defined. Its second advantage is a low attenuation of light at the wavelengths chosen for transmission. Those wavelengths are around 1300 nm and 1550 nm. At those wavelengths, tantalum has a relatively low attenuation of light. Also, Rayleigh scattering by tantalum is relatively low at those wavelengths. A third advantage is glass doped with tantalum has a lower thermal expansion than glass doped with germanium.
  • tantalum has a greater effect on refractive index, by weight, than does germanium. So, less tantalum is need to produce the same refraction that is produced by a germanium. Attenuation is also related to quantity. Hence, the attenuation of light in optical fibers using tantalum is less because less tantalum is used.
  • a fifth advantage is tantalum is chemically stable. It is insoluble in water and most acids and alkalis. It is slowly attacked by hot hydrofluoric acid. The invention is applicable to all optical fibers, including but not limited to single mode fibers, multimode fibers, dispersion shifted fibers, fibers with large effective areas, and high performance, ultra long distance fibers with controlled linear dispersion.
  • materials for the core and clad (inner and outer) regions of the optical fiber are made from glass having minimum light attenuation characteristics.
  • an optical quality glass may be used, fused silica is a particularly suitable glass.
  • the glass for the core and cladding glasses should have similar physical characteristics for structural and other practical considerations. Since the core glass must have a higher index of refraction than the clad glass, the core glass is formed from the same type of glass used for the clad and is doped with a small amount of material to slightly increase the refractive index of the core. So, the core is doped with germania.
  • a first annular depressed region may be formed in an initial portion of the inner clad, in adjacent portions of the core and inner clad, or entirely within an outer annulus of the core.
  • a central region of the core is doped with germanium.
  • An outer annulus of the core is left undoped.
  • the clad region adjacent the undoped core annulus and surrounding the core is doped with tantalum to increase its index of refraction.
  • the tantalum doped clad region extends from the undoped core annulus to the outside of the fiber.
  • Figure 1 is a crossectional view of an optical fiber made in accordance with the invention.
  • Figure 2 is a doping profile of one optical fiber with the invention.
  • Figures 3 and 4 show doping profiles of other optical fibers made with the invention.
  • Figure 5 is a graph showing the dispersion results of tantalum-doped silica overclad fiber.
  • Figure 6 is a graph showing the refractive index as a function of wavelength for tantalum and fused silica.
  • Figure 1 shows a cross-sectional view of a single mode optical fiber 1 made in accordance with the invention.
  • the optical fiber has a central core 10 that is defined by an outer surface 11.
  • An inner clad region 12 has an inner surface formed on the outer surface 11 of the core 10.
  • the inner clad region 12 has an outer surface 13.
  • Inner clad 12 is surrounded by outer clad 14 which has an outer surface 15.
  • the material of the core 10 is fused silica doped with germanium.
  • the inner clad layer 12 has at least one annular region 20 of substantially pure fused silica.
  • a second annular region 22 comprises fused silica doped with tantalum.
  • a dashed line 21 indicates the boundary between regions 20 and 22.
  • the tantalum doping extends from dashed line 21 to the outer surface 15. While the invention contemplates on inner clad with undoped region 20 and tantalum doped region 22, it also includes a fiber where the whole inner clad 12 is undoped and the outer clad 14 is doped with tantalum.
  • Figure 2 shows a typical doping profile for an optical fiber made with the invention.
  • the core region 10 is doped with germanium or a combination of germanium and tantalum to provide a gradient refractive index from a maximum at the center to zero at the outer surface 11 of the core 10.
  • Adjacent core 10 is first annular region 20 of substantially pure fused silica.
  • a second annular region 22 is doped with tantalum.
  • the tantalum doped region 22 has an index of refraction greater than region 20 but less than the maximum of core 10. As such, there is a significant change in the index of refraction between regions 20 and 22. Accordingly, region 20 forms a depressed annular region located between two adjoining regions 10, 22, each of which has an index of refraction greater than the depressed region 20.
  • the boundary 21 between undoped and tantalum doped regions may coincide with outer surface 13 of inner clad 12.
  • the core has a maximum index of refraction I 0 .
  • Adjacent the core is the first annular region 20 with a refractive index I,.
  • the second annular region 2 surrounds the first annular region 20 and has a refractive index of I 2 .
  • the first annular region 20 with the depressed index I may be formed entirely in an outer annulus of the core 10, in adjoining annular regions of the core and the inner clad, or entirely within the inner clad. So, I 0 )I 2 )I ⁇ -
  • a feature of the invention is a clad region that ranges from the outside edge of the outermost annulus A to the outside edge of the optical fiber B.
  • This clad region contains Si0 2 and tantalum that increases the clad's refractive index above at least one inner annulus, which would typically be pure silica.
  • the clad also may contain other dopants, such as titanium for added strength. Other useful profiles are shown in Figures 3 and 4.
  • the fiber of Figure 3 has a step index region 30 made by doping an annular portion of the fiber with germanium.
  • the tantalum doped region 32 extends from the step index region 30 to the outside surface of the fiber.
  • the fiber of Figure 4 has two step index regions, 30, 31, each formed by doping an annular portion of the fiber with germanium.
  • the region 30 is more heavily doped than is the region 31.
  • the tantalum doped region 32 has an index of refraction greater than region 31 but less than region 30. It extends to the outside of the fiber.
  • FIG. 5 shows the dispersion results of a tantalum-doped silica overclad fiber. These results indicate that tantalum doped silica material dispersion is quite similar to the material dispersion of germanium doped silica.
  • the core 10 may have a step index profile, an alpha index profile, a profile that changes at a constant rate, or a profile that changes at a combination of one or more rates.
  • the depressed region may also be formed in the core by terminating germanium doping before the core is complete.
  • the balance of the core would be undoped fused silica.
  • the invention may be used in any suitable optical fiber where it is desired to raise the index of the clad. So, the invention is applicable not only to single mode fibers, but also to multimode fibers, dispersion shifted fibers, fibers with large effective areas, and high performance, ultra long distance fibers with controlled linear dispersion. With the invention, the dispersion of any fiber can be modified.
  • the invention eliminates the unwanted side effects of index lowering dopants, such as boron and fluorine, since optical fibers made with the invention do not require such dopants.
  • Tantalum has low volatility so it does not migrate even when the fiber is subjected to high temperatures during drying and consolidation. As such, the doping profiles of tantalum doped regions remain relatively sharp. Tantalum has a low attenuation of light and low Rayleigh scattering at the wavelengths chosen for transmission. These wavelengths are around 1300 nm and 1550 nm. Glass doped with tantalum has a lower thermal expansion than glass doped with germanium. Tantalum has a greater effect on light, by weight, than does germanium. So, less tantalum is need to produce the same refraction that is produced by a germanium.
  • Tantalum is chemically stable. It is insoluble in water and most acids and alkalis and is only slowly attacked by hot hydrofluoric acid.
  • the inventive fiber 1 with a depressed index region is made by any conventional fiber manufacturing process.
  • the process for application of the remainder of the second coating of soot ultimately forming the clad 14 is modified from conventional teachings by the introduction of suitable concentrations of a tantalum precursor such as TaCI 5 .
  • a tantalum precursor such as TaCI 5 .
  • Those skilled in the art will appreciate that other materials may also raise the index of refraction. Such other materials include zirconium, lanthanum, yttrium, cerium, and germanium.
  • the concentration of Ta-.0 5 precursor in the Si0 2 soot precursor composition ranges up to about 10 weight percent and most preferably about 3 to about 5 weight percent.
  • the process aside from the tantalum addition to inner clad region 12 is entirely conventional.
  • modifications to the conventional process steps known to those of ordinary skilled in the art can be employed.
  • any of the various laydown processes can be used, including but not limited to outside vapor deposition, inside vapor deposition, vapor axial deposition, modified chemical vapor deposition, or plasma outside inside deposition.
  • Patent No. 4,125,388 Powers U.S. Patent No. 4,165,223; and Abbott U.S. Patent
  • Patent No. 5,284,499 Koening U.S. Patent No. 5,314,517; Amos U.S. Patent No.

Landscapes

  • Glass Compositions (AREA)

Abstract

La présente invention concerne une fibre optique (1) dont la région coeur centrale (10), est entourée d'une région intérieure de chemisage (12). La seconde région annulaire (14) est dopée au tantale. Le coeur (10) est dopé au germanium. La première région annulaire (20) est située entre deux régions contiguës dont les indices de réfraction sont relativement élevés. L'indice de réfraction de ces deux régions contiguës (10, 20) est supérieur à la région centrale (20).
EP97932380A 1996-07-01 1997-06-27 Fibre optique a chemisage dope au tantale Withdrawn EP0850431A4 (fr)

Applications Claiming Priority (4)

Application Number Priority Date Filing Date Title
US2114296P 1996-07-01 1996-07-01
US1214296P 1996-07-01 1996-07-01
US12142P 1996-07-01
PCT/US1997/011347 WO1998000739A1 (fr) 1996-07-01 1997-06-27 Fibre optique a chemisage dope au tantale

Publications (2)

Publication Number Publication Date
EP0850431A1 true EP0850431A1 (fr) 1998-07-01
EP0850431A4 EP0850431A4 (fr) 1999-08-18

Family

ID=26683205

Family Applications (1)

Application Number Title Priority Date Filing Date
EP97932380A Withdrawn EP0850431A4 (fr) 1996-07-01 1997-06-27 Fibre optique a chemisage dope au tantale

Country Status (1)

Country Link
EP (1) EP0850431A4 (fr)

Citations (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
EP0223466A2 (fr) * 1985-11-04 1987-05-27 Dow Corning Corporation Fibre optique
US4709987A (en) * 1985-12-10 1987-12-01 The United States Of America As Represented By The Secretary Of The Navy Pressure and temperature insensitive glass and optical coatings and fibers therefrom
US4715679A (en) * 1981-12-07 1987-12-29 Corning Glass Works Low dispersion, low-loss single-mode optical waveguide

Patent Citations (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US4715679A (en) * 1981-12-07 1987-12-29 Corning Glass Works Low dispersion, low-loss single-mode optical waveguide
EP0223466A2 (fr) * 1985-11-04 1987-05-27 Dow Corning Corporation Fibre optique
US4709987A (en) * 1985-12-10 1987-12-01 The United States Of America As Represented By The Secretary Of The Navy Pressure and temperature insensitive glass and optical coatings and fibers therefrom

Non-Patent Citations (1)

* Cited by examiner, † Cited by third party
Title
See also references of WO9800739A1 *

Also Published As

Publication number Publication date
EP0850431A4 (fr) 1999-08-18

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