MXPA98001693A - Optic fiber with lining impurified with tanta - Google Patents

Abstract

An improved optical wave fiber comprising a core region surrounded by an inner lining region is described, the second ring region is doped with tantalum, the core is doped with germanium, the first ring region of the inner lining is not doped, the fiber optic has a reduced annular region located between two adjacent regions of relatively high refractive indices, the refractive index of both contiguous regions is greater than the central region

Description

FIBER OPTICR WITH IMPURCIATED LINING CQN TANTALIO BACKGROUND OF THE INVENTION The U.S. Patent No. 4,715,679 discloses an optical fiber with little or no dispersion over a wide band of wavelengths. The optical fiber has a central core surrounded by an internal lining that is in turn surrounded by an external lining. The core and liner have one or more regions with a reduced Refractive Index compared to adjacent regions. The number has a maximum refractive index and this index can decrease with distance from the center. Adjacent to the core is a first annular region of the inner liner that has a reduced refractive index. Adjacent to the depressed region is a second annular region that has a refractive index greater than that of the first reduced annular region. Decreasing the index modifies the light energy propagation characteristics of a fiber to provide a desired ratio between waveguide dispersion and wavelength. In this way, the dispersion is controlled by reducing the refractive index of an internal lining region that is adjacent to the central node. The decrease of the index is created by adding a suitable reducing dopant such as fluorine or boron. However, reduced regions made with fluorine or boron dopers have undesirable limitations. The reduced regions made with fluorine have a maximum amount of index decrease of approximately 0.5% delta, but 0.3% delta is a more common result. Fluoride presents manufacturing problems because it is corrosive and a commercial source of dry fluorine is not currently available for a common external vapor deposition (OVD) process. Boron has a greater adverse effect on the propagation of light with wavelengths above 1200 nm. As such, boron is not usable for monomodal optical fibers that transmit light generally at approximately 1500 n. Instead of reducing the index of a region, others have proposed raising the liner index with germanium. However, germanium is not adequate to raise the liner index. Germanium reacts with chlorine during drying and consolidation to form a germanium monoxide. The monoxide is re- latively volatile and migrates out of the lining during the drying steps with chlorine and consolidation. In this way, it is difficult to maintain the germanium in the liner and thereby increase the liner index with respect to an adjacent region of reduced index, such as fused silica. Therefore, there is an unmet need for a fiber optic structure that is compatible with fused silica glass, which increases the refractive index of a coated region with a dopant that does not migrate from its initial location and does not absorb light in it. The wavelength transmitted throughout the optical fiber.

BRIEF DESCRIPTION OF THE INVENTION The present inventors have discovered unexpected and highly desirable results when a tantalum lining is impurified to increase the lining index above an adjacent reduced region of the number. This invention results in an optical fiber that uses only index increasing dopants to modify the chromatic dispersion. The invention eliminates the inconvenient side effects of index reducing dopants, such as boron and fluorine, since the optical fibers made with the invention do not require impurifier tails. Tantalum has several technical advantages. At least, the TantoLio does not migrate from its initial position. Tantalum has low volatility, so that it resists migration even when fiber is subjected to high temperatures during drying and consolidation. Resisting migration, the doping profile of the region contaminated with so much remains strictly defined. Its second advantage is a low attenuation of Light at the wavelengths chosen for transmission. These wavelengths are around 1300 nm at 1550 nm. At these wavelengths, tantalum has a relatively low light attenuation. Also, Rayleigh scattering by tantalum is relatively low at these wavelengths. A third advantage is glass impregnated with tantalum, which has a lower thermal expansion than glass contaminated with germanium. A fourth advantage is that tantalum has a greater effect on the refractive index, by weight, than germanium. In this way, less weight is required to produce the same refraction that is produced by germanium. The attenuation is also related to the quantity. Therefore, the light attenuation in fiber optic using soLio is smaller because less soLio is used. A fifth advantage is that the tanLio is chemically stable. It is insoluble in water and in most acids and alkalis. It is attacked slowly by hot hydrofluoric acid. The invention is applicable to all optical fibers, including but not limited to monomodal fibers, multimodal fibers, deviated dispersion fibers, fibers with large effective areas, and high-performance ultra-long distance fibers, with controlled linear dispersion. In the manufacture of optical fiber, the materials for the core and lining regions (internal and external) of the optical fiber are made of glass that has minimal attenuation characteristics of Light. Although an optical quality glass can be used, fused silica is a particularly suitable glass. Glass for Core and Liner Glasses should have similar physical characteristics for structural considerations and other tactical considerations. Since the core glass should have a higher refractive index than the lining glass, the core glass is formed from the same type of glass used for the liner and is contaminated with a small amount of material to increase the lightness of the glass. refraction of the nucleus. In this way, the number is contaminated with germanium. A first annular reduced region may be formed in an initial portion of the inner liner, in adjacent portions of the lining and the inner liner, or entirely within an outer ring of the core. In the preferred embodiment, a central region of the Leo cell is doped with germanium. An outer ring of the nucleus is left undoped. The lining region adjacent to the non-doped core ring surrounding the core is doped with tantalum to increase its refractive index. The lining region impregnated with tantalum extends from the unpurified core ring to the exterior of the fiber.

DESCRIPTION OF THE DRAWINGS Figure 1 is a cross-sectional view of an optical fiber made in accordance with the invention. Figure 2 is a doping profile of an optical fiber with the invention. Figures 3 and show doping profiles of other optical fibers made with the invention. Figure 5 is a graph showing the dispersion results of fiber coated with silica impregnated with tantalum. Figure 6 is a graph showing the refractive index as a function of wavelength for tantalum and fused silica.

DETAILED DESCRIPTION OF LR INVENTION Figure 1 shows a cross-sectional view of a monomodal optical fiber 1 made in accordance with the invention. The optical fiber has a central core 10 which is defined by an outer surface 11. An inner lining region 12 has an internal surface formed on the outer surface 11 of the core 10. The inner lining region 12 has an outer surface 13. inner liner 12 is surrounded by outer liner 14 having an outer surface 15. The material of number 10 is fused silica doped with germanium. The inner lining layer 12 has at least one annular region 20 of substantially pure fused silica. A second annular region 22 comprises fused silica impurified with so much. A line of dashes 21 indicates the boundary between Regions 20 and 22. The doping tanglia extends from the line of dashes 21 to the outer surface 15. Although the invention contemplates internal lining with non-doped region 20 and region doped with tantalum 22, it also includes a fiber in which the entire inner liner 12 is not contaminated and the outer liner 14 is contaminated with so much. Figure 2 shows a typical doping profile for a fiber made with the invention. The region of number 10 is doped with germanium or a combination of germanium and tanium to provide a refractive index from a maximum in the center to zero on the outer surface 11 of the core 10. Adjacent to the core 10 is a first annular region 20 of substantially pure fused silica. A second annular region 22 is doped with tantalum. The region impregnated with soLio 22 has a refractive index greater than region 20 but less than the maximum of core 10. As such, there is a significant change in the refractive index between regions 20 and 22. Therefore, the region 20 forms a reduced annular region located between two adjacent regions 10, 22, each of which has a refractive index greater than eL of the reduced region 20. The boundary 21 between the regions impregnated with tantalum and non-doped can match La. outer surface 13 of inner lining 12. In optical fiber 1, the number has a maximum refractive index I0. Adjacent to the nucleus is the first annular region 20 with a refractive index I. The second annular region 22 surrounds the first annular region 20 and has a refractive index of. The first annular region 20 with the reduced index IA may be formed completely in an outer ring of the core 10, or contiguous with the annular regions of the core and the inner liner, or completely within the inner liner. In this way, A characteristic feature of the invention is a lining region that varies from the outer edge of the outermost ring A to the outer edge of the optical fiber B. This lining region contains SiO and tantalum which increases the refractive index of the lining by above at least one inner ring, which would typically be pure silica. The liner may also contain other dopants, such as titanium to add strength. Other useful profiles are shown in Figures 3 and 4. The fiber of Figure 3 has a step index region 30 made by impurifying an annular portion of the fiber with germanium. The doped region with so much 32 extends from the graduated index region 30 to the outer surface of the fiber. The fiber of Figure 4 has two graduated index regions 30, 31, each formed by impurifying an annular portion of the fiber with germanium. Region 30 is more highly contaminated than region 31. The region impurified with so much 32 has a higher refractive index than region 31 but less than region 30. It extends outwardly from the fiber. Figure 5 shows the dispersion results of a fiber coated with silica impurified with soLio. These results indicate that the dispersion of the silica material impregnated with soLio is very similar to that of the dispersion of silica material doped with germanium. The previous speculations were confirmed by further experimentation. Experimental results for doped silica were compared with 7.26% by weight of tantalum for fused silica and doped silica with 5.9% by weight of Ge? Ffi and 9.26% by weight of GeOs ». The data shown in Figure 6 indicate that the silica impurified with soLio follows the expected refraction of the doped silica with 7.5 wt.% Germanium. The present invention also contemplates optical waveguides with cores having a constant or a varied refractive index. Modifications, alterations and additional changes to The profiles of the core 10 and the lining regions 5, 12 and 14 can be made in accordance with the teachings of the U.S. Patent. No. 4,715,679 which is incorporated herein by reference. For example, the core 10 may have a step-wise index profile, an alpha index profile, a profile that changes at a constant rate, or a profile that changes to a combination of one or more speeds. The reduced region can also be formed in the nucleus by finishing the doping with germanium before it completes the nucleus. The balance of the nucleus would be fused silica not impurified. The invention can also be used on any suitable optical fiber where it is desired to raise the liner index. In this way, the invention is applicable not only to fibers individually, but also to multimodal fibers, dispersion change fibers, fibers with large effective areas and high-performance fibers of ultra long distance with controlled linear dispersion. With the invention, the dispersion of any fiber can be modified. The invention eliminates the unwanted side effects of index reducing dopants, such as boron and fluorine, since optical fibers made with the invention do not require such dopants. As mentioned before, there are a number of technical advantages to using tantalum. The tanLio 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 soiled regions remain relatively acute. Tantalum has low light attenuation and low Rayleigh scattering at wavelengths chosen for transmission. These wavelengths are around 1300 nm and 1550 nm. Glass impregnated with tantalum has a lower thermal expansion than glass contaminated with germanium. The tanium has a greater effect on light, in weight, than germanium. In this way, less tantalum is needed to produce the same refraction that is produced by germanium. Since the attenuation is also proportional to the quantity, the attenuation of optical fibers that use so much Lio is smaller because less soLio is used. Tantalum is chemically stable. It is insoluble in water and most of the acid and alkaline materials and is only slowly attacked by hot hydrofluoric acid. The fiber 1 of the invention with a reduced index region is made by any conventional fiber manufacturing processes. According to the invention, the procedure for application of the remainder of the second soot liner that ultimately forms the liner 14 is modified from conventional teachings by the introduction of suitable concentrations of a tanLio precursor such as TaCls ~ -. Those skilled in the art will appreciate that other materials can also raise the refractive index. Those other materials include zirconium, lanthanum, yttrium, cerium and germanium. In addition, fluoride, zirconium, tetrachloride and hexafluoride, hexafluoroacetyletonates and analogous compounds of lanthanum, yttrium and cerium are compatible with the OVD process. Any of the foregoing in suitable concentrations can produce an index enhancing dopant in region 14. In preferred embodiments, the concentration of Taz0B precursor in the SiOa soot precursor composition varies up to about 10% by weight and most preferably about 10% by weight. 3 to about 5% by weight. Here it is noted that although the above description illustrates the method of the invention, the process in addition to the addition of tantalum to the inner lining region 12 is completely conventional. Therefore, modifications of conventional process steps known to those skilled in the art may be employed. For example, any of the various laying procedures may be used, including but not limited to, exterior vapor deposition, interior vapor deposition, axial vapor deposition, modified chemical vapor deposition or plasma outside of the interior deposition. Conventional optical waveguide fiber technology is easily employed by those skilled in the art in the practice of the invention, all of which is incorporated herein by reference, including by way of non-limiting examples the following. As for starting materials useful as soot precursors, see: Dobbins, U.S. Pat. No. 5,043,002; and BlackwelL Patent of E.U.A. No. 5, 152, 819. Regarding Procedures for Vaporization or Nebulization of Soot Precursors, see: Antos, Patent of E.U.A. No. 5,078,092; Cain, Patent of E.U.A. No. 5,356,451; BLankenship, Patent of E.U.A. No. 4,230,744; BLankenship, Patent of E.U.A. No. 4,314,837; and BLankenship, Patent of E.U.A. DO NOT. 4,173,305. As regards precursors of burning soot and the laying of the number and lining, see: Abbott, U.S. Pat.

No. 5,116,400; Abbott, Patent of E.U.A. No. 5,211,732; Berkey, Patent of E.U.A. No. 4,486,212; Powers, Patent of E.U.A. Do not. 4,568,370; Powers, Patent of E.U.A. No. 4,639,079; Berkey, Patent of E.U.A. No. 4,684,384; Powers, Patent of E.U.A. Do not. 4,714,488; Powers, Patent of E.U.A. No. 4,726,827; Schultz, Patent of E.U.A. No. 4,230,472; and Sarkar, Patent of E.U.A.

No. 4,233,045. Regarding the steps of consolidation of the preform of Nucle, stretch of cane of number and consolidation of preform of sobreforro see: Lane, Patent of E.U.A. Do not. 4,906,267; Lane, Patent of E.U.A. No. 4,906,268; Lane, Patent of E.U.A. No. 4,950,319; Blankenship, Patent of E.U.A. No. 4,251,251; Schultz, Patent of E.U.A. No. 4,263,031; Bailey, Patent of E.U.A. No. 4,286,978; Powers, Patent of E.U.A. Do not. 4,125,388; Powers, Patent of E.U.A. No. 4,165,223; and Abbott, Patent of E.U.A. No. 5,396,323. As for fiber stretching from a consolidated overburden preform, see: Hervey, U.S. Pat. Do not. ,284,499; Koening, Patent of E.U.A. No. 5,314,517; Amos, Patent of E.U.A. No. 5,366,527; Brown, Patent of E.U.A. Do not. 4,500,043; Darcangelo, Patent of E.U.A. No. 4,514,205; Kar, Patent of E.U.A. No. 4,531,959; Lane, Patent of E.U.A. No. 4,741,748; Deneka, Patent of E.U.A. No. 4,792,347; Ohls, Patent of E.U.A. No. 4,246,299; Claypoole, Patent of E.U.A.

No. 4,264,649; and Brundage, Patent of E.U.A. No. 5,410,567.

Claims (16)

NOVELTY OF THE INVENTION CLAIMS

1. - An optical fiber waveguide with a number and an inner liner comprising a central region having a maximum refractive index, lo, a first annular region adjacent to the central region and having a refractive index, Ix, which is smaller than that, a second annular region surrounding the first annular region and having a refractive index Ia, The second annular region comprising tantalum to increase the index of said region with sufficient index-enhancing dopant to raise the refractive index The second annular region Is above the refractive index of the first annular region I

2. 2. The optical fiber according to claim 1, further characterized in that the central region comprises the core and the second annular region contains multiple subregions at least one of which has a refractive index. I * smaller than Is. 3.- The fiber optic waveguide according to claim 1, further characterized in that Io > Is_ * > I ?. 4. The optical fiber according to claim 1, further characterized in that the doping agent for the second ring region comprises soLio. 5. The optical fiber according to claim 1, further characterized in that the optical fiber is one selected from the group consisting of fibers individually, fibers of multiple modes, fibers of change of dispersion, fibers with large effective areas and fibers High performance ultra long distance with controlled chromatic dispersion. 6. An optical fiber comprising: a core having a maximum refractive index, I0, an inner lining layer on the core having a first annular region surrounding said number and having a refractive index, an index of refraction I ±, which is smaller than that, a second region surrounding the first annular region and having a refractive index Ia doped with sufficient tantalum to raise the refractive index of the second annular region I »above the index of refraction of the first annular region I *, but smaller than Ia. 7. The optical fiber according to claim 6, further characterized in that the first annular region comprises fused silica and the second annular region comprises tantalum impurified with fused silica. 8. The optical fiber according to claim 6, further characterized in that the nucleus comprises fused silica impregnated with germanium. 9. The optical fiber according to claim 6, further characterized in that the optical fiber is one selected from the group consisting of fibers individually, fibers of multiple modes, fibers of change of dispersion, fibers with large effective areas, and high-performance ultra long-range fibers with controlled linear dispersion. 10. An optical fiber comprising a core region and first and second annular regions, which respectively surround said region of number, wherein the refractive index of the first annular region is reduced with respect to the adjacent number and the second regions. rings and the second ring region comprises tantalum. 11. The optical fiber according to claim 11, further characterized in that the region of num Leo comprises fused silica and tantalum. 12. The optical fiber according to claim 11, further characterized in that the central region comprises fused silica, germanium and tantalum. 1

3. The optical fiber according to claim 10, further characterized in that the second annular region comprises fused silica and tantalum. 1

4. The optical fiber according to claim 10, further characterized in that the amount of tantalum in the second annular region varies up to about 10%. 1

5. The optical fiber according to claim 14, further characterized in that the amount of tantalum in the second annular region varies from about 3% SUMMARY OF THE INVENTION An improved optical wave fiber comprising a core region surrounded by an inner lining region is described; the second annular region is contaminated with so much; The number is doped with germanium; The first annular region of the inner lining is not contaminated; The optical fiber has a reduced annular region located between two adjacent regions of relatively high refractive indices; the refractive index of both contiguous regions is greater than the central region. P97 / 1224F EA / D3 / elt * apm by weight at about 5% by weight. 1

6. The optical fiber according to claim 10, further characterized in that the optical fiber is one selected from the group consisting of fibers individually, fibers of multiple modes, fibers of change of dispersion, fibers with large effective areas and fibers High performance ultra long distance with controlled linear dispersion.