LARGE-EFFECTIVE-MODE-AREA LOW-LOSS OPTICAL FIBER WITH OPTIMIZED CLADDING COMPONENTS

Abstract

The present invention provides a large-effective-mode-area low-loss optical fiber with optimized cladding components, which comprises a core layer and a cladding comprising, from the inside to the outside, a first sinking layer, a second sinking layer, an optional third sinking layer, and an outer cladding. In the present invention, phosphorus and aluminum are co-doped in the optical fiber cladding, to form a tetrahedron [AlPO.sub.4] in glass, thus optimizing the viscosity of the cladding while effectively reducing the refractive index of the cladding, without causing increased hydrogen loss. The process is simple, and highly repeatable.

Claims

1. A large-effective-mode-area low-loss optical fiber with optimized cladding components, comprising a core layer and a cladding comprising, from inside to outside, a first sinking layer, a second sinking layer and an outer cladding, wherein the second sinking layer is a multi-doped quartz inner cladding, and dopants comprise fluorine, aluminum and phosphorus, wherein aluminum and phosphorus are doped in an amount of 0-10 mol %, and have a continuous distribution, the molar ratio of aluminum and phosphorus is 0.7-1.3:1, aluminum and phosphorus are co-doped in glass to form a [AlPO.sub.4] tetrahedron, the contribution of the [AlPO.sub.4] tetrahedron to the refractive index of the second sinking layer is −0.8%-0, the contribution of fluorine to the refractive index of the second sinking layer is −0.05%-0, the relative difference Δn2 in refractive index of the second sinking layer is −0.85%-0, and the radius R2 of the second sinking layer is 8-35 μm.

2. The optical fiber according to claim 1, wherein the first sinking layer is a pure quartz layer or a multi-doped quartz inner cladding, and when the first sinking layer is a multi-doped quartz inner cladding, dopants comprise fluorine, aluminum and phosphorus, wherein aluminum and phosphorus are doped in an amount of 0-10 mol %, and have a continuous distribution, the molar ratio of aluminum and phosphorus is 0.8-1.2:1, aluminum and phosphorus are co-doped in glass to form a [AlPO.sub.4]] tetrahedron, the contribution of the [AlPO.sub.4] tetrahedron to the refractive index of the first sinking layer is −0.8%-0, the contribution of fluorine to the refractive index of the first sinking layer is −0.05%-0, the relative difference Δn1 in refractive index of the first sinking layer is −0.85%-0, and the radius R1 of the first sinking layer is 6-20 μm.

3. The optical fiber according to claim 1, wherein the outer cladding is a pure quartz cladding or a multi-doped quartz cladding, and when the outer cladding is a multi-doped quartz cladding, dopants comprise fluorine, aluminum and phosphorus, wherein aluminum and phosphorus are doped in an amount of 0-5 mol %, and have a continuous distribution, the molar ratio of aluminum and phosphorus is 0.9-1.1:1, the contribution of fluorine to the refractive index of the outer cladding is −0.02%-0, the contribution of the [AlPO.sub.4] tetrahedron to the refractive index of the outer cladding is −0.4%-0, the relative difference Δn4 in refractive index of the outer cladding is −0.42%-0, and the radius R4 of the outer cladding is 62.5 μm.

4. The optical fiber according to claim 1, wherein the core layer is a multi-doped silica core layer, and dopants comprise germanium and fluorine, wherein the contribution of germanium to the refractive index of the core layer is 0-0.3%, the contribution of fluorine to the refractive index of the core layer is −0.05%-0, and the dopants have a continuous distribution in the core layer, the relative difference Δn0 in refractive index of the core layer is 0-0.25%, and the radius R0 of the core layer is 5-8 μm.

5. The optical fiber according to claim 1, wherein fluorine is introduced through freon or silicon tetrafluoride, the phosphorus is phosphorus pentoxide and introduced through the raw material phosphorus trichloride, aluminum is alumina and introduced through the raw material aluminum chloride.

6. The optical fiber according to claim 1, wherein the cladding further comprises a third sinking layer, located between the second sinking layer and the outer cladding.

7. The optical fiber according to claim 6, wherein the third sinking layer is a multi-doped quartz inner cladding, and dopants comprise fluorine, aluminum and phosphorus, wherein aluminum and phosphorus are doped in an amount of 0-5 mol %, and have a continuous distribution, the molar ratio of aluminum and phosphorus is 0.7-1.3:1, the contribution of fluorine to the refractive index of the third sinking layer is −0.05%-0, the contribution of the [AlPO.sub.4]tetrahedron to the refractive index of the third sinking layer is −0.4%-0, the relative difference Δn3 in refractive index of the third sinking layer is −0.45%-0, and the radius R3 of the third sinking layer is 8-62.5 μm.

8. The optical fiber according to claim 1, wherein the attenuation of the optical fiber at a wavelength of 1550 nm is less than or equal to 0.18 dB/km.

9. The optical fiber according to claim 1, wherein the attenuation of the optical fiber at a wavelength of 1550 nm is less than or equal to 0.16 dB/km.

10. The optical fiber according to claim 1, wherein after the optical fiber is reacted for at least 16 h in 0.01 vol % H.sub.2 at 70° C., the change in attenuation of the optical fiber at a wavelength of 1550 nm is less than or equal to 0.01 dB/km.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0040] The technical solution of the present application is further described below with reference to accompanying drawing in connection with embodiments.

[0041] FIG. 1 shows the distribution of aluminum and phosphorus content in a typical optical fiber.

[0042] FIG. 2 is a schematic view of the refractive index along a cross section of an optical fiber in Example 1.

[0043] FIG. 3 is a schematic view of the refractive index along a cross section of an optical fiber in Example 2.

[0044] FIG. 4 is another schematic view of the refractive index along a cross section suitable for the present invention.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0045] Hereinafter, the disclosure of the present invention is further elucidated and described with reference to specific examples. It should be noted that the embodiments and the features in the embodiments in the present application can be combined with each other without conflict.

[0046] In the following Example 1 and Comparative Examples 1-3, the optical fiber includes a core layer and a cladding. The radius of the core layer is R0, and the relative difference in refractive index of the core layer is Δn0. The cladding includes sequentially, from the inside to the outside, a first sinking layer, a second sinking layer, a third sinking layer and an outer cladding. The radius of the first sinking layer is R1, and the relative difference in refractive index is Δn1. The radius of the second sinking layer is R2, and the relative difference in refractive index is Δn2. The radius of the third sinking layer is R3, and the relative difference in refractive index is Δn3. The outer cladding has a radius of R4, and is a pure quartz cladding.

Example 1

[0047] The core layer of the optical fiber comprises germanium, fluorine, and silica, which have a continuous distribution in the core layer. The first sinking layer comprises fluorine, P.sub.2O.sub.5, Al.sub.2O.sub.3 and silica, where F has a content of 0.2 mol % and has a continuous distribution, the P.sub.2O.sub.5 content is 2.3 mol %, and the Al.sub.2O.sub.3 content is 2.3 mol %. The second sinking layer comprises P.sub.2O.sub.5, Al.sub.2O.sub.3 and silica, where the P.sub.2O.sub.5 content is 6.2 mol %, and the Al.sub.2O.sub.3 content is 6.5 mol %. The third sinking layer comprises fluorine, P.sub.2O.sub.5, Al.sub.2O.sub.3 and silica, where F has a content of 0.2 mol % and has a continuous distribution, the P.sub.2O.sub.5 content is 2.3 mol %, and the Al.sub.2O.sub.3 content is 2.3 mol %. The attenuation of the optical fiber at 1550 nm is 0.152 dB/km, and after the optical fiber is reacted for at least 16 h in 0.01% H.sub.2 at 70° C., the change in attenuation of the optical fiber at 1550 nm is 0.001 dB/km.

Comparative Example 1

[0048] The core layer of the optical fiber comprises germanium, fluorine, silica, an alkali metal oxide, and P.sub.2O.sub.5, where the alkali metal oxide has a content of 100 ppm and has a continuous distribution; and P.sub.2O.sub.5 has a content of 100 ppm and has a continuous distribution in the core layer. The first sinking layer adjacent to the core layer comprises germanium, fluorine, silica, and an alkali metal oxide, where the alkali metal oxide (K.sub.2O) has a content of 5 ppm and has a continuous distribution; and P.sub.2O.sub.5 has a content of 20 ppm and has a continuous distribution. The attenuation of the optical fiber at 1550 nm is 0.155 dB/km, and after the optical fiber is reacted for at least 16 h in 0.01% H.sub.2 at 70° C., the change in attenuation of the optical fiber at 1550 nm is 0.004 dB/km. The specific parameters are listed in Table 1.

Comparative Example 2

[0049] The core layer of the optical fiber comprises germanium, sodium and silica, which have a continuous distribution in the core layer. The first sinking layer comprises fluorine and silica, where fluorine has a content of 2 mol % and has a continuous distribution. The second sinking layer comprises fluorine and silica, where F has a content of 3.8 mol % and has a continuous distribution. The third sinking layer comprises fluorine and silica, where fluorine has a content of 2 mol % and has a continuous distribution. The attenuation of the optical fiber at 1550 nm is 0.156 dB/km, and after the optical fiber is reacted for at least 16 h in 0.01% H.sub.2 at 70° C., the change in attenuation of the optical fiber at 1550 nm is 0.008 dB/km.

Comparative Example 3

[0050] The core layer of the optical fiber comprises germanium, fluorine, potassium and silica, where the K content is 0.1 mol %, and the F content is 1.8 mol %. The first sinking layer comprises fluorine and silica, where fluorine has a content of 1.8 mol % and has a continuous distribution. The second sinking layer comprises fluorine and silica, where F has a content of 3.8 mol % and has a continuous distribution. The attenuation of the optical fiber at 1550 nm is 0.160 dB/km, and after the optical fiber is reacted for at least 16 h in 0.01% H.sub.2 at 70° C., the change in attenuation of the optical fiber at 1550 nm is 0.01 dB/km.

Example 2

[0051] The optical fiber includes a core layer and a cladding. The core layer of the optical fiber is doped with germanium, and has a radium R0 of 8 μm. The relative difference Δn0 in refractive index of the core layer is 0.15%. The cladding includes sequentially, from the inside to the outside, a first sinking layer, a second sinking layer and an outer cladding. The radius R1 of the first sinking layer is 14 μm, and the relative difference Δn1 in refractive index is −0.8%. The radius R2 of the second sinking layer is 26 μm, and the relative difference Δn2 in refractive index is −0.14%. The radius of the outer cladding is 62.5 μm, and the relative difference in refractive index is −0.07%. The first sinking layer comprises P.sub.2O.sub.5, Al.sub.2O.sub.3 and silica, where P.sub.2O.sub.5 has a content of 10 mol %, and has a continuous distribution; and Al.sub.2O.sub.3 has a content of 11 mol %, and has a continuous distribution. The second sinking layer comprises P.sub.2O.sub.5, Al.sub.2O.sub.3 and silica, where P.sub.2O.sub.5 has a content of 1.8 mol %, and has a continuous distribution; and Al.sub.2O.sub.3 has a content of 1.75 mol %, and has a continuous distribution. The outer cladding comprises 0.7 mol % fluorine. The attenuation of the optical fiber at 1550 nm is 0.154 dB/km, and after the optical fiber is reacted for at least 16 h in 0.01% H.sub.2 at 70° C., the change in attenuation of the optical fiber at 1550 nm is 0.0015 dB/km.

[0052] The doping parameters for the optical fiber prepared in the above Examples 1-2 and Comparative Examples 1-3 are shown in Table 1.

TABLE-US-00001 TABLE 1 Doping parameters for optical fiber prepared in examples of the present invention Core layer Example Comparative Comparative Comparative Example and cladding Parameter 1 Example 1 Example 2 Example 3 2 Core layer Al 0 0 0 0 0 P 0 100 ppm 0 0 0 K 0 100 ppm 0 0.1 mol % 0 F 0.1 mol % / 0 0.3 mol % 0 First sinking Al 2.3 mol % 0 0 0 11 mol % layer P 2.3 mol %  20 ppm 0 0 10 mol % K 0  5 ppm 0 0 0 F 0.2 mol % / 2 mol % 1.8 mol % 0 Second Al 6.5 mol % / 0 0 1.75 mol % sinking layer P 6.2 mol % / 0 0 1.75 mol % F 0 / 3.8 mol %   3.8 mol % 0 Third Al 2.3 mol % / 0 0 0 sinking layer P 2.3 mol % / 0 0 0 F 0.2 mol % / 2 mol %   2 mol % 0.7 mol %

[0053] In the optical fibers prepared in Example 1, Example 2, and Comparative Examples 1, 2 and 3, the values for the radius R1 of the first sinking layer, the relative difference Δn1 in refractive index, the radius R2 of the second sinking layer, the relative difference Δn2 in refractive index, the radius R3 of the third sinking layer, the relative difference Δn3 in refractive index, the radius R4 of the outer cladding, the radius R0 of the core layer, and the relative difference Δn0 in refractive index are shown in Table 2.

TABLE-US-00002 TABLE 2 Radius and relative difference in refractive index of the core layer and cladding of the optical fibers prepared in the examples of the present invention Exam- Comparative Comparative Comparative Exam- Parameter ple 1 Example 1 Example 2 Example 3 ple 2 Δn 0% 0 0 0 0 0.15 R0 [μm] 5 5 5 5 8 Δn1 [%] −0.2 −0.2 −0.2 −0.2 −0.8 R1 [μm] 13 13 13 13 14 Δn2 [%] −0.5 −0.5 −0.5 −0.5 −0.14 R2 [μm] 20 20 20 20 26 Δn3 [%] −0.2 −0.2 −0.2 −0.2 / R3 [μm] 50 50 50 50 / Δn4 [%] 0 0 0 0 −0.07 R4 [μm] 62.5 62.5 62.5 62.5 62.5

[0054] Optical fibers with other set doping parameters described in the present invention can be prepared by a method similar to those in Examples 1-2 of the present invention.

[0055] As suggested by desirable embodiments of the present application, a variety of changes and modifications can be made by those skilled in the art according to the disclosure and embodiments described above, the suggestions without departing from the technical idea of the present application. The technical scope of the present invention is not limited to the disclosure of the specification, and the technical scope thereof is defined by the scope of the claims.