阅读说明：本技术 一种包层组分优化的大有效模面积低损耗光纤 (Large effective mode area low-loss optical fiber with optimized cladding components ) 是由 王龙飞 李凡 眭立洪 于 2020-04-30 设计创作，主要内容包括：本发明提供了一种包层组分优化的大有效模面积低损耗光纤,包括芯层和包层,所述包层从内向外包括第一下陷层,第二下陷层,任选的第三下陷层,和外包层。本发明通过在光纤包层中进行磷和铝共掺,在玻璃中形成[AlPO<Sub>4</Sub>]四面体,在有效降低包层折射率的同时,可优化包层粘度,且不会导致氢损的增加,工艺简单,可重复性强。(The invention provides a large effective mode area low-loss optical fiber with optimized cladding components, which comprises a core layer and a cladding layer, wherein the cladding layer comprises a first sunken layer, a second sunken layer, an optional third sunken layer and an outer cladding layer from inside to outside. The invention forms [ AlPO ] in glass by co-doping phosphorus and aluminum in the cladding of the optical fiber 4 ]The tetrahedron can optimize the viscosity of the cladding while effectively reducing the refractive index of the cladding, does not cause the increase of hydrogen loss, and has simple process and strong repeatability.)

1. A large effective mode area low loss optical fiber with optimized cladding composition comprising a core layer and a cladding layer, said cladding layer comprising from the inside out a first depressed layer, a second depressed layer and an outer cladding layer,

the second sunken layer is a multi-element doped quartz inner cladding, the dopants comprise fluorine, aluminum and phosphorus, wherein the doping amount of the aluminum and the phosphorus is 0-10 mol%, the aluminum and the phosphorus are distributed continuously, the molar ratio of the aluminum to the phosphorus is 0.7-1.3: 1, and the aluminum and the phosphorus are co-doped in the glass to form [ AlPO ]₄]Tetrahedron, [ AlPO ]₄]]The refractive index contribution amount of the tetrahedron to the second depressed layer is-0.8% -0, the refractive index contribution amount of the fluorine to the second depressed layer is-0.05% -0, the relative refractive index difference △ n2 of the second depressed layer is-0.85% -0, and the radius R2 of the second depressed layer is 8-35 μm.

2. The optical fiber of claim 1, wherein the first depressed layer is a pure silica layer or a multi-doped silica inner cladding, and when the first depressed layer is the multi-doped silica inner cladding, the dopant comprises fluorine, aluminum and phosphorus, wherein the doping amount of aluminum and phosphorus is 0-10 mol%, the doping amount is continuously distributed, the molar ratio of aluminum to phosphorus is 0.8-1.2: 1, and the co-doping of aluminum and phosphorus forms [ AlPO ] in the glass₄]]Tetrahedron, andAlPO₄]the refractive index contribution amount of the tetrahedron to the first depressed layer is-0.8% -0, the refractive index contribution amount of the fluorine to the first depressed layer is-0.05% -0, the relative refractive index difference △ n1 of the first depressed layer is-0.85% -0, and the radius R1 of the first depressed layer is 6-20 μm.

3. The optical fiber of claim 1, wherein the outer cladding is a pure silica cladding or a multi-doped silica cladding, and when the outer cladding is a multi-doped silica cladding, the doping elements are fluorine, aluminum and phosphorus, wherein the doping amount of aluminum and phosphorus is 0 to 5 mol%, the doping elements are continuously distributed, the molar ratio of aluminum to phosphorus is 0.9 to 1.1:1, the refractive index contribution of fluorine to the outer cladding is-0.02 to 0, [ AlPO ] 0₄]The refractive index contribution of tetrahedron to the overcladding is-0.4% -0, the relative refractive index difference △ n4 of the overcladding is-0.42% -0, and the radius R4 of the overcladding is 62.5 μm.

4. The optical fiber of claim 1, wherein the core layer is a multi-doped silica core layer, the dopant comprises germanium and fluorine, wherein germanium contributes 0-0.3% to the refractive index of the core layer, fluorine contributes-0.05% -0% to the refractive index of the core layer, the dopant is distributed continuously in the core layer, the relative refractive index difference Δ n0 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 any one of claims 1 to 4, wherein fluorine is introduced by Freon or silicon tetrafluoride, phosphorus is phosphorus peroxypentoxide, by a raw material of phosphorus trichloride, and aluminum is aluminum oxide, by a raw material of aluminum chloride.

6. The optical fiber of any of claims 1-4, wherein the cladding further comprises a third depressed layer, the third depressed layer being located between the second depressed layer and the outer cladding.

7. The optical fiber of claim 6, wherein the third depressed layer is a multi-doped silica inner cladding and the dopant comprises fluorine, aluminum and phosphorus, wherein the aluminum and the phosphorusThe doping amount of (a) is 0-5 mol%, and the doping amount is continuously distributed, the molar ratio of aluminum to phosphorus is 0.7-1.3: 1, the refractive index contribution amount of fluorine to the third sunken layer is-0.05% -0, [ AlPO ]₄]The refractive index contribution amount of the tetrahedron to the third depressed layer is-0.4% -0, the relative refractive index difference △ n3 of the third depressed layer is-0.45% -0, and the radius R3 of the third depressed layer is 8-62.5 μm.

8. The optical fiber of any of claims 1 to 3, wherein the optical fiber has an attenuation of 0.18dB/km or less at a wavelength of 1550 nm.

9. The optical fiber of any of claims 1 to 3, wherein the optical fiber has an attenuation of 0.16dB/km or less at a wavelength of 1550 nm.

10. The optical fiber of any of claims 1 to 3, wherein the optical fiber has an attenuation change at a wavelength of 1550nm of less than or equal to 0.01dB/km after being reacted at 70 ℃ for at least 16 hours at a concentration of 0.01% H2 by volume.

Technical Field

The application belongs to the technical field of communication transmission, and particularly relates to a large effective mode area low-loss optical fiber with optimized cladding components.

Background

The long-distance communication has the characteristics of large capacity and high speed, which requires the optical fiber to have higher nonlinear threshold and lower transmission loss, and the proposal of the large-mode-field low-loss optical fiber meets the requirement, thereby causing extensive attention and research of global optical communication research and development institutions and companies.

The most direct way to improve the nonlinear threshold and the signal-to-noise ratio is to increase the effective area of the optical fiber, and the increase of the effective mode field area will result in the deterioration of the bending resistance of the optical fiber, so it is generally necessary to add a low refractive index cladding to the cladding of the optical fiber to improve the bending resistance. The low refractive index cladding is generally a cladding having a refractive index lower than that of pure silica and can be obtained by doping fluorine or boron, but since the doping of boron causes problems such as deterioration of dispersion and increase of loss of an optical fiber, the low refractive index cladding is mainly obtained by doping fluorine in the art. However, the fluorine doping can cause the high-temperature viscosity, softening temperature and expansion mismatch of the low-refractive-index cladding and the core, on one hand, residual stress can be generated in the preform and the optical fiber, on the other hand, the increase of broken bonds of the low-refractive-index layer can be caused in the drawing process, and finally, the transmission loss of the optical fiber is increased, and the mechanical strength is poor. Therefore, it is necessary to optimize the glass composition of the core and/or the low-refractive-index cladding layer, reduce the high-temperature viscosity, the softening temperature and the expansion difference of the core and the low-refractive-index cladding layer, and reduce the transmission loss of the optical fiber.

Patent CN106458696A discloses a method of diffusing alkali metal into optical fiber by thermal diffusion, resulting in a lower attenuation optical fiber, but single doping of alkali metal leads to increased hydrogen loss, which is not good for long-term operation stability of optical fiber.

Patent CN109445023A discloses that co-doping of phosphorus, fluorine and alkali metal in the core and the cladding realizes viscosity matching of the core package, and avoids attenuation increase under hydrogen treatment caused by single metal doping, but this method needs to dope three elements of phosphorus, fluorine and alkali metal, and has more components, complex process, high preparation difficulty, low repeatability, and is not favorable for cost reduction.

Disclosure of Invention

The following are definitions and descriptions of some terms involved in the present invention:

mol%: mole percent;

wt.%: mass percent;

from the most central axis of the fiber, the layer defined as the layer closest to the axis is the core layer and the outermost layer of the fiber, i.e., the pure silica layer, is defined as the fiber outer cladding layer, depending on the change in refractive index.

Relative index difference △ n between layers of optical fiber_iDefined by the following equation:

wherein n is_iIs the refractive index of the core or cladding, n_sIs a pure silica refractive index.

The optical fiber core germanium doped refractive index difference contribution Δ Ge is defined by the following equation:

nGe is the amount of change in the refractive index of the glass caused by germanium incorporated into the quartz glass alone.

The fluorine-doped index difference contribution Δ F in the fiber cladding is defined as follows:

where nF is the amount of change in the refractive index of the glass caused by fluorine alone when incorporated into the quartz glass.

In optical fiber cladding [ AlPO ]₄]The refractive index difference contribution △ AlP is defined as follows:

wherein nAlP is [ AlPO ] independently existing in quartz glass₄]The amount of change in refractive index of the glass caused by tetrahedron.

The invention aims to solve the technical problems that in the prior art, hydrogen loss of an optical fiber is increased and long-term working stability of the optical fiber is deteriorated due to single doping of alkali metal elements, and the problems that the elements involved are more, the process is complex, the preparation difficulty is high, the repeatability is low and the cost is not reduced due to co-doping of phosphorus, fluorine and alkali metal in a fiber core and a cladding are overcome, so that the optical fiber with large effective area and optimized cladding components is provided.

The technical scheme adopted by the invention for solving the problems is as follows: there is provided a large effective mode area low loss optical fiber optimized in clad composition, comprising a core layer and a clad layer, said clad layer comprising, from the inside to the outside, a first depressed layer, a second depressed layer and an outer clad layer, wherein,

the second depressed layer is a multi-element doped quartz inner cladding, the dopants comprise fluorine, aluminum and phosphorus, the doping amount of the aluminum and the phosphorus is 0-10 mol%, the aluminum and the phosphorus are distributed continuously, the molar ratio of the aluminum to the phosphorus is 0.7-1.3: 1, and the co-doping of the aluminum and the phosphorus forms [ AlPO4] in the glass]Tetrahedron, [ AlPO ]₄]The refractive index contribution amount of the tetrahedron to the second depressed layer is-0.8% -0, the refractive index contribution amount of the fluorine to the second depressed layer is-0.05% -0, the relative refractive index difference △ n2 of the second depressed layer is-0.85% -0, and the radius R2 of the second depressed layer is 8-35 μm.

In the above scheme, preferably, the first depressed layer is a pure quartz layer or a multi-element doped quartz inner cladding, and when the first depressed layer is the multi-element doped quartz inner cladding, the dopant includes fluorine, aluminum and phosphorus, wherein the doping amount of aluminum and phosphorus is 0-5 mol%, the doping amount is continuously distributed, the molar ratio of aluminum to phosphorus is 0.8-1.2: 1, and the co-doping of aluminum and phosphorus forms [ AlPO ] in the glass₄]Tetrahedron, [ AlPO ]₄]The refractive index contribution amount of the tetrahedron to the first depressed layer is-0.4% -0, the refractive index contribution amount of the fluorine to the first depressed layer is-0.05% -0, the relative refractive index difference △ n1 of the first depressed layer is-0.55% -0, and the radius R1 of the first depressed layer is 6-20 μm.

Further preferably, the outer cladding is a pure quartz cladding or a multi-doped quartz cladding, when the outer cladding is a multi-doped quartz cladding, the doping elements are fluorine, aluminum and phosphorus, wherein the doping amount of the aluminum and the phosphorus is 0-5 mol% and is continuously distributed, the molar ratio of the aluminum to the phosphorus is 0.9-1.1: 1, the refractive index contribution amount of the fluorine to the outer cladding is-0.02% -0, [ AlPO ] is₄]The refractive index contribution of tetrahedron to the overcladding is-0.4% -0, the relative refractive index difference △ n4 of the overcladding is-0.42% -0, and the radius R4 of the overcladding is 62.5 μm.

Furthermore, the core layer is a multi-element doped silicon dioxide core layer, the dopant comprises germanium and fluorine, wherein the contribution amount of the germanium to the refractive index of the core layer is 0-0.3%, the contribution amount of the fluorine to the refractive index of the core layer is-0.05% -0, the germanium and the fluorine are continuously distributed in the core layer, the relative refractive index difference delta n0 of the core layer is 0-0.25%, and the radius R0 of the core layer is 5-8 mu m.

In the above method, the dopants in the first and second depressed layers respectively include fluorine, aluminum and phosphorus, and preferably, wherein the doping amount of aluminum in the first and second depressed layers cannot be 0 mol% at the same time, and wherein the doping amount of phosphorus is not 0 mol% at the same time.

Further, in the above scheme, preferably, fluorine is introduced by freon or silicon tetrafluoride, phosphorus is phosphorus pentoxide, and introduced by phosphorus trichloride raw material, and aluminum is aluminum oxide, and introduced by aluminum chloride raw material.

In another preferred embodiment of the present invention, the above-described low loss optical fiber is optimized for cladding composition, wherein the cladding further comprises a third depressed layer, the third depressed layer being located between the second depressed layer and the outer cladding.

Preferably, the third depressed layer is a multi-element doped quartz inner cladding, the dopant comprises fluorine, aluminum and phosphorus, the doping amount of the aluminum and the phosphorus is 0-5 mol%, the aluminum and the phosphorus are distributed continuously, the molar ratio of the aluminum to the phosphorus is 0.7-1.3: 1, the refractive index contribution amount of the fluorine to the third depressed layer is-0.05% -0, [ AlPO ] - [₄]The refractive index contribution amount of the tetrahedron to the third depressed layer is-0.4% -0, the relative refractive index difference △ n3 of the third depressed layer is-0.45% -0, and the radius R3 of the third depressed layer is 8-62.5 μm.

Further, the attenuation of the optical fiber at a wavelength of 1550nm is less than or equal to 0.18dB/km, preferably less than or equal to 0.17dB/km, more preferably less than or equal to 0.16 dB/km.

Further, the optical fiber reacts for at least 16 hours at 70 ℃ in 0.01% H2 volume concentration, and the attenuation change value of the optical fiber at the wavelength of 1550nm is less than or equal to 0.01dB/km, more preferably less than or equal to 0.002 dB/km; wherein, the 0.01% H2 means that the volume concentration of H2 in the mixed gas of H2 and He is 0.01%.

In another more specific embodiment of the present invention, there is provided a large effective mode area low loss optical fiber optimized for cladding composition comprising a core layer and a cladding layer comprising from the inside out a first depressed layer, a second depressed layer, optionally including or not including a third depressed layer, and an outer cladding layer, wherein,

the core layer is a multi-element doped silicon dioxide core layer, the dopant comprises germanium, fluorine and the like, wherein the contribution amount of germanium to the refractive index of the core layer is 0-0.3%, the contribution amount of fluorine to the refractive index of the core layer is-0.05% -0, the germanium and the fluorine are continuously distributed in the core layer, the relative refractive index difference delta n0 of the core layer is 0-0.25%, and the radius R0 of the core layer is 5-8 mu m;

the first sunken layer is a pure quartz layer and can also be a multi-element doped quartz inner cladding, when the first sunken layer is the multi-element doped quartz inner cladding, the adulterants comprise fluorine, aluminum and phosphorus, wherein the doping amount of the aluminum and the phosphorus is 0-10 mol%, the adulterants are distributed continuously, the molar ratio of the aluminum to the phosphorus is 0.8-1.2: 1, and the co-doping of the aluminum and the phosphorus can form [ AlPO ] in the glass₄]Tetrahedron of [ AlPO4]]The tetrahedron can effectively reduce the refractive index of the glass, and the contribution amount of fluorine to the refractive index of the first depressed layer is-0.05% -0, [ AlPO ]₄]The refractive index contribution amount of the tetrahedron to the first depressed layer is-0.8% -0, the relative refractive index difference △ n1 of the first depressed layer is-0.85% -0, and the radius R1 of the first depressed layer is 6-20 μm;

the second depressed layer is a multi-element doped quartz inner cladding, the dopant comprises fluorine, aluminum and phosphorus, wherein the doping amount of the aluminum and the phosphorus is 0-10 mol%, the aluminum and the phosphorus are distributed continuously, the molar ratio of the aluminum to the phosphorus is 0.7-1.3: 1, the refractive index contribution amount of the fluorine to the second depressed layer is-0.05% -0, [ AlPO ] - [₄]The refractive index contribution amount of the tetrahedron to the second depressed layer is-0.8% -0, the relative refractive index difference △ n2 of the second depressed layer is-0.85% -0, and the radius R2 of the second depressed cladding is 8-35 μm;

optionally, the third depressed layer is a multi-element doped quartz inner cladding, the dopant comprises fluorine, aluminum and phosphorus, wherein the doping amount of the aluminum and the phosphorus is 0-5 mol% and is continuously distributed, the molar ratio of the aluminum to the phosphorus is 0.7-1.3: 1, the refractive index contribution amount of the fluorine to the third depressed layer is-0.05-0, the refractive index contribution amount of [ AlPO4] tetrahedron to the third depressed layer is-0.4-0, the relative refractive index difference delta n3 of the third depressed layer is-0.45-0, and the radius R3 of the third depressed layer is 8-62.5 μm;

the outer cladding layer is a pure quartz cladding layer or a multi-element doped quartz cladding layer, when the outer cladding layer is the multi-element doped quartz cladding layer, the doping elements are fluorine, aluminum and phosphorus, wherein the doping amount of the aluminum and the phosphorus is 0-5 mol%, the aluminum and the phosphorus are distributed continuously, the molar ratio of the aluminum to the phosphorus is 0.9-1.1: 1, the refractive index contribution amount of the fluorine to the outer cladding layer is-0.02% -0, [ AlPO ] and₄]the refractive index contribution amount of the tetrahedron to the outer cladding is-0.4% -0, the relative refractive index difference △ n4 of the outer cladding is-0.42% -0, and the radius R4 of the outer cladding is 62.5 mu m;

wherein, fluorine is introduced by Freon or silicon tetrafluoride, phosphorus is phosphorus pentoxide, phosphorus trichloride is introduced, aluminum is aluminum oxide, and aluminum chloride is introduced.

The invention has the beneficial effects that:

firstly, the cladding of the optical fiber provided by the invention is mainly co-doped with aluminum and phosphorus, and simultaneously doped with a small amount of fluorine, and the aluminum and the phosphorus are formed into [ AlPO ] in glass₄]The tetrahedron can optimize the viscosity of the cladding, reduce the defects in the preparation process of the optical fiber and reduce the axial stress of the optical fiber while effectively reducing the refractive index of the cladding, thereby further reducing the attenuation parameter of the optical fiber;

and secondly, no alkali metal is doped, so that extra loss caused by hydrogen loss is avoided, and the long-term working stability of the optical fiber is ensured.

And thirdly, the doping amount of fluorine in the fiber core layer and the fiber cladding layer provided by the invention can be lower than 0.15 wt.%, the doping amount of fluorine is greatly reduced, the manufacturing cost is reduced while better stability of the optical fiber is ensured, the environmental protection is facilitated, the process is simple, and the repeatability is strong.

Drawings

The technical solution of the present application is further explained below with reference to the drawings and the embodiments.

FIG. 1 is a graph of the aluminum and phosphorus content of a typical optical fiber.

FIG. 2 is a schematic view showing a cross-sectional view of the refractive index of an optical fiber in example 1.

FIG. 3 is a schematic view showing a cross-sectional view of the refractive index of an optical fiber in example 2.

FIG. 4 is a schematic representation of another refractive index profile suitable for use in the present invention.

Detailed Description

The present invention will be further illustrated and described with reference to specific embodiments, it should be noted that the embodiments and features of the embodiments may be combined with each other in the present application without conflict.

In the following example 1 and comparative examples 1 to 3, the optical fiber includes a core layer and a clad layer, the core layer has a radius of R0, the core layer has a relative refractive index difference of Δ n0, the clad layer sequentially covers a first depressed layer, a second depressed layer, a third depressed layer and an outer clad layer from inside to outside, the first depressed layer has a radius of R1, the relative refractive index difference of Δ n1, the second depressed layer has a radius of R2, the relative refractive index difference of Δ n2, the third depressed layer has a radius of R3, the relative refractive index difference of Δ n3, and the outer clad layer has a radius of R4 and is a pure silica clad layer.