阅读说明：本技术 Vad制备弯曲不敏感光纤预制棒的喷灯及光纤预制棒 (Blowtorch for preparing bending insensitive optical fiber preform by VAD and optical fiber preform ) 是由 梁后杰 孔明 伍淑坚 于 2020-07-10 设计创作，主要内容包括：本申请涉及VAD制备弯曲不敏感光纤预制棒的喷灯及光纤预制棒,包括柱形喷灯体,柱形喷灯体上设有中心供料孔以及围绕中心供料孔的多层环形分布气孔；多层环形分布气孔包括从内向外依次分布的内层火焰气孔和外层火焰气孔；内层火焰气孔包括从内向外依次分布的内层氧气气孔和内层氢气气孔；外层火焰气孔包括从内向外依次分布的外层氢气气孔和外层氧气气孔；外层火焰气孔沿气体喷射方向向外倾斜,且倾斜角度等于外层火焰气孔中心线与中心供料孔中心线的夹角。本申请能够解决相关技术中为了补偿光学包层中的氟元素向芯层扩散而引起芯层折射率下降,通过增加芯层GeO2掺杂,保证芯层折射率符合预期设计,进而引起光纤瑞利散射损耗增大的问题。(The application relates to a blowtorch for preparing a bending insensitive optical fiber perform rod by VAD and the optical fiber perform rod, which comprises a cylindrical blowtorch body, wherein the cylindrical blowtorch body is provided with a central material supply hole and a plurality of layers of annular distribution air holes surrounding the central material supply hole; the multilayer annular distribution air holes comprise inner layer flame air holes and outer layer flame air holes which are distributed from inside to outside in sequence; the inner layer flame air holes comprise inner layer oxygen air holes and inner layer hydrogen air holes which are distributed from inside to outside in sequence; the outer flame air holes comprise an outer hydrogen air hole and an outer oxygen air hole which are sequentially distributed from inside to outside; the outer flame air hole inclines outwards along the gas injection direction, and the inclination angle is equal to the included angle between the central line of the outer flame air hole and the central line of the central feeding hole. The method and the device can solve the problem that in the prior art, in order to compensate the decrease of the refractive index of the core layer caused by the diffusion of fluorine elements in the optical cladding layer to the core layer, the refractive index of the core layer is ensured to accord with the expected design by increasing the doping of GeO2 of the core layer, and then the Rayleigh scattering loss of the optical fiber is increased.)

1. A kind of VAD prepares the burner of the bending insensitive optical fiber preform, characterized by that: the cylindrical spray lamp comprises a cylindrical spray lamp body, wherein a central material supply hole (1) and a plurality of layers of annular distribution air holes surrounding the central material supply hole (1) are formed in the cylindrical spray lamp body;

the multiple layers of annular distribution air holes comprise inner layer flame air holes and outer layer flame air holes which are distributed from inside to outside in sequence;

the inner layer flame air holes comprise inner layer oxygen air holes (2) and inner layer hydrogen air holes (3) which are distributed from inside to outside in sequence;

the outer layer flame air holes comprise outer layer hydrogen air holes (4) and outer layer oxygen air holes (5) which are distributed from inside to outside in sequence;

the outer flame gas pocket leans out along the gas injection direction, and inclination equals the contained angle of outer flame gas pocket central line and central feeding hole (1) central line.

2. The burner for VAD fabricating a bend insensitive optical fiber preform according to claim 1 wherein: the inclination angle is 1-5 degrees.

3. The VAD fabricated bend insensitive fiber preform torch as defined in claim 2 wherein: the inclination angle is 3 °.

4. The burner for VAD fabricating a bend insensitive optical fiber preform according to claim 1 wherein: gas velocity V of inner flame air hole₁Gas flow velocity V with outer flame gas hole₂The conditions are satisfied: v₁＞1.5V₂。

5. The burner for VAD fabricating a bend insensitive optical fiber preform according to claim 1 wherein: the gas flow velocity V in the central feed hole (1)₀Gas flow velocity V less than inner flame gas hole₁。

6. The burner for VAD fabricating a bend insensitive optical fiber preform according to claim 1 wherein: the inner flame air holes comprise 1-2 inner oxygen air holes (2) and 1-2 inner hydrogen air holes (3).

7. The burner for VAD fabricating a bend insensitive optical fiber preform according to claim 1 wherein: the outer flame gas pocket includes 1 ~ 2 outer layer hydrogen gas pocket (4) and 1 ~ 2 outer layer oxygen gas pocket (5).

8. The burner for VAD fabricating a bend insensitive optical fiber preform according to claim 1 wherein: all the air holes in the annular distribution air holes are distributed in a circular ring shape, and each air hole is a circular straight hole.

9. The burner for VAD fabricating a bend insensitive optical fiber preform according to claim 1 wherein: the aperture of the central feeding hole (1) is 1.5-6 mm, the aperture of the inner layer flame air hole is 0.6-1.2 mm, and the aperture of the outer layer flame air hole is 0.8-1.6 mm.

10. An optical fiber preform characterized by: the optical fiber preform core is prepared by adopting a blowtorch for preparing a bending insensitive optical fiber preform by VAD according to any one of claims 1 to 9, and the interface density of the optical fiber preform core cladding ranges from 0.8 to 1.2g/cm³。

Technical Field

The application relates to the technical field of manufacturing of optical fiber preforms, in particular to a blowtorch for preparing a bent insensitive optical fiber preform by VAD and the optical fiber preform.

Background

The axial vapor deposition (VAD) is a high-efficiency optical fiber preform manufacturing technology, is used for preparing a bending insensitive optical fiber preform, can effectively eliminate the sinking of the center of a refractive index profile and improve the bending resistance of an optical fiber.

The VAD method is adopted to prepare the bending insensitive optical fiber preform, and a large amount of fluorine is usually doped in an optical cladding to reduce the refractive index of the optical cladding and form a depressed cladding refractive index profile structure. However, in the preform rod, fluorine in the optical cladding layer diffuses toward the core layer during high temperature processes such as sintering, and the refractive index of the core layer is reduced after the fluorine enters the core layer.

In order to ensure that the refractive index of the core layer meets the expected design, the GeO of the core layer needs to be further increased₂Doping to control the core refractive index. However, the core layer GeO₂The increase of the doping amount can cause the increase of the Rayleigh scattering loss of the optical fiber, which is not beneficial to the preparation of the low-loss bending insensitive optical fiber prefabricated rod.

Therefore, the density of the loose core-clad interface of the preform is improved, the diffusion of fluorine elements in the optical cladding to the core layer is inhibited under high-temperature conditions such as sintering and the like, and the method has important significance for preparing the low-loss bending-insensitive optical fiber preform.

Disclosure of Invention

The application provides a blowtorch and optical fiber perform of VAD preparation crooked insensitive optical fiber perform to in solving the correlation technique, in order to compensate the fluorine element in the optical cladding and to arouse that the sandwich layer refracting index descends to the diffusion of sandwich layer, through increasing sandwich layer GeO₂Doping, and ensuring that the refractive index of the core layer conforms to the expected design, thereby causing the problem of increasing the Rayleigh scattering loss of the optical fiber.

In a first aspect, a blowtorch for VAD preparation of a bending insensitive optical fiber preform is provided, which comprises a cylindrical blowtorch body, wherein a central feeding hole and a plurality of layers of annular distribution air holes surrounding the central feeding hole are arranged on the cylindrical blowtorch body;

the multiple layers of annular distribution air holes comprise inner layer flame air holes and outer layer flame air holes which are distributed from inside to outside in sequence;

the inner flame air holes comprise inner oxygen air holes and inner hydrogen air holes which are distributed from inside to outside in sequence;

the outer layer flame air holes comprise an outer layer hydrogen air hole and an outer layer oxygen air hole which are sequentially distributed from inside to outside;

outer flame gas pocket leans out along the gas injection direction, and inclination equals the contained angle of outer flame gas pocket central line and central feedhole central line.

In some embodiments, the angle of inclination is 1 ° to 5 °.

In some embodiments, the angle of inclination is 3 °.

In some embodiments, the inner flame hole has a gas flow velocity V₁Gas flow velocity V with outer flame gas hole₂The conditions are satisfied: v₁＞1.5V₂。

In some embodiments, the gas flow velocity V in the central feed hole₀Gas flow velocity V less than inner flame gas hole₁。

In some embodiments, the inner flame holes include 1-2 inner oxygen holes and 1-2 inner hydrogen holes.

In some embodiments, the outer flame holes include 1-2 outer hydrogen holes and 1-2 outer oxygen holes.

In some embodiments, all of the annularly distributed air holes are annularly distributed, and each air hole is a circular straight hole.

In some embodiments, the central feeding hole has a diameter of 1.5 to 6mm, the inner flame holes have a diameter of 0.6 to 1.2mm, and the outer flame holes have a diameter of 0.8 to 1.6 mm.

In a second aspect, an optical fiber preform is provided, which is prepared by a burner of the VAD bending insensitive optical fiber preform, and the interface density range of the core cladding of the optical fiber preform is 0.8-1.2 g/cm³。

The beneficial effect that technical scheme that this application provided brought includes:

the embodiment of the application provides a blowtorch for preparing a bending insensitive optical fiber preform by VAD and the optical fiber preform. However, fluorine in the optical cladding diffuses toward the core layer during high temperature processes such as sintering of the preform loose body, and the refractive index of the core layer is reduced after the fluorine enters the core layer. In order to ensure that the refractive index of the core layer meets the expected design, the GeO of the core layer needs to be further increased₂Doping to control the core refractive index. However, the core layer GeO₂The increase of the doping amount can cause the increase of the Rayleigh scattering loss of the optical fiber, which is not beneficial to the preparation of the low-loss bending insensitive optical fiber prefabricated rod.

Based on this, in the application, the blast burner is mentioned to improve the pre-sintering effect of the loose body of the bending insensitive optical fiber preform rod, namely, the density of the loose body core-package interface is increased during deposition, so as to inhibit the fluorine element in the optical cladding from diffusing to the core layer during subsequent high-temperature sintering, and reduce the GeO of the core layer₂Doping amount, thereby reducing Rayleigh scattering loss.

After repeated tests and verifications, the applicant finds that when VAD deposition is carried out, because the actual core layer is large, if flame is concentrated, the area of the flame finally contacting with the core layer is small, the flame can only be burned to the bottom of the core layer, and at the moment, the flame cannot wrap the core cladding interface, namely, the core cladding interface cannot be pre-sintered to improve the core cladding interface density, so that the diffusion of fluorine elements in an optical cladding to the core layer is not inhibited, and the method is not suitable for preparing a low-loss bending insensitive optical fiber preform.

Consequently, in order to carry out the presintering to the core package interface effectively, set up inlayer flame gas pocket and outer flame gas pocket on the blast lamp that this application provided, adjust the orientation of outer flame gas pocket simultaneously, make outer flame gas pocket lean out along the gas injection direction, inclination equals the contained angle theta of outer flame gas pocket central line and central feed hole central line, angle through adjusting outer flame, control outer flame direction, make outer flame firing point shift to core package interface department by the core bottom, directly carry out the presintering to the core package interface, thereby improve the density at core package interface effectively, therefore, fluorine element diffuses to the core when restraining follow-up high temperature sintering in the optics cladding, and then reduce the doping of core germanium content, reduce the rayleigh scattering loss, and the production cost is reduced.

This application is when using, and the gas flow velocity of inlayer flame gas pocket is greater than the gas flow velocity of outer flame gas pocket for outer flame speed is slower than inlayer flame speed, is favorable to flame to disperse, improves the area of contact of flame and sandwich layer, guarantees the abundant parcel of flame to the sandwich layer, thereby further improves the density at core package interface.

Drawings

In order to more clearly illustrate the technical solutions in the embodiments of the present application, the drawings needed to be used in the description of the embodiments are briefly introduced below, and it is obvious that the drawings in the following description are only some embodiments of the present application, and it is obvious for those skilled in the art to obtain other drawings based on these drawings without creative efforts.

FIG. 1 is a front view of a burner for fabricating a bend insensitive optical fiber preform by VAD provided in the embodiments of the present application;

FIG. 2 is a side cross-sectional view of a torch for VAD fabrication of a bend insensitive optical fiber preform according to an embodiment of the present application;

FIG. 3 is a schematic view of an angle between a centerline of an outer layer flame vent and a centerline of a center feed hole according to an embodiment of the present disclosure.

In the figure: 1. a central feed aperture; 2. inner layer oxygen pores; 3. inner hydrogen pores; 4. an outer layer hydrogen gas hole; 5. outer layer oxygen pores; A. a feed pipe; B. an inner oxygen line; C. an inner hydrogen pipeline; D. an outer hydrogen pipeline; E. an outer oxygen pipeline.

Detailed Description

In order to make the objects, technical solutions and advantages of the embodiments of the present application clearer, the technical solutions in the embodiments of the present application will be clearly and completely described below with reference to the drawings in the embodiments of the present application, and it is obvious that the described embodiments are some embodiments of the present application, but not all embodiments. All other embodiments, which can be derived by a person skilled in the art from the embodiments given herein without making any creative effort, shall fall within the protection scope of the present application.

The embodiment of the application provides a blowtorch for preparing a bending insensitive optical fiber preform by VAD, which can solve the problem that in the related technology, in order to compensate the decrease of the refractive index of a core layer caused by the diffusion of fluorine element in an optical cladding layer to the core layer, the GeO of the core layer is increased₂Doping, and ensuring that the refractive index of the core layer conforms to the expected design, thereby causing the problem of increasing the Rayleigh scattering loss of the optical fiber.

FIG. 1 is a front view of a burner for VAD manufacturing a bend-insensitive optical fiber preform according to an embodiment of the present application, wherein the burner for VAD manufacturing a bend-insensitive optical fiber preform includes a cylindrical burner body having a central feeding hole 1 and a plurality of annular distribution air holes surrounding the central feeding hole 1; the multilayer annular distribution air holes comprise inner layer flame air holes and outer layer flame air holes which are distributed from inside to outside in sequence;

referring to fig. 1 and 2, the central feeding hole 1 is used for feeding silicon tetrachloride and germanium tetrachloride, and when in use, the central feeding hole 1 is communicated with a feeding pipe A.

Referring to fig. 1 and 2, the inner flame holes include inner oxygen holes 2 and inner hydrogen holes 3 which are sequentially distributed from inside to outside; the inner layer oxygen air holes 2 are used for introducing oxygen and arranged on the inner side, and when the oxygen aeration device is used, the inner layer oxygen air holes 2 are communicated with the inner layer oxygen pipeline B; the inner layer hydrogen gas hole 3 is used for introducing hydrogen and is arranged on the outer side, and when the inner layer hydrogen gas hole 3 is used, the inner layer hydrogen gas hole is communicated with the inner layer hydrogen pipeline C.

Referring to fig. 1 and 2, the outer flame gas holes include an outer hydrogen gas hole 4 and an outer oxygen gas hole 5 which are sequentially distributed from inside to outside; the outer layer hydrogen holes 4 are used for introducing hydrogen and arranged on the inner side, and when the outer layer hydrogen holes 4 are used, the outer layer hydrogen pipelines D are communicated with the outer layer hydrogen holes 4; the outer layer oxygen air holes 5 are used for introducing oxygen and arranged on the outer side, and when the oxygen supplying device is used, the outer layer oxygen air holes 5 are communicated with the outer layer oxygen pipeline E.

Referring to fig. 3, the outer flame holes are inclined outward along the gas injection direction, and the inclination angle is equal to the included angle θ between the center line of the outer flame holes and the center line of the central feeding hole 1.

When VAD is adopted to prepare the bending insensitive optical fiber preform, a large amount of fluorine is usually doped in the optical cladding to reduce the refractive index of the optical cladding and form a depressed cladding refractive index profile structure. However, fluorine in the optical cladding diffuses toward the core layer during high temperature processes such as sintering of the preform loose body, and the refractive index of the core layer is reduced after the fluorine enters the core layer. In order to ensure that the refractive index of the core layer meets the expected design, the GeO of the core layer needs to be further increased₂Doping to control the core refractive index. However, the core layer GeO₂The increase of the doping amount can cause the increase of the Rayleigh scattering loss of the optical fiber, which is not beneficial to the preparation of the low-loss bending insensitive optical fiber prefabricated rod.

Based on this, in the application, the blast burner is mentioned to improve the pre-sintering effect of the loose body of the bending insensitive optical fiber preform rod, namely, the density of the loose body core-package interface is increased during deposition, so as to inhibit the fluorine element in the optical cladding from diffusing to the core layer during subsequent high-temperature sintering, and reduce the GeO of the core layer₂Doping amount, thereby reducing Rayleigh scattering loss.

After repeated tests and verifications, the applicant finds that when VAD deposition is carried out, because the actual core layer is large, if flame is concentrated, the area of the flame finally contacting with the core layer is small, the flame can only be burned to the bottom of the core layer, and at the moment, the flame cannot wrap the core cladding interface, namely, the core cladding interface cannot be pre-sintered to improve the core cladding interface density, so that the diffusion of fluorine elements in an optical cladding to the core layer is not inhibited, and the method is not suitable for preparing a low-loss bending insensitive optical fiber preform.

Therefore, in order to carry out the presintering to the core package interface effectively, set up inlayer flame gas pocket and outer flame gas pocket on the blast burner that this application provided, adjust the orientation of outer flame gas pocket simultaneously, make outer flame gas pocket lean out along the gas injection direction, inclination equals the contained angle theta of outer flame gas pocket central line and central feed hole 1 central line, through the angle of adjusting outer flame, control outer flame direction, make outer flame firing point shift to core package interface department by the core bottom, directly carry out the presintering to the core package interface, thereby improve the density at core package interface effectively, therefore, fluorine element diffuses to the core package in the optics cladding when restraining follow-up high temperature sintering, and then reduce the doping of core germanium content, reduce the scattering rayleigh loss, and the production cost is reduced.

In some preferred embodiments, the angle of inclination is from 1 ° to 5 °. In an embodiment with a better effect, the inclination angle is set to 3 °.

In some preferred embodiments, the gas velocity V of the inner flame holes₁Gas flow velocity V with outer flame gas hole₂The conditions are satisfied: v₁＞1.5V₂The outer flame speed is lower than the inner flame speed, so that flame divergence is facilitated, the contact area between the flame and the core layer is increased, the flame is fully wrapped on the core layer, and the interface density of the core cladding is effectively increased.

In some preferred embodiments, the gas flow velocity V in the central feed hole 1₀Gas flow velocity V less than inner flame gas hole₁The inner flame can wrap the raw materials, so that the raw materials can be fully reacted, and the utilization rate of the raw materials can be improved.

In some preferred embodiments, the inner flame holes include 1-2 inner oxygen holes 2 and 1-2 inner hydrogen holes 3.

In some preferred embodiments, the outer flame holes include 1-2 outer hydrogen holes 4 and 1-2 outer oxygen holes 5.

Referring to fig. 1, the outer hydrogen holes 4 are arranged in two layers, and the holes of the two layers are staggered.

In some preferred embodiments, all of the annularly distributed air holes are annularly distributed, and each air hole is a circular straight hole.

In some preferred embodiments, the diameter of the central feeding hole 1 is 1.5-6 mm, the diameter of the inner flame holes is 0.6-1.2 mm, and the diameter of the outer flame holes is 0.8-1.6 mm.

The embodiment of the application also provides an optical fiber perform, which is prepared by adopting any one of the blowlamps for preparing the bending insensitive optical fiber perform by VAD, and the interface density range of the core cladding of the optical fiber perform is 0.8-1.2 g/cm³。

Referring to table 1, the results of setting the parameters such as the number of the air holes, the gas flow rate, and the flow rate in the present embodiment are shown.

TABLE 1

The principle of the application is as follows:

when VAD is adopted to prepare the bending insensitive optical fiber preform, a large amount of fluorine is usually doped in the optical cladding to reduce the refractive index of the optical cladding and form a depressed cladding refractive index profile structure. However, fluorine in the optical cladding diffuses toward the core layer during high temperature processes such as sintering of the preform loose body, and the refractive index of the core layer is reduced after the fluorine enters the core layer. In order to ensure that the refractive index of the core layer meets the expected design, the GeO of the core layer needs to be further increased₂Doping to control the core refractive index. However, the core layer GeO₂The increase of the doping amount can cause the increase of the Rayleigh scattering loss of the optical fiber, which is not beneficial to the preparation of the low-loss bending insensitive optical fiber prefabricated rod.

Based on this, in the application, the blast burner is mentioned to improve the pre-sintering effect of the loose body of the bending insensitive optical fiber preform rod, namely, the density of the loose body core-package interface is increased during deposition, so as to inhibit the fluorine element in the optical cladding from diffusing to the core layer during subsequent high-temperature sintering, and reduce the GeO of the core layer₂Doping amount, thereby reducing Rayleigh scattering loss.

After repeated tests and verifications, the applicant finds that when VAD deposition is carried out, because the actual core layer is large, if flame is concentrated, the area of the flame finally contacting with the core layer is small, the flame can only be burned to the bottom of the core layer, and at the moment, the flame cannot wrap the core cladding interface, namely, the core cladding interface cannot be pre-sintered to improve the core cladding interface density, so that the diffusion of fluorine elements in an optical cladding to the core layer is not inhibited, and the method is not suitable for preparing a low-loss bending insensitive optical fiber preform.

Therefore, in order to effectively pre-sinter the core package interface, the present application starts from two aspects:

one of its aspect, set up inlayer flame gas pocket and outer flame gas pocket on the blast lamp that provides, the orientation of adjustment outer flame gas pocket simultaneously, make outer flame gas pocket lean out along the gas injection direction, inclination equals the contained angle theta of outer flame gas pocket central line and central feed hole 1 central line, angle through adjusting outer flame, control outer flame direction, make outer flame firing point shift to core package interface department by the sandwich layer bottom, directly carry out the presintering to the core package interface, thereby improve the density at core package interface effectively, fluorine element is to the sandwich layer diffusion in the optical cladding when suppressing follow-up high temperature sintering from this, and then reduce the doping of sandwich layer germanium content, reduce the rayleigh scattering loss, reduction in production cost.

On the other hand, the flow rate ratio of each gas is adjusted to control the flame temperature and the divergence degree, the contact area of the flame and the core layer is increased, the flame is fully wrapped on the core layer, the density of the core package interface is further increased, the pre-sintering effect of the core package interface is optimized, specifically, the gas flow rate V1 of the inner layer flame air holes and the gas flow rate V2 of the outer layer flame air holes meet the requirement of V₁>1.5V₂。

In the description of the present application, it should be noted that the terms "upper", "lower", and the like indicate orientations or positional relationships based on the orientations or positional relationships shown in the drawings, which are only for convenience in describing the present application and simplifying the description, and do not indicate or imply that the referred device or element must have a specific orientation, be constructed in a specific orientation, and operate, and thus, should not be construed as limiting the present application. Unless expressly stated or limited otherwise, the terms "mounted," "connected," and "connected" are intended to be inclusive and mean, for example, that they may be fixedly connected, detachably connected, or integrally connected; can be mechanically or electrically connected; they may be connected directly or indirectly through intervening media, or they may be interconnected between two elements. The specific meaning of the above terms in the present application can be understood by those of ordinary skill in the art as appropriate.

It is noted that, in the present application, relational terms such as "first" and "second", and the like, are used solely to distinguish one entity or action from another entity or action without necessarily requiring or implying any actual such relationship or order between such entities or actions. Also, the terms "comprises," "comprising," or any other variation thereof, are intended to cover a non-exclusive inclusion, such that a process, method, article, or apparatus that comprises a list of elements does not include only those elements but may include other elements not expressly listed or inherent to such process, method, article, or apparatus. Without further limitation, an element defined by the phrase "comprising an … …" does not exclude the presence of other identical elements in a process, method, article, or apparatus that comprises the element.

The above description is merely exemplary of the present application and is presented to enable those skilled in the art to understand and practice the present application. Various modifications to these embodiments will be readily apparent to those skilled in the art, and the generic principles defined herein may be applied to other embodiments without departing from the spirit or scope of the application. Thus, the present application is not intended to be limited to the embodiments shown herein but is to be accorded the widest scope consistent with the principles and novel features disclosed herein.