阅读说明：本技术 一种弯曲不敏感保偏光纤 (Bending insensitive polarization maintaining optical fiber ) 是由 柯一礼 罗文勇 杜城 李伟 曾凡球 田俊 朱侨 米凯峰 于 2021-01-12 设计创作，主要内容包括：本申请涉及一种弯曲不敏感保偏光纤,其包括芯层、内包层、下陷包层和外包层,且沿着径向,芯层、内包层、下陷包层和外包层由内而外依次设置,下陷包层内设有两个应力层,两个应力层分别位于内包层的两侧,并且两个应力层关于内包层呈中心对称,芯层掺杂有锗,下陷包层掺杂有氟和硼,应力层掺杂有硼,外包层采用纯石英。本申请的弯曲不敏感保偏光纤设有氟和硼共掺的下陷包层,其一方面,该下陷包层能够有效提升保偏光纤的抗弯曲能力,可以降低弯曲所带来的附加损耗影响；另一方面,通过氟和硼共掺工艺可以促使下陷包层与应力层的粘度匹配,同时也减少了保偏光纤受到的外界应力干扰,提升保偏光纤的串音稳定性。(The utility model relates to a crooked insensitive polarization maintaining optical fiber, it includes the sandwich layer, the inner cladding, the cladding and the surrounding cladding of sinking, and along radially, the sandwich layer, the inner cladding, the cladding and the surrounding cladding of sinking set gradually from inside to outside, be equipped with two stress layers in the cladding of sinking, two stress layers are located the both sides of inner cladding respectively, and two stress layers are central symmetry about the inner cladding, the sandwich layer is doped with germanium, the cladding of sinking is doped with fluorine and boron, the stress layer is doped with boron, the surrounding cladding adopts pure quartz. The bending insensitive polarization maintaining optical fiber is provided with the sunken cladding layer doped with fluorine and boron together, and on one hand, the sunken cladding layer can effectively improve the bending resistance of the polarization maintaining optical fiber and can reduce the additional loss influence caused by bending; on the other hand, the viscosity matching of the sunken cladding and the stress layer can be promoted through the fluorine and boron co-doping process, the external stress interference on the polarization-maintaining optical fiber is reduced, and the crosstalk stability of the polarization-maintaining optical fiber is improved.)

1. A bend-insensitive polarization-maintaining optical fiber, comprising:

the core layer (1), the inner cladding layer (2), the sunken cladding layer (3) and the outer cladding layer (5) are arranged from inside to outside in sequence;

two stress layers (4) which are centrosymmetric relative to the inner cladding (2) are arranged in the sunken cladding (3);

the core layer (1) is doped with germanium, the sunken cladding layer (3) is doped with fluorine and boron, and the outer cladding layer (5) is made of pure quartz.

2. The bend-insensitive polarization-maintaining fiber of claim 1, wherein: the inner cladding (2) is doped with fluorine.

3. The bend-insensitive polarization-maintaining fiber of claim 2, wherein: the inner cladding (2) is also doped with germanium.

4. The bend-insensitive polarization-maintaining fiber of claim 1, wherein:

the relative refractive index difference delta n1 of the core layer (1) is 0.3% -1.0%; and/or the presence of a gas in the gas,

the relative refractive index difference of the inner cladding (2) is-0.01%; and/or the presence of a gas in the gas,

the relative refractive index difference delta n2 of the depressed cladding (3) is-0.3% -0.1%; and/or the presence of a gas in the gas,

the relative refractive index difference delta n3 of the stress layer (4) is-0.80% -0.50%.

5. The bend-insensitive polarization-maintaining fiber of claim 1, wherein:

the diameter D1 of the core layer (1) is 3-9 mu m; and/or the presence of a gas in the gas,

the diameter D2 of the inner cladding (2) is 4.5-15 μm; and/or the presence of a gas in the gas,

the diameter D3 of the sunken cladding (3) is 40-100 mu m; and/or the presence of a gas in the gas,

the diameter D4 of the stress layer (4) is 16-35 μm; and/or the presence of a gas in the gas,

the diameter D5 of the outer cladding (5) is 60, 80 or 125 μm.

6. The bend-insensitive polarization-maintaining fiber of claim 1, wherein: the ratio of the diameter D3 of the sunken cladding layer (3) to the diameter D1 of the core layer (1) is 10-15.

7. The bend-insensitive polarization-maintaining fiber of claim 1, wherein: the refractive index sections of the core layer (1), the inner cladding layer (2), the sunken cladding layer (3) and the stress layer (4) are all horizontal straight lines.

8. The bend-insensitive polarization-maintaining fiber of claim 1, wherein: the working wavelength of the bending insensitive polarization maintaining optical fiber is 1310nm and 1550 nm.

9. The bend-insensitive polarization-maintaining fiber of claim 1, wherein: the bend insensitive polarization maintaining fiber has an additional loss of less than 0.2dB at a bend radius of 7.5mm 10 turns and a bend radius of 15mm 10 turns.

10. The bend-insensitive polarization-maintaining fiber of claim 1, wherein: the bend-insensitive polarization-maintaining fiber has a bend crosstalk degradation of less than 2dB/km at bend radii of 7.5mm 10 turns and 15mm 10 turns.

Technical Field

The application relates to the technical field of special optical fibers, in particular to a bending insensitive polarization maintaining optical fiber.

Background

Polarization maintaining optical fiber, polarization maintaining optical fiber for short, because of introducing birefringence into optical fiber, linearly polarized light can maintain its polarization state to transmit in optical fiber, and has been widely used in polarization related application field.

In recent years, as optical devices have been increasingly miniaturized, polarization-dependent devices have been required to have a higher bending radius of polarization-maintaining fibers.

In some related technologies, attenuation and crosstalk of a polarization maintaining fiber are degraded to different degrees under a bending condition, so that the attenuation and transmission polarization characteristics of an optical signal cannot be maintained, specifically, when the bending radius of the polarization maintaining fiber is less than 15mm, the additional loss is over 1dB, and the crosstalk change is greater than 3dB, and when the bending radius is less than 7.5mm, the additional loss is rapidly increased to reach over 2dB, the crosstalk change is greater than 5dB, and as the diameter of the polarization maintaining fiber is larger, the bending resistance is worse. Therefore, the polarization-maintaining optical fiber is difficult to manufacture a polarization-related device with a small size, and cannot meet the requirement of miniaturization of the device.

Disclosure of Invention

The embodiment of the application provides a bending insensitive polarization maintaining optical fiber which has excellent attenuation and crosstalk bending insensitive characteristics.

The application provides a bend insensitive polarization maintaining optical fiber, which includes:

the core layer, the inner cladding layer, the sunken cladding layer and the outer cladding layer are arranged from inside to outside in sequence;

two stress layers which are centrosymmetric with respect to the inner cladding are arranged in the sunken cladding;

the core layer is doped with germanium, the sunken cladding layer is doped with fluorine and boron, and the outer cladding layer is made of pure quartz.

In some embodiments, the inner cladding is doped with fluorine.

In some embodiments, the inner cladding is further doped with germanium.

In some embodiments, the relative refractive index difference Δ n1 of the core layer is 0.3% to 1.0%; and/or the presence of a gas in the gas,

the relative refractive index difference of the inner cladding is-0.01%; and/or the presence of a gas in the gas,

the relative refractive index difference delta n2 of the depressed cladding is-0.3% -0.1%; and/or the presence of a gas in the gas,

the relative refractive index difference delta n3 of the stress layer is-0.80% -0.50%.

In some embodiments, the core layer has a diameter D1 of 3-9 μm; and/or the presence of a gas in the gas,

the diameter D2 of the inner cladding is 4.5-15 μm; and/or the presence of a gas in the gas,

the diameter D3 of the sunken cladding is 40-100 mu m; and/or the presence of a gas in the gas,

the diameter D4 of the stress layer is 16-35 mu m; and/or the presence of a gas in the gas,

the diameter D5 of the outer cladding is 60, 80 or 125 μm.

In some embodiments, the ratio of the diameter D3 of the depressed cladding layer to the diameter D1 of the core layer is 10-15.

In some embodiments, the refractive index profiles of the core layer, inner cladding layer, depressed cladding layer and stress layer are all horizontally straight.

In some embodiments, the bend insensitive polarization maintaining fiber has an operating wavelength of 1310nm and 1550 nm.

In some embodiments, the bend-insensitive polarization maintaining fiber has an additional loss of less than 0.2dB at a bend radius of 7.5mm x 10 turns and a bend radius of 15mm x 10 turns.

In some embodiments, the bend-insensitive polarization-maintaining fiber exhibits less than 2dB/km bend crosstalk degradation at 7.5mm x 10 turns and 15mm x 10 turns.

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

the bending insensitive polarization maintaining optical fiber is provided with a fluorine and boron codoped sunken cladding layer, and on one hand, the sunken cladding layer can effectively improve the bending resistance of the polarization maintaining optical fiber and can reduce the additional loss influence caused by bending; on the other hand, the viscosity matching of the sunken cladding and the stress layer can be promoted through the fluorine and boron co-doping process, the external stress interference on the polarization-maintaining optical fiber is reduced, and the crosstalk stability of the polarization-maintaining optical fiber is improved.

The bend insensitive polarization maintaining fiber has an additional loss less than 0.2dB under the conditions of 7.5mm 10 turns of bending radius and 15mm 10 turns of bending radius, and has a bend crosstalk degradation less than 2dB/km under the conditions of 7.5mm 10 turns of bending radius and 15mm 10 turns of bending radius.

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 schematic cross-sectional view of a bend-insensitive polarization-maintaining fiber provided in an embodiment of the present application;

fig. 2 is a schematic perspective view of a bend-insensitive polarization maintaining fiber according to an embodiment of the present disclosure;

FIG. 3 is a refractive index profile of a bend insensitive polarization maintaining fiber according to an embodiment of the present application.

In the figure: 1. a core layer; 2. an inner cladding; 3. a depressed cladding layer; 4. a stress layer; 5. and (5) an outer cladding.

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 bending insensitive polarization maintaining optical fiber which has excellent attenuation and crosstalk bending insensitive characteristics.

Referring to fig. 1 and 2, a bending insensitive polarization maintaining optical fiber includes a core layer 1, an inner cladding layer 2, a depressed cladding layer 3 and an outer cladding layer 5, and the core layer 1, the inner cladding layer 2, the depressed cladding layer 3 and the outer cladding layer 5 are sequentially arranged from inside to outside along a radial direction, in this embodiment, the core layer 1, the inner cladding layer 2, the depressed cladding layer 3 and the outer cladding layer 5 are arranged in concentric circles; two stress layers 4 are arranged in the sunken cladding 3, the two stress layers 4 are respectively positioned on two sides of the inner cladding 2, the two stress layers 4 are centrosymmetric about the inner cladding 2, a gap is formed between each stress layer 4 and the inner cladding 2, and the centers of circles of the two stress layers 4, the core layer 1 and the inner cladding 2 are on the same straight line; the core layer 1 is doped with germanium, the sunken cladding layer 3 is doped with fluorine and boron, the stress layer 4 is doped with boron, and the outer cladding layer 5 is made of pure quartz.

The bending insensitive polarization maintaining fiber is provided with the fluorine and boron codoped sunken cladding 3, on one hand, the sunken cladding 3 can effectively improve the bending resistance of the polarization maintaining fiber and can reduce the additional loss influence caused by bending, and the additional loss of the bending insensitive polarization maintaining fiber is less than 0.2dB under the conditions of 7.5mm x 10 circles of bending radius and 15mm x 10 circles of bending radius; on the other hand, the viscosity matching of the sunken cladding 3 and the stress layer 4 can be promoted through a fluorine and boron co-doping process, meanwhile, the external stress interference on the polarization-maintaining fiber is reduced, the crosstalk stability of the polarization-maintaining fiber is improved, and the bending crosstalk degradation of the bending-insensitive polarization-maintaining fiber is less than 2dB/km under the conditions that the bending radius is 7.5mm x 10 circles and the bending radius is 15mm x 10 circles.

In some preferred embodiments, the inner cladding 2 is doped with fluorine.

In some preferred embodiments, the inner cladding 2 is doped with fluorine and germanium, and the bend-insensitive polarization maintaining optical fiber of the present embodiment is provided with the inner cladding 2 doped with germanium and fluorine, which can effectively reduce the viscosity and the attenuation increase caused by excessive interface stress.

In some preferred embodiments, referring to FIG. 3, the relative refractive index difference Δ n1 of the core layer 1 is between 0.3% and 1.0%, the relative refractive index difference of the inner cladding layer 2 is between-0.01% and 0.01%, the relative refractive index difference Δ n2 of the depressed cladding layer 3 is between-0.3% and-0.1%, and the relative refractive index difference Δ n3 of the stress layer 4 is between-0.80% and-0.50%.

The embodiment provided by the application calculates the relative refractive index difference Δ by using the following formula:

Δ＝(n_{folding device}-n)/(n_{Folding device}+n)*100％

Where n is the refractive index of pure quartz (i.e., the outer cladding 5), when the relative refractive index difference Δ n1 between the core layer 1 and the pure quartz is calculated, n in the above formula_{Folding device}Is the refractive index of the core layer 1;

when calculating the relative refractive index difference of the inner cladding 2 and the pure quartz, n in the above formula_{Folding device}The refractive index of the inner cladding 2;

when the relative refractive index difference Δ n2 between the depressed cladding 3 and pure quartz is calculated, n in the above formula_{Folding device}The refractive index of the depressed cladding 3;

when calculating the relative refractive index difference Δ n3 between the stress layer 4 and pure quartz, n in the above formula_{Folding device}The refractive index of the stress layer 4.

In some preferred embodiments, referring to FIG. 3, the diameter D1 of the core layer 1 is 3-9 μm, the diameter D2 of the inner cladding layer 2 is 4.5-15 μm, the diameter D3 of the depressed cladding layer 3 is 40-100 μm, the diameter D4 of the stress layer 4 is 16-35 μm, and the diameter D5 of the outer cladding layer 5 is 60, 80 or 125 μm.

In some preferred embodiments, the ratio of the diameter D3 of the depressed cladding 3 to the diameter D1 of the core layer 1 is 10-15, and the stable transmission of optical signals is realized by controlling the ratio of the diameter of the depressed cladding 3 of the polarization maintaining fiber to the diameter of the core layer 1.

In some preferred embodiments, referring to FIG. 3, the refractive index profiles of the core layer 1, inner cladding layer 2, depressed cladding layer 3 and stress layer 4 are all horizontally straight.

In some preferred embodiments, since germanium can increase the refractive index, germanium is doped in the core layer 1, so that the germanium-doped core layer 1 has an upwardly convex step-type waveguide structure with a higher relative refractive index difference and a smaller cut-off wavelength, so that the operating wavelength of the bend-insensitive polarization-maintaining optical fiber is 1310nm and 1550 nm.

The present application will be described in further detail with reference to specific examples.

The first embodiment is as follows:

the utility model provides a crooked insensitive polarization maintaining fiber, its includes sandwich layer 1, inner cladding 2, the cladding 3 that sink and surrounding layer 5, and along radial, sandwich layer 1, inner cladding 2, the cladding 3 that sink and surrounding layer 5 set gradually from inside to outside, are equipped with two stress layers 4 in the cladding 3 that sink, and two stress layers 4 are located the both sides of inner cladding 2 respectively to two stress layers 4 are central symmetry about inner cladding 2.

Control of core layer 1 deposition gas flow SiCl during preform deposition fabrication₄Vapor 100sccm, GeO₂Steam of 100sccm, inner cladding 2 deposition gas flow SiCl₄Vapor 300sccm, GeO₂Steam 50sccm, C₂F₆Gas 25sccm, sunken cladding 3 deposition gas flow SiCl₄Vapor 300sccm, C₂F₆Gas 20sccm, B₂O₃Gas 50sccm, stress layer 4 deposition gas flow SiCl₄Vapor 300sccm, B₂O₃The gas was 150 sccm.

In terms of geometric dimensions, the diameter D1 of the core layer 1 is controlled to be 3 μm, the diameter D2 of the inner cladding layer 2 is controlled to be 4.5 μm, the diameter D3 of the depressed cladding layer 3 is 45 μm, the diameter D4 of the stress layer 4 is 16 μm, and the diameter D5 of the outer cladding layer 5 is 60 μm.

In the refractive index, the relative refractive index difference Δ n1 of the core layer 1 was controlled to be 1.0%, the relative refractive index difference Δ n2 of the depressed clad layer 2 was controlled to be-0.1%, and the relative refractive index difference Δ n3 of the stress layer 4 was controlled to be-0.75%.

The main parameters and bending variation of the drawn bend insensitive polarization maintaining fiber are shown in Table 1.

TABLE 1

Example two:

the utility model provides a crooked insensitive polarization maintaining fiber, its includes sandwich layer 1, inner cladding 2, the cladding 3 that sink and surrounding layer 5, and along radial, sandwich layer 1, inner cladding 2, the cladding 3 that sink and surrounding layer 5 set gradually from inside to outside, are equipped with two stress layers 4 in the cladding 3 that sink, and two stress layers 4 are located the both sides of inner cladding 2 respectively to two stress layers 4 are central symmetry about inner cladding 2.

Control of core layer 1 deposition gas flow SiCl during preform deposition fabrication₄Vapor 150sccm, GeO₂120sccm of vapor, deposition gas flow SiCl for inner cladding 2₄Vapor 600sccm, GeO₂Steam 100sccm, C₂F₆Gas 30sccm, sunken cladding 3 deposition gas flow SiCl₄Steam 600sccm, C₂F₆Gas 30sccm, B₂O₃Gas 80sccm, stress layer 4 deposition gas flow SiCl₄Steam 600sccm, B₂O₃The gas was 200 sccm.

In terms of geometric dimensions, the diameter D1 of the core layer 1 is controlled to be 3.5 μm, the diameter D2 of the inner cladding layer 2 is controlled to be 5.2 μm, the diameter D3 of the depressed cladding layer 3 is controlled to be 52 μm, the diameter D4 of the stress layer 4 is controlled to be 18 μm, and the diameter D5 of the outer cladding layer 5 is controlled to be 60 μm.

In the aspect of refractive index, the relative refractive index difference Deltan 1 of the core layer 1 is controlled to be 0.8%, the relative refractive index difference Deltan 2 of the depressed cladding layer 2 is controlled to be-0.2%, and the relative refractive index difference Deltan 3 of the stress layer 4 is controlled to be-0.65%.

The main parameters and bend variation of the drawn bend insensitive polarization maintaining fiber are shown in Table 2.

TABLE 2

Example three:

the utility model provides a crooked insensitive polarization maintaining fiber, its includes sandwich layer 1, inner cladding 2, the cladding 3 that sink and surrounding layer 5, and along radial, sandwich layer 1, inner cladding 2, the cladding 3 that sink and surrounding layer 5 set gradually from inside to outside, are equipped with two stress layers 4 in the cladding 3 that sink, and two stress layers 4 are located the both sides of inner cladding 2 respectively to two stress layers 4 are central symmetry about inner cladding 2.

Control of core layer 1 deposition gas flow SiCl during preform deposition fabrication₄Vapor 200sccm, GeO₂Vapor of 180sccm, inner cladding 2 deposition gas flow SiCl₄Steam 1000sccm, GeO₂Vapor 150sccm, C₂F₆Gas 40sccm, sunken cladding 3 deposition gas flow SiCl₄Steam 1000sccm, C₂F₆Gas 40sccm, B₂O₃Gas 100sccm, stress layer 4 deposition gas flow SiCl₄Steam 1000sccm, B₂O₃The gas was 300 sccm.

In terms of geometric dimensions, the diameter D1 of the core layer 1 is controlled to be 5 μm, the diameter D2 of the inner cladding layer 2 is controlled to be 7.5 μm, the diameter D3 of the depressed cladding layer 3 is controlled to be 60 μm, the diameter D4 of the stress layer 4 is controlled to be 22 μm, and the diameter D5 of the outer cladding layer 5 is controlled to be 80 μm.

In the aspect of refractive index, the relative refractive index difference Δ n1 of the core layer 1 is controlled to be 0.6%, the relative refractive index difference Δ n2 of the depressed cladding layer 2 is controlled to be-0.25%, and the relative refractive index difference Δ n3 of the stress layer 4 is controlled to be-0.6%.

The main parameters and bend variation of the drawn bend insensitive polarization maintaining fiber are shown in Table 3.

TABLE 3

Example four:

the utility model provides a crooked insensitive polarization maintaining fiber, its includes sandwich layer 1, inner cladding 2, the cladding 3 that sink and surrounding layer 5, and along radial, sandwich layer 1, inner cladding 2, the cladding 3 that sink and surrounding layer 5 set gradually from inside to outside, are equipped with two stress layers 4 in the cladding 3 that sink, and two stress layers 4 are located the both sides of inner cladding 2 respectively to two stress layers 4 are central symmetry about inner cladding 2.

Control of core layer 1 deposition gas flow SiCl during preform deposition fabrication₄Vapor 250sccm, GeO₂Vapor 200sccm, inner cladding 2 deposition gas flow SiCl₄Vapor 1200sccm, GeO₂Vapor 300sccm, C₂F₆Gas 50sccm, sunken cladding 3 deposition gas flow SiCl₄Vapor 1200sccm, C₂F₆Gas 50sccm, B₂O₃Gas of 150sccm, deposition gas flow SiCl for the stress layer 4₄Vapor 1200sccm, B₂O₃The gas was 400 sccm.

In terms of geometric dimensions, the diameter D1 of the core layer 1 is controlled to be 9 μm, the diameter D2 of the inner cladding layer 2 is controlled to be 13.5 μm, the diameter D3 of the depressed cladding layer 3 is controlled to be 90 μm, the diameter D4 of the stress layer 4 is controlled to be 34 μm, and the diameter D5 of the outer cladding layer 5 is controlled to be 125 μm.

In the aspect of refractive index, the relative refractive index difference Δ n1 of the core layer 1 is controlled to be 0.3%, the relative refractive index difference Δ n2 of the depressed cladding layer 2 is controlled to be-0.3%, and the relative refractive index difference Δ n3 of the stress layer 4 is controlled to be-0.5%.

The main parameters and bend variations of the drawn bend insensitive polarization maintaining fiber are shown in Table 4.

TABLE 4

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.