WO2024119889A1

WO2024119889A1 - Low-loss anti-resonant hollow-core fiber

Info

Publication number: WO2024119889A1
Application number: PCT/CN2023/113978
Authority: WO
Inventors: 彭楚宇; 喻煌; 郭浩; 曾建军; 胡博
Original assignee: 烽火通信科技股份有限公司; 烽火藤仓光纤科技有限公司
Priority date: 2022-12-07
Filing date: 2023-08-21
Publication date: 2024-06-13
Also published as: CN115728863A

Abstract

A low-loss anti-resonant hollow-core fiber, comprising a fiber core region (1) and a cladding region, wherein the cladding region comprises an outer cladding layer (2), a first anti-resonant layer and a second anti-resonant layer, which are sequentially arranged from outside to inside; the first anti-resonant layer comprises a plurality of first elliptical capillaries (3), which are rotationally and symmetrically distributed; the first elliptical capillaries (3) are tangential to the outer cladding layer (2); the second anti-resonance layer comprises a plurality of second elliptical capillaries (4), which are rotationally and symmetrically distributed; the second elliptical capillaries (4) are tangential to the first elliptical capillaries (3); the second elliptical capillaries (4) and the first elliptical capillaries (3) are arranged in a staggered manner; and a region surrounded by the boundaries of the first anti-resonance layer and the second anti-resonance layer is the fiber core region (1). A circular cladding tube in the hollow-core fiber is changed to an elliptical cladding tube, and the impact of a high-order mode is suppressed by means of reducing the curvature radius of the cladding tube, such that the confinement loss of a fundamental mode can be reduced. Two layers of tangential elliptical capillaries support each other, such that deformation of the elliptical capillaries during a preparation process can be avoided, thereby improving the preparation accuracy.

Description

A low-loss antiresonant hollow-core optical fiber

Technical Field

The present application relates to the field of optical fiber communication technology, and in particular to a low-loss anti-resonant hollow-core optical fiber.

Background technique

With the development of 5G technology, the transmission capacity requirements for optical fiber communications are getting higher and higher. Solid-core optical fiber based on quartz glass transmission has gradually become a bottleneck affecting the development of optical fiber communication technology due to its intrinsic properties such as nonlinearity, low dispersion, and damage threshold. At the same time, in some special fields such as high power, ultrafast optics, and nonlinear optics, optical fiber also shows limitations due to materials.

Hollow-core optical fiber with air as the core can achieve more than 99% of light propagation in the air, thus greatly reducing the impact of optical fiber material characteristics on optical fiber performance. Compared with traditional solid-core optical fiber, hollow-core optical fiber has the advantages of low latency, low dispersion, low nonlinearity, high damage threshold, low thermal sensitivity, radiation resistance, and can guide light in any transmission window. Therefore, in important fields such as optical communications, high-power lasers, ultrafast optics, nonlinear optics, and optical fiber sensing, hollow-core optical fiber has more advantages than traditional solid-core optical fiber.

The cladding structure of traditional hollow-core optical fiber is a single-loop nodeless structure. Its cladding is generally composed of a circle of thin-walled capillaries without contact, and its confinement loss is relatively high. In addition, the cladding tube of the hollow-core optical fiber reported so far is prone to collapse and deformation during the preparation process, causing energy leakage and mode coupling, and the actual performance of the optical fiber is significantly different from the theoretical design value. The above problems have limited the development and application of hollow-core optical fiber to a certain extent.

In summary, how to reduce the loss of hollow-core optical fibers and at the same time significantly improve the preparation accuracy of hollow-core optical fibers is an urgent problem that needs to be solved.

Summary of the invention

The embodiment of the present application provides a low-loss anti-resonant hollow-core optical fiber to solve the problems in the related art of high loss of hollow-core optical fiber and low precision caused by easy collapse and deformation of the cladding tube.

In a first aspect, a low-loss anti-resonant hollow-core optical fiber is provided, comprising:

Core region;

A cladding region, wherein the cladding region includes an outer cladding, a first antiresonance layer, and a second antiresonance layer arranged in sequence from outside to inside; the first antiresonance layer includes a plurality of first elliptical capillaries distributed in a rotationally symmetrical manner, and the first elliptical capillaries are tangent to the outer cladding; the second antiresonance layer includes a plurality of second elliptical capillaries distributed in a rotationally symmetrical manner, and the second elliptical capillaries are tangent to the first elliptical capillaries, and the second elliptical capillaries are staggered with the first elliptical capillaries;

And, a region surrounded by the boundary between the first anti-resonance layer and the second anti-resonance layer is the core region.

In some embodiments, the short axis D _3x of the first elliptical capillary is greater than the short axis D _4x of the second elliptical capillary;

The major axis D _3y of the first elliptical capillary is greater than the major axis D _4y of the second elliptical capillary.

In some embodiments, the major axis D _3y of the first elliptical capillary ranges from 26.0 to 40.0 μm;

And/or, the value range of the major axis D _4y of the second elliptical capillary is 11.7 to 26.0 μm;

And/or, the ellipticity of the first elliptical capillary and the second elliptical capillary are both in the range of 0.70 to 0.85.

In some embodiments, the first elliptical capillary comprises a first refractive index layer and a second refractive index layer arranged sequentially from the inside to the outside, and the refractive index of the first refractive index layer is smaller than the refractive index of the second refractive index layer;

And/or, the second elliptical capillary comprises a first refractive index layer and a second refractive index layer arranged in sequence from the inside to the outside, and the refractive index of the first refractive index layer is smaller than that of the second refractive index layer. The refractive index of the layer.

In some embodiments, the refractive index of the first refractive index layer ranges from 1.32 to 1.44, and the refractive index of the second refractive index layer ranges from 1.40 to 1.45.

In some embodiments, the wall thickness _t5 of the first refractive index layer is equal to the wall thickness _t6 of the second refractive index layer.

In some embodiments, the wall thickness _t5 of the first refractive index layer and the wall thickness _t6 of the second refractive index layer are both in the range of 0.05-1.0 μm.

In some embodiments, the core region is filled with one or more gases, or is a vacuum;

And/or, the diameter d of the core region ranges from 30 to 50 μm.

In some embodiments, the number of the first elliptical capillaries in the first anti-resonance layer is equal to the number of the second elliptical capillaries in the second anti-resonance layer, and both are 4 to 6.

In some embodiments, the outer cladding is made of pure silica.

The beneficial effects of the technical solution provided by this application include:

The hollow-core optical fiber has high limiting loss and the cladding tube is prone to collapse and deformation during the preparation process, which reduces the manufacturing precision and causes energy leakage and mode coupling. The low-loss antiresonant hollow-core optical fiber provided by the present application has a core region with a low refractive index and a cladding region with a high refractive index. The cladding region with a high refractive index is further divided into an inner cladding and an outer cladding. The inner cladding is composed of two layers of tangent elliptical capillaries. Compared with conventional hollow-core optical fibers, the present application changes the circular cladding tube in the hollow-core optical fiber to an elliptical cladding tube. By reducing the radius of curvature of the cladding tube, the influence of the high-order mode is suppressed, thereby reducing the fundamental mode limiting loss. The two tangent layers of elliptical capillaries support each other, which can prevent them from being deformed during the preparation process and improve the preparation precision.

BRIEF DESCRIPTION OF THE DRAWINGS

In order to more clearly illustrate the technical solution in the embodiment of the present application, the embodiment will be described below. The drawings required for the description are briefly introduced. Obviously, the drawings described below are only some embodiments of the present application. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying any creative work.

FIG1 is a schematic diagram of a low-loss anti-resonant hollow-core optical fiber provided in an embodiment of the present application;

FIG2 is a schematic diagram of a hollow core optical fiber provided in a comparative example of the present application;

FIG3 is a schematic diagram of a hollow core optical fiber provided in another comparative example of the present application;

FIG4 is a limiting loss diagram of an embodiment and a comparative example provided in the present application;

FIG5 is a schematic diagram of a first elliptical capillary provided in an embodiment of the present application;

FIG. 6 is a schematic diagram of a second elliptical capillary provided in an embodiment of the present application.

In the figure: 1. core region; 2. outer cladding; 3. first elliptical capillary; 4. second elliptical capillary; 5. first refractive index layer; 6. second refractive index layer.

Detailed ways

In order to make the purpose, technical solution and advantages of the embodiments of the present application clearer, the technical solution in the embodiments of the present application will be clearly and completely described below in conjunction with the drawings in the embodiments of the present application. Obviously, the described embodiments are part of the embodiments of the present application, not all of the embodiments. Based on the embodiments in the present application, all other embodiments obtained by ordinary technicians in this field without making creative work are within the scope of protection of this application.

As shown in FIG1 , an embodiment of the present application provides a low-loss anti-resonant hollow-core optical fiber, which includes a core region 1 and a cladding region, wherein the cladding region includes an outer cladding 2, a first anti-resonant layer, and a second anti-resonant layer arranged in sequence from the outside to the inside; the first anti-resonant layer includes a plurality of first elliptical capillaries 3 that are rotationally symmetrically distributed, and the first elliptical capillaries 3 are tangent to the outer cladding 2; the second anti-resonant layer includes a plurality of second elliptical capillaries 4 that are rotationally symmetrically distributed, and the second elliptical capillaries 4 are tangent to the first elliptical capillaries 3, and the second elliptical capillaries 4 are staggered with the first elliptical capillaries 3; the second anti-resonant layer is closer to the central axis of the hollow-core optical fiber than the first anti-resonant layer, and the region surrounded by the boundary of the first anti-resonant layer and the second anti-resonant layer is the core region 1, and the core region 1 is the main region for optical signal transmission. The core region 1 may be filled with one or more gases, or may be a vacuum.

The hollow-core optical fiber has high limiting loss and the cladding tube is prone to collapse and deformation during the preparation process, which reduces the manufacturing precision and causes energy leakage and mode coupling. The low-loss antiresonant hollow-core optical fiber provided in the embodiment of the present application has a core region 1 with a low refractive index and a cladding region with a high refractive index. The cladding region with a high refractive index is further divided into an inner cladding and an outer cladding 2. The inner cladding is composed of two layers of tangent elliptical capillaries. Compared with conventional hollow-core optical fibers, the present application changes the circular cladding tube in the hollow-core optical fiber to an elliptical cladding tube. By reducing the radius of curvature of the cladding tube, the influence of the high-order mode is suppressed, thereby reducing the fundamental mode limiting loss. The two tangent layers of elliptical capillaries support each other, which can prevent them from being deformed during the preparation process and improve the preparation precision.

Referring to FIG. 2 , which is a comparative example, the antiresonant negative curvature hollow-core optical fiber provided in the comparative example is a single-layer tube ring structure, and the single-layer tube is circular; referring to FIG. 3 , which is another comparative example, the antiresonant negative curvature hollow-core optical fiber provided in the comparative example is a double-layer tube ring structure, and both layers of tubes are circular, while the hollow-core optical fiber provided in the embodiment of the present application is a double-layer elliptical tube ring structure. The limiting loss comparison results of the three hollow-core optical fibers are shown in FIG. 4 , and the limiting loss of the single-layer tube ring structure is the highest, the limiting loss of the double-layer tube ring structure is second, and the limiting loss of the double-layer elliptical tube ring structure is the lowest.

Preferably, as shown in Figures 5 and 6, the short axis D _3x of the first elliptical capillary 3 is greater than the short axis D _4x of the second elliptical capillary 4; the long axis D _3y of the first elliptical capillary 3 is greater than the long axis D _4y of the second elliptical capillary 4. An additional second anti-resonance layer with a small radius is added to the first anti-resonance layer to suppress the mode coupling effect and reduce the loss of the hollow core optical fiber.

The value range of the major axis D _3y of the first elliptical capillary 3 is 26.0-40.0 μm, the value range of the major axis D _4y of the second elliptical capillary 4 is 11.7-26.0 μm, the value range of the ellipticity of the first elliptical capillary 3 and the second elliptical capillary 4 are both 0.70-0.85, the ellipticity is the ratio of the minor axis to the major axis of the ellipse, the ellipticity e ₃ of the first elliptical capillary 3 is D _3x /D _3y , and the ellipticity e ₄ of the second elliptical capillary 4 is D _4x /D _4y .

The ellipticity of the first elliptical capillary 3 and the second elliptical capillary 4 can be equal. In order to be unequal, preferably, when selecting the capillaries, the ellipticity of the first elliptical capillary 3 and the second elliptical capillary 4 are equal.

In order to further reduce the limiting loss, as shown in Figure 5, the first elliptical capillary 3 includes a first refractive index layer 5 and a second refractive index layer 6 arranged in sequence from the inside to the outside, and the refractive index of the first refractive index layer 5 is smaller than the refractive index of the second refractive index layer 6; by introducing high and low refractive index material layers into the elliptical capillary, the light in the core region is totally reflected at the interface between the high and low refractive index materials, so that it is confined to the core region for transmission, further reducing the limiting loss.

As shown in Fig. 6, the second elliptical capillary 4 includes a first refractive index layer 5 and a second refractive index layer 6 arranged in sequence from the inside to the outside, and the refractive index of the first refractive index layer 5 is smaller than the refractive index of the second refractive index layer 6. By introducing high and low refractive index material layers into the elliptical capillary, the light in the core region is totally reflected at the interface between the high and low refractive index materials, so that the light is confined to the core region for transmission, further reducing the limiting loss.

Preferably, the refractive index of the first refractive index layer 5 is in the range of 1.32 to 1.44, and the refractive index of the second refractive index layer 6 is in the range of 1.40 to 1.45.

Preferably, the wall thickness t5 of the first refractive index layer ₅ is equal to the wall thickness t6 of the second refractive index layer _6. The wall thickness _t5 of the first refractive index layer 5 and the wall thickness t6 of the second refractive index layer ₆ are both in the range of 0.05 to 1.0 μm.

Preferably, the diameter d of the core region 1 is in the range of 30 to 50 μm.

Preferably, the number of the first elliptical capillaries 3 in the first anti-resonance layer is equal to the number of the second elliptical capillaries 4 in the second anti-resonance layer, and both are 4 to 6.

Preferably, the outer cladding 2 is made of pure silicon dioxide.

Embodiment 1:

The outer cladding 2 of the low-loss anti-resonant hollow-core optical fiber of this embodiment is made of pure silica material. In the first anti-resonant layer of the low-loss anti-resonant hollow-core optical fiber, the major axis diameter D _3y of the first elliptical capillary 3 is 32 μm, and the ellipticity e ₃ is 0.75; in the second anti-resonant layer, The major axis diameter D _4y of the second elliptical capillary 4 is 12.1 μm, and the ellipticity e ₄ is 0.75; in the first elliptical capillary 3 and the second elliptical capillary 4, the wall thickness t ₅ of the first refractive index layer 5 and the wall thickness t ₆ of the second refractive index layer 6 are 0.18 μm, the refractive index of the second refractive index layer 6 is 1.45, and the refractive index of the first refractive index layer 5 is 1.38. The number of the first elliptical capillary 3 and the second elliptical capillary 4 are both 6, and the diameter d of the core region 1 of the low-loss anti-resonant hollow-core optical fiber is 42 μm. The low-loss anti-resonant hollow-core optical fiber described in this embodiment has an average loss of 0.437 dB/km in the range of 1260 to 1565 nm.

Embodiment 2:

The outer cladding 2 of the low-loss antiresonant hollow-core optical fiber described in this embodiment uses pure silica material. In the first antiresonant layer of the low-loss antiresonant hollow-core optical fiber, the major axis diameter D _3y of the first elliptical capillary 3 is 34 μm, and the ellipticity e ₃ is 0.80; in the second antiresonant layer, the major axis diameter D _4y of the second elliptical capillary 4 is 16.0 μm, and the ellipticity e ₄ is 0.75; in the first elliptical capillary 3 and the second elliptical capillary 4, the wall thickness t ₅ of the first refractive index layer 5 and the wall thickness t ₆ of the second refractive index layer 6 are 0.26 μm, the refractive index of the second refractive index layer 6 is 1.42, and the refractive index of the first refractive index layer 5 is 1.33. The number of the first elliptical capillary 3 and the second elliptical capillary 4 are both 6, and the diameter d of the core region 1 of the low-loss antiresonant hollow-core optical fiber is 44 μm. The low-loss antiresonant hollow-core optical fiber described in this embodiment has an average loss of 0.464 dB/km in the range of 1260-1565 nm.

Embodiment three:

The outer cladding 2 of the low-loss anti-resonant hollow-core optical fiber described in this embodiment is made of pure silica material. In the first anti-resonant layer of the low-loss anti-resonant hollow-core optical fiber, the major axis diameter D _3y of the first elliptical capillary 3 is 35 μm, and the ellipticity e ₃ is 0.82; in the second anti-resonant layer, the major axis diameter D _4y of the second elliptical capillary 4 is 16.4 μm, and the ellipticity e ₄ is 0.73; in the first elliptical capillary 3 and the second elliptical capillary 4, the wall thickness t ₅ of the first refractive index layer 5 and the wall thickness t ₆ of the second refractive index layer 6 are 0.58 μm, and the refractive index of the second refractive index layer 6 is 1.45, the refractive index of the first refractive index layer 5 is 1.36, the number of the first elliptical capillary 3 and the number of the second elliptical capillary 4 are both 4, and the diameter d of the core region 1 of the low-loss anti-resonant hollow-core optical fiber is 38 μm. The low-loss anti-resonant hollow-core optical fiber in this embodiment has an average loss of 0.482 dB/km in the range of 1260 to 1565 nm.

In the description of the present application, it should be noted that the terms "upper", "lower", etc. indicate orientations or positional relationships based on the orientations or positional relationships shown in the accompanying drawings, and are only for the convenience of describing the present application and simplifying the description, rather than indicating or implying that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation, and therefore cannot be understood as a limitation on the present application. Unless otherwise clearly specified and limited, the terms "installed", "connected", and "connected" should be understood in a broad sense, for example, it can be a fixed connection, a detachable connection, or an integral connection; it can be a mechanical connection or an electrical connection; it can be a direct connection, or it can be an indirect connection through an intermediate medium, or it can be a connection between the two elements. For those of ordinary skill in the art, the specific meanings of the above terms in the present application can be understood according to the specific circumstances.

It should be noted that, in this application, relational terms such as "first" and "second" are only used to distinguish one entity or operation from another entity or operation, and do not necessarily require or imply any such actual relationship or order between these entities or operations. Moreover, the terms "include", "comprise" or any other variants thereof are intended to cover non-exclusive inclusion, so that a process, method, article or device including a series of elements includes not only those elements, but also other elements not explicitly listed, or also includes elements inherent to such process, method, article or device. In the absence of further restrictions, the elements defined by the sentence "comprise a ..." do not exclude the presence of other identical elements in the process, method, article or device including the elements.

The above description is only a specific implementation of the present application, so that those skilled in the art can understand or implement the present application. Various modifications to these embodiments will be obvious to those skilled in the art, and the general principles defined herein can be implemented in other embodiments without departing from the spirit or scope of the present application. Therefore, the present application will not be limited to The present invention is intended to be limited to the embodiments shown herein, but is to be consistent with the widest scope consistent with the principles and novel features claimed herein.

Claims

A low-loss anti-resonant hollow-core optical fiber, characterized in that it comprises:

Core region (1);

A cladding region, the cladding region comprising an outer cladding (2), a first anti-resonance layer and a second anti-resonance layer arranged in sequence from the outside to the inside; the first anti-resonance layer comprises a plurality of first elliptical capillaries (3) distributed in a rotationally symmetrical manner, and the first elliptical capillaries (3) are tangent to the outer cladding (2); the second anti-resonance layer comprises a plurality of second elliptical capillaries (4) distributed in a rotationally symmetrical manner, and the second elliptical capillaries (4) are tangent to the first elliptical capillaries (3), and the second elliptical capillaries (4) and the first elliptical capillaries (3) are arranged in a staggered manner;

Furthermore, the region surrounded by the boundary between the first anti-resonance layer and the second anti-resonance layer is the core region (1).
The low-loss antiresonant hollow-core optical fiber according to claim 1, characterized in that:

The short axis D 3x of the first elliptical capillary (3) is greater than the short axis D 4x of the second elliptical capillary (4);

The major axis D 3y of the first elliptical capillary (3) is greater than the major axis D 4y of the second elliptical capillary (4).
The low-loss antiresonant hollow-core optical fiber according to claim 2, characterized in that:

The value range of the major axis D 3y of the first elliptical capillary (3) is 26.0 to 40.0 μm;

And/or, the value range of the major axis D 4y of the second elliptical capillary (4) is 11.7 to 26.0 μm;

And/or, the ellipticity of the first elliptical capillary (3) and the second elliptical capillary (4) are both in the range of 0.70 to 0.85.
The low-loss antiresonant hollow-core optical fiber according to claim 1, characterized in that:

The first elliptical capillary (3) comprises a first refractive index layer (5) and a second refractive index layer (6) arranged in sequence from the inside to the outside, and the refractive index of the first refractive index layer (5) is less than the refractive index of the second refractive index layer (6);

And/or, the second elliptical capillary (4) comprises a first refractive index layer (5) and a second refractive index layer (6) arranged in sequence from the inside to the outside, and the refractive index of the first refractive index layer (5) is smaller than the refractive index of the second refractive index layer (6).
The low-loss antiresonant hollow-core optical fiber according to claim 4, characterized in that:

The refractive index of the first refractive index layer (5) ranges from 1.32 to 1.44, and the refractive index of the second refractive index layer (6) ranges from 1.40 to 1.45.
The low-loss antiresonant hollow-core optical fiber according to claim 4, characterized in that:

The wall thickness t5 of the first refractive index layer (5) and the wall thickness t6 of the second refractive index layer (6) are equal.
The low-loss antiresonant hollow-core optical fiber according to claim 6, characterized in that:

The wall thickness t5 of the first refractive index layer (5) and the wall thickness t6 of the second refractive index layer (6) are both in the range of 0.05 to 1.0 μm.
The low-loss antiresonant hollow-core optical fiber according to claim 1, characterized in that:

The core region (1) is filled with one or more gases, or is a vacuum;

And/or, the diameter d of the core region (1) is in the range of 30 to 50 μm.
The low-loss antiresonant hollow-core optical fiber according to claim 1, characterized in that:

The number of the first elliptical capillaries (3) in the first anti-resonance layer is equal to the number of the second elliptical capillaries (4) in the second anti-resonance layer, and both are 4 to 6.
The low-loss antiresonant hollow-core optical fiber according to claim 1, characterized in that:

The outer cladding (2) is made of pure silicon dioxide.