1. The multi-core optical fiber is manufactured by controlling the number of cores, the arrangement of the cores, the refractive index difference between the cores and the core spacing, and has crosstalk between different cores, and comprises a plurality of cores and a cladding coated outside the cores, wherein the cladding is punched, one core is inserted into each hole, the refractive index difference of each core is 0-1.5%, and each core comprises a core layer, an inner cladding and a sunken cladding which are sequentially arranged from inside to outside.

2. The multi-core optical fiber for different application scenarios as claimed in claim 1, wherein the difference between the core effective refractive index and the pure silica refractive index is 0.0044-0.0058.

3. The multi-core optical fiber for different application scenarios of claim 1, wherein the difference between the effective refractive index of the inner cladding and the refractive index of pure silica is-0.0005.

4. The multi-core optical fiber for different application scenarios as claimed in claim 1, wherein the difference between the depressed cladding effective refractive index and the pure silica refractive index is-0.0030 to-0.0060.

5. The method for preparing a multi-core optical fiber for different application scenarios as claimed in any one of claims 1 to 4, comprising the steps of:

preparing a core and a cladding, and punching the cladding, wherein the number of holes is matched with that of the core;

then, inserting a plurality of cores into a plurality of holes of the cladding respectively, inserting one core into each hole, and drawing to obtain the required multi-core optical fiber;

the distance between two adjacent cores after drawing is 20-50 mu m, and the crosstalk between any two cores of the drawn multi-core optical fiber is not more than-50 dB.

6. The method for preparing the multicore optical fiber according to claim 4, wherein after drawing, the inner cladding to core layer radius ratio is 2.0 to 3.0, and the depressed cladding to core layer radius ratio is 3.0 to 4.0.

7. The method for preparing the multicore optical fiber according to claim 6, wherein after drawing, the core layer has a radius of 3.0 to 4.5 μm.

8. The method as claimed in claim 5, wherein the diameter of the holes punched in the cladding is 10-30 mm, the pitch of the holes is 20-60 mm, and the outer diameter of the cladding is 50-120 mm.

Background

Although the traditional single-core optical fiber transmission technology has been rapidly developed in the past decades, the transmission capacity of a single optical fiber up to 100Tb/s is realized at present. However, with the continuous development of the 5G technology and the emergence of new services such as virtual reality and ultra-high-definition video, the data volume in the optical communication network is further increased, and therefore how to effectively expand the transmission capacity of the optical fiber is one of the problems that need to be solved at present. Space Division Multiplexing (SDM) technology has received increasing attention as it can further expand the communication capacity of optical fibers. At present, space division multiplexing mainly has 2 modes, one mode is a few-mode optical fiber based on mode multiplexing, and the other mode is multi-core multiplexing on space. When the multi-core fiber is used for space division multiplexing communication transmission, each fiber core is an independent physical channel, and two ends of the multi-core fiber are respectively connected with the single-mode fibers of the input end and the output end by virtue of a multi-core coupler, so that signals received by each single-mode fiber of a receiving end can be directly utilized, and the multi-core fiber is favored.

For the multi-core optical fiber to improve the communication distance and the communication capacity, the crosstalk between cores and the bending performance of the optical fiber need to be considered. At present, the method for reducing crosstalk mainly comprises the steps of designing a heterogeneous fiber core and designing a multi-core fiber with a sunken cladding structure, wherein the waveguide structure with the sunken cladding structure can improve the macro-bending performance.

The chinese invention patent CN105425335B proposes a method for preparing an anti-bending seven-core optical fiber, but mainly focuses on the low-crosstalk seven-core optical fiber and the compatibility with the G652 optical fiber, and does not focus on the requirements of other application scenarios.

The chinese invention patent CN108152879B proposes a crosstalk controllable multi-core fiber, but the asymmetric structure causes the problem of stress distribution inside the fiber, and the bending performance of the fiber is not mentioned.

Disclosure of Invention

In order to solve the problems in the prior art, the invention aims to provide a multi-core optical fiber for different application scenarios and a preparation method thereof.

In order to achieve the purpose and achieve the technical effect, the invention adopts the technical scheme that:

the multi-core optical fiber is manufactured by controlling the number of cores, the arrangement of the cores, the refractive index difference between the cores and the core spacing, and has crosstalk between different cores, and comprises a plurality of cores and a cladding coated outside the cores, wherein the cladding is perforated and one core is inserted into each hole, the refractive index difference of each core is 0-1.5%, and each core comprises a core layer, an inner cladding and a sunken cladding which are sequentially arranged from inside to outside.

Furthermore, the relative refractive index difference of the core layer, namely the difference Delta N1 between the effective refractive index N1 of the core layer and the refractive index N0 of pure silicon dioxide is 0.0044-0.0058.

Further, the relative refractive index difference of the inner cladding, i.e. the difference between the effective refractive index N2 of the inner cladding and the refractive index N0 of pure silica, is-0.0005.

Furthermore, the relative refractive index difference of the depressed cladding, namely the difference Delta N2 between the effective refractive index N3 of the depressed cladding and the refractive index N0 of pure silica is-0.0030 to-0.0060.

The invention discloses a preparation method of a multi-core optical fiber aiming at different application scenes, which comprises the following steps:

preparing a core and a cladding, and punching the cladding, wherein the number of holes is matched with that of the core;

then, inserting a plurality of cores into a plurality of holes of the cladding respectively, inserting one core into each hole, and drawing to obtain the required multi-core optical fiber;

the distance between two adjacent cores after drawing is 20-50 mu m, and the crosstalk between any two cores of the drawn multi-core optical fiber is not more than-50 dB.

Further, after wire drawing, the radius ratio of the inner cladding to the core layer is 2.0-3.0, and the radius ratio of the sunken cladding to the core layer is 3.0-4.0.

Further, after wire drawing, the radius of the core layer is 3.0-4.5 μm.

Furthermore, the aperture of the punched hole on the cladding is 10-30 mm, the hole pitch is 20-60 mm, and the outer diameter of the cladding is 50-120 mm.

Compared with the prior art, the invention has the beneficial effects that:

the invention discloses a multi-core fiber and a preparation method thereof aiming at different application scenes, wherein the multi-core fiber is designed by utilizing a method for controlling the number of cores, the arrangement of the cores, the refractive index difference between the cores and the core spacing and has crosstalk between different cores, the multi-core fiber comprises a plurality of cores and a cladding coated outside the cores, the refractive index difference of each core is 0-1.5%, each core comprises a core layer, an inner cladding and a sunken cladding which are sequentially arranged from inside to outside, holes are formed in the cladding, and one core is inserted into each hole. According to the invention, the core quantity and the core spacing of the multi-core optical fiber are diversified, the core quantity, the core arrangement and the core spacing can be designed according to the use environment, the relative refractive index difference among the core layer, the inner cladding and the sunken cladding is gradually reduced, the refractive index difference exists, the crosstalk among the cores can be controlled through the refractive index difference among the cores, the core spacing, the width and the relative refractive index of the sunken cladding, the energy leakage of the core layer at the center is avoided, the light loss is reduced, the bending performance of the optical fiber can be effectively improved through the arrangement of the sunken cladding, the design concept is ingenious, the process is simple and feasible, and the production efficiency is high and stable.

Drawings

FIG. 1 is a graph of the core refractive index profile of the present invention;

FIG. 2 is a schematic structural view of embodiment 1 of the present invention;

fig. 3 is a schematic structural diagram of embodiment 2 of the present invention.

Detailed Description

The present invention is described in detail below with reference to the attached drawings so that the advantages and features of the present invention can be more easily understood by those skilled in the art, thereby clearly defining the protection scope of the present invention.

The following presents a simplified summary of one or more aspects in order to provide a basic understanding of such aspects. This summary is not an extensive overview of all contemplated aspects, and is intended to neither identify key or critical elements of all aspects nor delineate the scope of any or all aspects. Its sole purpose is to present some concepts of one or more aspects in a simplified form as a prelude to the more detailed description that is presented later.

As shown in fig. 1-3, a multi-core fiber for different application scenarios is designed to obtain a multi-core fiber with crosstalk between different cores by using a method for controlling the number of cores, the arrangement of the cores, the refractive index difference between the cores, and the core spacing, the multi-core fiber includes a plurality of cores and a cladding layer covering the cores, a plurality of holes are punched in the cladding layer, a core is correspondingly inserted into each hole, and each core includes a core layer 1 (radius a), an inner cladding layer 2 (radius b), and a depressed cladding layer 3 (radius c) which are sequentially arranged from inside to outside.

The relative refractive index difference of the core layer 1, namely the difference delta N1 between the effective refractive index N1 of the core layer 1 and the refractive index N0 of pure silicon dioxide is 0.0044-0.0058.

The relative refractive index difference of the inner cladding 2, i.e. the difference between the effective refractive index N2 of the inner cladding 2 and the refractive index N0 of pure silica, is-0.0005.

The relative refractive index difference of the depressed cladding 3, namely the difference DeltaN 2 between the effective refractive index N3 of the depressed cladding 3 and the refractive index N0 of pure silica, is-0.0030 to-0.0060.

The cores can adopt homogeneous or heterogeneous cores, and the difference between the refractive indexes of the cores is 0-1.5%.

A preparation method of a multi-core optical fiber aiming at different application scenes comprises the following steps:

respectively preparing a core and a cladding, perforating the cladding, respectively inserting a plurality of cores into a plurality of holes of the cladding, inserting one core into each hole, and drawing to obtain the required multi-core optical fiber.

The cladding is prepared into a pure silica quartz rod or a pure silica core rod by VAD (vapor deposition) method (not limited to the process), and then is punched by high-precision punching equipment, wherein the aperture is 10-30 mm, the hole pitch is 20-60 mm, and the outer diameter of the cladding is 50-120 mm.

After wire drawing, the radius a of the core layer 1 is 3.0-4.5 μm, the radius ratio b/a of the inner cladding layer 2 to the core layer 1 is 2.0-3.0, and the radius ratio c/a of the sunken cladding layer 3 to the core layer 1 is 3.0-4.0.

After wire drawing, the distance between two adjacent cores is 20-50 mu m, and the number, the arrangement mode and the distance between the adjacent cores can be freely designed.

Typical values of the diameter of the multi-core optical fiber after drawing are 125 + -1 μm, but the diameter is not limited to these typical values.

Example 1

As shown in fig. 1-2, a multi-core fiber for different application scenarios, the outer diameter of which is 125 μm, is a four-core fiber composed of four cores and a cladding layer coated outside the cores, each core includes a core layer 1 (radius a), an inner cladding layer 2 (radius b), and a depressed cladding layer 3 (radius c) which are sequentially arranged from inside to outside, the cladding layer is made by high-precision drilling four holes with a pure silicon core rod according to a four-core fiber end face structure with an adjacent core spacing of 40 μm, the four cores are respectively inserted into the four holes of the cladding layer, and then drawing is performed to obtain the required multi-core fiber.

The 1550nm attenuation of the drawn optical fiber is less than or equal to 0.20, and 1550 macrobending 1 turn (R is 10mm) is not more than 0.02dB and reaches the G.657.B3 standard.

The crosstalk between any two cores of the drawn optical fiber is not more than-50 dB.

Example 2

As shown in fig. 1 and 3, a multi-core optical fiber for different application scenarios, the outer diameter of which is 125 μm, is a seven-core optical fiber composed of seven cores and a cladding layer coated outside the seven cores, each core includes a core layer 1 (radius a), an inner cladding layer 2 (radius b) and a sunken cladding layer 3 (radius c) which are sequentially arranged from inside to outside, the cladding layer is made by high-precision drilling of seven holes by a pure silicon core rod according to a seven-core optical fiber end face structure with an adjacent core spacing of 30 μm, the seven cores are respectively inserted into the seven holes of the sunken cladding layer 3, and then drawing is performed to obtain the required multi-core optical fiber.

The 1550nm attenuation of the drawn optical fiber is less than or equal to 0.20, and 1550 macrobending 1 turn (R is 10mm) is not more than 0.02dB and reaches the G.657.B3 standard.

The crosstalk between any two cores of the drawn optical fiber is not more than-50 dB.

The parts of the invention not specifically described can be realized by adopting the prior art, and the details are not described herein.

The above description is only an embodiment of the present invention, and not intended to limit the scope of the present invention, and all modifications of equivalent structures and equivalent processes, which are made by the present specification, or directly or indirectly applied to other related technical fields, are included in the scope of the present invention.