Multi-core optical fiber with various heterostructures and design method thereof

Abstract

The invention discloses a multi-core optical fiber with various heterostructures and a design method thereof.The multi-core optical fiber comprises a cladding and at least two core layers arranged in the cladding, the core layers are distributed on at least one distribution layer, at most one core layer is arranged at the center point of the cladding, and at least one distribution layer is arranged at the center point of the cladding. And a heterostructure is arranged between each core layer and two adjacent core layers closest to the core layer. According to the invention, the number of the core layers and the variety number of the heterostructures are meticulously designed, so that the variety of the heterostructures can meet the requirement that the adjacent core layers are heterogeneous; the core layers on two adjacent distribution layers are distributed in a crossed manner at a certain rotation angle; the radius of every two adjacent distribution layers meets the following formula # imgabs0 #; by elaborately designing the refractive index distribution of different core layers and adopting a heterostructure to optimize the arrangement and spacing between the core layers, the inter-core crosstalk is effectively reduced, the mutual interference between signals is inhibited, the transmission capacity and transmission quality of an optical fiber communication system are expected to be further improved, and the higher requirements of the future communication technology are met.

Description

Technical Field

[0001] The present invention belongs to the technical field of optical communications, and in particular relates to a multi-core optical fiber with multiple heterogeneous structures and a design method thereof. Background Art

[0002] With the rapid development of 5G / 6G communication technologies, data transmission capacity in areas such as big data, cloud computing, artificial intelligence, the Internet of Things, and AI / VI is increasing dramatically, placing higher demands on the transmission capabilities of optical fiber communication systems. The transmission capacity of traditional single-mode optical fiber is gradually approaching its physical limits, making it difficult to meet the growing demand for communication capacity. Therefore, space division multiplexing (SDM) technology has emerged as an effective solution to address this capacity bottleneck.

[0003] Multi-core fiber, a key form of spatial division multiplexing, relies on placing multiple cores within the same fiber to form parallel spatial channels, significantly improving the fiber's multiplexing capabilities. Multi-core fiber is primarily categorized as weakly coupled multi-core fiber and strongly coupled multi-core fiber. Weakly coupled multi-core fiber enables independent and parallel signal transmission within each core, thus holding broad potential for application in communications. However, current weakly coupled multi-core fibers suffer from significant inter-core crosstalk and require improved transmission quality. Summary of the Invention

[0004] In order to solve the technical problems existing in the prior art, the object of the present invention is to provide a multi-core optical fiber with multiple heterogeneous structures and a design method thereof.

[0005] In order to achieve the above-mentioned purpose and the above-mentioned technical effect, the technical solution adopted by the present invention is: A multi-core optical fiber with multiple heterogeneous structures includes a cladding and at least two core layers arranged therein. The core layers are distributed on at least one distribution layer, with at most one core layer arranged at the center point of the cladding. Each core layer and its two nearest adjacent core layers form a heterogeneous structure, and the core layers on the two adjacent distribution layers are arranged in a cross-distribution at a certain rotation angle.

[0006] Furthermore, the distribution layer has a symmetrical structure, and the shape of the distribution layer is a triangle, a circle, a rectangle, a square, a hexagon, an octagon or other polygons.

[0007] Furthermore, the distribution layer is a symmetrical structure, and the number of core layers of the multi-core optical fiber and the number of types of heterogeneous structures satisfy the following formula:

[0008] Where a is the total number of core layers of the multi-core optical fiber, a is an integer greater than 1, b minis the minimum number of heterostructure types.

[0009] Furthermore, the minimum rotation angle between adjacent core layers of two adjacent distribution layers is 0-90°.

[0010] Furthermore, the radius of two adjacent distribution layers satisfies the following formula:

[0011] Among them, R N is the radius of the Nth distribution layer, R N-1 is the radius of the N-1th distribution layer, θ N-1 is the minimum rotation angle between the adjacent core layers of the Nth distribution layer and the N-1th distribution layer, d N-1 It is the minimum core spacing between any core layer on the N-1th distribution layer and any core layer on the Nth distribution layer.

[0012] Furthermore, the diameter r of the core layer x 1-50μm.

[0013] Furthermore, the refractive index of the core layer is n core , the refractive index of the cladding is n clad , n core >n clad , n core With n clad The relative refractive index difference ranges from 0.003 to 0.007.

[0014] The present invention also discloses a method for designing a multi-core optical fiber with multiple heterogeneous structures, comprising the following steps: a) determining the diameter range and refractive index structure of the core layer based on the required number of modes and capacity requirements, and determining the minimum number of heterostructure types based on the relationship between the number of core layers and heterostructures as defined in claim 3; The total number of core layers of a multi-core optical fiber is denoted as a, where a is an integer greater than 1, and the minimum number of types of core heterogeneous structures is denoted as b. min , when designing, the following formula is required:

[0015] This ensures that the type of heterogeneous structure can meet the requirement that adjacent core layers are heterogeneous; b) Based on the parameters determined in step a), combined with the design requirements for fiber attenuation and crosstalk, calculate and determine the minimum core spacing between any core layers on adjacent distribution layers through simulation; There are N distribution layers in a multi-core optical fiber, where N ≥ 1. The distribution layer closest to the center of the cladding is recorded as the first distribution layer, and from the inside to the outside are recorded as the second distribution layer, the third distribution layer, and so on. The number of core layers on the first distribution layer is recorded as Q1, the number of core layers on the second distribution layer is recorded as Q2, and so on. The number of core layers on the N distribution layer is recorded as Q N The minimum core spacing between any core layer on the first distribution layer and any core layer on the second distribution layer is recorded as d1, the minimum core spacing between any core layer on the second distribution layer and any core layer on the third distribution layer is recorded as d2, and the minimum core spacing between any core layer on the N-1 distribution layer and any core layer on the N distribution layer is recorded as d N-1 The minimum core spacing between any core layer on the Nth distribution layer and any core layer on the N+1th distribution layer is d N The radius of the first distribution layer is recorded as R1, the radius of the second distribution layer is R2, and so on, the radius of the Nth distribution layer is R N ; The core layers on two adjacent distribution layers are arranged in a cross-distribution with a certain rotation angle. The minimum rotation angle between the second distribution layer and the adjacent core layer of the first distribution layer is θ1, the minimum rotation angle between the third distribution layer and the adjacent core layer of the second distribution layer is θ2, and so on. The minimum rotation angle between the Nth distribution layer and the adjacent core layer of the N-1th distribution layer is θ N-1 ; c) performing a structural design simulation using the structural design formula of claim 5 based on the parameters determined in step b) to derive at least one multi-core optical fiber structural solution that satisfies the constraints of the formula; During design, the radius of two adjacent distribution layers must satisfy the following formula:

[0016] d) performing a performance simulation analysis on one or more optical fiber structure solutions obtained in step c), and optimizing and selecting a multi-core optical fiber structure with an optimal distribution layer radius and minimum rotation angle based on the final output performance parameters, thereby determining the multi-core optical fiber structure and number of cores to achieve a crosstalk value of less than or equal to -60 dB / 100 km.

[0017] Compared with the prior art, the present invention has the following beneficial effects: The present invention discloses a multi-core optical fiber with multiple heterogeneous structures and a design method thereof. By carefully designing the number of core layers and the number of types of heterogeneous structures, it is ensured that the types of heterogeneous structures can meet the requirement that adjacent core layers are heterogeneous; the core layers on two adjacent distribution layers are arranged in a cross-distribution with a certain rotation angle; the radius of the two adjacent distribution layers satisfies the following formula: R N = By carefully designing the refractive index distribution of different core layers and using heterogeneous structures to optimize the arrangement and spacing between core layers, the crosstalk between cores can be effectively reduced and mutual interference between signals can be suppressed. This is expected to further improve the transmission capacity and transmission quality of optical fiber communication systems and meet the higher demands of future communication technologies. BRIEF DESCRIPTION OF THE DRAWINGS

[0018] Figure 1 This is a schematic structural diagram of Example 1 of the present invention; Figure 2 This is a schematic structural diagram of Example 2 of the present invention; Figure 3 This is a structural diagram of Example 3 of the present invention. DETAILED DESCRIPTION

[0019] The present invention is described in detail below so that the advantages and features of the present invention can be more easily understood by those skilled in the art, thereby making a clearer and more precise definition of the protection scope of the present invention.

[0020] The following is a brief summary of one or more aspects to provide a basic understanding of these aspects. This summary is not an exhaustive overview of all conceivable aspects and is neither intended to identify key or critical elements of all aspects nor to define 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 will be provided later.

[0021] like Figure 1-3 As shown, a multi-core optical fiber with multiple heterogeneous structures includes a cladding and at least one distribution layer arranged therein. The number and shape of the distribution layers vary depending on design requirements. The cladding is coated on the outside of all distribution layers, and a core layer is arranged on the distribution layer. There are at least two core layers, and the core layers are distributed on at least one distribution layer. At most one core layer is arranged at the center point of the cladding, that is, the core layer may or may not be arranged at the center point of the cladding. Each core layer and its two nearest adjacent core layers have a heterogeneous structure. The types of heterogeneity include but are not limited to differences in the refractive index of the core layer, differences in the refractive index distribution shape of the core layer, differences in the type of core layer material, etc. The core layers on two adjacent distribution layers are arranged in a cross-distribution at a certain rotation angle.

[0022] The distribution layer is in a symmetrical structure, including but not limited to a rectangle, square, triangle, circle, hexagon, octagon or other polygons.

[0023] The shape of the distribution layer is determined by calculation based on design requirements such as the number of core layers and the minimum core spacing. Different distribution layers can have the same or different shapes.

[0024] In the design, the number of core layers in the multi-core optical fiber is a, a is an integer greater than 1, and the type of core heterogeneous structure is b. When a≤6, the minimum number of heterogeneous structure types b min is 2, when a≥7, b min is 3 to ensure that the type of heterostructure can meet the requirement that adjacent core layers are heterogeneous. The expression for the type of heterostructure is:

[0025] When designing a multi-core optical fiber, there are N distribution layers. The first distribution layer is closest to the center of the cladding, followed by the second distribution layer, the third distribution layer, and so on. The number of core layers on the first distribution layer is Q1, the number of core layers on the second distribution layer is Q2, and so on. The number of core layers on the Nth distribution layer is Q. N The number of core layers on each distribution layer is determined according to the fiber design requirements. The minimum core spacing between any core layer on the first distribution layer and any core layer on the second distribution layer is d1, the minimum core spacing between any core layer on the second distribution layer and any core layer on the third distribution layer is d2, and the minimum core spacing between any core layer on the Nth distribution layer and any core layer on the N+1th distribution layer is d N The distance between the core and cladding center points on the first distribution layer is R1, the distance between the core and cladding center points on the second distribution layer is R2, and so on. The distance between the core and cladding center points on the Nth distribution layer is R N .

[0026] During design, the core layers on two adjacent distribution layers are arranged in a cross-distribution with a certain rotation angle. The minimum rotation angle between the second distribution layer and the adjacent core layer of the first distribution layer is θ1, the minimum rotation angle between the third distribution layer and the adjacent core layer of the second distribution layer is θ2, and so on. The minimum rotation angle of the core layer between the Nth distribution layer and the N-1th distribution layer is θ N-1 The minimum rotation angle is 0-90°.

[0027] During design, if the radius R1 of the first distribution layer is known, the radius R2 of the second distribution layer = By analogy, it is known that the radius of the N-1th distribution layer is R N-1 , then the radius of the Nth distribution layer R N = .

[0028] The minimum core spacing d between adjacent core layers is determined by calculation based on the attenuation and crosstalk performance of the designed optical fiber. Once determined, the above formula is used to find the optimal values of R and θ, which then determines the shape of the distribution layer and the number of core layers within it.

[0029] The diameter of any core layer is r x , rx The r of each core layer is 1-50μm. x The value can be within this range.

[0030] The refractive index structure of any core layer can be a step-index structure, a graded-index structure, or a refractive index structure with multiple cladding layers. core , the cladding refractive index is n clad , n core >n clad .n core With n clad The relative refractive index difference ranges from 0.003 to 0.007.

[0031] By reasonably designing the rotation angle θ between the distribution layers N The shortest distance d between adjacent core layers N , which can effectively reduce the crosstalk between cores and make the crosstalk value less than or equal to -60dB / 100km.

[0032] The present invention also discloses a method for designing a multi-core optical fiber with multiple heterogeneous structures, comprising the following steps: a) determining the diameter range and refractive index structure of the core layer based on the required number of modes and capacity requirements, and determining the minimum number of heterostructure types based on the relationship between the number of core layers and heterostructures as defined in claim 3; The total number of core layers of a multi-core optical fiber is denoted as a, where a is an integer greater than 1, and the minimum number of types of core heterogeneous structures is denoted as b. min , when designing, the following formula is required:

[0033] This ensures that the type of heterogeneous structure can meet the requirement that adjacent core layers are heterogeneous; b) Based on the parameters determined in step a), combined with the design requirements for fiber attenuation and crosstalk, calculate and determine the minimum core spacing between any core layers on adjacent distribution layers through simulation; There are N distribution layers in a multi-core optical fiber, where N ≥ 1. The distribution layer closest to the center of the cladding is recorded as the first distribution layer, and from the inside to the outside are recorded as the second distribution layer, the third distribution layer, and so on. The number of core layers on the first distribution layer is recorded as Q1, the number of core layers on the second distribution layer is recorded as Q2, and so on. The number of core layers on the N distribution layer is recorded as Q N The minimum core spacing between any core layer on the first distribution layer and any core layer on the second distribution layer is recorded as d1, the minimum core spacing between any core layer on the second distribution layer and any core layer on the third distribution layer is recorded as d2, and the minimum core spacing between any core layer on the N-1 distribution layer and any core layer on the N distribution layer is recorded as dN-1 The minimum core spacing between any core layer on the Nth distribution layer and any core layer on the N+1th distribution layer is d N The radius of the first distribution layer is recorded as R1, the radius of the second distribution layer is R2, and so on, the radius of the Nth distribution layer is R N ; The core layers on two adjacent distribution layers are arranged in a cross-distribution with a certain rotation angle. The minimum rotation angle between the second distribution layer and the adjacent core layer of the first distribution layer is θ1, the minimum rotation angle between the third distribution layer and the adjacent core layer of the second distribution layer is θ2, and so on. The minimum rotation angle between the Nth distribution layer and the adjacent core layer of the N-1th distribution layer is θ N-1 ; c) performing a structural design simulation using the structural design formula of claim 5 based on the parameters determined in step b) to derive at least one multi-core optical fiber structural solution that satisfies the constraints of the formula; During design, the radius of two adjacent distribution layers must satisfy the following formula:

[0034] d) performing a performance simulation analysis on one or more optical fiber structure solutions obtained in step c), and optimizing and selecting a multi-core optical fiber structure with an optimal distribution layer radius and minimum rotation angle based on the final output performance parameters, thereby determining the multi-core optical fiber structure and number of cores to achieve a crosstalk value of less than or equal to -60 dB / 100 km.

[0035] Example 1

[0036] like Figure 1 The nine-core optical fiber with multiple heterogeneous structures shown in the figure is designed to have one core layer at the center of the cladding, four core layers on the first distribution layer, and four core layers on the second distribution layer. There are three types of core layer heterogeneous structures. The first distribution layer adopts a rectangular structure, and the second distribution layer adopts a square structure. The minimum distance between the core layer at the center of the cladding and the core layer on the first distribution layer is 30.5μm, that is, R1=30.5μm. The minimum distance between the core layer on the first distribution layer and the core layer on the second distribution layer is 30.5μm, that is, d1=30.5μm. The minimum rotation angle θ1 between the core layer of the second distribution layer and the core layer of the first distribution layer is 40°. The optimal value found by calculation is that the distance between the core layer on the second distribution layer and the center of the cladding is R2=46.7μm, and the cladding radius is 65.0μm. The radius r of all core layers x =6.5μm. The inter-core crosstalk value is less than or equal to -62dB / 100km.

[0037] Example 2

[0038] like Figure 2The nine-core optical fiber with multiple heterogeneous structures shown in the figure is designed to have three core layers in the first distribution layer, three core layers in the second distribution layer, and three core layers in the third distribution layer. There are three types of core layer heterogeneous structures. The first, second, and third distribution layers adopt circular structures. The minimum distance between the core layer on the first distribution layer and the core layer on the second distribution layer is 35 μm, that is, d1 = 35 μm. The minimum distance between the core layer on the second distribution layer and the core layer on the third distribution layer is 30 μm, that is, d2 = 30 μm. The minimum rotation angle between the second distribution layer and the core layer of the first distribution layer is θ1 = 70°, and the minimum rotation angle between the third distribution layer and the core layer of the second distribution layer is θ2 = 30°. The distance between the core layer and the center point of the cladding in the first distribution layer is R1 = 25 μm. The optimal values found by calculation are R2 = 34.5 μm for the distance between the core layer and the center point of the cladding in the second distribution layer, and R3 = 54.4 μm for the distance between the core layer and the center point of the cladding in the third distribution layer. The cladding radius is 75 μm. The radius r of all core layers x =4.5μm. The inter-core crosstalk value is less than or equal to -65dB / 100km.

[0039] Example 3

[0040] like Figure 3 The sixteen-core optical fiber with various heterogeneous structures shown in the figure has eight core layers in the first distribution layer and eight core layers in the second distribution layer. There are three types of core layer heterogeneous structures. The distribution layer adopts a polygonal structure. The minimum distance d1 between the core layer on the first distribution layer and the core layer on the second distribution layer is 35μm. The minimum rotation angle θ1 between the core layer of the second distribution layer and the core layer of the first distribution layer is 22.5°. The distance R1 between the core layer and the center point of the cladding on the first distribution layer is 45μm. The optimal value found by calculation is R2 = 72.0μm between the core layer and the center point of the cladding on the second distribution layer, and the cladding radius is 92.5μm. The radius r of all core layers x =6.5μm. The inter-core crosstalk value is less than or equal to -65dB / 100km.

[0041] Parts or structures not specifically described in the present invention may adopt existing technologies or existing products and will not be described in detail here.

[0042] The above descriptions are merely embodiments of the present invention and are not intended to limit the patent scope of the present invention. Any equivalent structure or equivalent process transformation made using the contents of the present invention specification, or directly or indirectly applied in other related technical fields, are also included in the patent protection scope of the present invention.

Claims

1. A multi-core optical fiber having multiple heterogeneous structures, characterized in that: It includes a cladding and at least two core layers arranged therein, wherein the core layers are distributed on at least one distribution layer, and at most one core layer is arranged at the center point of the cladding. Each core layer and its two nearest adjacent core layers are heterogeneous structures, and the core layers on the two adjacent distribution layers are arranged in a cross-distribution at a certain rotation angle.

2. The multi-core optical fiber with multiple heterogeneous structures according to claim 1, characterized in that: The distribution layer has a symmetrical structure, and the shape of the distribution layer is triangle, circle, rectangle, square, hexagon, octagon or other polygons.

3. The multi-core optical fiber with multiple heterogeneous structures according to claim 1, characterized in that: The distribution layer has a symmetrical structure, and the number of core layers of the multi-core optical fiber and the number of types of heterogeneous structures satisfy the following formula: ； Where a is the total number of core layers of the multi-core optical fiber, a is an integer greater than 1, b min is the minimum number of heterostructure types.

4. The multi-core optical fiber with multiple heterogeneous structures according to claim 1, characterized in that: The minimum rotation angle between adjacent core layers of two adjacent distribution layers is 0-90°.

5. The multi-core optical fiber with multiple heterogeneous structures according to claim 1, characterized in that: The radius of two adjacent distribution layers satisfies the following formula: ； Among them, R N is the radius of the Nth distribution layer, R N-1 is the radius of the N-1th distribution layer, θ N-1 is the minimum rotation angle between the adjacent core layers of the Nth distribution layer and the N-1th distribution layer, d N-1 It is the minimum core spacing between any core layer on the N-1th distribution layer and any core layer on the Nth distribution layer.

6. The multi-core optical fiber with multiple heterogeneous structures according to claim 1, characterized in that: The diameter r of the core layer x 1-50μm.

7. The multi-core optical fiber with multiple heterogeneous structures according to claim 1, characterized in that: The refractive index of the core layer is n core , the refractive index of the cladding is n clad , n core >n clad , n core With n clad The relative refractive index difference ranges from 0.003 to 0.

007.

8. A method for designing a multi-core optical fiber with multiple heterogeneous structures, characterized in that: The following steps are involved: a) determining the diameter range and refractive index structure of the core layer based on the required number of modes and capacity requirements, and determining the minimum number of heterostructure types based on the relationship between the number of core layers and heterostructures as defined in claim 3; The total number of core layers of a multi-core optical fiber is denoted as a, where a is an integer greater than 1, and the minimum number of types of core heterogeneous structures is denoted as b. min , when designing, the following formula is required: ； This ensures that the type of heterogeneous structure can meet the requirement that adjacent core layers are heterogeneous; b) Based on the parameters determined in step a), combined with the design requirements for fiber attenuation and crosstalk, calculate and determine the minimum core spacing between any core layers on adjacent distribution layers through simulation; There are N distribution layers in a multi-core optical fiber, where N ≥ 1. The distribution layer closest to the center of the cladding is recorded as the first distribution layer, and from the inside to the outside are recorded as the second distribution layer, the third distribution layer, and so on. The number of core layers on the first distribution layer is recorded as Q1, the number of core layers on the second distribution layer is recorded as Q2, and so on. The number of core layers on the N distribution layer is recorded as Q N The minimum core spacing between any core layer on the first distribution layer and any core layer on the second distribution layer is recorded as d1, the minimum core spacing between any core layer on the second distribution layer and any core layer on the third distribution layer is recorded as d2, and the minimum core spacing between any core layer on the N-1 distribution layer and any core layer on the N distribution layer is recorded as d N-1 The minimum core spacing between any core layer on the Nth distribution layer and any core layer on the N+1th distribution layer is d N The radius of the first distribution layer is recorded as R1, the radius of the second distribution layer is R2, and so on, the radius of the Nth distribution layer is R N ; The core layers on two adjacent distribution layers are arranged in a cross-distribution with a certain rotation angle. The minimum rotation angle between the second distribution layer and the adjacent core layer of the first distribution layer is θ1, the minimum rotation angle between the third distribution layer and the adjacent core layer of the second distribution layer is θ2, and so on. The minimum rotation angle between the Nth distribution layer and the adjacent core layer of the N-1th distribution layer is θ N-1 ; c) performing a structural design simulation using the structural design formula of claim 5 based on the parameters determined in step b) to derive at least one multi-core optical fiber structural solution that satisfies the constraints of the formula; During design, the radius of two adjacent distribution layers must satisfy the following formula: ； d) performing a performance simulation analysis on one or more optical fiber structure solutions obtained in step c), and optimizing and selecting a multi-core optical fiber structure with an optimal distribution layer radius and minimum rotation angle based on the final output performance parameters, thereby determining the multi-core optical fiber structure and number of cores to achieve a crosstalk value of less than or equal to -60 dB / 100 km.

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