Single-mode large-core-diameter microstructure optical fiber for anti-interference communication of multiple SVGs (Static Var Generator) connected in parallel and preparation method

Abstract

The invention discloses a single-mode large-core-diameter microstructure optical fiber for multi-SVG parallel anti-interference communication and a preparation method. The single-mode large-core-diameter microstructure optical fiber sequentially comprises a fiber core area, a cladding area and a matrix material from inside to outside. The cladding area is of a hexagonal structure formed by arranging a plurality of layers of rounded hexagonal air holes according to a hexagonal period; the fiber core region is a region formed by a plurality of rounded hexagonal air holes in the center of the cladding-removed region; a fiber core wall with a certain thickness is arranged between the cladding area and the fiber core area; the matrix material wraps the cladding region; part of the air holes in the twelve axial symmetry directions in the cladding area are symmetrically scaled according to three different scaling rules, the scaling center of the air hole in the innermost layer is arranged in the center of the fiber core wall, and the thickness of the fiber core wall is not changed in the scaling process.

Description

Technical Field

[0001] The present invention relates to the technical field of microstructure optical fibers, and in particular to a single-mode large-core microstructure optical fiber for parallel anti-interference communication of multiple SVGs and a preparation method thereof. Background Art

[0002] It is crucial for multiple SVG parallel systems used in new energy charging stations to propagate light wave signals while maintaining the spatial distribution and polarization state of light without external interference. Electromagnetic interference generated by high-frequency switching in an electrical signal environment greatly affects the charging efficiency of new energy charging piles. A more practical and efficient solution is to use the flexibility and ultra-low loss of optical fiber to improve the charging efficiency of the system. However, environmental disturbances in the charging pile and manufacturing defects of the optical fiber will produce random birefringence, resulting in unpredictable output.

[0003] Large-core microstructured optical fibers can support multiple mode transmissions. In practical applications, severe mode coupling can occur when the optical fiber is faced with slight external disturbances, causing the mode components of the optical fiber to become chaotic, limiting its application. Summary of the invention

[0004] Purpose of the invention: In order to solve the problems faced by the parallel anti-interference communication of multiple SVGs in the new energy charging station scenario and to solve the problems of the large number of transmission modes and the difficulty of mode control in large-core microstructure optical fibers, the present invention proposes a single-mode large-core microstructure optical fiber and a preparation method for parallel anti-interference communication of multiple SVGs, which can stably transmit a single vector mode.

[0005] Technical solution: A single-mode large-core microstructure optical fiber for parallel anti-interference communication of multiple SVGs, comprising, from the inside to the outside, a core region, a cladding region and a matrix material; the cladding region is a hexagonal structure formed by multiple rounded hexagonal air holes arranged in a hexagonal period; the core region is a region formed by removing multiple rounded hexagonal air holes at the center of the cladding region; there is a core wall of a certain thickness between the cladding region and the core region; the matrix material wraps the cladding region;

[0006] Part of the air holes along 12 axial symmetry directions in the cladding region are symmetrically scaled according to three different scaling rules, wherein the scaling center of the innermost air hole is set at the center of the core wall, and the thickness of the core wall remains unchanged during the scaling process;

[0007] The air holes scaled according to scaling rule 1 and scaling rule 2 are used to filter the TM, HE and EH modes with out-of-plane polarization directions;

[0008] The air holes scaled according to scaling rule three are used to filter the high-order TE modes with in-plane polarization direction.

[0009] Furthermore, the matrix material is one of quartz material, polymer material, fluoride material or chalcogenide material.

[0010] Furthermore, the diameter of the scaled air hole is 0.8 to 1 of the center distance between the two air holes.

[0011] Furthermore, the thickness t of the core wall satisfies the anti-resonance condition at the operating wavelength, which is expressed as:

[0012]

[0013] Wherein, m is a natural number, and its value is 0, 1, 2, ...; n is the refractive index of the matrix material, and λ is the wavelength.

[0014] The present invention discloses a method for preparing a single-mode large-core microstructure optical fiber for parallel anti-interference communication of multiple SVGs, comprising the following steps:

[0015] A cladding region is obtained by forming a hexagonal structure by arranging multiple layers of rounded hexagonal air holes according to a hexagonal period.

[0016] A plurality of rounded hexagonal air holes at the center of the cladding region are removed to form a hollow region, and a core wall with a certain thickness is placed in the hollow region to form a core region;

[0017] In the cladding region, some air holes along 12 axial symmetry directions are symmetrically scaled according to three different scaling rules, wherein the scaling center of the innermost air hole is set at the center of the core wall, and the thickness of the core wall remains unchanged during the scaling process, thereby obtaining the cladding region after the scaling operation; wherein, the air holes scaled according to scaling rule 1 and scaling rule 2 are used to filter TM, HE and EH modes with out-of-plane polarization directions; and the air holes scaled according to scaling rule 3 are used to filter high-order TE modes with in-plane polarization directions;

[0018] The cladding area after the scaling operation is wrapped with a matrix material to form a single-mode large-core microstructure optical fiber for parallel anti-interference communication of multiple SVGs.

[0019] Furthermore, the diameter of the scaled air hole is 0.8 to 1 of the center distance between the two air holes.

[0020] Furthermore, the thickness t of the core wall satisfies the anti-resonance condition at the operating wavelength, which is expressed as:

[0021]

[0022] Wherein, m is a natural number, and its value is 0, 1, 2, ...; n is the refractive index of the matrix material, and λ is the wavelength.

[0023] The present invention discloses a method for realizing pure TE 01 The mode transmission method comprises the following steps:

[0024] Produce the above-disclosed single-mode large-core microstructure optical fiber for parallel anti-interference communication of multiple SVGs;

[0025] By modulating the air hole duty cycle at a specific cladding region, pure TE is achieved in the operating wavelength range of more than 50nm. 01 Mode transmission.

[0026] Beneficial effects: Compared with the prior art, the present invention has the following advantages:

[0027] (1) The optical fiber proposed in the present invention selects a portion of the lattice in a specific direction in the conventional 37-core hollow-core photonic bandgap fiber cladding structure and scales it proportionally, which can fully filter out more than 40 modes and achieve single-mode low-loss transmission characteristics with extremely high mode purity, which can be achieved using conventional hollow-core fiber drawing processes;

[0028] (2) The present invention ensures that the thickness of the optical fiber core wall remains unchanged while scaling the innermost lattice of the cladding, which is of great significance for achieving single-mode transmission because the high-order TE mode and TE 01 With the same polarization direction, the present invention cleverly filters out the energy of the high-order TE mode outer ring, thereby retaining only the TE 01 ;

[0029] (3) The optical fiber structure proposed in the present invention ensures high purity TE 01 While the mode has low-loss transmission, it also has large mode field area and low nonlinear characteristics, and ensures stable anti-bending and wavelength tunability, thus having broad application potential in the field of signal transmission in narrow environments;

[0030] (4) The core diameter of the optical fiber proposed in the present invention exceeds 40 μm, and supports pure TE01 mode transmission with a minimum loss of 0.127 dB / km over a working bandwidth of more than 50 nm. In addition, while having a large mode field area and an extremely low nonlinear coefficient, the optical fiber also ensures stable anti-bending characteristics, and can be used for parallel anti-interference communication of multiple SVGs in a charging system;

[0031] (5) The conduction modes in the optical fiber proposed in the present invention have different polarization directions. In the lattice cladding composed of high and low refractive indexes of the hollow-core microstructure optical fiber, an anisotropic optical potential well structure is designed to regulate the mode field components inside the degenerate mode. The mode with a specific polarization direction will be independently confined in the potential well, thereby realizing single-vector mode transmission in large-size microstructure optical fibers. BRIEF DESCRIPTION OF THE DRAWINGS

[0032] Figure 1This is a cross-sectional view of a single-mode large-core microstructure optical fiber for parallel anti-interference communication of multiple SVGs proposed by the present invention:

[0033] Figure 2 for Figure 1 A partial enlarged view of

[0034] Figure 3 The present invention proposes a single-mode large-core microstructure optical fiber TE for parallel anti-interference communication of multiple SVGs. 01 Schematic diagram of total loss comparison with other modes with the lowest loss;

[0035] Figure 4 The present invention proposes a single-mode large-core microstructure optical fiber TE for parallel anti-interference communication of multiple SVGs. 01 Schematic diagram comparing limiting loss and scattering loss with other modes with the lowest loss;

[0036] Figure 5 The bending loss characteristics and TE of a single-mode large-core microstructured optical fiber for parallel anti-interference communication of multiple SVGs proposed by the present invention 01 and HE 11 Plots of the mode field and power loss in the bent state. DETAILED DESCRIPTION

[0037] The technical solution of this embodiment is now further described in conjunction with the accompanying drawings.

[0038] This embodiment proposes a single-mode large core diameter microstructure optical fiber for parallel anti-interference communication of multiple SVGs, which mainly includes a matrix material 1, a cladding region 2 and a core region 3. The cladding region 2 is a large hexagonal structure formed by six layers of rounded hexagonal lattice holes arranged in a hexagonal periodic pattern, and the partial lattices along the 12 axial symmetry directions in the cladding region 2 are symmetrically scaled according to three different scaling rules, such as Figure 1 As shown in the reference numerals a1, b1, c1 in FIG. 1 , the core region 3 is formed by removing 37 small lattice holes to form a large-sized air hole. Between the cladding region 2 and the core region 3 is a core wall with a specific thickness.

[0039] In this embodiment, the matrix material 1 is a material that can be drawn into an optical fiber, including but not limited to one of a quartz material, a polymer material, a fluoride material or a chalcogenide material. The scaling lattices in the 12 axially symmetric directions in the cladding region 2 are scaled at three different scaling ratios, respectively, and the diameter of the scaling lattice is 0.8 to 1 of the distance between the centers of the two lattices.

[0040] The key to achieving single-mode transmission of optical fiber in this embodiment is to set the scaling center of the innermost lattice c1 at the center of the core wall to ensure that the thickness of the core wall remains unchanged during the scaling process, thereby fully filtering out high-order TE modes.

[0041] The core wall thickness t satisfies the anti-resonance condition at the operating wavelength to ensure that the optical fiber has low loss characteristics: Where m is a natural number, with values ​​of 0, 1, 2, etc.; n is the refractive index of the quartz material, and λ is the wavelength.

[0042] By modulating the lattice duty cycle in 12 directions of the cladding, the TM, HE and EH modes with out-of-plane polarization can be completely filtered out in the optical fiber, leaving only the TE mode with in-plane polarization direction. Large-core hollow-core microstructured optical fibers can support dozens of modes, so there are still high-order TE modes (such as TE 02 TE 03 etc.) are not filtered. By studying the mode field polarization of these modes, it can be found that TE 01 The mode field is a single ring, TE 02 It is a double ring, TE 03 It is a three-ring shape, that is, the energy of the outer ring of the mode field of the high-order TE mode overlaps more with the inner surface glass of the core wall, so the innermost lattice of the modulation cladding can easily filter out the high-order TE mode, so that only TE is achieved in the core. 01 Single mode transmission.

[0043] like Figure 2 Detailed structural parameters of the optical fiber proposed in this embodiment. The photonic crystal structure in the cladding region 2 is formed by an arrangement of hexagonal air holes with a lattice constant of Λ = 6 μm. By removing 37 unit air holes in the cladding region 2, a large-size core structure with a radius of R = 20 μm is introduced. The diameter of the cladding air hole is d0 = 0.98Λ, and the diameter of the cladding air hole fillet is d c =0.2Λ, the core wall thickness is t core =370nm. The key to single-mode transmission is to optimize the lattice structure in 12 specific directions in the cladding. In the figure, a1 and b1 are used to filter TM, HE and EH modes with out-of-plane polarization directions, and c1 is used to filter high-order TE modes with in-plane polarization directions. Among them, c1 needs to keep the thickness in the core wall direction unchanged during the scaling process to ensure TE 01 The low loss characteristic (that is, the scaling center needs to be set at the center of the core wall). The diameters of the three scaling lattices are: d1 = 0.93Λ, d2 = 0.89Λ, d3 = 0.96Λ. The base material used for the optical fiber in this embodiment is pure silica, and the refractive index of different wavelengths is determined by the Sellmeier equation.

[0044] like Figure 3As shown, the fiber can support more than 40 modes, the highest order mode is TE 03 In the range of 1786nm-1840nm, TE 01 The loss of the mode is always less than 0.5dB / km. In contrast, the loss of other modes is always greater than 100dB / km.

[0045] Figure 4 The reason for the loss difference is shown. The loss of hollow core microstructured optical fiber mainly includes scattering loss and limiting loss. The mode filtering mechanism of this embodiment is achieved by increasing the limiting loss, while the scattering loss does not change. Because the limiting loss is very sensitive to the defects in a specific direction of the cladding, the TE 01 The energy of other core modes is lost to the cladding, while the scattering loss remains basically unchanged, so the loss difference between modes comes from the confinement loss.

[0046] like Figure 5 As shown in (a), the bending characteristics of the optical fiber at different bending radii are tested. It can be seen that even if the optical fiber bending radius reaches 1 cm, TE 01 The loss is only 1.6dB / km. Figure 5 In (b), the TE curve is plotted when the fiber bending radius in the x direction is 0.5 cm. 01 and HE 11 Mode field and power loss diagram.

[0047] The relevant principles of the optical fiber proposed in this embodiment are as follows:

[0048] When the transmission mode in the hollow core microstructured optical fiber is transmitted over a long distance in the fiber core, the energy distribution of different types of modes will be affected by the shape of the cladding structure. For example, the energy flow direction of HE, EH and TM type modes all have out-of-plane parts, so these mode energies can be selectively lost to the cladding by scaling the lattice in a specific direction of the cladding structure. TE modes are all in-plane polarization modes, and high-order TE modes have multi-layer light wave shapes, so the lattice of the innermost layer of the cladding can be scaled to filter out high-order TE modes, thereby retaining only TE. 01 .

[0049] In summary, the optical fiber proposed in this embodiment achieves pure TE with a minimum loss of 0.127 dB / km in the working wavelength range exceeding 50 nm by modulating the lattice duty cycle at a specific cladding position. 01 mode transmission, and the optical fiber also has many advantages such as low dispersion, low nonlinearity, bending resistance and single-mode window tunability. It can support low-loss transmission of a unique independent mode in the working band, and has stable bending resistance and wavelength tunability.

Claims

1. A single-mode large-core microstructured optical fiber for parallel anti-interference communication of multiple SVGs, characterized by: From the inside to the outside, it includes: a core region, a cladding region and a matrix material; the cladding region is a hexagonal structure formed by multiple rounded hexagonal air holes arranged in a hexagonal period; the core region is formed by removing multiple rounded hexagonal air holes at the center of the cladding region; there is a core wall of a certain thickness between the cladding region and the core region; the matrix material wraps the cladding region; Part of the air holes along 12 axial symmetry directions in the cladding region are symmetrically scaled according to three different scaling rules, wherein the scaling center of the innermost air hole is set at the center of the core wall, and the thickness of the core wall remains unchanged during the scaling process; The air holes scaled according to scaling rule 1 and scaling rule 2 are used to filter the TM, HE and EH modes with out-of-plane polarization directions; The air holes scaled according to scaling rule three are used to filter the high-order TE modes with in-plane polarization direction.

2. The single-mode large-core microstructured optical fiber for parallel anti-interference communication of multiple SVGs according to claim 1, characterized in that: The matrix material is one of quartz material, polymer material, fluoride material or chalcogenide material.

3. The single-mode large-core microstructured optical fiber for parallel anti-interference communication of multiple SVGs according to claim 1, characterized in that: The diameter of the scaled air hole is 0.8 to 1 of the center distance between the two air holes.

4. The single-mode large-core microstructure optical fiber for parallel anti-interference communication of multiple SVGs according to claim 1, characterized in that: The thickness t of the core wall satisfies the anti-resonance condition at the operating wavelength, expressed as: Wherein, m is a natural number, and its value is 0, 1, 2, ...; n is the refractive index of the matrix material, and λ is the wavelength.

5. A method for preparing a single-mode large-core microstructure optical fiber for parallel anti-interference communication of multiple SVGs, characterized in that: The following steps are involved: A cladding region is obtained by forming a hexagonal structure by arranging multiple layers of rounded hexagonal air holes according to a hexagonal period. A plurality of rounded hexagonal air holes at the center of the cladding region are removed to form a hollow region, and a core wall with a certain thickness is placed in the hollow region to form a core region; In the cladding region, some air holes along 12 axial symmetry directions are symmetrically scaled according to three different scaling rules, wherein the scaling center of the innermost air hole is set at the center of the core wall, and the thickness of the core wall remains unchanged during the scaling process, thereby obtaining the cladding region after the scaling operation; wherein, the air holes scaled according to scaling rule 1 and scaling rule 2 are used to filter TM, HE and EH modes with out-of-plane polarization directions; and the air holes scaled according to scaling rule 3 are used to filter high-order TE modes with in-plane polarization directions; The cladding area after the scaling operation is wrapped with a matrix material to form a single-mode large-core microstructure optical fiber for parallel anti-interference communication of multiple SVGs.

6. The method for preparing a single-mode large-core microstructure optical fiber for parallel anti-interference communication of multiple SVGs according to claim 5, characterized in that: The diameter of the scaled air hole is 0.8 to 1 of the center distance between the two air holes.

7. The method for preparing a single-mode large-core microstructure optical fiber for parallel anti-interference communication of multiple SVGs according to claim 5, characterized in that: The thickness t of the core wall satisfies the anti-resonance condition at the operating wavelength, expressed as: Wherein, m is a natural number, and its value is 0, 1, 2, ...; n is the refractive index of the matrix material, and λ is the wavelength.

8. A method to achieve pure TE 01 A mode transmission method, characterized in that: The following steps are involved: Produce a single-mode large-core microstructure optical fiber for parallel anti-interference communication of multiple SVGs as described in any one of claims 1 to 4; By modulating the air hole duty cycle at a specific cladding region, pure TE is achieved in the operating wavelength range of more than 50nm. 01 Mode transmission.

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