A multi-core low crosstalk orbital angular momentum fiber

Abstract

The application belongs to the technical field of optical fiber communication, and discloses a kind of multi-core low crosstalk orbital angular momentum optical fiber, comprising a plurality of cores and the common outer cladding covered outside the core;Each core is sequentially provided with three core layers and sunken cladding layer from inside to outside;The relative refractive index difference Δ1 of first core layer is 0.65%~0.69%, and radius R1 is 2 μm~4 μm;The relative refractive index difference Δ2 of second core layer is 0.78%~0.82%, and radius R2 is 6.8 μm~8.8 μm;The relative refractive index difference Δ3 of third core layer is-0.02%~0.02%, and radius R3 is 9 μm~11 μm;The relative refractive index difference Δ4 of sunken cladding layer is-0.74%~‑0.78%, and radius R4 is 14 μm~19 μm;Core spacing is 43 μm~45 μm.The application not only supports multiple order OAM modes in communication band, but also can reduce inter-core crosstalk while ensuring transmission capacity.

Description

Technical Field

[0001] This invention belongs to the field of optical fiber communication technology, and more specifically, relates to a multi-core low crosstalk orbital angular momentum optical fiber. Background Technology

[0002] Traditional single-mode optical fiber, as the main medium for current optical communication, has reached the nonlinear Shannon limit of 100 Tbit / s in terms of communication capacity. To improve transmission capacity, possible solutions include mode multiplexing and spatial multiplexing technologies. Among these, multiplexing technology based on orbital angular momentum (OAM) has attracted widespread attention both domestically and internationally.

[0003] OAM optical communication utilizes different OAM light sources as channels for communication. OAM light can be represented by symbols.<s,1> Let be the topological charge, where s can only be ±1, representing left-handed or right-handed optical rotation; 1 is the topological charge number, representing the ratio of the phase change after one clockwise rotation to 2π, and also the ratio of the OAM carried by a single photon to Planck's constant h. The topological charge number 1 can have infinitely many values, therefore, OAM optical communication technology can theoretically expand the existing communication capacity to infinity.

[0004] Multi-core optical fiber is an important form of spatial division multiplexing (SDM). Its basic principle is to place multiple cores within the same cladding to form parallel spatial channels. Each core in a multi-core fiber is an independent optical waveguide. Theoretically, N cores in a multi-core fiber can increase the total transmission capacity of the system by N times. Combined with mode division multiplexing (MDM), which utilizes different mode groups within the fiber to transmit multiple signals simultaneously in multiple spatial channels, the transmission capacity of a single fiber is significantly improved by implementing MDM within each core. However, because the inter-core spacing of multi-core fibers is generally very small, crosstalk can easily occur between different cores when transmitting optical signals, leading to lower transmission quality in multi-core optical fibers.

[0005] How to provide a multi-core orbital angular momentum optical fiber that not only supports multiple orders of OAM modes in the communication band, but also reduces inter-core crosstalk while ensuring transmission capacity is a technical problem that needs to be solved in this field. Summary of the Invention

[0006] The purpose of this invention is to provide a multi-core low-crosstalk orbital angular momentum optical fiber, so as to not only support multiple orders of OAM modes in the communication band, but also reduce inter-core crosstalk while ensuring transmission capacity.

[0007] This invention provides a multi-core low crosstalk orbital angular momentum optical fiber, comprising: a plurality of fiber cores and a common outer cladding covering the fiber cores; each fiber core is provided with a first core layer, a second core layer, a third core layer and a recessed cladding layer from the inside to the outside; the relative refractive index difference Δ1 of the first core layer is 0.65% to 0.69%, and the radius R1 is 2μm to 4μm; the relative refractive index difference Δ2 of the second core layer is 0.78% to 0.82%, and the radius R2 is 6.8μm to 8.8μm; the relative refractive index difference Δ3 of the third core layer is -0.02% to 0.02%, and the radius R3 is 9μm to 11μm; the relative refractive index difference Δ4 of the recessed cladding layer is -0.74% to -0.78%, and the radius R4 is 14μm to 19μm; the core spacing is 43μm to 45μm.

[0008] Preferably, the diameter of the common outer cladding layer is 245μm to 255μm.

[0009] Preferably, the common outer cladding layer is a pure silica glass cladding layer.

[0010] Preferably, the first core layer, the second core layer, and the third core layer are all composed of fluorine- and germanium-doped quartz glass.

[0011] Preferably, the multi-core low crosstalk orbital angular momentum fiber is a step-index fiber.

[0012] Preferably, the multi-core low crosstalk orbital angular momentum fiber supports stable three-order OAM modes at a wavelength of 1550nm.

[0013] Preferably, the multi-core low crosstalk orbital angular momentum fiber has an inter-core crosstalk of less than -30dB between any core and its adjacent core at wavelengths of 1310nm and 1550nm, and an inter-core crosstalk of less than -50dB between any core and other cores besides its adjacent core.

[0014] Preferably, the attenuation coefficient of the OAM mode supported by the multi-core low crosstalk orbital angular momentum fiber at a wavelength of 1550nm is less than or equal to 0.25dB / km.

[0015] Preferably, the macrobending loss of the multi-core low crosstalk orbital angular momentum fiber at wavelengths of 1310nm and 1550nm is less than or equal to 0.08dB when bent 100 times with a bending radius of R60mm.

[0016] Preferably, the effective area of ​​the OAM mode supported by the multi-core low crosstalk orbital angular momentum fiber at a wavelength of 1550 nm is greater than or equal to 130 μm. 2 .

[0017] One or more technical solutions provided in this invention have at least the following technical effects or advantages:

[0018] (1) Through simulation design, the first core layer of the optical fiber has a lower refractive index than the second core layer, and the mode field distribution of the optical fiber is Gaussian within the ring core, increasing the mode field area of ​​the optical fiber. The optical fiber profile parameters obtained by calculating the normalized frequency enable the optical fiber to transmit multiple modes. The present invention has a multi-level step-index profile structure, supporting up to the third-order OAM mode in the 1550nm communication band. The three orders of OAM modes transmitted stably in the optical fiber have ultra-low attenuation and strong bending resistance, which can be applied to the stable transmission of long-distance optical fiber communication systems. In trunk transmission, it can also reduce the cost of building related base stations and other system equipment, and the modes are easy to separate, facilitating multiplexing and demultiplexing. The present invention, through the design of the optical fiber plenum structure and the rational design of the optical fiber profile of each layer, combined with the specific structural parameters of the design, makes the plenum cladding of each core region similar, which is equivalent to increasing the plenum ring width of each core region, giving the multi-core optical fiber excellent bending resistance, with minimal impact on crosstalk between any cores. The crosstalk performance fully meets the bit error rate requirements of high-speed transmission under bending conditions, and has good practicality. The present invention has a reasonable arrangement of adjacent fiber cores in the entire fiber core region. While ensuring the transmission density of space division multiplexing, it can not only reduce the inter-core crosstalk and macro bending loss of the optical fiber, but also greatly reduce the additional attenuation caused by the core layer being close to the edge of the cladding.

[0019] (2) The symmetrical structure of the fiber core in this invention facilitates the splicing operation between multi-core optical fibers. This invention adopts a multi-core structure with the same fiber core pitch between adjacent fiber core areas and the same spacing between each outer fiber core area and the central fiber core area. The fiber core areas are rationally arranged, and the stress distribution within the optical fiber is relatively uniform. At the same time, the optical fiber structure is compact, which improves the communication density and is particularly suitable for use in dense cabling or long-distance optical fiber communication environments such as data centers. Attached Figure Description

[0020] Figure 1 A schematic diagram of the radial cross-section of a multi-core low crosstalk orbital angular momentum optical fiber provided for an embodiment of the present invention;

[0021] Figure 2 This is a refractive index profile of a multi-core low crosstalk orbital angular momentum optical fiber provided in an embodiment of the present invention. Detailed Implementation

[0022] To better understand the above technical solutions, the following will provide a detailed explanation of the technical solutions in conjunction with the accompanying drawings and specific implementation methods.

[0023] This invention provides a multi-core low crosstalk orbital angular momentum optical fiber, see [link to relevant documentation]. Figure 1 and Figure 2The fiber comprises: several fiber cores and a common outer cladding covering the fiber cores; each fiber core is provided with a first core layer, a second core layer, a third core layer and a recessed cladding layer from the inside to the outside; the relative refractive index difference Δ1 of the first core layer is 0.65% to 0.69%, and the radius R1 is 2μm to 4μm; the relative refractive index difference Δ2 of the second core layer is 0.78% to 0.82%, and the radius R2 is 6.8μm to 8.8μm; the relative refractive index difference Δ3 of the third core layer is -0.02% to 0.02%, and the radius R3 is 9μm to 11μm; the relative refractive index difference Δ4 of the recessed cladding layer is -0.74% to -0.78%, and the radius R4 is 14μm to 19μm; the intercore spacing is 43μm to 45μm.

[0024] The first core layer, the second core layer, and the third core layer may all be composed of fluorine-doped and germanium-doped quartz glass. Specifically, the first core layer is composed of fluorine-doped (F) and a small amount of germanium (Ge) quartz glass, the second core layer is composed of germanium-doped (Ge) and a small amount of fluorine-doped (F) quartz glass, and the third core layer is composed of fluorine-doped (F) and a small amount of germanium-doped (Ge) quartz glass.

[0025] The sunken cladding is deeply doped with fluorine (F).

[0026] The diameter of the common outer cladding layer is 245 μm to 255 μm. The common outer cladding layer is a pure silica glass cladding layer.

[0027] The multi-core low crosstalk orbital angular momentum fiber is a step-index fiber.

[0028] The optical fiber provided by this invention comprises multiple cores (e.g., 7, 8, or 19 cores) arranged in a circular ring, with all cores being of equal size. Each core in this invention comprises three core layers and one cladding layer. Overall, the multi-core low crosstalk orbital angular momentum optical fiber provided by this invention can also be understood as comprising core layers and cladding layers, with the core layers covered by cladding layers. Specifically, it comprises three core layers and two cladding layers. The core layers are prepared by plasma chemical vapor deposition (PCVD), and the relative refractive index difference between the three core layers satisfies: Δ2 > Δ1 > Δ3. The two cladding layers are a recessed cladding and a pure silica glass outer cladding, respectively. The recessed cladding tightly surrounds the core layers and is prepared by PCVD or outside vapor deposition (OVD) processes. It is used to ensure a large core-cladding refractive index difference and total internal reflection conditions in the optical fiber, and satisfies: Δ4 < Δ1.

[0029] Furthermore, the multi-core low crosstalk orbital angular momentum optical fiber provided by the present invention may also include a coating layer, which may be prepared by a double-layer coating process.

[0030] The multi-core low-crosstalk orbital angular momentum fiber supports stable three-order OAM modes at a wavelength of 1550 nm. In practical communication systems, only the second-order and third-order higher-order OAM modes need to be used.

[0031] The multi-core low crosstalk orbital angular momentum fiber exhibits inter-core crosstalk of less than -30dB between any core and its adjacent core at wavelengths of 1310nm and 1550nm, and inter-core crosstalk of less than -50dB between any core and other cores besides its adjacent core.

[0032] The OAM mode supported by the multi-core low-crosstalk orbital angular momentum fiber has an attenuation coefficient of less than or equal to 0.25 dB / km at a wavelength of 1550 nm. Under further optimized structural parameters, the attenuation coefficient is less than or equal to 0.22 dB / km.

[0033] The multi-core low crosstalk orbital angular momentum fiber has a macrobending loss of less than or equal to 0.08dB at wavelengths of 1310nm and 1550nm, with a bending radius of R60mm and 100 turns.

[0034] The effective area of ​​the OAM mode supported by the multi-core low crosstalk orbital angular momentum fiber at a wavelength of 1550 nm is greater than or equal to 130 μm. 2 .

[0035] The structural parameters and main performance parameters corresponding to five specific embodiments containing seven fiber cores are given below, as shown in Tables 1 to 3. OAM1,1 represents the first-order OAM mode, OAM2,1 represents the second-order OAM mode, and OAM3,1 represents the third-order OAM mode. According to the above technical solution for OAM optical fibers, the fiber parameters are designed within the specified range, and the core rod is manufactured according to the fiber design requirements using the known PCVD core rod manufacturing process. The entire preform is manufactured using external processes such as sleeve manufacturing.

[0036] Table 1 Structural parameters of multi-core low-crosstalk orbital angular momentum optical fiber

[0037]

[0038] Table 2. Attenuation coefficient and crosstalk performance parameters of multi-core low-crosstalk orbital angular momentum optical fibers

[0039]

[0040]

[0041]

[0042] Table 3 Performance parameters of macrobending loss and effective area for multi-core low crosstalk orbital angular momentum optical fibers

[0043]

[0044]

[0045] In summary, this invention proposes a multi-core low-crosstalk orbital angular momentum optical fiber for optical communication systems. It not only supports multiple orders of OAM modes in the communication band, but also reduces inter-core crosstalk while ensuring transmission capacity. In addition, this invention can reduce macro bending loss and has the characteristics of low attenuation and large effective area, making long-distance high-power optical transmission possible.

[0046] Finally, it should be noted that the above specific embodiments are only used to illustrate the technical solutions of the present invention and not to limit it. Although the present invention has been described in detail with reference to examples, those skilled in the art should understand that modifications or equivalent substitutions can be made to the technical solutions of the present invention without departing from the spirit and scope of the technical solutions of the present invention, and all such modifications or substitutions should be covered within the scope of the claims of the present invention.

Claims

1. A multi-core low crosstalk orbital angular momentum fiber, characterized by, include: The fiber comprises several fiber cores and a common outer cladding covering the fiber cores; each fiber core is provided with a first core layer, a second core layer, a third core layer, and a recessed cladding layer from the inside out; the relative refractive index difference Δ1 of the first core layer is 0.65% to 0.69%, and the radius R1 is 2 μm to 4 μm; the relative refractive index difference Δ2 of the second core layer is 0.78% to 0.82%, and the radius R2 is 6.8 μm to 8.8 μm; the relative refractive index difference Δ3 of the third core layer is -0.02% to 0.02%, and the radius R3 is 9 μm to 11 μm; the relative refractive index difference Δ4 of the recessed cladding layer is -0.74% to -0.78%, and the radius R4 is 14 μm to 19 μm; the intercore spacing is 43 μm to 45 μm.

2. The multicore low crosstalk orbital angular momentum fiber according to claim 1, wherein, The diameter of the common outer cladding is 245 μm to 255 μm.

3. The multicore low crosstalk orbital angular momentum fiber according to claim 1, wherein, The common outer cladding layer is a pure silica glass cladding layer.

4. The multicore low crosstalk orbital angular momentum fiber according to claim 1, wherein, The first core layer, the second core layer, and the third core layer are all composed of fluorine- and germanium-doped quartz glass.

5. The multicore low crosstalk orbital angular momentum fiber according to claim 1, wherein, The multi-core low crosstalk orbital angular momentum fiber is a step-index fiber.

6. The multicore low crosstalk orbital angular momentum fiber according to claim 1, wherein, The multi-core low crosstalk orbital angular momentum fiber supports stable three-order OAM modes at a wavelength of 1550 nm.

7. The multicore low crosstalk orbital angular momentum fiber according to claim 1, wherein, The multi-core low crosstalk orbital angular momentum fiber exhibits inter-core crosstalk of less than -30dB between any core and its adjacent core at wavelengths of 1310nm and 1550nm, and inter-core crosstalk of less than -50dB between any core and other cores besides its adjacent core.

8. The multi-core low crosstalk orbital angular momentum optical fiber according to claim 1, characterized in that, The OAM mode supported by the multi-core low crosstalk orbital angular momentum fiber has an attenuation coefficient of less than or equal to 0.25 dB / km at a wavelength of 1550 nm.

9. The multi-core low crosstalk orbital angular momentum optical fiber according to claim 1, characterized in that, The multi-core low crosstalk orbital angular momentum fiber has a macrobending loss of less than or equal to 0.08dB at wavelengths of 1310nm and 1550nm, with a bending radius of R60mm and 100 turns.

10. The multi-core low crosstalk orbital angular momentum optical fiber according to claim 1, characterized in that, The effective area of the OAM mode supported by the multicore low crosstalk orbital angular momentum optical fiber at a wavelength of 1550 nm is greater than or equal to 130 μm 2 .

Images