Ultralow-attenuation random coupling multi-core optical fiber, manufacturing method thereof and multi-core optical cable

Abstract

The invention belongs to the technical field of optical fiber communication, and discloses an ultralow-attenuation random coupling multi-core optical fiber, a manufacturing method thereof and a multi-core optical cable. The ultra-low attenuation random coupling multi-core optical fiber provided by the invention comprises a common outer cladding and a plurality of fiber cores arranged in the common outer cladding, each fiber core sequentially comprises a core layer and an inner wrapping layer from inside to outside; the core layer is made of germanium-fluorine co-doped silicon dioxide, and the influence of germanium-fluorine co-doping on the viscosity of the core layer is defined as delta eta 1; the inner cladding layer is made of germanium-fluorine co-doped silicon dioxide, and the influence of germanium-fluorine co-doping on the viscosity of the inner cladding layer is defined as delta eta 2; the delta eta 1 and the delta eta 2 meet the following conditions: 1.1 delta eta 2lt; delta eta 1lt; 0.9 delta eta < 2 >. The attenuation of the random coupling multi-core optical fiber can be reduced.

Description

Technical Field

[0001] This invention belongs to the field of optical fiber communication technology, and more specifically, relates to an ultra-low attenuation randomly coupled multi-core optical fiber and its manufacturing method, as well as a multi-core optical cable. Background Technology

[0002] Space division multiplexing (SDM) and mode division multiplexing (MDM) technologies can break the traditional Shannon limit and achieve higher bandwidth transmission. SDM technology based on few-mode fiber has shown great potential in improving the transmission capacity of single-fiber communication systems, with capacity increases of tens of times becoming possible, providing an effective way to solve the capacity bottleneck problem of future optical communication systems. Currently, most multi-core fiber applications are based on independent signal transmission between each core, i.e., weakly coupled multi-core fibers. However, this type of weakly coupled multi-core fiber has the following disadvantages: 1. To avoid crosstalk between cores, heterogeneous cores in multi-core fibers lead to complex processes and high costs; 2. If homogeneous cores are used, insufficient spacing between cores will increase crosstalk, while increasing the core spacing will reduce core density; 3. In fiber-to-the-home (FTTH) applications, to optimize fiber bending performance, it is necessary to ensure the distance between the outer core and the cladding edge to avoid signal leakage from the outer core, which is not conducive to reducing the fiber cladding diameter; 4. Multi-core fibers have extremely high requirements for fusion splicing, and even slight deviations in core spacing can lead to a significant increase in splice loss.

[0003] To overcome the aforementioned shortcomings or limitations, randomly coupled optical fibers have emerged. However, current designs for randomly coupled optical fibers are complex and difficult to fabricate. In particular, there is a lack of research on the impact of cross-section on attenuation. Furthermore, the lack of optimization of fiber attenuation means that the fabricated fibers are mainly used for short-distance applications and are not suitable for long-distance applications. Summary of the Invention

[0004] This invention solves the problem of high attenuation in existing random-coupled multi-core optical fibers by providing an ultra-low attenuation random-coupled multi-core optical fiber, its manufacturing method, and a multi-core optical cable.

[0005] In a first aspect, the present invention provides an ultra-low attenuation randomly coupled multi-core optical fiber, comprising: a common outer cladding and a plurality of fiber cores disposed in the common outer cladding; each fiber core comprises, from the inside out, a core layer and an inner cladding. The core layer is made of germanium-fluorine co-doped silicon dioxide, and the effect of germanium-fluorine co-doping on the viscosity of the core layer is defined as Δη1. The inner cladding is made of germanium-fluorine co-doped silicon dioxide, and the effect of germanium-fluorine co-doping on the viscosity of the inner cladding is defined as Δη2. Δn1 and Δn2 satisfy: 1.1Δn2<Δn1<0.9Δn2.

[0006] Preferably, the effect of germanium-fluorine co-doping on the core layer viscosity Δη1 is expressed as: Δη1 = -ΔGe1 + 3ΔF1, where ΔGe1 is the effect of germanium in the core layer on the refractive index, and ΔF1 is the effect of fluorine in the core layer on the refractive index; The effect of germanium-fluorine co-doping on the viscosity of the inner cladding, Δη2, is expressed as: Δη2 = -ΔGe2 + 3ΔF2, where ΔGe2 is the effect of germanium in the inner cladding on the refractive index, and ΔF2 is the effect of fluorine in the inner cladding on the refractive index.

[0007] Preferably, the plurality of fiber cores are evenly distributed circumferentially, the number of fiber cores is greater than 2, and the value of the spacing P between adjacent fiber cores ranges from 10μm to 25μm.

[0008] Preferably, the radius r1 of the core layer ranges from 3μm to 6μm, the radius r2 of the inner cladding layer ranges from 6μm to 10μm, and r2>r1; the material of the common outer cladding layer is pure silicon dioxide or fluorine-doped silicon dioxide.

[0009] Preferably, the optical waveguide is randomly coupled in multiple cores of the ultra-low attenuation randomly coupled multi-core optical fiber; In the O-band, the attenuation of each core of the ultra-low attenuation randomly coupled multi-core fiber is less than 0.27 dB / km; In the C-band, the attenuation of each core of the ultra-low attenuation randomly coupled multi-core optical fiber is less than 0.175 dB / km; In the L-band, the attenuation of each core of the ultra-low attenuation randomly coupled multi-core optical fiber is less than 0.19 dB / km.

[0010] Preferably, the spatial mode dispersion of the ultra-low attenuation randomly coupled multi-core fiber is less than... .

[0011] Preferably, in the O-band, C-band, and L-band, when the bending radius is R30mm and the fiber is bent 100 times, the macro bending loss of each core of the ultra-low attenuation random-coupled multi-core fiber is less than or equal to 0.01dB.

[0012] Preferably, in the O-band, C-band and L-band, the fusion loss of each core of the ultra-low attenuation random-coupled multi-core optical fiber is less than or equal to 0.1dB.

[0013] In a second aspect, the present invention provides a method for manufacturing an ultra-low attenuation randomly coupled multi-core optical fiber as provided in the first aspect of the present invention, comprising the following steps: Multiple homogeneous core rods were prepared using plasma chemical vapor deposition (PCVD). Multiple homogeneous core rods are fitted together with multi-core sleeves to obtain randomly coupled multi-core optical fiber preforms. The randomly coupled multi-core fiber preform is drawn into fibers to obtain an ultra-low attenuation randomly coupled multi-core fiber. The ultra-low attenuation random-coupled multi-core optical fiber satisfies the following condition: 1.1Δη2 < Δη1 < 0.9Δη2; where Δη1 is the effect of germanium-fluorine co-doping on the core viscosity and Δη2 is the effect of germanium-fluorine co-doping on the inner cladding viscosity.

[0014] Thirdly, the present invention provides a multi-core optical cable, comprising: a first number n1 loose tubes, each of the loose tubes containing a second number n2 ultra-low attenuation randomly coupled multi-core optical fibers as provided in the first aspect of the present invention; when the number of fiber cores in the ultra-low attenuation randomly coupled multi-core optical fibers is n3, the number of channels contained in the multi-core optical cable is n1×n2×n3.

[0015] One or more technical solutions provided in this invention have at least the following technical effects or advantages: The ultra-low attenuation randomly coupled multi-core optical fiber provided by this invention includes a common outer cladding and multiple fiber cores arranged within the common outer cladding. Each fiber core includes a core layer and an inner cladding layer from the inside out. The core layer is made of germanium-fluorine co-doped silicon dioxide, and the effect of germanium-fluorine co-doping on the viscosity of the core layer is defined as Δη1. The inner cladding layer is also made of germanium-fluorine co-doped silicon dioxide, and the effect of germanium-fluorine co-doping on the viscosity of the inner cladding layer is defined as Δη2. Δη1 and Δη2 satisfy the condition: 1.1Δη2 < Δη1 < 0.9Δη2. This invention, without changing the refractive index profile, limits the viscosity changes between layers by optimizing the germanium-fluorine doping ratio of each layer of the fiber core, reducing the viscosity differences between layers (i.e., reducing viscosity fluctuations between fiber layers), thereby reducing the attenuation of the randomly coupled multi-core optical fiber. Compared to ordinary randomly coupled multi-core optical fibers and ordinary multi-core optical cables, the ultra-low attenuation randomly coupled multi-core optical fibers and multi-core optical cables obtained based on multi-core optical fibers provided by this invention have low link attenuation, which can increase the relay distance, reduce the number and cost of optical cable relay stations, and facilitate the realization of space division multiplexing communication systems with high distance capacity product, low implementation cost, and low complexity, thus promoting the application of randomly coupled multi-core optical fibers and optical cables in long-distance trunk lines. Attached Figure Description

[0016] Figure 1 This is a schematic diagram of the end face structure of an ultra-low attenuation randomly coupled multi-core optical fiber provided in Embodiment 1 of the present invention; Figure 2 This is a schematic diagram of the end face structure of an ultra-low attenuation randomly coupled multi-core optical fiber provided in Embodiment 2 of the present invention. Detailed Implementation

[0017] 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.

[0018] In a first aspect, the present invention provides an ultra-low attenuation randomly coupled multi-core optical fiber, comprising: a common outer cladding and a plurality of fiber cores disposed in the common outer cladding; each fiber core comprises a core layer and an inner cladding layer from the inside out; the core layer is made of germanium-fluorine co-doped silicon dioxide, and the effect of germanium-fluorine co-doping on the viscosity of the core layer is defined as Δη1; the inner cladding layer is made of germanium-fluorine co-doped silicon dioxide, and the effect of germanium-fluorine co-doping on the viscosity of the inner cladding layer is defined as Δη2; Δη1 and Δη2 satisfy: 1.1Δη2 < Δη1 < 0.9Δη2.

[0019] To reduce viscosity fluctuations between layers in the fiber core and prepare ultra-low attenuation optical fiber, this invention regulates the viscosity variation of each layer through doping, ensuring that the influence of doping on the viscosity of each layer, Δη1 and Δη2, satisfies the following condition: 1.1Δη2 < Δη1 < 0.9Δη2. That is, this invention correlates the viscosity variation relationship (constraint) of each layer with the attenuation of the optical fiber to obtain ultra-low attenuation random-coupled multi-core optical fiber. Based on this, an ultra-low attenuation randomly coupled multi-core optical fiber is obtained, in which the optical waveguide is randomly coupled in multiple cores of the ultra-low attenuation randomly coupled multi-core optical fiber; in the O-band (1260nm to 1360nm), the attenuation of each core of the ultra-low attenuation randomly coupled multi-core optical fiber is less than 0.27dB / km; in the C-band (1530nm to 1565nm), the attenuation of each core of the ultra-low attenuation randomly coupled multi-core optical fiber is less than 0.175dB / km; and in the L-band (1565nm to 1625nm), the attenuation of each core of the ultra-low attenuation randomly coupled multi-core optical fiber is less than 0.19dB / km.

[0020] The effect of germanium-fluorine co-doping on the core layer viscosity, Δη1, is expressed as: Δη1 = -ΔGe1 + 3ΔF1, where ΔGe1 is the effect of germanium on the refractive index in the core layer, and ΔF1 is the effect of fluorine on the refractive index in the core layer. Alternatively, Δη1 can be understood as the change in viscosity of the core layer after germanium-fluorine doping relative to pure silicon.

[0021] The effect of germanium-fluorine co-doping on the viscosity of the inner cladding, Δη2, is expressed as: Δη2 = -ΔGe2 + 3ΔF2, where ΔGe2 is the effect of germanium in the inner cladding on the refractive index, and ΔF2 is the effect of fluorine in the inner cladding on the refractive index.

[0022] That is, the effect of germanium-fluorine co-doping on the viscosity of a certain layer, Δη, is expressed as: Δη = -ΔGe + 3ΔF. Germanium is used to increase the refractive index while simultaneously reducing viscosity; fluorine is used to reduce the refractive index while simultaneously reducing viscosity. The effect of fluorine on viscosity is much stronger than that of germanium. For the same absolute refractive index change, fluorine's viscosity-reducing effect is three times that of germanium.

[0023] The fiber cores are evenly distributed circumferentially, the number of fiber cores is greater than 2, and the spacing P between adjacent fiber cores ranges from 10μm to 25μm.

[0024] The radius of a layer is defined as the distance between the outer boundary of that layer and its center point. The radius r1 of the core layer ranges from 3 μm to 6 μm, and the radius r2 of the inner cladding layer ranges from 6 μm to 10 μm, with r2 > r1.

[0025] The common outer cladding layer is made of pure silicon dioxide or fluorine-doped silicon dioxide.

[0026] The spatial mode dispersion (SMD) of the ultra-low attenuation randomly coupled multi-core fiber is less than... .

[0027] In the O-band, C-band, and L-band, after bending 100 times with a bending radius of R30mm, the macro-bending loss of each core of the ultra-low attenuation randomly coupled multi-core optical fiber is less than or equal to 0.01dB. The macro-bending additional loss test method can refer to the method specified in IEC60793-1-47.

[0028] In the O-band, C-band, and L-band, the fusion loss of each core of the ultra-low attenuation randomly coupled multi-core optical fiber is less than or equal to 0.1 dB.

[0029] Secondly, the present invention provides a method for manufacturing an ultra-low attenuation randomly coupled multi-core optical fiber, comprising the following steps: Multiple homogeneous core rods were prepared using plasma chemical vapor deposition (PCVD). Multiple homogeneous core rods are fitted together with multi-core sleeves to obtain randomly coupled multi-core optical fiber preforms. The randomly coupled multi-core fiber preform is drawn into fibers to obtain an ultra-low attenuation randomly coupled multi-core fiber. The ultra-low attenuation random-coupled multi-core optical fiber satisfies the following condition: 1.1Δη2 < Δη1 < 0.9Δη2; where Δη1 is the effect of germanium-fluorine co-doping on the core viscosity and Δη2 is the effect of germanium-fluorine co-doping on the inner cladding viscosity.

[0030] The above describes the manufacturing method of the ultra-low attenuation randomly coupled multi-core optical fiber provided in the first aspect of the present invention. The manufacturing process parameters are adjusted with the aim of preparing the ultra-low attenuation randomly coupled multi-core optical fiber provided in the first aspect of the present invention. Therefore, the manufacturing method can be understood by referring to the description of the first aspect of the present invention, and will not be repeated here.

[0031] Thirdly, the present invention provides a multi-core optical cable, comprising: a first number n1 loose tubes, each loose tube containing a second number n2 ultra-low attenuation randomly coupled multi-core optical fibers; when the number of fiber cores in the ultra-low attenuation randomly coupled multi-core optical fibers is n3, the number of channels contained in the multi-core optical cable is n1×n2×n3.

[0032] The ultra-low attenuation randomly coupled multi-core optical fiber included in the multi-core optical cable is the ultra-low attenuation randomly coupled multi-core optical fiber provided in the first aspect of the present invention.

[0033] The following examples, 1 and 2, are given in conjunction with the parameters to further illustrate the present invention.

[0034] Example 1: Example 1 provides an ultra-low attenuation randomly coupled multi-core optical fiber, see [link to example]. Figure 1 The number of fiber cores is 4, that is, the common outer cladding contains four homogeneous fiber cores. The main parameters of the corresponding refractive index profile structure are shown in Table 1, and the main performance parameters are shown in Table 2.

[0035] Table 1. Main structural parameters of the four-core optical fiber provided in Example 1

[0036] Table 2. Main performance parameters of the four-core optical fiber provided in Example 1 at 1625nm

[0037] As shown in Table 2, the present invention can ensure that the optical fiber supports random coupling propagation of four fiber cores in the L-band. The attenuation of the four fiber cores is very low. In addition, the macro bending and spatial mode dispersion performance of the optical fiber are also very good, and the splicing loss of each fiber core is also very small, making it suitable for long-distance communication transmission.

[0038] The corresponding fabrication method for ultra-low attenuation randomly coupled multi-core optical fiber includes: using a four-core sleeve with an outer diameter (OD) of 80 mm, the sleeve containing four holes with an OD of 11 mm, the center of each hole being 9.05 mm away from the center of the sleeve. Four core rods with an OD of 10 mm are fabricated using PCVD technology. The four core rods have identical cross-sections, and both the core layer and inner cladding are germanium-fluorine co-doped silica glass. The core layer has a radius of 1.98 mm, and the effect of germanium-fluorine co-doping on the core layer viscosity (Δη1) is -0.7. The inner cladding has a radius of 4.04 mm, and the effect of germanium-fluorine co-doping on the inner cladding viscosity (Δη2) is -0.74. These four core rods are then assembled with the sleeve and drawn into an ultra-low attenuation random coupled four-core optical fiber with each core having an attenuation of less than 0.19 dB / km at 1625 nm and a glass portion diameter of 124.9 μm.

[0039] To better understand the present invention and its advantages and to verify them, a comparative example (denoted as Comparative Example 1) is given below.

[0040] Comparative Example 1 shows a conventional attenuation random-coupled multi-core fiber with 4 cores, meaning that the common outer cladding contains four homogeneous cores. The main parameters of the corresponding refractive index profile structure are shown in Table 3, and the main performance parameters are shown in Table 4.

[0041] Table 3 shows the main parameters for the four-core fiber optic design as comparative example 1.

[0042] Table 4 shows the main performance parameters of the four-core optical fiber at 1625 nm, which serves as Comparative Example 1.

[0043] As can be seen from Tables 1 and 3, the optical fibers of Example 1 and Comparative Example 1 have the same structure, the same width of each layer, and the same refractive index (ΔGe+ΔF) of each layer (i.e., ΔGe1+ΔF1 and ΔGe2+ΔF2 of the two optical fibers are the same). However, the Δη of each layer is different (i.e., Δη1 and Δη2 of the two optical fibers are different). The Δη of each layer in Comparative Example 1 has a larger difference.

[0044] Comparing Tables 2 and 4, it can be seen that the optical fiber corresponding to Comparative Example 1 has significantly higher attenuation.

[0045] The above data also confirms that, without changing the refractive index profile, the present invention, through optimized doping design, limits the viscosity changes between layers, reduces the viscosity differences between layers, and lowers fiber attenuation.

[0046] Example 2: Example 2 provides an ultra-low attenuation randomly coupled multi-core optical fiber, see [link to example]. Figure 2 The number of fiber cores is 7, that is, the common outer cladding contains seven homogeneous fiber cores, and the main parameters of the corresponding refractive index profile structure are shown in Table 5.

[0047] Table 5. Main parameters of seven-core fiber design

[0048] The corresponding method for fabricating ultra-low attenuation randomly coupled multi-core optical fiber includes: using a seven-core sleeve with an OD of 80 mm, the sleeve containing seven holes with an OD of 10 mm, wherein the outer six holes are arranged in a regular hexagon with a side length of 12.48 mm, and the central hole is 12.48 mm away from the central hole of the sleeve. Seven core rods with an OD of 9 mm are fabricated using PCVD process. The seven core rods have the same cross-section, and both the core layer and the inner cladding are germanium-fluorine co-doped silica glass. The radius of the core layer is 2.24 mm, and the effect of germanium-fluorine co-doping on the viscosity of the core layer is Δη1 -1.14. The radius of the inner cladding is 4.61 mm, and the effect of germanium-fluorine co-doping on the viscosity of the inner cladding is Δη2 -1.22. The above seven core rods are drawn together with the sleeve rods to obtain an ultra-low attenuation randomly coupled seven-core optical fiber with a glass portion diameter of 125.2 μm.

[0049] A multi-core optical cable was prepared using the aforementioned ultra-low attenuation randomly coupled multi-core optical fiber. The cable type was GYTA-12, containing 6 loose tubes. Each loose tube contained 12 ultra-low attenuation randomly coupled seven-core optical fibers. The diameter of the loose tubes was 2.4 mm, and the final outer diameter of the optical cable was 11 mm. The optical cable contained 504 channels.

[0050] If a single-core optical cable of the same specifications is manufactured, the number of channels is only 72. It can be seen that the transmission capacity of the ultra-low attenuation random-coupled seven-core optical fiber provided by this invention is 7 times that of the traditional single-core optical fiber, which greatly improves the channel density of the optical cable, that is, the optical cable of the same diameter has a greater transmission capacity.

[0051] The present invention also tested the main parameters of the optical cable (i.e., the multi-core optical cable made of ultra-low attenuation random coupling seven-core optical fiber). The maximum values ​​of the main parameters of the 504 channels in the 1310nm and 1550nm bands are shown in Table 6.

[0052] Table 6 Main parameters of multi-core optical cable

[0053] Based on the above data, it can be seen that the ultra-low attenuation randomly coupled multi-core optical fiber provided by this invention has a homogeneous core and a much smaller core spacing than that of weakly coupled multi-core optical fibers. This effectively increases the core density without increasing the cladding diameter. The large distance between the core and the cladding edge avoids energy leakage during fiber bending, resulting in excellent macro-bending performance. The fiber attenuation is less than 0.27 dB / km in the 1310 nm band and less than 0.174 dB / km in the 1550 nm band. Since optical signal energy can be transmitted within the area enclosed by the multi-core, the impact of core geometric errors on splice loss is greatly reduced. Therefore, the ultra-low attenuation randomly coupled multi-core optical fiber provided by this invention overcomes the shortcomings of weakly coupled multi-core optical fibers while significantly expanding the information capacity of optical fiber communication. Furthermore, through the design of the fiber profile, core doping, and fiber structure, this fiber exhibits very low attenuation, bending loss, and spatial mode dispersion, meeting the requirements of long-distance communication applications. This invention not only facilitates manufacturing and production but also reduces production costs. The multi-core optical cable provided by this invention can increase channel density while keeping the optical cable size unchanged, or reduce the optical cable size while keeping the number of channels consistent, which is beneficial for realizing a space division multiplexing communication system with high distance capacity product, low implementation cost, and low complexity.

[0054] In summary, the random-coupled multi-core optical fiber provided by this invention has very low attenuation. In addition, the optical fiber has low spatial mode dispersion, macrobending and splice loss, which can increase the optical cable channel density or reduce the optical cable size.

[0055] 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. An ultra-low attenuation randomly coupled multi-core optical fiber, characterized in that, include: A common outer cladding and multiple fiber cores disposed in the common outer cladding; each fiber core includes a core layer and an inner cladding layer from the inside to the outside. The core layer is made of germanium-fluorine co-doped silicon dioxide, and the effect of germanium-fluorine co-doping on the viscosity of the core layer is defined as Δη1. The inner cladding is made of germanium-fluorine co-doped silicon dioxide, and the effect of germanium-fluorine co-doping on the viscosity of the inner cladding is defined as Δη2. Δn1 and Δn2 satisfy: 1.1Δn2<Δn1<0.9Δn2.

2. The ultra-low attenuation randomly coupled multi-core optical fiber according to claim 1, characterized in that, The effect of germanium-fluorine co-doping on the core layer viscosity Δη1 is expressed as: Δη1 = -ΔGe1 + 3ΔF1, where ΔGe1 is the effect of germanium in the core layer on the refractive index, and ΔF1 is the effect of fluorine in the core layer on the refractive index; The effect of germanium-fluorine co-doping on the viscosity of the inner cladding, Δη2, is expressed as: Δη2 = -ΔGe2 + 3ΔF2, where ΔGe2 is the effect of germanium in the inner cladding on the refractive index, and ΔF2 is the effect of fluorine in the inner cladding on the refractive index.

3. The ultra-low attenuation randomly coupled multi-core optical fiber according to claim 1, characterized in that, The multiple fiber cores are evenly distributed circumferentially, the number of fiber cores is greater than 2, and the value of the spacing P between adjacent fiber cores ranges from 10μm to 25μm.

4. The ultra-low attenuation randomly coupled multi-core optical fiber according to claim 1, characterized in that, The radius r1 of the core layer ranges from 3μm to 6μm, and the radius r2 of the inner cladding layer ranges from 6μm to 10μm, with r2>r1; the common outer cladding layer is made of pure silicon dioxide or fluorine-doped silicon dioxide.

5. The ultra-low attenuation randomly coupled multi-core optical fiber according to claim 1, characterized in that, The optical waveguide is randomly coupled in multiple cores of the ultra-low attenuation random-coupled multi-core optical fiber; In the O-band, the attenuation of each core of the ultra-low attenuation randomly coupled multi-core fiber is less than 0.27 dB / km; In the C-band, the attenuation of each core of the ultra-low attenuation randomly coupled multi-core fiber is less than 0.175 dB / km; In the L-band, the attenuation of each core of the ultra-low attenuation randomly coupled multi-core fiber is less than 0.19 dB / km.

6. The ultra-low attenuation randomly coupled multi-core optical fiber according to claim 1, characterized in that, The spatial mode dispersion of the ultra-low attenuation randomly coupled multi-core optical fiber is less than... .

7. The ultra-low attenuation randomly coupled multi-core optical fiber according to claim 1, characterized in that, In the O-band, C-band, and L-band, when the bending radius is R30mm and the fiber is bent 100 times, the macro bending loss of each core of the ultra-low attenuation randomly coupled multi-core fiber is less than or equal to 0.01dB.

8. The ultra-low attenuation randomly coupled multi-core optical fiber according to claim 1, characterized in that, In the O-band, C-band, and L-band, the fusion loss of each core of the ultra-low attenuation randomly coupled multi-core optical fiber is less than or equal to 0.1 dB.

9. A method for manufacturing an ultra-low attenuation randomly coupled multi-core optical fiber as described in any one of claims 1 to 8, characterized in that, Includes the following steps: Multiple homogeneous core rods were prepared using plasma chemical vapor deposition (PCVD). Multiple homogeneous core rods are fitted together with multi-core sleeves to obtain randomly coupled multi-core optical fiber preforms. The randomly coupled multi-core fiber preform is drawn into fibers to obtain an ultra-low attenuation randomly coupled multi-core fiber. The ultra-low attenuation random-coupled multi-core optical fiber satisfies: 1.1Δη2<Δη1<0.9Δη2; Δη1 is the effect of germanium-fluorine co-doping on the core viscosity, and Δη2 is the effect of germanium-fluorine co-doping on the inner cladding viscosity.

10. A multi-core optical cable, characterized in that, include: A first number of n1 loose tubes, each of which contains a second number of n2 ultra-low attenuation randomly coupled multi-core optical fibers as described in any one of claims 1 to 8; when the number of fiber cores in the ultra-low attenuation randomly coupled multi-core optical fibers is n3, the number of channels contained in the multi-core optical cable is n1×n2×n3.

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