Preparation method of multi-core optical fiber and multi-core optical fiber

Abstract

The invention provides a preparation method of a multi-core optical fiber and the multi-core optical fiber. The invention provides a preparation method of a multi-core optical fiber. The preparation method of the multi-core optical fiber comprises the following steps: providing a plurality of core rods; providing a first sleeve, wherein a plurality of core holes corresponding to the core rods are formed in the first sleeve; and the multiple core rods are assembled in the corresponding core holes correspondingly. A second sleeve is provided, an eccentric hole is machined in the second sleeve, and the molar doping concentration of the fluorine element in the second sleeve is smaller than that of the fluorine element in the first sleeve. And the first sleeve is assembled in the eccentric hole, and a mother rod is formed. And drawing the mother rod to obtain the multi-core optical fiber. The invention further provides the multi-core optical fiber, the multi-core optical fiber is prepared by using the preparation method of the multi-core optical fiber, the multi-core optical fiber comprises a plurality of core rods, a first sleeve and a second sleeve, and the plurality of core rods are connected to the first sleeve. The second sleeve is provided with an eccentric hole, the first sleeve is assembled in the eccentric hole, and the first sleeve is connected with the second sleeve.

Description

Technical Field

[0001] The present application relates to the field of optical fiber communication technology, and in particular to a method for preparing a multi-core optical fiber and the multi-core optical fiber. Background Art

[0002] With the continuous development of communication technology, the demand for optical fiber capacity is becoming increasingly higher. Currently, to increase single-fiber capacity, multi-core multiplexing is commonly used. Multi-core optical fiber can effectively increase optical fiber spatial density. However, multi-core optical fiber can cause problems such as inter-core crosstalk. To address this problem, optical fibers generally use a ring-core deep depression and a larger core spacing design to reduce inter-core crosstalk. However, due to the rod manufacturing process, the width and depth of the deep depression layer are limited, which has limited effect on suppressing inter-core crosstalk. When the core spacing is increased, the core layer is too close to the outer cladding, which is prone to light leakage and a significant increase in attenuation. Summary of the Invention

[0003] In order to solve the problem of high inter-core crosstalk and high transmission loss in multi-core optical fibers, the embodiments of the present application provide a method for preparing a multi-core optical fiber and a multi-core optical fiber capable of obtaining low transmission loss and low crosstalk characteristics.

[0004] An embodiment of the present application provides a method for preparing a multi-core optical fiber, the method comprising: providing a plurality of mandrels; Providing a first sleeve, wherein the first sleeve is provided with a plurality of core holes corresponding to the core rods; Assembling the plurality of core rods into the corresponding core holes respectively; Providing a second sleeve, processing an eccentric hole on the second sleeve, wherein the molar doping concentration of fluorine in the second sleeve is less than the molar doping concentration of fluorine in the first sleeve; Assembling the first sleeve into the eccentric hole to form a female rod; The mother rod is drawn to obtain a multi-core optical fiber.

[0005] It is understandable that by making the molar doping concentration of fluorine in the second sleeve lower than the molar doping concentration of fluorine in the first sleeve, the refractive index of the second sleeve is higher than that of the first sleeve. During drawing, the material hardness near the second sleeve is higher and can bear more tensile stress, which is conducive to the formation of compressive stress in the core layer of the core rod, reducing the amplitude of the stress fluctuation in the core layer, thereby further reducing attenuation. In addition, by adjusting the refractive index of the first sleeve and the second sleeve, the position of the optical cable cutoff wavelength migration of the multi-core optical fiber can be controlled and the bending performance of the optical fiber can be improved. In addition, the method opens an eccentric hole on the second sleeve, eliminating the need for an identification hole. While facilitating the identification of the core orientation during optical fiber fusion, a double-sleeve assembly method is adopted to reduce the steps and difficulty of processing the mother rod and reduce the manufacturing cost.

[0006] In one embodiment, the molar doping concentration of the fluorine element in the first sleeve is in a range of 1.0% to 1.5%, and the refractive index difference is in a range of -0.30% to -0.20%.

[0007] In one embodiment, the molar doping concentration of the fluorine element in the second sleeve is in a range of 0% to 0.05%, and the refractive index difference is in a range of -0.10% to 0%.

[0008] In one embodiment, the distance between the center of the eccentric hole and the center of the second sleeve is 5-10 μm.

[0009] In one embodiment, the diameter of the eccentric hole ranges from (D1+1.0) mm to (D1+2.0) mm, where D1 is the outer diameter of the first sleeve.

[0010] In one embodiment, the method for preparing the multi-core optical fiber further includes a first extension tube and a second extension tube; Before the step of respectively assembling the plurality of core rods into the corresponding core holes, the method further includes the steps of: connecting the first extension tube to the first sleeve; Before the step of assembling the first sleeve in the eccentric hole to form the mother rod, the method further includes the step of connecting the second extension tube to the second sleeve.

[0011] In one embodiment, the diameter of the core hole ranges from (D2+0.6) mm to (D2+1.0) mm, where D2 is the outer diameter of the core rod.

[0012] The present application also provides a multi-core optical fiber produced using the above-described method for producing a multi-core optical fiber. The multi-core optical fiber includes a plurality of core rods, a first sleeve, and a second sleeve. The plurality of core rods are connected to the first sleeve. The second sleeve has an eccentric hole, the first sleeve is assembled into the eccentric hole, and the first sleeve is connected to the second sleeve.

[0013] It can be understood that the multi-core optical fiber prepared by the above preparation method can reduce the inter-core crosstalk and attenuation at 1550nm, thereby improving the performance of the multi-core optical fiber and making its use effect better.

[0014] In one embodiment, the inter-core crosstalk of the multi-core optical fiber at 1550 nm is ≤-65 dB / km; and / or The mode field diameter of the multi-core optical fiber at 1550 nm is 10.5±0.5 μm; and / or The attenuation coefficient of the multi-core optical fiber at 1550 nm is ≤0.170 dB / KM.

[0015] In one embodiment, the optical cable cutoff wavelength of the multi-core optical fiber is ≤1500 nm; and / or The single-core fusion loss value of the multi-core optical fiber at 1550nm is ≤0.2dB; and / or The 1550nm single-core macrobending loss of the multi-core optical fiber with a bending radius of 10mm and 20 turns is ≤0.005dB. BRIEF DESCRIPTION OF THE DRAWINGS

[0016] Figure 1 A schematic diagram of a method for preparing a multi-core optical fiber provided in one embodiment of the present application.

[0017] Figure 2 A schematic cross-sectional view of a multi-core optical fiber provided in another embodiment of the present application.

[0018] Figure 3 A schematic diagram of the assembly structure of a multi-core optical fiber sleeve mother rod provided in another embodiment of the present application.

[0019] Figure 4 A schematic diagram of the refractive index distribution of a multi-core optical fiber cross section provided in another embodiment of the present application.

[0020] Figure 5 A schematic diagram of the cross-sections of a first ferrule and a second ferrule of a multi-core optical fiber provided in another embodiment of the present application.

[0021] Description of main component symbols: 100. Multi-core optical fiber; 1. Core rod; 2. First sleeve; 21. Core hole; 3. Second sleeve; 31. Eccentric hole; 4. First extension tube; 5. Second extension tube; 6. Drawing cone head.

[0022] The following specific implementation methods will further illustrate the present application in conjunction with the above-mentioned drawings. DETAILED DESCRIPTION

[0023] The following description will refer to the accompanying drawings to more fully describe the contents of this application. Illustrated in the accompanying drawings are exemplary embodiments of the present application. However, the present application can be implemented in many different forms and should not be construed as limited to the exemplary embodiments set forth herein. These exemplary embodiments are provided so that this application will be thorough and complete and will fully convey the scope of the application to those skilled in the art. Similar reference numerals represent identical or similar components. The terms used herein are for the purpose of describing specific exemplary embodiments only and are not intended to limit this application. As used herein, the singular forms "a," "an," and "the" are intended to include the plural forms as well, unless the context clearly indicates otherwise. Furthermore, when used herein, "including" and / or "comprising" and / or "having" refer to integers, steps, operations, components, and / or parts, but do not preclude the presence or addition of one or more other features, regions, integers, steps, operations, components, and / or groups thereof. Unless otherwise defined, all terms (including technical and scientific terms) used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this application belongs. Furthermore, unless explicitly defined herein, terms such as those defined in commonly used dictionaries should be interpreted as having a meaning consistent with their meaning in the relevant art and the content of this application, and will not be interpreted as an idealized or overly formal meaning.

[0024] like Figure 1 and Figure 2 As shown, an embodiment of the present application provides a method for preparing a multi-core optical fiber 100, and the method for preparing the multi-core optical fiber 100 includes: S1: A plurality of mandrels 1 are provided.

[0025] In this embodiment, a modified in-tube chemical vapor deposition method, namely the MCVD (Modified Chemical Vapor Deposition) process, an in-tube plasma chemical vapor deposition method, namely the PCVD (Plasma Chemical Vapor Deposition) process, or an out-of-tube axial vapor deposition method, namely the VAD (Vapor-phase Axial Deposition) process, can be used to prepare a prefabricated core rod 1. The core rod 1 is the core rod 1 provided in the step. The core rod 1 includes a core layer and a ring core deep recessed layer. The core layer is doped with one or more of germanium, fluorine, and alkali metal elements. Multiple core rods 1 have the same structure.

[0026] After the core rod 1 is prepared, it is stretched using an oxyhydrogen flame or a high-temperature graphite furnace to a size that matches the core hole 21 defined in the first sleeve 2, ensuring a single-side clearance between the core rod 1 and the inner wall of the core hole 21 of 0.3 mm to 0.5 mm. It is understood that the single-side clearance between the core rod 1 and the inner wall of the core hole 21 can be 0.3 mm, 0.4 mm, or 0.5 mm.

[0027] Then, all the core rods 1 are treated with hydrofluoric acid in a pickling device to corrode and remove metal impurities and other pollutants that may be contaminated on the surface, and the remaining acid solution is purified and then used for standby.

[0028] S2: providing a first sleeve 2 , wherein the first sleeve 2 is provided with a plurality of core holes 21 corresponding to the core rod 1 .

[0029] In this embodiment, the parent material for the first sleeve 2 is first prepared, specifically using solid fluorine-doped quartz to facilitate subsequent processing to form the first sleeve 2. At least two core holes 21 are punched into the parent material, with the number of core holes 21 corresponding to the number of core rods 1. Each core hole 21 has consistent geometric dimensions and is evenly and symmetrically distributed within the first sleeve 2.

[0030] In one embodiment, the diameter of the core hole 21 ranges from (D2+0.6) mm to (D2+1.0) mm, where D2 is the outer diameter of the core rod 1 .

[0031] In this embodiment, the diameter of the core hole 21 can be (D2 + 0.6) mm, (D2 + 0.7) mm, (D2 + 0.8) mm, (D2 + 0.9) mm, or (D2 + 1.0) mm, or can be any other value within the range of (D2 + 0.6) mm to (D2 + 1.0) mm, without further limitation. The outer diameter of the first sleeve 2 is determined by the cross-sectional requirements and has a wide range of variations, without further limitation. By maintaining an appropriate gap between the core rod 1 and the core hole 21, the multi-core optical fiber 100 formed by subsequent processing can achieve better performance.

[0032] Further integration Figure 3 and Figure 4 As shown, Figure 4 The horizontal axis represents the radius of the multi-core fiber cross section, and the vertical axis represents the relative refractive index difference of the multi-core fiber cross section. In one embodiment, the molar doping concentration of fluorine in the first sleeve 2 ranges from 1.0% to 1.5%, and the refractive index difference ranges from -0.30% to -0.20%.

[0033] It can be understood that the molar doping concentration of the fluorine element in the first sleeve 2 can be 1.0%, 1.1%, 1.2%, 1.3%, 1.4%, and 1.5%, and the refractive index difference can be -0.30%, -0.29%, -0.28%, -0.27%, -0.26%, -0.25%, -0.24%, -0.23%, -0.22%, -0.21%, and -0.20%.

[0034] In this embodiment, the refractive index difference can be varied by changing the molar doping concentration of fluorine in the first sleeve 2. Here, the refractive index difference represents the relative difference between the refractive index of the fluorine-doped layer of the first sleeve 2 and the refractive index of the pure silica cladding. When the molar doping concentration of fluorine in the first sleeve 2 is 1.0%, the refractive index difference is -0.20%. When the molar doping concentration of fluorine in the first sleeve 2 is 1.2%, the refractive index difference is -0.24%. When the molar doping concentration of fluorine in the first sleeve 2 is 1.5%, the refractive index difference is -0.30%.

[0035] It is understandable that by adjusting the molar doping concentration of the fluorine element in the first sleeve 2 to change the refractive index difference, combined with the arrangement of the second sleeve 3 , the performance of the multi-core optical fiber 100 can be further improved.

[0036] In one embodiment, the method for preparing the multi-core optical fiber 100 further provides a first extension tube 4 , and connects the first extension tube 4 to the first sleeve 2 .

[0037] In this embodiment, the outer diameter of the first extension tube 4 is substantially the same as that of the first sleeve 2. The inner diameter of the first extension tube 4 is configured to not completely cover the end of the core hole 21, thereby allowing for the creation of a vacuum pressure within the core hole 21 during wire drawing. The first extension tube 4 is welded to the first sleeve 2 using an oxyhydrogen flame lathe. During welding, the end of the first sleeve 2 containing the core holes 21 collapses and shrinks slightly at high temperatures, preventing the core rod 1 from slipping out of the sleeve. The first sleeve 2 is treated with hydrofluoric acid in an acid-washing facility to corrode and remove any contaminants, such as metal impurities, that may have contaminated the surface. The remaining acid is then purified and set aside for later use.

[0038] S3: Assemble the plurality of core rods 1 into the corresponding core holes 21 respectively.

[0039] In this embodiment, the core rod 1 is cut to approximately the same length as the first sleeve 2. The tail end of the core rod 1 is chamfered to prevent it from fitting too tightly against the core hole 21 at the tail end of the first sleeve 2, which would hinder vacuum extraction. The rods are then inserted one by one from the head end of the first sleeve 2 into place. A pre-prepared drawing taper tip 6 is welded to the head end of the first sleeve 2 using an oxyhydrogen flame lathe, securing the core rod 1 within the first sleeve 2.

[0040] S4: providing a second sleeve 3 , processing an eccentric hole 31 on the second sleeve 3 , wherein the molar doping concentration of the fluorine element in the second sleeve 3 is lower than the molar doping concentration of the fluorine element in the first sleeve 2 .

[0041] In this embodiment, the mother material of the second sleeve 3 is prepared, specifically pure quartz or quartz solid material lightly doped with fluorine, so as to facilitate subsequent processing to form the second sleeve 3. The mother material is extended to the required target length and eccentrically punched to form an offset hole.

[0042] In one embodiment, the molar doping concentration of the fluorine element in the second sleeve 3 is in a range of 0% to 0.05%, and the refractive index difference is in a range of -0.10% to 0%.

[0043] It can be understood that the molar doping concentration of the fluorine element in the second sleeve 3 can be 0%, 0.01%, 0.02%, 0.03%, 0.04%, 0.05%, and the refractive index difference can be -0.10%, -0.09%, -0.08%, -0.07%, -0.06%, -0.05%, -0.04%, -0.03%, -0.02%, -0.01%, and 0%.

[0044] In this embodiment, the refractive index difference can be varied by changing the molar doping concentration of fluorine in the second sleeve 3. Here, the refractive index difference represents the relative difference between the refractive index of the fluorine-doped layer of the second sleeve 3 and the refractive index of the pure silica cladding. When the molar doping concentration of fluorine in the second sleeve 3 is 0%, the refractive index difference is 0%. When the molar doping concentration of fluorine in the second sleeve 3 is 0.025%, the refractive index difference is -0.05%. When the molar doping concentration of fluorine in the second sleeve 3 is 0.05%, the refractive index difference is -0.10%.

[0045] It is understood that by adjusting the molar doping concentration of the fluorine element in the second sleeve 3 to change the refractive index difference, in conjunction with the configuration of the first sleeve 2, the performance of the multi-core optical fiber 100 is further improved. The molar doping concentration of the fluorine element in the second sleeve 3 is lower than the molar doping concentration of the fluorine element in the first sleeve 2, so that the refractive index of the second sleeve 3 is higher than the refractive index of the first sleeve 2. During drawing, the hardness of the material near the second sleeve 3 is relatively high, so that it can bear more tensile stress, which is conducive to the formation of compressive stress in the core layer of the core rod 1, reducing the stress fluctuation amplitude of the core layer, and thus further reducing attenuation.

[0046] In one embodiment, the distance between the center of the eccentric hole 31 and the center of the second sleeve 3 is 5-10 μm.

[0047] Further integration Figure 5 As shown, in this embodiment, the eccentric distance L between the center point b of the eccentric inner hole circle and the center point a of the second circle is controlled to be 5-10 μm (converted into data for the drawn multi-core optical fiber 100). The eccentric distance L can be 5 μm, 6 μm, 7 μm, 8 μm, 9 μm, or 10 μm. Controlling the eccentric distance within a certain range facilitates identification of the orientation of each core rod 1 during fiber splicing and prevents core light from escaping the second ferrule 3 due to the proximity of some core rods 1 to the boundary of the second ferrule 3.

[0048] In one embodiment, the diameter of the eccentric hole 31 ranges from (D1+1.0) mm to (D1+2.0) mm, where D1 is the outer diameter of the first sleeve 2 .

[0049] In this embodiment, the diameter of the eccentric hole 31 can be (D1+1.0) mm, (D1+1.2) mm, (D1+1.4) mm, (D1+1.6) mm, or (D1+2.0) mm, or can be other values ​​within the range of (D1+1.0) mm to (D2+2.0) mm, without further restrictions. The outer diameter of the second sleeve 3 is determined by the cross-sectional requirements and has a wide range of variables, without further restrictions. By leaving an appropriate gap between the first sleeve 2 and the second sleeve 3, the performance of the multi-core optical fiber 100 formed by subsequent processing is improved.

[0050] In one embodiment, the method for preparing the multi-core optical fiber 100 further provides a second extension tube 5 , and connects the second extension tube 5 to the second sleeve 3 .

[0051] In this embodiment, one end of the second sleeve 3 is first tapered using an oxyhydrogen flame lathe to form a taper head for wire drawing. A second extension tube 5 is welded to the other end of the second sleeve 3 using an oxyhydrogen flame lathe. The second extension tube 5 has substantially the same inner and outer diameters as the second sleeve 3 and the same eccentricity as the second sleeve 3. The second sleeve 3 is then treated with hydrofluoric acid in an acid wash facility to remove any contaminants, such as metal impurities, that may have contaminated the surface. The remaining acid is then purified and set aside.

[0052] S5: Assemble the first sleeve 2 into the eccentric hole 31 to form a female rod.

[0053] In this embodiment, the pickled, cleaned, and dried first and second sleeves 2 and 3 are assembled in the desired orientation to prevent friction between the sleeves and to prevent any impact on fiber optic screening. Finally, the drawing taper 6 of the first sleeve 2 rests on the drawing taper of the second sleeve 3, with the height of the first sleeve 2 ≤ that of the second sleeve 3, facilitating installation of the vacuum seal.

[0054] S6: Drawing the mother rod to obtain the multi-core optical fiber 100.

[0055] In this embodiment, the mother rod is clamped to the drawing chuck, and the chuck jaws clamp the second extension tube 5. A corresponding vacuum sealing component is installed above the second extension tube 5. The mother rod is in a negative pressure state in the vacuum tube, and the multi-core optical fiber 100 is drawn at high temperature.

[0056] It is understandable that in order to identify the orientation of the fiber cores during multi-core fusion splicing, in addition to adding identification holes in the cladding, the method of non-rotationally symmetrically distributing the cores in the cladding can also be used. However, the different orientations of the core holes 21 in the non-rotationally symmetrical distribution require high processing precision for the multi-hole sleeve and are more difficult to process. In addition, if the first sleeve 2 and the second sleeve 3 with different refractive indices are separately melt-molded, the processing steps are more complicated and the preparation cycle is long. By assembling two sleeves, the wire drawing melt-molding can be achieved in an integrated manner, reducing the processing steps, shortening the preform preparation cycle and processing difficulty, and reducing manufacturing costs. Alternatively, by assembling two sleeves, under the premise that the cross-section of the core rod 1 remains unchanged, the cut-off wavelength migration position of the drawn optical fiber cable can be controlled and the bending performance can be improved by adjusting the refractive index of the first sleeve 2 and the second sleeve 3.

[0057] By ensuring that the molar doping concentration of fluorine in the second sleeve 3 is lower than that in the first sleeve 2, the refractive index of the second sleeve 3 is higher than that of the first sleeve 2. During drawing, the material near the second sleeve 3 is harder and can bear more tensile stress, which is beneficial for forming compressive stress in the core layer of the core rod 1, reducing the amplitude of stress fluctuations in the core layer, thereby further reducing attenuation. Furthermore, by adjusting the refractive indices of the first sleeve 2 and the second sleeve 3, the position of the optical cable cutoff wavelength shift of the multi-core optical fiber 100 can be controlled and the bending performance of the optical fiber can be improved. Furthermore, this method provides an eccentric hole 31 in the second sleeve 3, eliminating the need for an identification hole. This facilitates identification of the fiber core orientation during fiber fusion splicing while adopting a double-sleeve assembly method, reducing the number of steps and difficulty in the mother rod processing and molding, and lowering manufacturing costs.

[0058] The present application also provides a multi-core optical fiber 100, which is prepared using the above-described method for preparing the multi-core optical fiber 100. The multi-core optical fiber 100 includes a plurality of core rods 1, a first sleeve 2, and a second sleeve 3. The plurality of core rods 1 are connected to the first sleeve 2. The second sleeve 3 has an eccentric hole 31, and the first sleeve 2 is assembled in the eccentric hole 31. The first sleeve 2 and the second sleeve 3 are connected.

[0059] In this embodiment, the core rod 1 includes a core layer and a ring-core deep depression layer. The core layer of the core rod 1 is a silica glass layer doped with one or more of germanium, fluorine, and alkali metal elements. The first sleeve 2 is provided with a core hole 21 to allow the core rod 1 to be inserted into the core hole 21 to achieve assembly between the core rod 1 and the first sleeve 2. The diameter of the core hole 21 ranges from (D2+0.6) mm to (D2+1.0) mm, where D2 is the outer diameter of the core rod 1. The diameter of the eccentric hole 31 ranges from (D1+1.0) mm to (D1+2.0) mm, where D1 is the outer diameter of the first sleeve 2. The multi-core optical fiber 100 also includes a first extension tube 4 and a second extension tube 5. The first extension tube 4 is connected to the first sleeve 2, and the second extension tube 5 is connected to the second sleeve 3. The multi-core optical fiber 100 also includes a drawing cone 6 to facilitate subsequent drawing and forming.

[0060] It can be understood that the multi-core optical fiber 100 prepared by the above preparation method can reduce the inter-core crosstalk and attenuation at 1550 nm, thereby improving the performance of the multi-core optical fiber 100 and making its use effect better.

[0061] In one embodiment, the multi-core optical fiber 100 prepared by the above preparation method has an inter-core crosstalk of ≤-65 dB / km at 1550 nm.

[0062] In one embodiment, the mode field diameter of the multi-core optical fiber 100 prepared by the above preparation method at 1550 nm is 10.5±0.5 μm.

[0063] In one embodiment, the attenuation coefficient of the multi-core optical fiber 100 manufactured by the above manufacturing method at 1550 nm is ≤0.170 dB / km.

[0064] In one embodiment, the optical cable cutoff wavelength of the multi-core optical fiber 100 prepared by the above preparation method is ≤1500 nm.

[0065] In one embodiment, the multi-core optical fiber 100 prepared by the above preparation method has a single-core fusion loss value of ≤0.2 dB at 1550 nm.

[0066] In one embodiment, the multi-core optical fiber 100 prepared by the above preparation method has a single-core macrobending loss of ≤0.005 dB at 1550 nm after 20 turns with a bending radius of 10 mm.

[0067] It is understood that the inter-core crosstalk of the multi-core optical fiber 100 is closely related to the core spacing, the overall refractive index difference between the core and cladding, and the depth and width of the core-ring depressed layer. To achieve low inter-core crosstalk in the multi-core optical fiber 100, a deeper and wider depressed layer is generally provided near the core layer, while the spacing between adjacent cores is maintained at ≥40 microns. However, the larger the inter-core spacing, the smaller the distance between the core layer and the outer cladding boundary point, which can easily cause light to escape from the cladding and cause a significant increase in 1550nm attenuation. Therefore, providing a low-refractive-index inner cladding composed of a first fluorine-doped sleeve 2, while ensuring low inter-core crosstalk, further reducing the inter-core spacing is beneficial to reducing 1550nm attenuation.

[0068] Several possible embodiments are provided below: Example 1: The processed core layer radius is 5.5μm, the core layer refractive index is 0.15%, the distance between adjacent cores is 38.0μm, the deep depression layer refractive index is -0.52%, the deep depression layer width is 6.1μm, the first sleeve 2 forms the inner cladding, the second sleeve 3 forms the outer cladding, the inner cladding refractive index is -0.24%, the inner cladding outer diameter is 94μm, the outer cladding refractive index is -0.10%, and the outer cladding outer diameter is 125μm. The performance parameters of the multi-core optical fiber 100 manufactured by the above parameters are: mode field diameter at 1550nm is 10.4μm, optical cable cut-off wavelength is 1430nm, attenuation coefficient at 1550nm is 0.167dB / KM, inter-core crosstalk at 1550nm is -65dB / km, single-core macrobending loss at 1550nm with 20 turns of 10mm bending radius is 0.003dB, and single-core fusion loss at 1550nm is 0.11dB.

[0069] Example 2: The fabricated core radius is 5.5 μm, the core refractive index is 0.15%, the distance between adjacent cores is 40.0 μm, the refractive index of the deep depressed layer is -0.52%, the width of the deep depressed layer is 6.1 μm, the refractive index of the inner cladding is -0.24%, the outer diameter of the inner cladding is 94 μm, and the refractive index of the outer cladding is -0.10%, with an outer diameter of 125 μm. The performance parameters of the multi-core optical fiber 100 fabricated using these parameters are: a mode field diameter of 10.5 μm at 1550 nm, a cable cutoff wavelength of 1432 nm, an attenuation coefficient of 0.168 dB / km at 1550 nm, an inter-core crosstalk of -69 dB / km at 1550 nm, a single-core macrobending loss of 0.005 dB at 1550 nm with 20 turns at a 10 mm bending radius, and a single-core fusion loss of 0.15 dB at 1550 nm.

[0070] Example 3: The fabricated core radius is 5.5μm, the core refractive index is 0.15%, the distance between adjacent cores is 38.0μm, the deep depressed layer refractive index is -0.52%, the deep depressed layer width is 6.1μm, the inner cladding refractive index is -0.28%, the inner cladding outer diameter is 94μm, and the outer cladding refractive index is -0.10%, with an outer cladding outer diameter of 125μm. The performance parameters of the multi-core optical fiber 100 fabricated using these parameters are: a mode field diameter of 10.3μm at 1550nm, a cable cutoff wavelength of 1480nm, an attenuation coefficient of 0.167dB / km at 1550nm, an inter-core crosstalk of -73dB / km at 1550nm, a single-core macrobending loss of 0.001dB at 1550nm with 20 turns at a 10mm bending radius, and a single-core fusion splicing loss of 0.12dB at 1550nm.

[0071] The above are feasible embodiments of the present invention, and the following are comparative examples: Comparative Example 1: The fabricated core radius is 5.5μm, the core refractive index is 0.15%, the distance between adjacent cores is 42.6μm, the deep depressed layer refractive index is -0.52%, the deep depressed layer width is 6.2μm, the inner cladding refractive index is -0.24%, the inner cladding outer diameter is 94μm, and the outer cladding refractive index is -0.10%, with an outer cladding outer diameter of 125μm. The performance parameters of the multi-core optical fiber 100 fabricated using these parameters are: a mode field diameter of 10.5μm at 1550nm, a cable cutoff wavelength of 1426nm, an attenuation coefficient of 0.171dB / km at 1550nm, an inter-core crosstalk of -72dB / km at 1550nm, a single-core macrobending loss of 0.003dB at 1550nm with 20 turns at a 10mm bending radius, and a single-core fusion loss of 0.16dB at 1550nm.

[0072] Comparative Example 2: The fabricated core radius is 5.5 μm, the core refractive index is 0.15%, the distance between adjacent cores is 40.0 μm, the deep depressed layer refractive index is -0.52%, the deep depressed layer width is 6.2 μm, the inner cladding refractive index is -0.20%, the inner cladding outer diameter is 94 μm, and the outer cladding refractive index is -0.15%, with an outer cladding outer diameter of 125 μm. The performance parameters of the multi-core optical fiber 100 fabricated using these parameters are: a mode field diameter of 10.5 μm at 1550 nm, a cable cutoff wavelength of 1435 nm, an attenuation coefficient of 0.171 dB / km at 1550 nm, an inter-core crosstalk of -68 dB / km at 1550 nm, a single-core macrobending loss of 0.004 dB at 1550 nm with 20 turns at a 10 mm bending radius, and a single-core fusion splicing loss of 0.16 dB at 1550 nm.

[0073] Comparative Example 3: The fabricated core radius is 5.6μm, the core refractive index is 0.15%, the distance between adjacent cores is 40.0μm, the refractive index of the deep depressed layer is -0.52%, the deep depressed layer width is 6.1μm, only one sleeve is provided, with a refractive index of -0.15%, and the outer cladding outer diameter is 125μm. The performance parameters of the multi-core optical fiber 100 fabricated using these parameters are: mode field diameter of 10.6μm at 1550nm, cable cutoff wavelength of 1420nm, attenuation coefficient of 0.173dB / km at 1550nm, inter-core crosstalk of -67dB / km at 1550nm, single-core macrobending loss of 0.005dB at 1550nm with 20 turns at a 10mm bending radius, and single-core fusion loss of 0.18dB at 1550nm.

[0074] The specific embodiments of the present application have been described above with reference to the accompanying drawings. However, those skilled in the art will appreciate that various modifications and substitutions may be made to the specific embodiments of the present application without departing from the spirit and scope of the present application. Such modifications and substitutions are intended to fall within the scope of the present application.

Claims

1. A method for preparing a multi-core optical fiber, characterized in that: The preparation method of the multi-core optical fiber comprises: providing a plurality of mandrels; Providing a first sleeve, wherein the first sleeve is provided with a plurality of core holes corresponding to the core rods; Assembling the plurality of core rods into the corresponding core holes respectively; providing a second sleeve, and machining an eccentric hole on the second sleeve; Assembling the first sleeve into the eccentric hole to form a female rod; The mother rod is drawn to obtain a multi-core optical fiber.

2. The method for preparing a multi-core optical fiber according to claim 1, wherein: The molar doping concentration of fluorine element in the second sleeve is less than the molar doping concentration of fluorine element in the first sleeve.

3. The method for preparing a multi-core optical fiber according to claim 1, wherein: The molar doping concentration of the fluorine element in the second sleeve is in the range of 0% to 0.05%, and the refractive index difference is in the range of -0.10% to 0%; and / or The molar doping concentration of the fluorine element in the first sleeve is in the range of 1.0% to 1.5%, and the refractive index difference is in the range of -0.30% to -0.20%.

4. The method for preparing a multi-core optical fiber according to claim 1, wherein: The distance between the center of the eccentric hole and the center of the second sleeve is 5-10 μm.

5. The method for preparing a multi-core optical fiber according to claim 1, wherein: The diameter range of the eccentric hole is (D1+1.0) mm to (D1+2.0) mm, where D1 is the outer diameter of the first sleeve.

6. The method for preparing a multi-core optical fiber according to claim 1, wherein: The method for preparing the multi-core optical fiber further provides a first extension tube and a second extension tube; Before the step of respectively assembling the plurality of core rods into the corresponding core holes, the method further includes the steps of: connecting the first extension tube to the first sleeve; Before the step of assembling the first sleeve in the eccentric hole to form the mother rod, the method further includes the step of connecting the second extension tube to the second sleeve.

7. The method for preparing a multi-core optical fiber according to claim 1, wherein: The diameter range of the core hole is (D2+0.6) mm to (D2+1.0) mm, where D2 is the outer diameter of the core rod.

8. A multi-core optical fiber prepared using the method for preparing a multi-core optical fiber according to any one of claims 1 to 7, characterized in that: The multi-core optical fiber comprises: multiple mandrels; a first sleeve, wherein the plurality of mandrels are connected to the first sleeve; The second sleeve is provided with an eccentric hole, the first sleeve is assembled in the eccentric hole, and the first sleeve is connected to the second sleeve.

9. The multi-core optical fiber according to claim 8, wherein The inter-core crosstalk of the multi-core optical fiber at 1550nm is ≤-65dB / km; and / or The mode field diameter of the multi-core optical fiber at 1550 nm is 10.5±0.5 μm; and / or The attenuation coefficient of the multi-core optical fiber at 1550 nm is ≤0.170 dB / KM.

10. The multi-core optical fiber according to claim 8, wherein The optical cable cut-off wavelength of the multi-core optical fiber is ≤1500nm; and / or The single-core fusion loss value of the multi-core optical fiber at 1550nm is ≤0.2dB; and / or The 1550nm single-core macrobending loss of the multi-core optical fiber with a bending radius of 10mm and 20 turns is ≤0.005dB.

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