Multi-core polymer optical fiber preforming mold, generating equipment and manufacturing method

Abstract

The embodiment of the invention relates to the technical field of polymer optical fibers, in particular to a pre-forming mold, production equipment and a manufacturing method of a multi-core polymer optical fiber. A fiber core extrusion part of the pre-forming mold comprises an injection tube assembly and a sleeve assembly, the second end of each injection tube in the injection tube assembly extends into an inner cavity of a first barrel of a cladding extrusion part, so that the inner wall of the first barrel is matched with the outer wall of each injection tube to define a cladding forming cavity, and the cladding forming cavity is matched with the sleeve assembly. The sleeve assembly is provided with a containing cavity used for containing melt of fiber core materials, and the containing cavity is communicated with the injection pipes. In the process of manufacturing the optical fiber prefabricated part of the multi-core polymer optical fiber, the first feeding port is used for inputting a melt of a cladding material into the cladding forming cavity, so that the melt of the cladding material is formed in the cladding forming cavity, and a prefabricated cladding structure is obtained; and each injection pipe is used for injecting the melt of the fiber core material in the accommodating cavity into each vacant fiber core channel in the prefabricated cladding structure to obtain an optical fiber prefabricated part.

Description

Technical Field

[0001] This application relates to the field of multi-core polymer optical fiber technology, and in particular to a preform mold, production equipment and manufacturing method for multi-core polymer optical fiber. Background Technology

[0002] Polymer optical fiber (POF) refers to optical fibers with a core of high-refractive-index polymer material and a cladding of low-refractive-index polymer material. With the rapid development of science and technology, traditional single-core polymer optical fibers are gradually showing bottlenecks in transmission capacity, flexibility, integration, and cost control.

[0003] To overcome the shortcomings of single-core polymer optical fibers, multi-core polymer optical fibers (MC-POF) have gradually emerged based on single-core polymer optical fibers. MC-POF combines the advantages of "multi-core structure" and "polymer substrate", and has characteristics such as high bandwidth and bending resistance.

[0004] Existing methods for manufacturing MC-POF typically involve first preparing multiple single-core polymer fiber preforms, stacking these preforms, and then stretching them to obtain a multi-core polymer fiber. This method is relatively cumbersome and does not improve the production efficiency of MC-POF. Summary of the Invention

[0005] To improve the production efficiency of multi-core polymer optical fibers, this application provides a pre-forming mold, production equipment, and manufacturing method for multi-core polymer optical fibers.

[0006] To address the aforementioned technical problems, the embodiments of this application provide the following technical solutions: In a first aspect of this application, a preforming mold for a multi-core polymer optical fiber is provided. The preforming mold includes a cladding extrusion section and a core extrusion section. The cladding extrusion section includes a first cylindrical body with at least one first inlet port on its wall. The core extrusion section is connected to the cladding extrusion section. The core extrusion section includes a sleeve assembly, a connecting seat, and an injection tube assembly connected in sequence, with the sleeve assembly and the injection tube assembly respectively disposed on opposite sides of the connecting seat. The injection tube assembly includes a plurality of injection tubes arranged in an array. The first end of each injection tube is connected to the connecting seat, and the second end of each injection tube extends outwards. The first cylindrical body has an inner wall that mates with the outer wall of each injection tube to define a cladding forming cavity. The sleeve assembly has a receiving cavity that communicates with each injection tube and is used to receive the molten core material. The first inlet port is used to input the molten cladding material into the cladding forming cavity, where the molten cladding material is formed to obtain a pre-fabricated cladding structure. The pre-fabricated cladding structure includes multiple empty core channels. Each injection tube is used to inject the molten core material from the receiving cavity into each of the multiple empty core channels to obtain a multi-core polymer optical fiber preform.

[0007] In embodiments of this application, the fiber core extrusion section includes an injection tube assembly and a sleeve assembly. The second end of each injection tube in the injection tube assembly extends into the inner cavity of the first cylinder of the cladding extrusion section, thereby the inner wall of the first cylinder and the outer wall of each injection tube fit together to define a cladding forming cavity. The sleeve assembly has a receiving cavity for receiving the melt of the fiber core material, and this receiving cavity is connected to each injection tube. During the fabrication of the fiber preform of the multi-core polymer optical fiber, the first inlet is used to input the melt of the cladding material into the cladding forming cavity, so that the melt of the cladding material is formed in the cladding forming cavity to obtain a preformed cladding structure. The preformed cladding structure includes multiple empty fiber core channels. Each injection tube is used to inject the melt of the fiber core material in the receiving cavity into each of the multiple empty fiber core channels to obtain the fiber preform.

[0008] In some embodiments, the receiving cavity includes a first to Nth chambers spaced apart radially from the inside to the outside of the second cylinder; the sleeve assembly includes N second cylinders, one end of each of the N second cylinders is connected to the connecting seat, and the second cylinders are sequentially sleeved to define the first to Nth chambers; the injection tube assembly includes a plurality of first to Nth injection tube arrays arranged radially from the inside to the outside, the position of the Mth chamber among the first to Nth chambers is adapted to the position of the Mth injection tube array among the first to Nth injection tube arrays, and the Mth chamber communicates with each injection tube in the Mth injection tube array, the Mth chamber being used to input the melt of the core material into each injection tube in the Mth injection tube array; wherein, M [1, N].

[0009] In some embodiments, the first to Nth chambers include an intermediate chamber and at least one annular outer chamber distributed outside the intermediate chamber; the N second cylinders include the first to Nth second cylinders arranged sequentially from the inside to the outside, the cylinder wall of the first second cylinder forming the first chamber, and an annular outer chamber is defined between the cylinder walls of every two adjacent second cylinders in the first to Nth second cylinders.

[0010] In some embodiments, the sleeve assembly has a first to an Nth second inlet, which are respectively connected to corresponding chambers in the first to Nth chambers, and are respectively used to input melt of fiber core material into the corresponding chambers in the first to Nth chambers. The first to Nth second inlets are respectively connected to different feeding systems; wherein, the first second inlet is the end opening of the first second cylinder, and the second to Nth second inlets are respectively opened on the cylinder wall of the second to Nth cylinder.

[0011] In some embodiments, the preforming mold further includes a plurality of first inlets, which are symmetrically distributed on the wall of the first cylinder.

[0012] In some embodiments, the preforming mold includes: a coating extrusion section, wherein the fiber core extrusion section, the cladding extrusion section, and the coating extrusion section are connected in sequence; the coating extrusion section includes a third cylinder, the inner cavity of the third cylinder is connected to the cladding forming cavity, and the third cylinder has a third inlet, which is connected to the inner cavity of the third cylinder; when the optical fiber preform moves to the inner cavity of the third cylinder, the melt of the coating material input from the third inlet into the inner cavity of the third cylinder forms a preformed coating layer on the surface of the optical fiber preform.

[0013] In a second aspect of this application, a production apparatus for multi-core polymer optical fibers is also provided. The production apparatus includes a first extruder, a second extruder, and the preforming mold described in the first aspect. The first extruder and the second extruder are respectively connected to the preforming mold. The first extruder is used to melt solid cladding material to obtain a melt of cladding material, and inputs the melt of cladding material into the cladding forming cavity through a first feed port. The second extruder is used to melt solid core material to obtain a melt of core material, and inputs the melt of core material into the receiving cavity.

[0014] In a third aspect of this application, a method for manufacturing a multi-core polymer optical fiber is also provided, the method comprising: using the preforming mold described in the first aspect to manufacture an optical fiber preform of the multi-core polymer optical fiber; and drawing the optical fiber preform to obtain the multi-core polymer optical fiber.

[0015] In some embodiments, the method further includes: determining the number of cooling regions Q and the cooling index based on the number of fiber cores in the multi-core polymer optical fiber; determining the temperature of each of the Q cooling regions based on the number of cooling regions and the cooling index; and performing stepwise cooling of the multi-core polymer optical fiber based on the temperature of each cooling region during the fiber preform drawing process.

[0016] In some embodiments, the temperature of each cooling zone is calculated using the following formula:

[0017] in, The value represents the temperature of the nth cooling zone, where T1 is the temperature at the exit of the preformed mold, T0 is the target temperature of the multi-core polymer optical fiber after cooling, r is the cooling exponent, Q is the number of cooling zones, and n represents the nth zone among the Q cooling zones. [1, Q].

[0018] It should be understood that the description in the Summary of the Invention section is not intended to limit the key or essential features of this disclosure, nor is it intended to restrict the scope of this disclosure. Other features of this disclosure will become readily apparent from the following description. Attached Figure Description

[0019] To more clearly illustrate the technical solutions of the embodiments of the present invention, the accompanying drawings used in the embodiments of the present invention will be briefly described below. Obviously, the drawings described below are merely some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without any creative effort.

[0020] Figure 1 This is a schematic diagram of the end face structure of a multi-core polymer optical fiber provided in some embodiments of this application; Figure 2 This is a schematic diagram of the end face structure of a multi-core polymer optical fiber provided in some other embodiments of this application; Figure 3 This is a schematic diagram of the structure of a preform mold for multi-core polymer optical fiber provided in some embodiments of this application; Figure 4 This is a schematic diagram of a cross-section of a preform mold for multi-core polymer optical fiber provided in some embodiments of this application; Figure 5 These are schematic diagrams of the cladding extrusion section provided in some embodiments of this application; Figure 6 This is a schematic diagram of the fiber core extrusion section from one perspective, provided in some embodiments of this application; Figure 7 This is a schematic diagram of the core extrusion section provided in some embodiments of this application from another perspective; Figure 8 This is a schematic diagram of the coating extrusion section from another perspective, provided in some embodiments of this application; Figure 9 This is a schematic diagram of the structure of a multi-core polymer optical fiber production equipment provided in some embodiments of this application; Figure 10 These are schematic diagrams of the feeding system provided in some embodiments of this application; Figure 11 This is a schematic flowchart illustrating a method for fabricating multi-core polymer optical fibers according to some embodiments of this application. Detailed Implementation

[0021] The principles and spirit of this disclosure will be described below with reference to several exemplary embodiments illustrated in the accompanying drawings. It should be understood that these specific embodiments are described merely to enable those skilled in the art to better understand and implement this disclosure, and are not intended to limit the scope of this disclosure in any way. In the following description and claims, unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art.

[0022] As used herein, the term "comprising" and similar terms should be understood as open-ended inclusion, i.e., "including but not limited to". The term "based on" should be understood as "at least partially based on". The term "an embodiment" or "the embodiment" should be understood as "at least one embodiment". The terms "first", "second", etc., may refer to different or the same objects and are used only to distinguish the objects referred to, without implying a particular spatial order, temporal order, order of importance, etc., of the objects referred to.

[0023] For example, Figure 1 Schematic diagrams of the end faces of multi-core polymer optical fibers provided in some embodiments of this application are shown. For example... Figure 1 As shown, the multi-core polymer optical fiber 10 includes a core array 11 and a cladding 12; wherein, the core array 11 includes a plurality of cores 111 arranged in an array, and the individual cores 111 are spaced apart. The cladding material fills the gaps between adjacent cores 111 to form the cladding 12; that is, each core 111 in the core array 11 is embedded in the cladding 12 to form the multi-core polymer optical fiber 10. The core array 11 is arranged in a regular hexagonal pattern.

[0024] For example, Figure 2 Schematic diagrams of the end faces of multi-core polymer optical fibers provided in other embodiments of this application are shown. For example... Figure 2 As shown, each fiber 211 in the fiber core array 21 is embedded in the cladding 22. The fiber core array 21 is arranged in concentric circles.

[0025] In the embodiments of this application, the cores of the multi-core polymer optical fiber can be arranged in an axially symmetrical manner at the end face, for example, Figure 1 The regular hexagonal arrangement shown or Figure 2 The concentric circle arrangement shown is an example. Arranging the cores of a multi-core polymer fiber in an axially symmetrical manner at the end face ensures that the fiber maintains similar bending performance regardless of the direction of bending. Arranging the cores in a regular hexagonal or concentric circle configuration at the end face increases the area ratio of the cores within the fiber, making it easier to couple with a light source. During vibration, the fiber and light source are less likely to deviate, allowing the optical signal to couple normally into the fiber.

[0026] In some embodiments, the number of fiber cores in the fiber core array is typically 100 to 1000. When the number of fiber cores is 100 to 300, the outer diameter of the multi-core polymer fiber is 0.25 mm to 1.0 mm, and the diameter of each fiber core is 14 μm to 90 μm. When the number of fiber cores is 300 to 1000, the outer diameter of the multi-core polymer fiber is 0.5 mm to 1.0 mm, and the diameter of each fiber core is 15 μm to 57 μm. In the embodiments of this application, setting the outer diameter of the multi-core polymer fiber to 0.25 μm to 1.0 μm is beneficial to reducing the minimum bending radius of the multi-core polymer fiber; at this time, the minimum bending radius of the multi-core polymer fiber is 1 mm to 3 mm; wherein, the minimum bending radius refers to the minimum bending arc radius value that the multi-core polymer fiber can withstand without generating excessive transmission loss and without damaging its own structural integrity.

[0027] In the embodiments of this application, by setting multiple fiber cores in the multi-core polymer fiber, the area ratio of the fiber core region in the end face of the multi-core polymer fiber can be increased, which is beneficial to improving the transmission optical channel of the multi-core polymer and facilitating the docking and coupling of the multi-core polymer fiber with the light source.

[0028] In some embodiments, the relative refractive index difference Δ between the core material and the cladding material satisfies: 0.0208 < Δ < 0.0576, ensuring that the numerical aperture of each core is maintained between 0.3 and 0.5. The relative refractive index difference Δ is calculated using the following formula:

[0029] Where n1 is the refractive index of the core material and n2 is the refractive index of the cladding material.

[0030] For example, in some embodiments of this application, the core material may be at least one selected from polymethyl methacrylate, polystyrene, polycarbonate, polybutyl methacrylate, and cyclic olefin copolymers. The cladding material may be a fluoropolymer.

[0031] Multi-core polymer optical fibers are often used in applications with small bending radii, where they not only need to withstand the stress caused by bending over long periods but are also susceptible to the effects of the external environment. For example... Figure 2 As shown, in some embodiments, to reduce stress caused by bending and the influence of the external environment, the multicore polymer optical fiber further includes a coating layer 23; the coating layer 23 is used to wrap around the cladding layer 22. The coating layer 23 is used to increase the toughness of the multicore polymer optical fiber and improve its mechanical strength. The material of the coating layer 23 includes at least one selected from acrylic resin, polyimide, and fluoropolymers.

[0032] like Figure 2 As shown, in some other embodiments, the multicore polymer optical fiber 20 further includes a sheath 24 disposed outside the coating layer 23, the material of the sheath 24 including at least one of polyurethane (PUR), thermoplastic elastomer (TPE), modified polyester (PBT), polyethylene (PE) and polyvinyl chloride (PVC).

[0033] In practical applications, multi-core polymer optical fibers are inevitably subjected to various bending stresses, causing the transmission modes in the multi-core polymer optical fibers to transform into radiation modes and leak out, resulting in optical power loss.

[0034] The bending loss α of an optical fiber is related to its refractive index distribution parameters, such as the relative refractive index difference, core refractive index, and core radius. For example, increasing the relative refractive index difference can effectively reduce the bending loss. Under the same bending conditions, the lower the bending sensitivity of the optical fiber, the smaller the bending loss α; therefore, reducing the bending sensitivity can also reduce the bending loss. The bending sensitivity of an optical fiber is often evaluated using the dimensionless constant MAC, which is calculated using the following formula:

[0035] Where MFD is the mode field diameter. This is the cutoff wavelength.

[0036] From the above formula for calculating MAC, it can be seen that the smaller the MFD, The larger the MFD (Mean Difference), the lower the bending sensitivity and the smaller the bending loss of the optical fiber. Therefore, this can be addressed by reducing the MFD or increasing its size. Methods to reduce the MAC of optical fibers include reducing the core diameter of multi-core polymer fibers.

[0037] Therefore, increasing the relative refractive index difference between the core material and the cladding material, as well as reducing the diameter of each core, are beneficial to reducing the minimum bending radius of multi-core polymer optical fibers.

[0038] To reduce the minimum bending radius of multi-core polymer optical fiber, embodiments of this application reduce the diameter of each core of the multi-core polymer optical fiber to below 100 μm; and set the range of the relative refractive index difference between the core material and the cladding material to 0.0208 < Δ < 0.0576.

[0039] Conventional step-index polymer optical fibers typically have a core diameter of 980 μm and an outer diameter of 1000 μm. Therefore, even though conventional step-index polymer optical fibers have good flexibility, their minimum bending radius is generally only 25 times the outer diameter, or 25 mm. However, the embodiments of this application can reduce the minimum bending radius of multi-core polymer optical fibers to 1 mm to 3 mm.

[0040] In the embodiments of this application, the diameter of each fiber core can be reduced to below 100 μm, which is about an order of magnitude smaller than the core diameter of a conventional step-index polymer fiber (980 μm). This reduces the number of optical modes that can couple into the multi-core polymer fiber, thereby reducing the mode dispersion of the multi-core polymer fiber and increasing the fiber bandwidth; wherein, the fiber bandwidth can be increased to 3 GHz * 50 m. Fiber bandwidth refers to the maximum range of signal frequencies that can be effectively transmitted through each fiber core.

[0041] For example, Figure 3This application presents some embodiments of a preforming mold for multi-core polymer optical fibers, which is used to fabricate fiber preforms for multi-core polymer optical fibers, such as... Figure 3 As shown, the preform mold 100 includes: a core extrusion section 200 and a cladding extrusion section 300 connected to the core extrusion section 200; the core extrusion section 200 and the cladding extrusion section 300 are arranged sequentially along the extrusion direction of the optical fiber preform.

[0042] For example, Figure 4 Schematic diagrams of the cladding extrusion section 300 provided in some embodiments of this application are shown, such as... Figure 4 As shown, the cladding extrusion section 300 includes a first cylinder 310, the walls of which enclose an inner cavity 320. The first cylinder 310 has at least one first inlet 330, and each of the at least one first inlet 330 communicates with the inner cavity 320 of the first cylinder 310. Each first inlet 330 is located on the cylinder wall of the first cylinder 310. Each first inlet 330 is used to feed molten cladding material into the inner cavity 320 of the first cylinder 310.

[0043] like Figure 4 As shown, in some embodiments, the cladding extrusion section 300 further includes at least one first input pipe 340. The number of first input pipes 340 is the same as the number of first feed ports 330. Each of the at least one first input pipe 340 is disposed on the outer wall of the first barrel 310. Each first input pipe 340 communicates with the inner cavity of the first barrel 310 through a first feed port 330. Each first input pipe 340 inputs the molten cladding material into the inner cavity of the first barrel 310 through a corresponding first feed port 330.

[0044] For example, Figure 5 A cross-sectional structural schematic diagram of a multi-core polymer optical fiber preform mold provided in some embodiments of this application is shown; Figure 6 and Figure 7 Schematic diagrams of the fiber core extrusion section from different perspectives are shown for some embodiments of this application. For example... Figure 5 , Figure 6 and Figure 7 As shown, the fiber core extrusion section 200 includes a sleeve assembly 210 and an injection tube assembly 220, and the sleeve assembly 210 and the injection tube assembly 220 are connected by a connecting seat 230.

[0045] like Figure 5 and Figure 6As shown, the injection tube assembly 220 includes a plurality of injection tubes 221 arranged in an array. The arrangement of the injection tubes 221 in the injection tube assembly 220 is adapted to the arrangement of the cores of the produced multi-core polymer optical fiber. The arrangement of the injection tubes 221 in the injection tube assembly 220 can be axially symmetric, such as a regular hexagonal arrangement or a concentric circle arrangement. The number of injection tubes 221 in the injection tube assembly 220 is the same as the number of cores of the multi-core polymer optical fiber. The number of injection tubes 221 in the injection tube assembly 220 can be, for example, 100 to 1000.

[0046] like Figure 5 , Figure 6 and Figure 7 As shown, the first end of each of the plurality of injection tubes 221 is connected to the connecting seat 230, and the second end of each injection tube 221 extends into the inner cavity 320 of the first cylinder 310. The inner wall of the first cylinder 310 mates with the outer wall of each injection tube 221 to define a cladding forming cavity 350. The sleeve assembly 210 has a receiving cavity 2100, which communicates with each injection tube 221 and is used to receive the melt of the fiber core material.

[0047] In the process of fabricating the fiber preform of multi-core polymer optical fiber, the first inlet 330 is used to input the molten cladding material into the cladding forming cavity 350. The molten cladding material is formed in the cladding forming cavity 350 to obtain the preformed cladding structure. The preformed cladding structure includes multiple empty fiber core channels. Each injection tube 221 is used to inject the molten fiber core material in the receiving cavity 2100 into each of the multiple empty fiber core channels to obtain the fiber preform of multi-core polymer optical fiber.

[0048] Specifically, in the embodiments of this application, during the fabrication of the fiber preform of a multi-core polymer optical fiber, when the molten cladding material enters the cladding forming cavity 350 through multiple first inlets 330, it first fills the gaps between the injection tubes 221. Because the injection tubes 221 are densely arranged, the resistance encountered by the molten cladding material when it enters the cladding forming cavity 350 is too great, causing the molten cladding material to not fill the gaps between the injection tubes 221 evenly and fully. This results in air bubbles appearing inside the fiber preform, affecting the optical fiber's optical conductivity. This embodiment of the application, by providing multiple first inlets 330, ensures that the molten cladding material can promptly fill the gaps between the injection tubes 221, reducing the occurrence of air bubbles inside the fiber preform. For example, the number of first inlets 330 can be multiple, such as 4, 6, or 8. The multiple first inlets 330 are symmetrically distributed on the wall of the first cylinder 310.

[0049] In some embodiments, the receiving cavity 2100 includes a first to Nth chambers arranged radially from the inside to the outside along the second cylinder; the sleeve assembly 210 includes N second cylinders, one end of each of the N second cylinders is connected to a connecting seat 230, and the second cylinders are sequentially sleeved to define the first to Nth chambers; the injection tube assembly 220 includes a plurality of first to Nth injection tube arrays arranged radially from the inside to the outside, the position of the Mth chamber among the first to Nth chambers is adapted to the position of the Mth injection tube array among the first to Nth injection tube arrays, and the Mth chamber communicates with each injection tube in the Mth injection tube array, the Mth chamber being used to input the melt of the core material into each injection tube in the Mth injection tube array; wherein, M [1, N].

[0050] like Figure 7 As shown, N second cylinders divide the connecting seat 230 into regions 1 to N, which are distributed sequentially from the inside to the outside. The first injection tube array is connected to the first region of the connecting seat 230; the second injection tube array is connected to the second region of the connecting seat 230; ...; the Nth injection tube array is connected to the Nth region of the connecting seat 230.

[0051] For example, please see Figure 5 The receiving cavity 2100 includes a first chamber 2110, a second chamber 2120, and a third chamber 2130, which are arranged radially from the inside to the outside along the second cylinder. The sleeve assembly 210 includes three second cylinders, namely, a second cylinder 211, a second cylinder 212, and a second cylinder 213. One end of each of the three second cylinders is connected to a connecting seat 230, and the two second cylinders are sequentially sleeved to define the first to third chambers. Figure 7 As shown, the three second cylinders divide the connecting seat 230 into three regions, which are distributed from the inside to the outside in a radial direction. The first injection tube array is connected to the first region a of the connecting seat 230; the second injection tube array is connected to the second region b of the connecting seat 230; and the third injection tube array is connected to the third region c of the connecting seat 230.

[0052] like Figure 5 As shown, the first to Nth chambers include an intermediate chamber 2110 and at least one annular outer chamber distributed outside the intermediate chamber, such as chamber 2120 and chamber 2130; the N second cylinders include the first to Nth second cylinders nested from the inside out, wherein the cylinder wall of the first second cylinder forms the first chamber (such as chamber 2110), and an annular outer chamber (such as chamber 2120 and chamber 2130) is defined between the cylinder walls of every two adjacent second cylinders in the first to Nth second cylinders.

[0053] In some embodiments, the sleeve assembly 210 has a first to Nth second inlet (such as a first second inlet 21100 and a second second inlet 21210), the first to Nth second inlets are respectively connected to the corresponding chambers in the first to Nth chambers, and the first to Nth second inlets are respectively used to input the melt of the fiber core material into the corresponding chambers in the first to Nth chambers; wherein, the first second inlet is the end opening of the first second cylinder, and the second to Nth second inlets are respectively opened on the cylinder wall of the second to Nth cylinder.

[0054] Please see Figure 4 In some embodiments, the cladding extrusion section 300 further includes a plurality of first input pipes 340, each of the plurality of first input pipes 340 being connected to the outer wall of the first cylinder 310, and one first input pipe 340 communicating with the cladding forming cavity 350 through a first feed port 330, and one first input pipe 340 being used to input the melt of the cladding material into the cladding forming cavity 350 through a first feed port 330.

[0055] Please see Figure 6 and Figure 7 In some embodiments, the core extrusion section 200 further includes N-1 second input pipes, such as a second input pipe 2121 connected to a second second cylinder and a second input pipe 2131 connected to a third second cylinder. Each of the N-1 second input pipes is connected to the outer wall of a second cylinder, and each second input pipe communicates with a chamber through a second feed port. Each second input pipe is used to input the melt of the core material into a chamber through a second feed port.

[0056] In some embodiments, such as Figure 3 and Figure 5 As shown, the preforming mold 100 includes a coating extrusion section 400, and the core extrusion section 200, the cladding extrusion section 300, and the coating extrusion section 400 are connected in sequence. Specifically, as... Figure 5 and Figure 8As shown, the coating extrusion section 400 includes a third cylinder 410, the inner cavity 420 of which is connected to the cladding forming cavity 350. The third cylinder has a third inlet 430, which is connected to the inner cavity 420 of the third cylinder 410. When the optical fiber preform moves to the inner cavity 420 of the third cylinder 410, the molten coating material input from the third inlet 430 into the inner cavity 420 forms a pre-formed coating layer on the surface of the optical fiber preform. Specifically, the coating extrusion section 400 also includes a third input pipe 440, which is connected to the inner cavity 420 of the third cylinder 410 through the third inlet 430, and the third input pipe 440 inputs the molten coating material into the inner cavity 420 of the third cylinder 410 through the third inlet 430.

[0057] This application also provides a production equipment for multi-core polymer optical fibers, such as... Figure 9 As shown, the production equipment 90 includes a first extruder 91, a second extruder 92, and a preforming mold provided in the above embodiments, such as a preforming mold 100; wherein, the first extruder 91 and the second extruder 92 are respectively connected to the preforming mold, the first extruder 91 is used to melt the solid cladding material to obtain the cladding material melt, and input the cladding material melt into the cladding forming cavity 350 through the first feed port 330; the second extruder 92 is used to melt the solid core material to obtain the core material melt, and input the core material melt into the receiving cavity 2100.

[0058] In the embodiments of this application, each injection tube is used to inject the molten core material from the receiving cavity into each empty core channel in the prefabricated cladding. Due to the small diameter of each injection tube, feeding difficulties are prone to occur. Furthermore, because the injection tubes are arranged periodically, such as in a regular hexagonal or concentric circle distribution, in actual feeding, if the same feeding system is used, the pressure and temperature experienced by the syringe tubes at different positions during feeding will vary, easily resulting in different feeding and discharge rates for injection tubes at different positions. Because the injection tubes are thin, the feeding speed needs to be strictly controlled. If the feeding speed is too slow, insufficient core material will result in air bubbles in the core, severely affecting the photoconductive effect; if the feeding speed is too fast, the injection tube will be subjected to excessive pressure, causing displacement or deformation, resulting in the molten core material sticking together when extruded from the injection tube, or the mold (injection tube) falling off or being damaged. Therefore, the fiber core extrusion section of this application embodiment is provided with multiple chambers for injecting the melt of fiber core material into the injection tube assembly. Thus, during the process of making optical fiber preforms using the preform mold, injection tubes of the same layer or adjacent m layers (generally, m≤4) are formed into a single injection tube array communicating with a chamber. A single feeding system is used to feed material to each corresponding chamber, thereby allowing the use of a layered co-extrusion process to inject the melt of fiber core material into each empty fiber core channel in the preformed cladding.

[0059] Specifically, such as Figure 10 As shown, in some embodiments, each feeding system includes a screw extruder 81 and a precision metering pump 82. Solid fiber core material entering from the feed port 83 of the screw extruder 81 is melted in the screw extruder 81 to obtain a melt of fiber core material. The precision metering pump 82 is used to input the melt of fiber core material into the corresponding chamber of the fiber core extrusion section according to a preset flow rate. Each feeding system also includes a temperature sensor and a pressure sensor 84, which are used to monitor the temperature and pressure of the feeding system, respectively. Specifically, the temperature sensor includes a first temperature sensor 85 and a second temperature sensor 86. The first temperature sensor 85 can be used to monitor the temperature of the melt of fiber core material in the screw extruder 81, and the second temperature sensor 86 can be used to monitor the temperature of the melt of fiber core material in the precision metering pump 82. Each feeding system may also include an exhaust device 87, which discharges water vapor and waste gas from the feeding system through an exhaust port 88 to improve the cleanliness of the melt of fiber core material.

[0060] This application also provides a method for fabricating a multi-core polymer optical fiber, the method comprising: Step 101: Use the preforming mold provided in the above embodiments to fabricate fiber preforms of multi-core polymer optical fibers.

[0061] In some embodiments, step 101 specifically includes: inputting molten cladding material into the cladding forming cavity through the first inlet of the preforming mold, causing the molten cladding material to form in the cladding forming cavity to obtain a pre-fabricated cladding structure, the pre-fabricated cladding structure including multiple empty core channels. Then, inputting molten core material into the receiving cavity, and injecting the molten core material from the receiving cavity into each of the multiple empty core channels through various injection tubes to obtain a fiber preform of a multi-core polymer optical fiber.

[0062] In some embodiments, the method further includes: when the optical fiber preform is running into the inner cavity of the third cylinder, inputting a molten coating material into the inner cavity of the third cylinder from the third inlet, so that the molten coating material forms a pre-formed coating on the surface of the optical fiber preform.

[0063] Step 102: The optical fiber preform is drawn to obtain a multi-core polymer optical fiber.

[0064] In some embodiments, after the optical fiber preform is extruded from the preforming mold, the optical fiber drawing machine begins to draw the optical fiber preform to obtain a multi-core polymer optical fiber; during the drawing process, the multi-core polymer optical fiber is cooled in stages until it is completely cooled and shaped to obtain a multi-core polymer optical fiber, for example... Figure 1 Multi-core polymer fiber 10 and Figure 2 The multi-core polymer optical fiber 20 is described above. The specific structure of the multi-core polymer optical fiber fabricated in this embodiment is described in the above embodiment.

[0065] In some embodiments, the method further includes: determining the number N of cooling regions and the cooling index r based on the number of fiber cores in the multi-core polymer optical fiber; and determining the temperature of the N cooling regions based on the number N of cooling regions and the cooling index r. In some embodiments, the more fiber cores there are, the larger the number N of cooling regions, and the larger the cooling index r.

[0066] Specifically, the number of fiber cores (unit: number), the number of cooling zones Q (unit: number), and the cooling index r are shown in Table 1: Table 1:

[0067] In some embodiments, the temperature of each cooling zone is calculated using the following formula:

[0068] in, This represents the temperature of the nth cooling zone, where T1 is the temperature at the exit of the preform mold, T0 is the target temperature of the multi-core polymer optical fiber after cooling (T0 is generally room temperature), r is the cooling exponent, Q is the number of cooling zones, and n represents the nth zone among the Q cooling zones, where n is a positive integer. [1, Q].

[0069] Because multi-core polymer optical fibers contain multiple cores that are axially symmetrically distributed, and cladding materials exist between adjacent core channels, the different thermal conductivity of the materials during the cooling and shaping process can cause significant temperature variations at different locations along the fiber's radial direction. For example, the coating material, the outer core, and the cladding material cool first, while the inner core material remains at a higher temperature. During the traction and coiling process, materials at different temperatures undergo varying degrees of thermal deformation, ultimately affecting the stability of the multi-core structure. This application employs a zoned cooling method, gradually decreasing the temperature of the multi-core polymer optical fiber. This ensures that the temperature of the materials at different locations along the fiber's radial direction is the same or similar when the fiber is in each cooling zone. Furthermore, this application uses an exponential zoned cooling method, resulting in slower cooling near the die exit and faster cooling further away. This prevents stress changes in the polymer material during cooling, which could lead to fiber brittleness and enhance the fiber's toughness and mechanical strength, enabling it to maintain a small bending radius for extended periods.

[0070] The production mold and production process of the multi-core polymer optical fiber provided in this application embodiment can industrially produce multi-core polymer optical fibers with stable structure and excellent mechanical properties. The multi-core polymer optical fiber produced in this application embodiment has the following advantages: (1) It can maintain stable operation under a small bending radius of 1mm~3mm for a long time; (2) The fiber bandwidth of each fiber core channel can reach 3GHz*50m; (3) The multiple fiber cores can increase the area ratio of the fiber core area to the fiber end face, making the fiber easier to couple and connect, and even if there is a slight deviation between the light source and the fiber end face during vibration, the optical signal can still be transmitted into the fiber; (4) The fiber cores are axially symmetrically distributed, so that the fiber can have similar bending performance no matter which direction it is bent.

[0071] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, and not to limit them; under the concept of the present invention, the technical features of the above embodiments or different embodiments can also be combined, the steps can be implemented in any order, and there are many other variations of different aspects of the present invention as described above, which are not provided in detail for the sake of brevity; although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some of the technical features; and these modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the scope of the technical solutions of the embodiments of the present invention.

Claims

1. A preforming mold for a multi-core polymer optical fiber, characterized in that, The preforming mold includes: The cladding extrusion section includes a first cylinder, the cylinder wall of which has at least one first inlet port. The fiber core extrusion section is connected to the cladding extrusion section. The fiber core extrusion section includes a sleeve assembly, a connecting seat, and an injection tube assembly connected in sequence, and the sleeve assembly and the injection tube assembly are respectively disposed on opposite sides of the connecting seat. The injection tube assembly includes multiple injection tubes arranged in an array. The first end of each injection tube is connected to the connecting seat, and the second end of each injection tube extends into the inner cavity of the first cylinder. The inner wall of the first cylinder cooperates with the outer wall of each injection tube to define a cladding forming cavity. The sleeve assembly has a receiving cavity that communicates with each injection tube and is used to receive the melt of the fiber core material. The first inlet is used to input the molten cladding material into the cladding forming cavity, and the molten cladding material is formed in the cladding forming cavity to obtain a pre-fabricated cladding structure. The pre-fabricated cladding structure includes multiple empty core channels. Each injection tube is used to inject the molten core material in the receiving cavity into each of the multiple empty core channels to obtain a fiber preform of a multi-core polymer optical fiber.

2. The preforming mold according to claim 1, characterized in that, The receiving cavity includes a first to Nth chambers that are spaced apart from the inside to the outside along the radial direction of the second cylinder. The sleeve assembly includes N second cylinders, one end of each of the N second cylinders is connected to the connecting seat, and the second cylinders are sequentially sleeved to define the first to Nth chambers. The injection tube assembly includes multiple injection tube arrays arranged sequentially from the inside to the outside. The position of the Mth chamber among the 1st to Nth chambers is adapted to the position of the Mth injection tube array among the 1st to Nth injection tube arrays, and the Mth chamber is connected to each injection tube in the Mth injection tube array. The Mth chamber is used to input the melt of the core material into each injection tube in the Mth injection tube array. Among them, M [1, N].

3. The preforming mold according to claim 2, characterized in that, The first to Nth chambers include an intermediate chamber and at least one annular outer chamber distributed outside the intermediate chamber; The N second cylinders include the first to the Nth second cylinders nested sequentially from the inside out. The cylinder wall of the first second cylinder forms the first chamber, and an annular outer chamber is defined between the cylinder walls of every two adjacent second cylinders from the first to the Nth second cylinders.

4. The preforming mold according to claim 3, characterized in that, The sleeve assembly has 1 to N second inlets, which are respectively connected to the corresponding chambers in the 1 to N chambers. The 1 to N second inlets are respectively used to input the melt of the fiber core material into the corresponding chambers in the 1 to N chambers. The 1 to N second inlets are respectively connected to different feeding systems. The first second inlet is the end opening of the first second cylinder, and the second to Nth second inlets are respectively opened on the cylinder wall of the second to Nth cylinder.

5. The preforming mold according to claim 4, characterized in that, The preforming mold also includes a plurality of first inlets, which are symmetrically distributed on the wall of the first cylinder.

6. The preforming mold according to any one of claims 1-5, characterized in that, The preforming mold includes: The coating extrusion section, the core extrusion section, the cladding extrusion section, and the coating extrusion section are connected in sequence; The coating extrusion section includes a third cylinder, the inner cavity of which is connected to the cladding forming cavity, and the third cylinder has a third inlet, which is connected to the inner cavity of the third cylinder. When the optical fiber preform moves into the inner cavity of the third cylinder, the molten coating material input from the third inlet into the inner cavity of the third cylinder forms a pre-formed coating layer on the surface of the optical fiber preform.

7. A production equipment for multi-core polymer optical fibers, characterized in that, The production equipment includes a first extruder, a second extruder, and a preforming mold as described in any one of claims 1-6; The first extruder and the second extruder are respectively connected to the preforming mold. The first extruder is used to melt the solid cladding material to obtain the cladding material melt, and input the cladding material melt into the cladding forming cavity through the first feed port. The second extruder is used to melt the solid core material to obtain a melt of the core material, and to input the melt of the core material into the receiving cavity.

8. A method for fabricating a multi-core polymer optical fiber, characterized in that, The method includes: An optical fiber preform for fabricating a multi-core polymer optical fiber using the preforming mold according to any one of claims 1-6; The optical fiber preform is drawn to obtain a multi-core polymer optical fiber.

9. The method according to claim 8, characterized in that, The method further includes: The number of cooling zones Q and the cooling index are determined based on the number of cores in a multi-core polymer optical fiber. The temperature of each cooling zone in the Q cooling zones is determined based on the number of cooling zones and the cooling index. During the fiber drawing process of the optical fiber preform, the multi-core polymer optical fiber is cooled in stages based on the temperature of each cooling zone.

10. The method according to claim 9, characterized in that, The temperature of each cooling zone is calculated using the following formula: in, The value represents the temperature of the nth cooling zone, where T1 is the temperature at the exit of the preformed mold, T0 is the target temperature of the multi-core polymer optical fiber after cooling, r is the cooling exponent, Q is the number of cooling zones, and n represents the nth zone among the Q cooling zones. [1, Q].

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