Method for manufacturing polymer optical fiber and polymer optical cable

Abstract

This application relates to the field of plastic optical fiber technology, and in particular to a method for fabricating polymer optical fibers and polymer optical cables. In the embodiments of this application, the cladding of the polymer optical fiber can be divided into multiple ring-shaped stacked structures arranged sequentially from the inside to the outside along the radial direction of the optical fiber. At least two adjacent stacked structures in the multiple ring-shaped stacked structures are stacked to form several cavities, with each cavity spaced apart. In the fabrication method of this polymer optical fiber, a layered co-extrusion process is used to extrude the prefabricated stacked structure corresponding to each layer of the multi-layered stacked structure layer by layer. At least two adjacent prefabricated stacked structures in the multi-layered prefabricated stacked structure are stacked to form several spaced prefabricated cavities. Therefore, an optical fiber preform with prefabricated cavities can be obtained through the layered co-extrusion process. After the optical fiber preform is drawn, the prefabricated cavities correspond to the cavities of the polymer optical fiber, thereby obtaining the polymer optical fiber.

Description

Technical Field

[0001] This application relates to the field of plastic optical fiber technology, and in particular to a method for preparing polymer optical fiber and polymer optical cable. Background Technology

[0002] Polymer optical fiber (POF) is a new type of optical fiber that uses a high-transmittance polymer as the light guiding medium, and its core diameter is generally less than one millimeter. Polymer optical fiber possesses excellent flexibility, vibration resistance, and electromagnetic interference resistance.

[0003] Traditional optical fibers play a vital role in optical communication, but they suffer from problems such as light loss and dispersion. To overcome these issues, ring cavity fibers have gradually been developed. Ring cavity fibers include photonic bandgap photonic crystal fibers (PBG-PCF) and Bragg fibers, whose cross-section consists of an array of extremely small air holes. These air holes are capillaries with diameters on the order of optical wavelength, extending parallel to each other within the fiber.

[0004] Currently, the production method for annular cavity optical fibers is mostly based on the preform drawing process. That is, microstructures are created by drilling holes in a silica optical fiber preform, and then the fibers are further drawn into filaments to make the fiber structure dimensions meet the requirements. However, the preform drawing process is currently only suitable for the industrial production of annular cavity silica optical fibers, and not for the industrial production of annular cavity polymer optical fibers. Summary of the Invention

[0005] This application provides a method for preparing annular cavity polymer optical fiber and optical cable, which enables the industrial production of annular cavity polymer optical fiber.

[0006] To address the aforementioned technical problems, the embodiments of this application provide the following technical solutions:

[0007] In a first aspect of this application, a method for fabricating a polymer optical fiber is provided. The polymer optical fiber includes a core layer and a cladding layer, wherein the cladding layer includes multiple annular stacked structures arranged sequentially from the inside to the outside along the radial direction of the optical fiber, and at least two adjacent stacked structures in the multiple stacked structures are stacked to form a plurality of spaced cavities. In this method, a layered co-extrusion process is used to extrude a prefabricated stacked structure corresponding to each stacked structure in the multiple stacked structures layer by layer, thereby obtaining an optical fiber preform with prefabricated cavities. The optical fiber preform is then drawn to make the prefabricated cavities correspond to the cavities of the polymer optical fiber, thereby obtaining the polymer optical fiber.

[0008] In the embodiments of this application, the cladding of the polymer optical fiber can be divided into a multi-layer annular stacked structure arranged sequentially from the inside to the outside along the radial direction of the optical fiber. At least two adjacent layers of the multi-layer annular stacked structure are stacked to form several cavities, with each cavity spaced apart. In the fabrication method of this polymer optical fiber, a layered co-extrusion process is used to extrude the prefabricated stacked structure corresponding to each layer of the multi-layer stacked structure layer by layer. At least two adjacent layers of the prefabricated stacked structure are stacked to form several spaced prefabricated cavities. Therefore, an optical fiber preform with prefabricated cavities can be obtained through the layered co-extrusion process. After drawing the optical fiber preform, a polymer optical fiber can be obtained; wherein, the prefabricated cavities of the optical fiber preform correspond to the cavities of the polymer optical fiber after the drawing process.

[0009] In some embodiments, the core layer is a hollow core layer, the hollow core layer is vacant, and the optical fiber preform also has a pre-formed hollow core layer; the step of drawing the optical fiber preform to make the pre-formed cavity correspond to the cavity of the polymer optical fiber to obtain the polymer optical fiber specifically includes: drawing the optical fiber preform to make the pre-formed cavity and the pre-formed hollow core layer correspond to the cavity and hollow core layer of the polymer optical fiber respectively to obtain the polymer optical fiber.

[0010] In some embodiments, the step of extruding the prefabricated stacked structure corresponding to each layer of the multi-layer stacked structure layer by layer using a layered co-extrusion process includes: extruding the prefabricated stacked structure corresponding to each layer of the multi-layer stacked structure layer by layer in the order from the inside to the outside using a layered co-extrusion process.

[0011] In some embodiments, the multilayer stacked structure includes an Nth stacked structure and an N+1th stacked structure, wherein N≥1 and N is a positive integer. The N+1th stacked structure includes an annular polymer layer and a plurality of support strips, the plurality of support strips being distributed on the side of the annular polymer layer near the Nth stacked structure, and the cavity being disposed between two adjacent support strips. The step of extruding the prefabricated stacked structure corresponding to each layer of the multilayer stacked structure in the order from the inside to the outside using a layered co-extrusion process includes: when the Nth layer polymer melt enters the... The Nth layer of prefabricated stack structure is formed after the Nth layer flow channel of the co-extrusion die; when the Nth layer prefabricated stack structure moves along the fiber exit direction to the feed area of ​​the N+1th layer polymer melt, under the action of the co-extrusion die, part of the N+1th layer polymer melt covers the Nth layer stack structure to form several support strips, and part of the N+1th layer polymer forms an N+1th layer annular polymer on the side of the support strip away from the Nth layer prefabricated stack structure; wherein, the feed area of ​​the N+1th layer polymer melt is located at the front end of the fiber exit direction relative to the feed area of ​​the Nth layer polymer melt.

[0012] In some embodiments, the method further includes: during the layered co-extrusion process, controlling the flow rate of each layer of polymer melt entering each flow channel of the layered co-extrusion die by a metering pump; wherein the flow rate of each layer of polymer melt is positively correlated with the cross-sectional area of ​​the corresponding annular stacked structure.

[0013] In some embodiments, the optical fiber preform further includes a coating layer disposed on the side of the cladding away from the hollow core layer; before the optical fiber preform is drawn, the method further includes: when the cladding runs along the fiber exit direction to the feed area of ​​the coating layer polymer melt, the coating layer polymer melt forms the coating layer on the surface of the cladding on the side away from the core layer; wherein the feed area of ​​the coating layer polymer melt is located at the front end of the fiber exit direction relative to the feed area of ​​the cladding.

[0014] In some embodiments, the method further includes: during the fiber drawing process of the optical fiber preform, introducing a first gas into the preform cavity and controlling the first gas pressure within a first preset pressure range; and / or, during the fiber drawing process of the optical fiber preform, introducing a second gas into the hollow core layer of the optical fiber preform and controlling the second gas pressure within a second preset pressure range.

[0015] In some embodiments, the method specifically includes: during the fiber drawing process of the optical fiber preform, introducing a first gas into the preform cavity, and adjusting the first gas pressure by adjusting the temperature of the first gas so that the first gas pressure is within a first preset gas pressure range; and / or, during the fiber drawing process of the optical fiber preform, introducing a second gas into the hollow core layer of the optical fiber preform, and adjusting the second gas pressure by adjusting the temperature of the second gas so that the second gas pressure is within a second preset gas pressure range.

[0016] In some embodiments, the method specifically includes: adjusting the temperature of a first gas by adjusting the temperature of a layered co-extrusion die, thereby controlling the first gas pressure within a first preset pressure range; and / or adjusting the temperature of a second gas by adjusting the temperature of a layered co-extrusion die, thereby controlling the second gas pressure within a second preset pressure range.

[0017] In a second aspect of this application, a method for preparing an optical cable is also provided, wherein a polymer optical fiber is prepared according to the method described in the first aspect; and a protective sleeve is provided on the outer surface of at least one of the polymer optical fibers to obtain an optical cable.

[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 These are schematic diagrams of the polymer optical fiber provided in some embodiments of this application;

[0021] Figure 2 These are schematic diagrams of the polymer optical fiber provided in some embodiments of this application;

[0022] Figure 3 These are schematic diagrams of the structure of polymer optical fibers provided in some embodiments of this application;

[0023] Figure 4 This is a schematic diagram showing the distribution of the stacked layers of polymer optical fiber provided in some embodiments of this application;

[0024] Figure 5This is a refractive index distribution of polymer optical fibers provided in some embodiments of this application;

[0025] Figure 6 This is a schematic diagram of the structure of a layered co-extrusion die provided in some embodiments of this application from one perspective;

[0026] Figure 7 This is a schematic diagram of the structure and layered co-extrusion principle of a layered co-extrusion die from another perspective, provided by some embodiments of this application;

[0027] Figure 8 This is a schematic diagram of the structure of a layered co-extrusion die provided in some embodiments of this application;

[0028] Figure 9 This is a schematic diagram of the structure of a polymer optical fiber production equipment provided in some embodiments of this application;

[0029] Figure 10 This is a flowchart of a method for fabricating polymer optical fibers provided in some embodiments of this application;

[0030] Figure 11 These are schematic diagrams illustrating the structure of a layered co-extrusion die and the principle of layered co-extrusion provided in some embodiments of this application;

[0031] Figure 12 This is a diagram showing the feeding sequence of each layer of polymer melt provided in some embodiments of this application. Detailed Implementation

[0032] To make the objectives, technical solutions, and advantages of this invention clearer, the invention will be further described in detail below with reference to the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are merely illustrative and not intended to limit the invention.

[0033] It should be noted that, unless otherwise specified, the various features in the embodiments of the present invention can be combined with each other, and all are within the protection scope of the present invention. Furthermore, although functional modules are divided in the device schematic diagram and a logical order is shown in the flowchart, in some cases, the steps shown or described may be performed in a different module division or in a different order than that shown in the device schematic diagram or the flowchart.

[0034] Unless otherwise defined, all technical and scientific terms used in this specification have the same meaning as commonly understood by one of ordinary skill in the art to which this invention pertains. The terminology used in this specification is for the purpose of describing particular embodiments only and is not intended to limit the invention. The term "and / or" as used in this specification includes any and all combinations of one or more of the associated listed items.

[0035] Polymer optical fiber (POF), also known as plastic optical fiber or high-polymer optical fiber, is made of high-molecular polymer materials (such as polymethyl methacrylate), and its core diameter is generally less than one millimeter. Using high-transmittance polymers as the light-guiding medium, plastic optical fiber possesses excellent flexibility, vibration resistance, and electromagnetic interference resistance.

[0036] Currently, the most widely used plastic optical fibers on the market are step-index plastic optical fibers (SI-POF), with low-loss operating wavelength windows of 520nm and 650nm. At a working wavelength of 650nm, the theoretical loss limit of SI-POF is approximately 100dB / km. However, in actual production, the loss of plastic optical fiber products used for communication reaches as high as 140dB / km to 200dB / km, and the loss is even greater in the near-infrared region. Therefore, plastic optical fibers with polymethyl methacrylate (PMMA) as the core material are mainly used in short-distance communication applications. Furthermore, SI-POF is a multimode fiber, and its nonlinear effects affect the transmission bandwidth. Subsequently, Japanese companies introduced deuterated plastic optical fibers, which greatly reduced the attenuation of SI-POF. However, deuterated plastic optical fibers have a narrower spectral bandwidth, limiting their applications, and the high cost of raw materials hinders market promotion.

[0037] To reduce the optical loss of plastic optical fibers and increase communication bandwidth, Japanese universities, research institutes, and companies have successively introduced perfluorinated and partially fluorinated plastic optical fibers, which exhibit a graded refractive index distribution (GI-POF). However, due to the high cost of raw materials and the complex and difficult manufacturing process, the production cost is too high, making it difficult to enter the market and achieve widespread application.

[0038] Photonic bandgap photonic crystal fiber (PBG-PCF), also known as microstructure fiber, has a complex refractive index distribution in its cross-section. It typically contains pores (also called cavities) arranged in various patterns. These pores are roughly on the same order of magnitude as the wavelength of light and extend throughout the entire length of the device, confining light propagation within the fiber core region of the refractive index defect area. PBG-PCF includes a structure with periodically varying refractive index, thus generating photonic bands. Photons with frequencies within the bandgap of these bands are prevented from propagating in the cladding structure. Disrupting the introduced periodic structure creates defects, forming a photonic bandgap with a specific frequency width, allowing light waves of a particular frequency to propagate within this defect region—essentially, the light wave is radially confined to the defect area. The light guiding mechanism of photonic bandgap photonic crystal fiber differs from the total internal reflection principle of traditional optical fibers; it guides light through the photonic bandgap.

[0039] Bragg fiber is a special type of optical fiber composed of multiple concentric rings of dielectric materials with a periodic radial refractive index. Relying on the Bragg reflection principle, it confines light to a defect state, i.e., the central hollow core region, for transmission. The core of Bragg fiber is typically hollow, but a high-refractive-index core can also be used. The cladding exhibits a periodic radial refractive index distribution, and it can be approximated as a one-dimensional photonic bandgap photonic crystal fiber. By using the Bragg reflection principle to confine light of specific frequencies to the hollow core region, absorption losses in the material are significantly reduced. Furthermore, since the Bragg reflection principle requires nλ = 2dsinθ, only specific modes of light can propagate in the core layer. Therefore, Bragg fiber can reduce nonlinear effects in the material and increase communication bandwidth.

[0040] The use of air as a low-refractive-index material in plastic optical fibers avoids the hassle of finding two materials with a significant difference in refractive index, good optical performance, and similar and compatible thermal, mechanical, and fabrication properties. The hollow core layer, consisting of an air layer or other low-refractive-index gas layer, avoids the inherent absorption losses of other materials while reducing nonlinear effects, thus lowering light attenuation and increasing transmission bandwidth. The introduction of the Bragg stack structure allows light to be radially confined within the hollow core layer, preventing leakage and reducing loss. Different dimensional designs of the Bragg stack structure can yield optical fibers with different operating wavelength windows, offering particular advantages in the visible to infrared light transmission field. This fiber cladding, with its periodically varying refractive index stack structure, according to photonic bandgap theory and the Bragg reflection principle, can confine light of specific frequencies and modes to the central refractive index defect layer, i.e., the hollow core layer, for propagation.

[0041] The polymer optical fiber of this application embodiment is also called a ring cavity polymer optical fiber. The polymer optical fiber includes a cladding structure with a periodic refractive index distribution. The cladding structure is formed by stacking multiple ring cavities and polymer rings to form a periodic refractive index distribution. The fiber core is a hollow core layer, formed by gas defects such as air. In the embodiments of this application, the introduction of a stacked structure with a periodic refractive index distribution into the polymer optical fiber can form a photonic bandgap polymer optical fiber or a Bragg polymer optical fiber. Compared with traditional plastic optical fibers, it has the advantages of low attenuation, high bandwidth, and wide transmission optical frequency, while possessing the characteristics of vibration resistance and electromagnetic interference resistance. It can play a greater role in short-distance communication in various local area networks (such as automobiles, large vehicles, military equipment, and residential office networks). Its application will greatly promote the process of realizing all-optical networks in communication systems.

[0042] The polymer optical fiber in this application embodiment is also called a ring cavity polymer optical fiber, specifically such as a bandgap photonic crystal fiber or a Bragg fiber. Exemplarily, Figure 1 A cross-sectional view of the annular cavity polymer optical fiber 100 is shown. (See figure.) Figure 1As shown, the annular cavity polymer fiber 100 includes a core layer 110 and a cladding layer 120 arranged sequentially from the inside to the outside along the radial direction of the annular cavity polymer fiber 100. The core layer 110 can be a solid core layer or a hollow core layer. This embodiment of the application uses a hollow core layer 110 as an example for illustration.

[0043] Specifically, the core layer 110 is designed as a hollow layer to enable light to propagate in a low-loss medium. This avoids the hassle of finding two materials with significantly different refractive indices but good optical properties, and similar and compatible thermal, mechanical, and fabrication properties, while also allowing the product to achieve high bandwidth, low attenuation, and low latency. The hollow layer employs a hollow structure. Typically, the hollow layer 110 can be filled with air as a low-refractive-index material. In other embodiments, the hollow layer can also be filled with other low-loss gases to minimize material absorption loss during light propagation in the optical fiber.

[0044] To ensure that light is radially confined within the hollow core layer, i.e., to reduce radial leakage, the cladding 120 comprises multiple cavities arranged sequentially from the inside to the outside along the radial direction of the annular cavity polymer fiber 100. Several cavities 121 within each cavity layer are arranged in a ring around the axis of the annular cavity polymer fiber 100. The cavities 121 can be filled with air as a low-refractive-index material, or they can be filled with other low-loss gases to minimize material absorption loss during light propagation in the fiber.

[0045] Optionally, in some embodiments, to increase the flexibility of the annular cavity polymer fiber 100, the annular cavity polymer fiber 100 further includes a coating layer 130, and the hollow core layer 110, cladding layer 120, and coating layer 130 are sequentially arranged from the inside to the outside along the radial direction of the annular cavity polymer fiber 100. Those skilled in the art can choose whether or not to provide a coating layer for the annular cavity polymer fiber according to actual needs. The coating layer is a high-toughness polymer used to increase the flexibility of the fiber.

[0046] Figure 2 and Figure 3 Cross-sectional views of annular cavity polymer optical fibers of other embodiments are shown as examples. Figure 2 and Figure 3 As shown, the cross-sectional shape of cavity 121 can be any suitable shape, such as a polygon or a circle. Several cavities 121 in each layer are arranged in any suitable shape, such as a polygon or a circle, around the axis of the annular cavity polymer optical fiber 100.

[0047] In some embodiments, the hollow core layer of the annular cavity polymer fiber has a hollow structure, and the cladding also contains a large number of cavities. If a traditional extrusion process is used, the stress of the material during extrusion drawing will affect the size of the cavities and disrupt the Bragg reflection condition. In addition, if a one-time feeding method is chosen, the gap between the axial hollow pillars in the die may be too small, resulting in the feed not being able to completely fill the extrusion die, leading to irregular air bubbles in the polymer fiber and significantly affecting the light guiding performance of the polymer fiber.

[0048] Currently, most of the more mature photonic bandgap photonic crystal fibers are made of silica fiber. Microstructures are fabricated by drilling holes in silica fiber preforms, which are then further drawn into filaments to meet the required fiber dimensions. At present, domestic and international production methods for photonic bandgap polymer fibers or Bragg polymer fibers based on preform drawing processes are only in the experimental stage and far from meeting the requirements for industrialization. Classical methods for fabricating photonic bandgap photonic crystal fibers or Bragg fibers involve stacking many pre-fabricated air tubes together, performing multi-layer stacking, and then drawing; or creating numerous micro-holes in a certain length of fiber material before drawing. These methods are not suitable for the industrial production of toroidal cavity polymer fibers.

[0049] To achieve the industrial-scale production of annular cavity polymer optical fibers, embodiments of this application divide the cladding of the annular cavity polymer optical fiber into a multi-layered annular stacked structure, thereby enabling the industrial-scale production of annular cavity polymer optical fibers using a layered co-extrusion process. At least two adjacent stacked layers in the multi-layered stacked structure are stacked together to form several spaced cavities.

[0050] Specifically, in some embodiments, the multilayer stacked structure includes an Nth stacked structure and an N+1th stacked structure, where N ≥ 1 and N is a positive integer. The N+1th stacked structure includes an annular polymer layer and several support strips, which are distributed on the side of the annular polymer layer near the Nth stacked structure. A cavity is disposed between two adjacent support strips. The support strips are used to improve the structural stability and mechanical properties of the annular cavity polymer fiber and increase the size of the cavity along the radial direction of the annular cavity polymer fiber.

[0051] For example, Figure 4 Showed Figure 1 The stacked structure of the annular cavity polymer optical fiber (or optical fiber preform) in the fiber. For example... Figure 4As shown, the polymer optical fiber comprises a five-layer stacked structure arranged sequentially from the inside out. The first stacked structure 410 is a ring-shaped polymer, and each of the second to fourth stacked structures includes a ring-shaped polymer layer and several support strips. For example, the fourth stacked structure 420 includes several support strips 421 and a ring-shaped polymer 422; wherein two adjacent support strips 421 and ring-shaped polymer 422, together with the ring-shaped polymer in the third stacked structure, form a cavity 440. The coating layer 430 is a ring-shaped polymer. In other embodiments, the stacked structures can be divided in other ways, for example, the innermost stacked structure (e.g., ... Figure 4 The first layer of the stacked structure (in the middle) includes a ring polymer and support strips, and the outermost layer of the stacked structure (e.g., Figure 4 The fifth layer of the stacked structure is a cyclic polymer. Figure 4 In the middle, each layer of cyclic polymer is a hollow ring arranged in concentric circles.

[0052] This is about the book. Figure 4 The relevant parameters of the annular cavity polymer optical fiber are described as follows: Inner diameter of the hollow core layer D1, outer diameter of the optical fiber D2, and polymer coating thickness h; refractive index of the polymer material n1, refractive index of the hollow core layer n2, and refractive index of the polymer coating layer n3; thickness of each polymer layer d1, distance between two adjacent annular polymer layers d2, thickness of one period of the stacked structure Λ = d1 + d2, and number of stacked structure layers η; in each stacked structure, the thickness of the support strip structure is d3, and the number is W. Specifically, in some embodiments, the outer diameter D2 of the optical fiber preform (excluding the coating thickness) ranges from 55-65 mm, such as 55 mm, 60 mm, or 65 mm, etc.; the inner diameter D1 of the hollow core layer of the optical fiber preform ranges from 15-25 mm, such as 15 mm, 20 mm, or 25 mm, etc.; and the coating thickness h of the optical fiber preform ranges from 1-3 mm, such as 1 mm, 2 mm, or 3 mm, etc. The distance d2 between two adjacent annular polymer layers in the optical fiber preform ranges from 0.3mm to 5mm, for example, 0.3mm, 1mm, 2mm, 3mm, 4mm or 5mm, etc.; the thickness of the annular polymer is 0.036-2.4mm, for example, 0.036mm, 0.03mm, 0.1mm, 1mm, 2mm or 2.4mm, etc.

[0053] Figure 5 Polymer optical fibers (e.g., provided in some embodiments of this application) are examples of polymer optical fibers. Figure 4 The refractive index distribution of polymer optical fibers (such as those in polymer optical fibers). Figure 5 As shown, the refractive index of the polymer optical fiber cladding exhibits a periodic variation. Figure 5 In the given information, n1 > n3 > n2.

[0054] To achieve the industrial-scale production of polymer optical fibers, embodiments of this application provide a layered co-extrusion mold for manufacturing polymer optical fibers, for example, for manufacturing... Figures 1 to 3 The fiber preform is a polymer optical fiber with an annular cavity. The fiber preform includes a preformed cavity. A layered co-extrusion die body includes a die body, and the die body includes a plurality of annular components spaced apart from the inside out. A flow channel for the polymer melt is disposed between two adjacent annular components. Among the plurality of annular components, at least two adjacent annular components are further provided with a plurality of hollow core pillars extending axially along the annular components, with each hollow core pillar spaced apart. During the fabrication of the fiber preform through the die, the sidewalls of the hollow core pillars prevent the polymer melt from flowing into the inner cavity of the hollow core pillars, thereby forming a preformed cavity. In this embodiment, at least one flow channel of the polymer melt is provided with a plurality of hollow core pillars extending axially along the annular components. During the layered co-extrusion process with the polymer melt, the polymer melt in the flow channel cannot enter the inner cavity of the hollow core pillars, thus forming a preformed cavity.

[0055] In some embodiments, when the core layer is a hollow layer, the hollow layer is left vacant; the sidewall of the innermost annular component among a plurality of annular components is used to prevent the polymer melt from flowing into the inner cavity of the innermost annular component to form a prefabricated hollow layer. In other embodiments, when the core layer is a solid layer, the inner cavity of the innermost annular component serves as a flow channel for the polymer melt of the core layer.

[0056] Figure 6 An exemplary structural schematic diagram of the mold body from one perspective is shown, which can be used to prepare... Figure 4 In polymer optical fiber preforms, such as Figure 6 As shown, the mold body 600 has several annular components spaced apart from the inside to the outside. Specifically, these annular components can be cylindrical structures spaced apart along the same axis. The annular components include a first annular component 610, a second annular component 620, and a third annular component 630 spaced apart from the inside to the outside; wherein the gap between the first annular component 610 and the second annular component 620 is used to form a first prefabricated stacked structure (e.g., Figure 4The sidewall of the first annular component 610 in the first layer flow channel of the first layer stack structure 410 (corresponding to the prefabricated stack structure) is used to prevent the polymer melt in the first layer flow channel from entering the inner cavity of the first annular component 610 to form a prefabricated hollow layer. A plurality of hollow pillars 640 extending axially along the annular component are disposed between the second annular component 620 and the third annular component 630, with each hollow pillar 640 distributed in a ring-shaped interval around the axis of the annular component. In some embodiments, each hollow pillar 640 may be fixed to the sidewall of the second annular component 620 near the third annular component 630. The cross-sectional shape of the hollow pillar 640 can be any suitable shape such as polygonal, circular, or elliptical. The outer sidewall of the second annular component 620, the outer sidewall of the hollow pillar 640, and the inner sidewall of the third annular component 620 enclose the second layer flow channel of the second prefabricated stack structure. The outer wall of the hollow column 640 is used to prevent the polymer melt in the second layer flow channel from entering the inner cavity of the hollow column 640 to form a pre-formed cavity.

[0057] The cladding of a photonic bandgap photonic crystal fiber includes strictly regularly arranged pores, which can be filled with air or other media. The arrangement and size of the pores in the PBG-PCF cladding must strictly meet requirements to form a photonic bandgap. In some embodiments, photonic bandgap photonic crystal fibers with different properties can be designed by varying the shape, size, spacing, and arrangement of the hollow core pillars 640, and by filling the hollow core pillars 640 with different media.

[0058] Specifically, the flow channels of the layered co-extrusion die include cladding flow channels, which represent the flow channels used for the passage of cladding polymer melt. The cladding flow channels include an Nth layer flow channel and an N+1th layer flow channel; wherein, the Nth layer flow channel is used to: form an Nth layer prefabricated stack structure using the Nth layer polymer melt entering the Nth layer flow channel; the N+1th layer flow channel is used to: when the Nth layer prefabricated stack structure moves along the fiber exit direction to the feed area of ​​the N+1th layer polymer melt, cause a portion of the N+1th layer polymer melt to cover the Nth layer stack structure to form several support strips, and a portion of the N+1th layer polymer melt forms an N+1th layer annular polymer on the side of the support strips away from the Nth layer prefabricated stack structure.

[0059] In some embodiments, when the polymer optical fiber includes a coating layer, the optical fiber preform accordingly also includes a pre-coated coating layer. See also Figure 7 The polymer melt flow channel also includes a coating layer flow channel 650 disposed outside the cladding flow channel, wherein the coating layer flow channel is a flow channel for passing through the coating layer polymer melt; when the prefabricated cladding of the optical fiber preform runs to the feed area of ​​the coating layer melt, the polymer melt in the coating layer flow channel forms a prefabricated coating layer on the outer surface of the prefabricated cladding.

[0060] Please see Figure 8In some embodiments, the mold body 810 is provided with a fiber outlet 811 for outputting optical fiber preforms. The mold 800 also includes an air chamber 820, which is located at the end of the mold body 810 away from the fiber outlet 811. The air chamber 820 is used to: introduce gas into the preform cavity through the inner cavity of the hollow core column during the fiber drawing process of the optical fiber preform; and / or, the air chamber 820 is used to: introduce gas, such as air, into the preform hollow layer through the inner cavity of the innermost annular component during the fiber drawing process of the optical fiber preform.

[0061] After the optical fiber leaves the mold, it undergoes drawing to form a fiber optic product that meets specifications. During the drawing process, without a hollow column to provide support, the radial stress of the material may compress the cavity. To prevent material stress during fiber drawing from compressing the cavity and causing deformation, an air chamber is designed at the front end of the feeding mold. Gas in the air chamber enters from the axial hollow column through a pressure difference, providing internal pressure to the cavity during the final drawing stage, supporting the cavity structure and preventing radial stress from compressing and deforming the cavity during the drawing process.

[0062] In some embodiments, the mold 800 further includes a pressure regulating device 830 disposed on the mold body; the pressure regulating device 830 is used to: control the pressure of the first gas in the preform cavity within a preset first pressure range during the fiber preform drawing process; and / or, the pressure regulating device 830 is used to control the pressure of the second gas in the preform hollow layer within a preset second pressure range during the fiber preform drawing process.

[0063] In some embodiments, the pressure regulating device 830 includes a temperature control device 831; the temperature control device 831 is used to regulate the pressure of the first gas and / or the second gas by controlling the temperature of the mold body 810 during the fiber drawing process of the optical fiber preform.

[0064] In some embodiments, the pressure regulating device 830 further includes a pressure sensor 832 disposed on the mold body. The pressure sensor 832 is used to: monitor the pressure of a first gas within the prefabricated cavity during the fiber preform drawing process; and / or, the pressure sensor 832 is used to: monitor the pressure of a second gas within the prefabricated hollow core layer during the fiber preform drawing process. For example, in some embodiments, the pressure sensor 832 includes one or more first pressure sensors for monitoring the pressure of the first gas within each prefabricated cavity; specifically, the pressure of the first gas within all prefabricated cavities can be monitored simultaneously by one pressure sensor, or the pressure of the first gas within each prefabricated cavity can be monitored separately by multiple pressure sensors. In other embodiments, the pressure sensor 832 further includes a second pressure sensor for monitoring the pressure of the second gas within the prefabricated hollow core layer.

[0065] During fiber drawing: Without the support of an axial hollow column in the die, radial stress in the fiber material can compress the cavity. Therefore, a structure providing internal pressure support is needed. A pressure-controlled gas chamber is placed at the front end of the extrusion die. By adjusting the die temperature, the chamber temperature is changed, controlling the gas pressure (other methods can also be used). The pressure difference allows gas to be injected from the axial hollow column into the fiber cavity, providing a certain internal pressure during end-drawing to counteract the radial stress caused by drawing and ensure that the cavity's dimensions and structure remain unchanged.

[0066] Specifically, the mold body is also provided with several inlet ports, each inlet port is connected to a corresponding flow channel, and the inlet port is used to input polymer melt into the corresponding flow channel; the several flow channels are arranged sequentially from the inside to the outside, wherein the inlet port of the outer flow channel is closer to the fiber outlet of the mold body than the inlet port of the inner flow channel.

[0067] In some embodiments, the flow channels of the polymer melt include a cladding flow channel and a coating flow channel disposed outside the cladding flow channel, wherein the cladding flow channel is used for passing through the cladding polymer melt, and the coating flow channel is used for passing through the coating polymer melt; the inlet of the coating flow channel is closer to the fiber outlet of the mold than the inlet of the cladding flow channel.

[0068] In some embodiments, the mold further includes a plurality of metering pumps 840 disposed on the main body, each metering pump 840 being connected to the inlet of each layer of flow channel. The metering pumps 840 are used to control the flow rate of each layer of polymer melt entering each layer of flow channel; wherein, the flow rate of each layer of polymer melt is positively correlated with the area of ​​the corresponding prefabricated annular stacked structure. By controlling the feed flow rate of each layer of polymer melt through the metering pumps 840, a smaller volume of melt is injected into each layer, ensuring a consistent temperature of the melt in the mold. Simultaneously, this facilitates the filling of the gaps between the axial hollow columns by the polymer melt, reducing the material stress generated during melt flow and preventing the stress of the flowing melt from affecting the cavity structure dimensions.

[0069] In the embodiments of this application, the metering pump controls the feed flow rate of each layer of polymer melt within a preset flow range. The feed flow rate is also called the feed velocity; if the feed flow rate is too low, too little material is fed, which can easily generate bubbles or reduce the thickness of the stacked structure during the melt's advance; if the feed velocity is too high, too much material is fed, which can easily cause overflow or even compress the cavity structure.

[0070] This application also provides a production apparatus for polymer optical fibers. Exemplarily, Figure 9 A structural schematic diagram of production equipment 90 was presented, such as... Figure 9 As shown, the production equipment 90 includes an extruder 91, an optical fiber drawing machine 93, and a mold 92 provided in the above embodiment. The mold 92 is, for example, a... Figure 6 or Figure 7 The mold 600 includes an extruder 91, a mold 92, and an optical fiber drawing machine 93 arranged sequentially. The extruder 91 is used to melt polymer particles to form a polymer melt and output the polymer melt to the mold 92; the mold 92 is used to form an optical fiber preform using the polymer melt; and the optical fiber drawing machine 93 is used to draw the optical fiber preform to obtain a polymer optical fiber of suitable size.

[0071] This application also provides a method for fabricating polymer optical fibers, used to prepare the annular cavity polymer optical fibers provided in the above embodiments, for example... Figures 1-3 The annular cavity polymer optical fiber provided in this application has the following advantages: first, it ensures sufficient fiber feed and prevents air bubbles from forming during the extrusion and drawing process; second, it makes the dimensions of each stacked structure controllable and monitorable; and third, it ensures that the cavity structure in each stacked structure is less affected by material stress, while using variable air pressure to protect the dimensions of the cavity structure.

[0072] Specifically, please refer to Figure 10 The method includes the following steps:

[0073] Step 11: Using a layered co-extrusion process, each layer of the multi-layer stacked structure is extruded layer by layer to obtain the prefabricated fiber preform with a prefabricated cavity.

[0074] Step 11 above specifically includes the following steps:

[0075] Step 110: Using a layered co-extrusion process, prefabricated stacked structures corresponding to each layer of the multi-layer stacked structure are extruded layer by layer from the inside out.

[0076] In the embodiments of this application, when the Nth layer polymer melt enters the Nth layer flow channel of the layered co-extrusion die, it forms the Nth layer prefabricated stack structure; when the Nth layer prefabricated stack structure moves along the fiber exit direction to the feeding area of ​​the N+1th layer polymer melt, under the action of the layered co-extrusion die, part of the N+1th layer polymer melt covers the Nth layer stack structure to form several support strips, and part of the N+1th layer polymer forms the N+1th layer annular polymer on the side of the support strip away from the Nth layer prefabricated stack structure; wherein, the feeding area of ​​the N+1th layer polymer melt is located at the front end of the fiber exit direction relative to the feeding area of ​​the Nth layer polymer melt.

[0077] In some embodiments, the above method further includes the following steps:

[0078] Step 111: During the layered co-extrusion process, the flow rate of each layer of polymer melt entering each flow channel of the layered co-extrusion die is controlled by a metering pump; wherein, the flow rate of each layer of polymer melt is positively correlated with the cross-sectional area of ​​the corresponding annular stacked structure.

[0079] In this embodiment, a metering pump controls the feed rate of each layer of polymer melt, ensuring that each layer receives a smaller volume of melt. This maintains a consistent melt temperature within the mold and facilitates the filling of gaps between the axial hollow columns, reducing material stress generated during melt flow and preventing stress from affecting the cavity structure dimensions. The metering pump controls the feed rate of each layer of polymer melt within a preset range. Feed rate, also known as feed velocity, is crucial. Too low a flow rate results in insufficient material input, potentially causing air bubbles or reduced thickness of the stacked structure during melt propagation. Conversely, too high a feed velocity leads to excessive material input, potentially causing overflow or even compressing the cavity structure.

[0080] In some embodiments, the optical fiber preform further includes a coating layer disposed on the side of the cladding away from the hollow core layer; the method further includes the following steps:

[0081] Step 112: When the cladding layer moves along the fiber exit direction to the feed area of ​​the coating polymer melt, the coating polymer melt forms the coating layer on the surface of the cladding layer away from the core layer; wherein, the feed area of ​​the coating polymer melt is located at the front end of the fiber exit direction relative to the feed area of ​​the cladding layer.

[0082] Step 12: The optical fiber preform is drawn to form the cavity of the polymer optical fiber, thereby obtaining the polymer optical fiber.

[0083] When the core layer is a hollow core layer, the hollow core layer is empty, and the optical fiber preform also has a pre-fabricated hollow core layer. Step 12 above specifically includes the following steps:

[0084] Step 120: The optical fiber preform is drawn to form the cavity and hollow core layer of the polymer optical fiber, respectively, thereby obtaining the polymer optical fiber.

[0085] In some embodiments, step 12 specifically includes: during the fiber preform drawing process, introducing a first gas into the preform cavity and controlling the first gas pressure within a first preset pressure range. In other embodiments, during the fiber preform drawing process, introducing a second gas into the hollow core layer of the fiber preform and controlling the second gas pressure within a second preset pressure range. The types of the first gas and the second gas can be the same or different, and those skilled in the art can set them according to actual needs.

[0086] Specifically, in some embodiments, during the fiber preform drawing process, a first gas is introduced into the preform cavity, and the first gas pressure is adjusted by regulating the temperature of the first gas to ensure that the first gas pressure is within a first preset pressure range. In other embodiments, during the fiber preform drawing process, a second gas is introduced into the hollow core layer of the fiber preform, and the second gas pressure is adjusted by regulating the temperature of the second gas to ensure that the second gas pressure is within a second preset pressure range. The magnitudes of the first and second gas pressures can be the same or different, and the gas pressures within different preform cavities can also be the same or different; those skilled in the art can set these parameters according to actual needs.

[0087] Specifically, in some embodiments, the temperature of the first gas is adjusted by adjusting the temperature of the layered co-extrusion die, thereby controlling the first gas pressure within a first preset pressure range; and / or, the temperature of the second gas is adjusted by adjusting the temperature of the layered co-extrusion die, thereby controlling the second gas pressure within a second preset pressure range.

[0088] During fiber drawing: Without the support of an axial hollow column in the die, radial stress in the fiber material can compress the cavity. Therefore, a structure providing internal pressure support is needed. A pressure-controlled gas chamber is placed at the front end of the extrusion die. By adjusting the die temperature, the gas chamber temperature is changed, controlling the gas pressure (other methods can also be used to control the gas pressure). The pressure difference allows gas from the axial hollow column to be injected into the fiber cavity, providing a certain internal pressure during end drawing to counteract the radial stress caused by drawing and ensure that the cavity's dimensions and structure remain unchanged.

[0089] Figure 11 An exemplary diagram illustrating the structure and layered co-extrusion principle of the mold body from another perspective is provided. Figure 11 As shown, the cladding feed inlets include a first feed inlet 710, a second feed inlet 720, a third feed inlet 730, a fourth feed inlet 740, a fifth feed inlet 750, and a sixth feed inlet 760 arranged sequentially along the fiber exit direction. The first to fifth feed inlets are for the cladding polymer melt, and the sixth feed inlet is for the coating layer polymer melt. The types of polymers entering each cladding polymer melt inlet can be the same or different. The first to sixth feed inlets 710 are connected to the first layer flow channel 711, the second layer flow channel 712, the third layer flow channel 713, the fourth layer flow channel 714, the fifth layer flow channel 715, and the sixth layer flow channel 716, respectively. The polymer melts of each layer are sequentially fed into the flow channels from the first feed inlet 710 to the sixth feed inlet 760. The feed flow rate of each flow channel is strictly controllable.

[0090] In some embodiments, the same first polymer material is input into the first to fifth inlets; a second polymer material is input into the sixth inlet, and the first and second polymer materials are of different types. The second polymer material is a high-toughness polymer material, such as a polyester polymer. The end of the mold body furthest from the fiber outlet is a pressure-controlled air chamber. By adjusting the local temperature of the end of the mold body near the air chamber, the temperature within the air chamber can be changed, resulting in different air pressures within the chamber. This pressure difference is used to guide the gas along the axial hollow column into the optical fiber (as shown by the arrow in the figure), protecting the cavity structure. Finally, the fiber exit direction represents the direction in which the optical fiber is drawn after being extruded from the mold.

[0091] In other embodiments, the air pressure can also be controlled in other ways, for example, by controlling the flow rate of gas into the innermost annular component cavity 780 and the hollow column cavity 770.

[0092] like Figure 12As shown, after each layer of raw material enters the extrusion die, it continues to advance within the die and adheres to the next layer of feed, forming a structure of polymer ring-cavity-next polymer ring, until all the stacked structures and coating layers are adhered layer by layer in the die and extruded from the die. Among them, the first to fifth feed layers are polymer materials, and the sixth feed layer is the coating material, which is selected as a high-toughness polymer material as needed.

[0093] In the embodiments of this application, a layered co-extrusion technology is used to produce annular cavity polymer optical fibers, eliminating the cumbersome steps of preform fabrication and providing greater control over the design of each layer's stacked structure. The layered co-extrusion technology feeds each layer of the stacked structure separately, reducing the internal stress of the material during melt flow and preventing irregular bubbles or deformation of the cavity structure due to extrusion traction. A temperature-controlled gas chamber is introduced at the front of the extrusion die. By controlling the temperature of the gas chamber and adjusting the gas pressure, the pressure difference continuously feeds gas into the axially extending hollow column. The internal pressure supports the cavity structure, counteracting the internal stress generated by the molten material during traction flow, compressing the cavity, and causing dimensional changes. The feed flow rate of each layer is controlled by a metering pump to ensure that each layer of the stacked structure does not leak material, generate bubbles, or overflow and compress the cavity structure.

[0094] The design of the layered co-extrusion die and the extrusion process, including the design of the feed flow rate, air pressure, temperature, and die structure, ensure that each layer of the stacked structure fits tightly during the covering process, preventing air bubbles or gaps between layers. Based on this principle, the working wavelength window of annular cavity polymer optical fibers can be changed by designing annular cavity polymer optical fibers with different cavity sizes. In production, by designing and processing the cavity size structure of the die differently, annular cavity polymer optical fibers with working wavelengths in different windows can be produced.

[0095] This application provides a layered co-extrusion mold and process for photonic bandgap polymer optical fiber or Bragg polymer optical fiber, which is not yet available domestically or internationally. Based on the photonic bandgap principle and the Bragg reflection principle, the structure of these two special polymer optical fibers is analyzed. Combined with actual production and equipment conditions, the concept of annular cavity polymer optical fiber is established, and a layered co-extrusion production process is proposed for this novel optical fiber structure.

[0096] This application's embodiments enable continuous extrusion production of annular cavity polymer optical fibers, producing high-performance, structurally stable annular cavity polymer optical fibers. This eliminates the cumbersome and difficult process steps of the preform drawing production method, reducing production difficulty and improving efficiency. Extrusion production eliminates the need for preform processing; only the design and fabrication of a layered co-extrusion die are required for continuous extrusion production. The layered co-extrusion technology allows for real-time monitoring of the stacked structure in the fiber cladding, enabling timely adjustment of process parameters and making the production process flexible and controllable.

[0097] The layered co-extrusion mold proposed in this application is designed to enable the continuous extrusion-based industrial production of annular cavity polymer optical fibers. In some embodiments, the fiber cladding is a stacked structure with periodically varying refractive index. According to the photonic bandgap theory and the Bragg reflection principle, light of a specific frequency and mode can be confined to the central refractive index defect layer, i.e., the hollow core layer, for propagation. From the photonic bandgap theory and the Bragg reflection principle, it can be deduced that optical fibers with different stacked structure sizes in the cladding can be used for different operating wavelengths. Therefore, by designing different molds, annular cavity polymer optical fibers with different structures can be produced, enabling the optical fiber to exhibit excellent light guiding performance in the visible light band and even the micrometer wave band.

[0098] In some embodiments, based on the above theory, the annular cavity polymer optical fiber produced by the process proposed in this application can radially confine light of a specific frequency in the central hollow core layer, reduce the absorption loss of the material and the nonlinear effect of the optical fiber, and have good light guiding performance in various working wavelength bands.

[0099] Layered co-extrusion technology enables continuous extrusion production of annular cavity polymer optical fibers, ensuring product structural and performance stability while significantly improving production efficiency and price competitiveness. Eliminating the preform fabrication step makes the fiber production process more controllable, allowing for timely detection and correction of defects, thus reducing production accident rates and product defect rates.

[0100] This application also provides a method for manufacturing an optical cable, which includes: manufacturing a polymer optical fiber according to the method provided in the above embodiments; and setting a protective sleeve on the outer surface of at least one polymer optical fiber to obtain an optical cable. Before use, optical fibers must be covered by several layers of protective structures; the covered cable is then called an optical cable. The optical cable of this application includes annular cavity polymer optical fiber and a protective sleeve disposed on the outer surface of the annular cavity polymer optical fiber.

[0101] 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 method for preparing polymer optical fibers, characterized in that, The polymer optical fiber includes a core layer and a cladding layer. The cladding layer comprises multiple annular stacked structures arranged radially from the inside to the outside of the optical fiber. At least two adjacent stacked structures in the multiple stacked structures are stacked together to form several spaced cavities. The multiple stacked structures include an Nth stacked structure and an N+1th stacked structure, wherein N... 1 and N is a positive integer, when N In step 1, both the Nth layer stacked structure and the N+1th layer stacked structure include an annular polymer layer and several support strips. The several support strips are distributed on the side of the annular polymer layer close to the Nth layer stacked structure, and the cavity is disposed between two adjacent support strips. The method includes: The prefabricated stacked structure corresponding to each layer of the multi-layer stacked structure is extruded layer by layer using a layered co-extrusion process, thereby obtaining an optical fiber preform with a prefabricated cavity; The optical fiber preform is drawn to make the preform cavity correspond to the cavity of the polymer optical fiber, thereby obtaining the polymer optical fiber; The process of extruding each layer of the multi-layer stacked structure using a layered co-extrusion process to create a prefabricated stacked structure, including: When the Nth layer of polymer melt enters the Nth layer flow channel of the layered co-extrusion die, it forms the Nth layer of prefabricated stacked structure; When the Nth prefabricated stack structure moves along the fiber exit direction to the feed area of ​​the N+1th layer polymer melt in the N+1th layer channel, under the action of the layered co-extrusion die, part of the N+1th layer polymer melt covers the Nth stack structure to form several support strips, and part of the N+1th layer polymer melt forms an N+1th layer annular polymer on the side of the support strip away from the Nth prefabricated stack structure. The feed area of ​​the N+1th layer polymer melt is located at the front end of the fiber exit direction relative to the feed area of ​​the Nth layer polymer melt. The layered co-extrusion die includes a die body, which includes several annular components arranged sequentially from the inside to the outside. A flow channel for polymer melt is provided between two adjacent annular components. The flow channel for polymer melt includes the Nth layer flow channel and the N+1th layer flow channel. In the plurality of annular components, at least two adjacent annular components are further provided with a plurality of hollow columns extending along the axial direction of the annular components, and the hollow columns are spaced apart. During the fabrication of the optical fiber preform using the mold, the sidewalls of the hollow core column are used to prevent the polymer melt from flowing into the inner cavity of the hollow core column, thereby forming the preformed cavity.

2. The method according to claim 1, characterized in that, The core layer is a hollow core layer, and the hollow core layer is empty. The optical fiber preform also has a pre-made hollow core layer. The step of drawing the optical fiber preform to form the cavity of the polymer optical fiber corresponding to the preform cavity, thereby obtaining the polymer optical fiber, specifically includes: The fiber preform is drawn to form the cavity and hollow core of the polymer fiber, respectively, thereby obtaining the polymer fiber.

3. The method according to claim 1, characterized in that, The step of extruding each layer of the multi-layer stacked structure using a layered co-extrusion process to create a prefabricated stacked structure corresponding to each layer of the multi-layer stacked structure includes: The prefabricated stacked structure is produced by extruding each layer of the multi-layer stacked structure in a layer-by-layer manner from the inside out using a layer-by-layer co-extrusion process.

4. The method according to claim 1, characterized in that, The method further includes: During the layered co-extrusion process, the flow rate of each layer of polymer melt in each flow channel of the layered co-extrusion die is controlled by a metering pump. The flow rate of the polymer melt in each layer is positively correlated with the cross-sectional area of ​​the corresponding annular stacked structure.

5. The method according to claim 2, characterized in that, The optical fiber preform also includes a coating layer, which is disposed on the side of the cladding away from the hollow core layer; Before the fiber preform is drawn, the method further includes: When the cladding layer moves along the fiber exit direction to the feed area of ​​the coating layer polymer melt, the coating layer polymer melt forms the coating layer on the surface of the cladding layer away from the core layer; The feed zone of the polymer melt in the coating layer is located at the front end of the fiber exit direction relative to the feed zone of the cladding layer.

6. The method according to any one of claims 2-5, characterized in that, The method further includes: During the fiber drawing process of the optical fiber preform, a first gas is introduced into the preform cavity, and the first gas pressure is controlled within a first preset pressure range; and / or, During the fiber drawing process of the optical fiber preform, a second gas is introduced into the hollow core layer of the optical fiber preform, and the second gas pressure is controlled within a second preset pressure range.

7. The method according to claim 6, characterized in that, The method specifically includes: During the fiber drawing process of the optical fiber preform, a first gas is introduced into the preform cavity, and the first gas pressure is adjusted by regulating the temperature of the first gas to ensure that the first gas pressure is within a first preset pressure range; and / or During the fiber drawing process of the optical fiber preform, a second gas is introduced into the hollow core layer of the optical fiber preform, and the second gas pressure is adjusted by regulating the temperature of the second gas so that the second gas pressure is within a second preset gas pressure range.

8. The method according to claim 7, characterized in that, The method specifically includes: The temperature of the first gas is adjusted by regulating the temperature of the co-extrusion die, thereby controlling the first gas pressure within a first preset pressure range; and / or, The temperature of the second gas is adjusted by regulating the temperature of the layered co-extrusion die, thereby controlling the second gas pressure within a second preset pressure range.

9. A method for manufacturing an optical cable, characterized in that, The method includes: Polymer optical fibers are prepared according to any one of claims 1-8; An optical cable is obtained by placing a protective sleeve on the outer surface of at least one of the polymer optical fibers.

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