CN116330610A

CN116330610A - Polymer optical fiber and preparation method of polymer optical cable

Info

Publication number: CN116330610A
Application number: CN202310412301.4A
Authority: CN
Inventors: 陈鹏达; 许泽楷; 林国通
Original assignee: Shen Zhen Sinno Optoelectronics Technology Co ltd
Current assignee: Shen Zhen Sinno Optoelectronics Technology Co ltd
Priority date: 2023-04-10
Filing date: 2023-04-10
Publication date: 2023-06-27

Abstract

The embodiment of the application relates to the technical field of plastic optical fibers, in particular to a polymer optical fiber and a preparation method of a polymer optical cable. In an embodiment of the present application, the cladding layer of the polymer optical fiber may be divided into a plurality of layers of annular stack structures sequentially disposed from inside to outside along the radial direction of the optical fiber, and at least two adjacent layers of stack structures in the plurality of layers of annular stack structures are stacked to form a plurality of cavities, and each cavity in the plurality of cavities is distributed at intervals. In the preparation method of the polymer optical fiber, a layering coextrusion process is adopted to extrude each prefabricated stack structure corresponding to each layered stack structure in the multilayer stack structure layer by layer, and a plurality of prefabricated cavities distributed at intervals are formed between at least two adjacent layers of prefabricated stack structures in the multilayer prefabricated stack structure in a stacking mode. Thus, an optical fiber preform having a preform cavity can be obtained by a layered coextrusion process. After the optical fiber preform is subjected to drawing treatment, the prefabricated cavity corresponds to a cavity for forming a polymer optical fiber, so that the polymer optical fiber can be obtained.

Description

Polymer optical fiber and preparation method of polymer optical cable

Technical Field

The embodiment of the application relates to the technical field of plastic optical fibers, in particular to a polymer optical fiber and a preparation method of a polymer optical cable.

Background

The polymer optical fiber (Plastic Optical Fiber, POF) is a new type of optical fiber using high transmittance polymers as the light guiding medium, and its core diameter is generally less than one millimeter. The plastic optical fiber has the characteristics of excellent flexibility, vibration resistance, electromagnetic interference resistance and the like.

The conventional optical fiber plays an important role in optical communication, but has problems of optical loss, chromatic dispersion and the like. In order to overcome the problems of the conventional optical fiber, the annular cavity optical fiber is gradually developed. The annular cavity optical fiber comprises a photonic band gap type photonic crystal fiber (PBG-PCF), a Bragg optical fiber and the like, and the cross section of the annular cavity optical fiber consists of a very tiny air hole array. The air holes are capillaries with diameters on the order of the wavelength of light, and extend in parallel in the optical fiber.

At present, the production method of the annular cavity optical fiber is mostly a preform drawing process, namely, a microstructure is drilled in a quartz optical fiber preform, and the preform is further stretched into filaments, so that the structural dimension of the optical fiber meets the requirement. However, the preform drawing process is only suitable for the industrialized production of the annular cavity quartz optical fiber at present, and is not suitable for the industrialized production of the annular cavity polymer optical fiber.

Disclosure of Invention

The embodiment of the application provides a preparation method of an annular cavity polymer optical fiber and an optical cable, which can realize the industrialized production of the annular cavity polymer optical fiber.

In order to solve the technical problems, the embodiment of the application provides the following technical scheme:

in a first aspect of the present application, a method for preparing a polymer optical fiber is provided, where the polymer optical fiber includes a core layer and a cladding layer, the cladding layer includes a plurality of layers of annular stack structures sequentially arranged from inside to outside along a radial direction of the optical fiber, and at least two layers of adjacent stack structures in the plurality of layers of stack structures are stacked with each other to form a plurality of cavities distributed at intervals; in the method, a layering co-extrusion process is adopted to extrude a prefabrication stack structure corresponding to each layering stack structure in the multilayer stack structures layer by layer, so that an optical fiber prefabricated member with a prefabrication cavity is obtained; and drawing the optical fiber preform to enable the prefabricated cavity to correspond to the cavity of the polymer optical fiber, thereby obtaining the polymer optical fiber.

In an embodiment of the present application, the cladding layer of the polymer optical fiber may be divided into a plurality of layers of annular stack structures sequentially disposed from inside to outside along the radial direction of the optical fiber, and at least two adjacent layers of stack structures in the plurality of layers of annular stack structures are stacked to form a plurality of cavities, and each cavity in the plurality of cavities is distributed at intervals. In the preparation method of the polymer optical fiber, a layering coextrusion process is adopted to extrude each prefabricated stack structure corresponding to each layered stack structure in the multilayer stack structure layer by layer, and a plurality of prefabricated cavities distributed at intervals are formed between at least two adjacent layers of prefabricated stack structures in the multilayer prefabricated stack structure in a stacking mode. Thus, an optical fiber preform having a preform cavity can be obtained by a layered coextrusion process. Drawing the optical fiber preform to obtain a polymer optical fiber; wherein the preformed cavity of the optical fiber preform corresponds to the cavity of the polymer optical fiber after the drawing process.

In some embodiments, the core layer is a hollow core layer, the hollow core layer is hollow, and the optical fiber preform further has a prefabricated hollow core layer; the step of drawing the optical fiber preform so that the preform cavity corresponds to a cavity in which the polymer optical fiber is formed, thereby obtaining the polymer optical fiber specifically includes: and drawing the optical fiber prefabricated member so that the prefabricated cavity and the prefabricated hollow layer respectively form a cavity and a hollow layer of the polymer optical fiber, thereby obtaining the polymer optical fiber.

In some embodiments, the step of extruding each layer of the multilayer stack structure layer by layer using a layered coextrusion process comprises: and extruding each layer of the stack structure in the plurality of layers layer by layer according to the sequence from inside to outside by adopting a layered coextrusion process to obtain a prefabricated stack structure corresponding to the stack structure.

In some embodiments, the multilayer stack structure comprises an nth stack structure and an n+1 stack structure, wherein N is greater than or equal to 1 and N is a positive integer, the n+1 stack structure comprises an annular polymer layer and a plurality of support bars distributed on a side of the annular polymer layer adjacent to the nth stack structure, and the cavity is disposed between two adjacent support bars; the step of extruding each layer of the stack structure in the multilayer stack structure layer by adopting a layered coextrusion process according to the sequence from inside to outside comprises the following steps of: when the Nth layer polymer melt enters an Nth layer runner of the layering co-extrusion die, an Nth layer prefabricated stack structure is formed; when the Nth layer of prefabricated stacking structure moves to a feeding area of the N+1 layer of polymer melt along the fiber outlet direction, under the action of the layering coextrusion die, part of the N+1 layer of polymer melt covers the Nth layer of prefabricated stacking structure to form a plurality of supporting strips, and part of the N+1 layer of polymer forms an N+1 layer of annular polymer on one side of the supporting strips, which is far away from the Nth layer of prefabricated stacking structure; the feeding area of the (N+1) th layer polymer melt is positioned at the front end of the fiber outlet direction relative to the feeding area of the (N) th layer polymer melt.

In some embodiments, the method further comprises: controlling the flow rate of each layer of polymer melt entering each runner of the layered co-extrusion die through a metering pump in the layered co-extrusion process; wherein the flow rate of the polymer melt of each layer is positively correlated with the cross-sectional area of the annular stack structure of the corresponding layer.

In some embodiments, the optical fiber preform further comprises a coating layer disposed on a side of the cladding layer remote from the hollow core layer; before the drawing process of the optical fiber preform, the method further comprises: when the cladding layer moves to a feeding area of the coating layer polymer melt along the fiber outlet direction, the coating layer polymer melt forms the coating layer on the surface of the side, far away from the core layer, of the cladding layer; the feeding area of the coating layer polymer melt is positioned at the front end of the fiber outlet direction relative to the feeding area of the cladding layer.

In some embodiments, the method further comprises: inputting a first gas into the prefabricated cavity in the process of drawing the optical fiber prefabricated member, and controlling the first air pressure of the first gas to be within a first preset air pressure range; and/or, in the process of drawing the optical fiber prefabricated member, inputting a second gas into the hollow layer of the optical fiber prefabricated member, and controlling the second gas pressure of the second gas to be within a second preset gas pressure range.

In some embodiments, the method specifically comprises: inputting a first gas into the prefabricated cavity in the process of drawing the optical fiber prefabricated member, 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, in the process of drawing the optical fiber preform, inputting a second gas into the hollow 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.

In some embodiments, the method specifically comprises: adjusting the temperature of the first gas by adjusting the temperature of the layered coextrusion die, so that the first gas pressure is controlled within a first preset pressure range; and/or adjusting the temperature of the second gas by adjusting the temperature of the layered co-extrusion die, thereby controlling the second gas pressure within a second preset pressure range.

In a second aspect of the present application, there is also provided a method of preparing an optical cable, in which method a polymer optical fiber is prepared according to the method of the first aspect; and arranging a protective sleeve on the outer surface of at least one polymer optical fiber to obtain the optical cable.

It should be understood that the description in this summary is not intended to limit the critical or essential features of the disclosure, nor is it intended to limit the scope of the disclosure. Other features of the present disclosure will become apparent from the following description.

Drawings

In order to more clearly illustrate the technical solution of the embodiments of the present invention, the drawings that are required to be used in the embodiments of the present invention will be briefly described below. It is evident that the drawings described below are only some embodiments of the present invention and that other drawings may be obtained from these drawings without inventive effort for a person of ordinary skill in the art.

FIG. 1 is a schematic illustration of the structure of a polymer optic fiber provided in some embodiments of the present application;

FIG. 2 is a schematic illustration of the structure of a polymer optic fiber provided in some embodiments of the present application;

FIG. 3 is a schematic illustration of the structure of a polymer optic fiber provided in some embodiments of the present application;

FIG. 4 is a schematic distribution diagram of the various stacked structures of polymer optical fibers provided in some embodiments of the present application;

FIG. 5 is a refractive index profile of a polymer optical fiber provided by some embodiments of the present application;

FIG. 6 is a schematic diagram of a layered coextrusion die according to some embodiments of the present application;

FIG. 7 is a schematic illustration of the structure and layered co-extrusion principle of another view of a layered co-extrusion die provided in some embodiments of the present application;

FIG. 8 is a schematic structural view of a layered co-extrusion die provided in some embodiments of the present application;

FIG. 9 is a schematic structural view of a polymer optic fiber production facility provided in some embodiments of the present application;

FIG. 10 is a flow chart of a method of making a polymer optic fiber provided in some embodiments of the present application;

FIG. 11 is a schematic illustration of the structure and layered co-extrusion principle of a layered co-extrusion die provided in some embodiments of the present application;

fig. 12 is a sequence diagram of the feeding of polymer melts of various layers provided in some embodiments of the present application.

Detailed Description

The present invention will be described in further detail with reference to the drawings and examples, in order to make the objects, technical solutions and advantages of the present invention more apparent. It should be understood that the specific embodiments described herein are for purposes of illustration only and are not intended to limit the scope of the invention.

It should be noted that, if not in conflict, the features of the embodiments of the present invention may be combined with each other, which are all within the protection scope of the present invention. In addition, while the division of functional blocks is performed in a device diagram and the logic sequence is shown in a flowchart, in some cases, the steps shown or described may be performed in a different order than the block division in a device diagram or the sequence in a flowchart.

Unless defined otherwise, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this invention belongs. The terminology used in the description of the invention herein is for the purpose of describing particular embodiments only and is not intended to be limiting of 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.

Polymer optical fibers (Plastic Optical Fiber, POF), also known as plastic optical fibers or polymer optical fibers, are made from high molecular polymer materials (e.g., polymethyl methacrylate) and typically have a core diameter of less than one millimeter. The plastic optical fiber uses high-transmittance polymer as light guide medium, and has excellent flexibility, vibration resistance, electromagnetic interference resistance and other characteristics.

Currently, the plastic optical fibers widely used in the market are step index plastic optical fibers (SI-POF) with low loss operating wavelength windows of 520nm and 650nm. At an operating wavelength of 650nm, the theoretical loss limit for SI-POF is about 100dB/km. However, in practical production, the loss of plastic optical fiber products for communication is as high as 140dB/km to 200dB/km, and the loss in the near infrared region is still larger. Therefore, plastic optical fibers using polymethyl methacrylate (PMMA) as a core material are mainly used in the field of short-distance communication. Furthermore, SI-POF is a multimode fiber, whose nonlinear effects affect the transmission bandwidth. Subsequently, japanese enterprises push out deuterated plastic optical fibers to greatly reduce attenuation of SI-POF, but deuterated plastic optical fibers have narrow spectrum width, limited application, and excessively high raw material cost, which is unfavorable for market popularization of products.

In order to reduce the optical loss of the plastic optical fiber and improve the communication bandwidth, the university institute and the enterprise in japan push out perfluorinated plastic optical fiber and partially fluorinated plastic optical fiber in order to make the refractive index of the perfluorinated plastic optical fiber gradually distributed (GI-POF). However, the raw materials are high in cost, the production process is complicated and difficult, the production cost is too high, and the raw materials are difficult to enter the market and are widely popularized and applied.

Photonic bandgap-type photonic crystal fibers (PBG-PCFs), also known as microstructured fibers. The PBG-PCF cross-section has a relatively complex refractive index profile, typically comprising various arrangements of air holes (also called cavities) having dimensions of approximately the same order of magnitude as the wavelength of the light wave and extending the entire length of the device, the light wave being confined to the core region of the fiber in the region of the refractive index defect. The PBG-PCF includes a structure having a periodically varying refractive index, thereby generating a photonic band, and photons having frequencies within a forbidden band in the photonic band are forbidden to propagate in the cladding structure. The defect is formed by destroying the introduced periodic structure, so that the photon energy gap can form a defect area with a certain frequency width, and light waves with a specific frequency can propagate in the defect area, namely, the light waves are radially bound to the defect area. The light guiding mechanism of the photonic band gap type photonic crystal fiber is different from the principle of total internal reflection conduction light in the traditional fiber, and light is guided through the photonic band gap.

The Bragg fiber is a special fiber formed by concentric rings of multilayer media with periodically distributed radial refractive indexes. Light is bound to the defect state, i.e. transmitted in the central hollow region, by means of the bragg reflection principle. The Bragg fiber core layer is usually of a hollow core structure, a high refractive index core can be used, the radial refractive index of the cladding layer is periodically distributed, and the Bragg fiber core layer can be approximately regarded as a one-dimensional photonic band gap type photonic crystal fiber. The Bragg reflection principle is utilized to limit the light with specific frequency to be transmitted in the hollow area, so that the absorption loss of the material is greatly reduced. Meanwhile, as the Bragg reflection principle needs to meet the requirement of nλ=2dsinθ, only light waves in a specific mode can be transmitted in the core layer, so that the Bragg fiber can reduce the nonlinear effect of materials and improve the communication bandwidth.

The plastic optical fiber uses air as the low refractive index material, so as to avoid the trouble of searching for two materials with larger refractive index difference distance, good optical performance, and similarity and compatibility in thermal and mechanical properties and manufacturing process. The hollow layer is an air layer or other low-refractive-index gas layers, so that inherent absorption loss of other materials can be avoided, nonlinear effect can be reduced, light attenuation is reduced, and meanwhile, transmission bandwidth is improved. The Bragg stack structure is introduced, so that light can be radially bound in the hollow core layer, leakage is prevented, and loss is reduced. The Bragg stack structure is designed in different sizes, so that optical fibers with different working wavelength windows can be obtained, and the Bragg stack structure has advantages in the field of visible light to infrared light transmission. The optical fiber cladding has a stack structure with periodically changing refractive index, and can restrict the light of a specific mode with a specific frequency to the central refractive index defect layer, namely the hollow core layer for propagation according to the photonic band gap theory and the Bragg reflection principle.

The polymer optical fiber of the embodiment of the application is also called an annular cavity polymer optical fiber, the polymer optical fiber comprises a cladding structure with refractive index periodically distributed, the cladding structure is formed by stacking a plurality of layers of annular cavities and polymer rings in sequence to form periodic refractive index distribution, and an optical fiber core layer is an air core layer and forms a fiber core by air and other gas defects. In the embodiment of the application, the stack structure with the refractive index periodically distributed is introduced into the polymer optical fiber, so that the photonic band gap polymer optical fiber or the Bragg polymer optical fiber can be formed, and compared with the traditional plastic optical fiber, the optical fiber has the characteristics of vibration resistance and electromagnetic interference resistance, has the advantages of low attenuation, high bandwidth and light bandwidth transmission, can play advantages in the short-distance communication of various local area networks (such as automobiles, large-scale vehicles, military equipment and residential office networks), and greatly promotes the progress of a communication system to the realization of an all-optical network.

The polymer optical fiber of the embodiment of the application is also called an annular cavity polymer optical fiber, and specifically includes: bandgap photonic crystal fibers or bragg fibers. Illustratively, FIG. 1 shows a cross-sectional view of an annular cavity polymer optical fiber 100. As shown in fig. 1, the annular cavity polymer optical fiber 100 includes a core layer 110 and a cladding layer 120 disposed in order from inside to outside in the radial direction of the annular cavity polymer optical fiber 100. The core layer 110 may be a solid core layer or a hollow core layer. The embodiment of the present application will be described by taking the core layer 110 as a hollow core layer as an example.

Specifically, the core layer 110 is configured as a hollow core layer in order to enable light to propagate in a low-loss medium. The method is not only used for omitting the trouble of searching two materials with larger refractive index difference distance and good optical performance and having similarity and compatibility in thermal, mechanical and other performances and manufacturing process, but also can ensure that the product performance reaches high bandwidth, low attenuation and low time delay. The hollow core layer adopts a hollow structure. In general, the hollow core layer 110 may be filled with air as a low refractive index material. In other embodiments, the hollow core layer may be filled with other low loss gases to minimize absorption losses of materials that propagate light in the fiber.

To ensure radial confinement of light within the hollow core layer, i.e., to reduce radial leakage of light, cladding 120 includes multiple layers of cavities arranged sequentially from inside to outside in the radial direction of annular cavity polymer optical fiber 100, with cavities 121 in each layer being arranged annularly about the axis of annular cavity polymer optical fiber 100. The cavity 121 may be filled with air as a low refractive index material, and the cavity 121 may also be filled with other low loss gases to minimize absorption losses of the material propagating in the fiber.

Optionally, in some embodiments, to increase flexibility of the annular cavity polymer optical fiber 100, the annular cavity polymer optical fiber 100 further includes a coating layer 130, and the hollow core layer 110, the cladding layer 120, and the coating layer 130 are disposed sequentially from inside to outside in a radial direction of the annular cavity polymer optical fiber 100. One skilled in the art can choose whether the annular cavity polymer optical fiber is provided with a coating layer or not according to actual needs. The coating layer is a high-toughness polymer for increasing the flexibility of the optical fiber.

Fig. 2 and 3 illustrate cross-sectional views of other embodiments of annular cavity polymer optical fibers. As shown in fig. 2 and 3, the cross-sectional shape of the cavity 121 may be any suitable shape, such as polygonal or circular. The cavities 121 in each layer of cavities are arranged in any suitable shape, such as polygonal or circular, about the axis of the annular cavity polymer optical fiber 100.

In some embodiments, the hollow core layer of the annular cavity polymer optical fiber is hollow, while the cladding layer has a plurality of hollow structures. If the traditional extrusion process is adopted, the stress of the material can influence the size of the cavity and destroy the Bragg reflection condition during extrusion wire drawing; in addition, if the disposable feeding is selected, the gap between the axial hollow columns in the die is too small, so that the situation that the feeding cannot completely fill the extrusion die is caused, irregular bubbles exist in the polymer optical fiber, and the light guiding performance of the polymer optical fiber is greatly affected.

At present, relatively mature photonic bandgap type photonic crystal fibers, mostly quartz fibers, are studied. And drilling a hole in the quartz optical fiber preform to manufacture a microstructure, and further stretching the microstructure into filaments to ensure that the structural dimension of the optical fiber meets the requirement. At present, the production method of the photonic band gap polymer optical fiber or the Bragg polymer optical fiber based on the preform drawing process at home and abroad is only trial-produced in an experimental stage, and is far from reaching the requirement of industrialization. The manufacturing method of the classical photonic band gap type photonic crystal fiber or the Bragg fiber comprises the steps of stacking a plurality of manufactured air pipes together, stacking the air pipes, and drawing the air pipes; alternatively, a length of optical fiber material is provided with a plurality of micro-holes, and then drawn. None of these methods is suitable for the industrial production of annular cavity polymer optical fibers.

In order to realize the industrialized production of the annular cavity polymer optical fiber, the embodiment of the application divides the cladding of the annular cavity polymer optical fiber into a multilayer annular stack structure, so that the industrialized production of the annular cavity polymer optical fiber can be realized by adopting a layered coextrusion process. At least two adjacent stacked structures in the multi-layer stacked structure are stacked to form a plurality of cavities distributed at intervals.

Specifically, in some embodiments, the multilayer stack structure includes an nth stack structure and an n+1 stack structure, where N is greater than or equal to 1 and N is a positive integer, the n+1 stack structure includes an annular polymer layer and a plurality of support bars, the plurality of support bars are distributed on a side of the annular polymer layer adjacent to the nth stack structure, and the cavity is disposed between two adjacent support bars. The support bars are used for improving the structural stability and mechanical properties of the annular cavity polymer optical fiber and increasing the radial dimension of the cavity along the annular cavity polymer optical fiber.

Illustratively, FIG. 4 shows the respective stack structure of the annular cavity polymer optical fiber (or optical fiber preform) of FIG. 1. As shown in fig. 4, the polymer optical fiber includes five layers of stack structures sequentially arranged from inside to outside, wherein the first stack structure 410 is an annular polymer, and each of the second to fourth stack structures includes an annular polymer layer and a plurality of support bars. For example, the fourth stacked structure 420 includes a number of support bars 421 and an annular polymer 422; wherein, two adjacent support bars 421 and annular polymers 422 are enclosed with the annular polymers in the third layer stack structure to form a cavity 440. Coating layer 430 is a cyclic polymer. In other embodiments, the stack structures may be divided in other ways, for example, the innermost stack structure (e.g., the first stack structure in fig. 4) includes an annular polymer and support bars, and the outermost stack structure (e.g., the fifth stack structure in fig. 4) is an annular polymer. In fig. 4, each layer of the annular polymer is a hollow annular ring arranged in concentric circles.

The relevant parameters of the annular cavity polymer optical fiber of this fig. 4 are described herein: an inner diameter D1 of the hollow core layer, an outer diameter D2 of the optical fiber and a coating layer polymer thickness h; the refractive index of the polymer material is n1, the refractive index of the hollow layer is n2, and the refractive index of the coating layer polymer material is n3; the thickness of each layer of polymer material is d1, the distance between two adjacent layers of annular polymers is d2, the thickness lambda=d1+d2 of one period of the stack structure, and the number of layers of the stack structure is eta; in each laminated pile structure, the thickness of the supporting bar structure is d3, and the number of the supporting bar structures is W. Specifically, in some embodiments, the optical fiber preform has an optical fiber outer diameter D2 (excluding coating layer thickness) in the range of 55-65mm, such as 55mm, 60mm, 65mm, or the like; the hollow core layer inner diameter D1 of the optical fiber preform is in the range of 15 to 25mm, and may be 15mm, 20mm, 25mm, or the like, for example. The coating layer thickness h of the optical fiber preform ranges from 1 to 3mm, and may be, for example, 1mm, 2mm, 3mm, or the like. The distance d2 between two adjacent layers of annular polymer 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 cyclic polymer is 0.036-2.4mm, e.g., 0.036mm, 0.03mm, 0.1mm, 1mm, 2mm, 2.4mm, etc.

Fig. 5 is a refractive index profile of a polymer optical fiber (e.g., the polymer optical fiber of fig. 4) provided by some embodiments of the present application. As shown in fig. 5, the refractive index of the polymer optical fiber cladding changes periodically, and in fig. 5, n1 > n3 > n2.

In order to achieve the industrial production of polymer optical fibers, embodiments of the present application provide a layered coextrusion die for making polymer optical fibers, for example, optical fiber preforms for making annular cavity polymer optical fibers in fig. 1-3. The optical fiber preform includes a preform cavity. The layered co-extrusion die body comprises a die body, wherein the die body comprises a plurality of annular parts which are sequentially arranged at intervals from inside to outside, and a flow passage of polymer melt is arranged between two adjacent layers of annular parts; a plurality of hollow columns extending along the axial direction of the annular components are also arranged between at least two layers of adjacent annular components in the plurality of annular components, and the hollow columns are distributed at intervals; during the preparation of an optical fiber preform by a mold, the sidewalls of the hollow stem are used to prevent the polymer melt from flowing into the cavity of the hollow stem to form a preform cavity. In this embodiment, a plurality of hollow columns extending in the axial direction of the annular member are disposed in the flow channel of at least one polymer melt, and in the process of layering and co-extrusion with the polymer melt, the polymer melt in the flow channel cannot enter the inner cavity of the hollow column, so that a prefabricated cavity is formed.

In some embodiments, when the core layer is an empty core layer, the empty core layer is empty; the side wall of the innermost annular member of the plurality of annular members is configured to inhibit the flow of the polymer melt into the inner cavity of the innermost annular member to form a preformed hollow core layer. In other embodiments, when the core is a solid core, the inner cavity of the innermost annular member is a runner for the core polymer melt.

Fig. 6 illustrates a schematic structural view of a mold body, which may be used to manufacture an optical fiber preform for the polymer optical fiber in fig. 4, as shown in fig. 6, in which a plurality of annular members are sequentially disposed at intervals from inside to outside, and the plurality of annular members may be cylindrical structures disposed at intervals along the same axis. The plurality of annular components comprise a first annular component 610, a second annular component 620 and a third annular component 630 which are sequentially arranged at intervals from inside to outside; wherein the gap between the first annular component 610 and the second annular component 620 is used to form a first layer of runner first annular component 610 of a first pre-stack structure (e.g., a pre-stack structure corresponding to the first stack structure 410 in fig. 4) and the sidewall of the first layer of runner is used to prevent polymer melt in the first layer of runner from entering the inner cavity of the first annular component 610 to form a pre-fabricated hollow core layer. Between the second annular member 620 and the third annular member 630, a plurality of hollow columns 640 extending in the axial direction of the annular member are provided, and the hollow columns 640 are distributed at intervals in an annular shape around the axis of the annular member. In some embodiments, each hollow stem 640 may be specifically fixed to a side wall of the second annular member 620 near the side of the third annular member 630. The cross-section of the hollow stem 640 may have any suitable shape, such as polygonal, circular, or elliptical. The outer sidewall of the second annular member 620, the outer sidewall of the hollow stem 640, and the inner sidewall of the third annular member 620 enclose a second layer flow path that forms a second layer of the prefabricated stack structure. The outer sidewall of the hollow stem 640 serves to prevent the polymer melt in the second layer of runners from entering the interior cavity of the hollow stem 640 to form a preformed cavity.

The cladding of the photonic band gap crystal fiber comprises strictly-arranged air holes, wherein the air holes can be air or other mediums. The arrangement and the size of the air holes in the PBG-PCF cladding layer can form a photon forbidden band under the condition of strictly meeting the requirement. In some embodiments, photonic bandgap photonic crystal fibers with different characteristics may be designed by methods such as the shape, size, spacing, arrangement of the hollow pillars 640, filling different media into the hollow pillars 640, and the like.

In particular, the runners of the layered coextrusion die comprise cladding runners, which represent runners for passing through the cladding polymer melt. The cladding runner comprises an N layer runner and an n+1 layer runner; wherein, the nth layer flow path is used for: forming an nth layer preform stack structure using the nth layer polymer melt entering the nth layer flow channel; the n+1th layer flow path is for: when the N layer prefabricated stack structure moves to the feeding area of the N+1 layer polymer melt along the fiber outlet direction, part of the N+1 layer polymer melt is covered on the N layer stacked stack structure to form a plurality of supporting bars, and part of the N+1 layer polymer melt forms an N+1 layer annular polymer on one side of the supporting bars, which is far away from the N layer prefabricated stack structure.

In some embodiments, when the polymer optical fiber includes a coating layer, the optical fiber preform correspondingly further includes a preform coating layer. Referring to fig. 7, the polymer melt flow channel further includes a coating layer flow channel 650 disposed outside the cladding layer flow channel, wherein the coating layer flow channel represents a flow channel for passing the coating layer polymer melt; when the prefabricated cladding of the optical fiber prefabricated member moves to the feeding area of the coating layer melt, the polymer melt in the coating layer runner forms a prefabricated coating layer on the outer surface of the prefabricated cladding.

Referring to fig. 8, in some embodiments, the mold body 810 is provided with a fiber outlet 811, the fiber outlet 811 is used for outputting an optical fiber preform, the mold 800 further includes a gas chamber 820, and the gas chamber 820 is disposed at an end of the mold body 810 away from the fiber outlet 811; the air chamber 820 is for: in the process of carrying out wire drawing treatment on the optical fiber prefabricated member, introducing gas into the prefabricated cavity through the inner cavity of the hollow core column; and/or, the plenum 820 is configured to: in the process of carrying out wire drawing treatment on the optical fiber prefabricated member, gas such as air and the like is introduced into the prefabricated hollow core layer through the inner cavity of the innermost annular component.

And (3) after the optical fiber leaves the die, drawing and forming the optical fiber, and drawing the optical fiber into an optical fiber product meeting the specification. During wire drawing, the radial stress of the material may squeeze the cavity because there is no support provided by the hollow post. In order to prevent the material stress in the optical fiber stretching process from extruding the cavity to deform, an air chamber is designed at the front end of the feeding mould, air in the air chamber enters from the axial hollow column through pressure difference, internal pressure is provided for the cavity in the terminal wire drawing link, the cavity structure is supported, and the radial stress of the material in the wire drawing process is prevented from extruding the cavity to deform.

In some embodiments, the mold 800 further comprises an air pressure adjustment device 830 disposed on the mold body; the air pressure adjusting device 830 is configured to: controlling the pressure of the first gas in the prefabricated cavity to be within a preset first pressure range in the process of carrying out wire drawing treatment on the optical fiber prefabricated member; and/or, the air pressure adjusting device 830 is configured to control the pressure of the second air in the prefabricated hollow core layer within a preset second pressure range during the fiber drawing process of the optical fiber prefabricated member.

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

In some embodiments, the air pressure regulating device 830 further includes an air pressure sensor 832 disposed on the mold body. The air pressure sensor 832 is for: monitoring the pressure of the first gas in the prefabricated cavity in the process of carrying out wire drawing treatment on the optical fiber prefabricated member; and/or, the air pressure sensor 832 is configured to: the pressure of the second gas in the preform core layer is monitored during the drawing process of the optical fiber preform. For example, in some embodiments, the air pressure sensor 832 includes one or more first air pressure sensors for monitoring the pressure of the first air within each of the preformed cavities; specifically, the pressure of the first gas in all the prefabricated cavities can be monitored simultaneously through one air pressure sensor, and the pressure of the first gas in each prefabricated cavity can also be monitored through a plurality of air pressure sensors respectively. In other embodiments, the air pressure sensor 832 also includes a second air pressure sensor for monitoring the pressure of the second air within the preformed air core layer.

During the wire drawing process: since there is no support for the axial hollow column in the mold, radial stress of the fiber material may be caused to squeeze the cavity during drawing, and thus a structure for providing an internal pressure support cavity to the cavity is required. An air chamber with controllable air pressure is arranged at the front end of the extrusion die, the temperature of the air chamber is changed by adjusting the temperature of the die, and the air pressure is controlled (other methods can be used for controlling the air pressure). The air chamber gas is filled into the optical fiber cavity from the axial hollow column by utilizing the pressure difference, a certain internal pressure is provided when the tail end is drawn, the radial stress of the material caused by drawing is counteracted, and the dimensional structure of the cavity is ensured not to be changed.

Specifically, the die main body is also provided with a plurality of feeding ports, each feeding port is communicated with each corresponding runner, and the feeding ports are used for inputting polymer melt into the corresponding runners; the runners are sequentially arranged from inside to outside, wherein a feed inlet of the outer runner is close to a fiber outlet of the die body relative to a feed inlet of the inner runner.

In some embodiments, the flow channels of the polymer melt include a cladding flow channel for passing the cladding polymer melt and a coating flow channel disposed outside the cladding flow channel for passing the coating polymer melt; the inlet of the coating layer runner is close to the fiber outlet of the die relative to the inlet of the cladding layer runner.

In some embodiments, the mold further comprises a plurality of metering pumps 840 disposed on the main body, each metering pump 840 being connected to the feed inlet of each layer of runners, the metering pump 840 being configured to control the flow rate of each layer of polymer melt entering each layer of runners; wherein the flow rate of each layer of polymer melt is positively correlated to the area of the corresponding layer of preformed annular stack structure. The feeding flow of each layer of polymer melt can be controlled through the metering pump 840, so that each layer of melt with smaller volume is injected, the temperature of the melt in the die is kept consistent, gaps between the axial hollow columns can be filled with the polymer melt, material stress generated during melt flow is reduced, and the stress of the flowing melt is prevented from influencing the structural size of the cavity.

In embodiments of the present application, the metering pump controls the feed flow rate of each layer of polymer melt to be within a preset flow rate range. The feeding flow is also called as feeding speed; if the feeding flow is too low, the feeding is too low, and bubbles are easy to generate or the thickness of the stacked structure is reduced in the advancing process of the melt; too high feeding speed can cause excessive feeding, and can easily cause flash and even extrude the cavity structure.

The embodiment of the application also provides production equipment of the polymer optical fiber. Illustratively, fig. 9 shows a schematic structural diagram of a production apparatus 90, and as shown in fig. 9, the production apparatus 90 includes an extruder 91, an optical fiber drawing machine 93, and a die 92 provided in the above embodiment, the die 92 being, for example, a die 600 in fig. 6 or fig. 7, wherein the extruder 91, the die 92, and the optical fiber drawing machine 93 are disposed in this order. Extruder 91 is used to melt the polymer particles to form a polymer melt and output the polymer melt to die 92; the mold 92 is used to form an optical fiber preform from the polymer melt; the optical fiber drawing machine 93 is used to draw an optical fiber preform to obtain a polymer optical fiber of a suitable size.

The embodiment of the application also provides a preparation method of the polymer optical fiber, which is used for preparing the annular cavity polymer optical fiber provided by the embodiment, such as the annular cavity polymer optical fiber in fig. 1-3, and firstly, in order to ensure that the optical fiber is sufficient in feeding, no bubbles appear in the extrusion drawing process; secondly, the size of each laminated pile structure is controllable and monitorable; thirdly, the cavity structure in each laminated pile structure is ensured to be affected by less material stress, and meanwhile, the variable air pressure is adopted to protect the size of the cavity structure.

Specifically, referring to fig. 10, the method includes the steps of:

step 11: extruding each layer of the prefabricated stack structure corresponding to each layer of the stack structure layer by adopting a layered coextrusion process, so as to obtain an optical fiber prefabricated member with a prefabricated cavity;

the step 11 specifically includes the following steps:

step 110: and extruding each layer of the stack structure in the plurality of layers layer by adopting a layered coextrusion process according to the sequence from inside to outside to obtain a prefabricated stack structure corresponding to the stack structure.

In the embodiment of the application, an Nth layer prefabricated stack structure is formed after an Nth layer polymer melt enters an Nth layer runner of a layered co-extrusion die; when the N layer prefabricated stacking structure moves to the feeding area of the N+1 layer polymer melt along the fiber outlet direction, under the action of the layering coextrusion die, part of the N+1 layer polymer melt is covered on the N layer stacked stacking structure to form a plurality of supporting bars, and part of the N+1 layer polymer forms an N+1 layer annular polymer on one side of the supporting bars, which is far away from the N layer prefabricated stacking structure; wherein the feeding area of the N+1th layer polymer melt is positioned at the front end of the fiber outlet direction relative to the feeding area of the N layer polymer melt.

In some embodiments, the above method further comprises the steps of:

step 111: controlling the flow rate of each layer of polymer melt entering each runner of the layered co-extrusion die through a metering pump in the layered co-extrusion process; wherein the flow rate of the polymer melt of each layer is positively correlated with the cross-sectional area of the annular stack structure of the corresponding layer.

In this embodiment, the feeding amount of each layer of polymer melt can be controlled by the metering pump, so that each layer of melt with a smaller volume is injected, the temperature of the melt in the mold is kept consistent, the gap between the axial hollow columns can be filled with the polymer melt, the material stress generated during melt flow is reduced, and the stress of the flowing melt is prevented from affecting the structural size of the cavity. The metering pump controls the feed flow of each layer of polymer melt within a preset flow range. The feeding flow is also called as feeding speed; if the feeding flow is too low, the feeding is too low, and bubbles are easy to generate or the thickness of the stacked structure is reduced in the advancing process of the melt; too high feeding speed can cause excessive feeding, and can easily cause flash and even extrude the cavity structure.

In some embodiments, the optical fiber preform further comprises a coating layer disposed on a side of the cladding layer remote from the hollow core layer; the method further comprises the following steps:

Step 112: when the cladding layer moves to a feeding area of the coating layer polymer melt along the fiber outlet direction, the coating layer polymer melt forms the coating layer on the surface of the side, far away from the core layer, of the cladding layer; the feeding area of the coating layer polymer melt is positioned at the front end of the fiber outlet direction relative to the feeding area of the cladding layer.

Step 12: and drawing the optical fiber prefabricated member so that the prefabricated cavity corresponds to the cavity for forming the polymer optical fiber, thereby obtaining the polymer optical fiber.

When the core layer is a hollow layer, the hollow layer is hollow, the optical fiber preform further has a prefabricated hollow layer, and the step 12 specifically includes the following steps:

step 120: and drawing the optical fiber prefabricated member so that the prefabricated cavity and the prefabricated hollow layer respectively form a cavity and a hollow layer of the polymer optical fiber, thereby obtaining the polymer optical fiber.

In some embodiments, the step 12 specifically includes: in the process of carrying out wire drawing treatment on an optical fiber prefabricated member, inputting first gas into a prefabricated cavity, and controlling first air pressure of the first gas within a first preset air pressure range. In other embodiments, a second gas is introduced into the hollow core layer of the optical fiber preform during the drawing process of the optical fiber preform, and a second gas pressure of the second gas is controlled to be within a second preset gas pressure range. The types of the first gas and the second gas may be the same or different, and may be set by those skilled in the art according to actual requirements.

Specifically, in some embodiments, during the process of performing the drawing process on the optical fiber preform, a first gas is introduced into the preform cavity, and the first gas pressure is adjusted by adjusting the temperature of the first gas, so that the first gas pressure is within a first preset gas pressure range. In other embodiments, during the 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 adjusting the temperature of the second gas so that the second gas pressure is within a second preset gas pressure range. The first air pressure and the second air pressure can be the same or different, and the air pressures in different prefabricated cavities can be the same or different, and can be set according to actual requirements by a person skilled in the art.

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 adjusting the temperature of the second gas by adjusting the temperature of the layered co-extrusion die, thereby controlling the second gas pressure within a second preset pressure range.

Fig. 11 illustrates a schematic view of the structure and layered coextrusion principle of another view of the die body. As shown in fig. 11, the cladding inlet includes a first inlet 710, a second inlet 720, a third inlet 730, a fourth inlet 740, a fifth inlet 750, and a sixth inlet 760, which are sequentially disposed along the fiber-out direction. The first to fifth feed inlets are feed inlets of the cladding polymer melt, and the sixth feed inlet is a feed inlet of the coating polymer melt. The types of polymers entering the feed ports of the respective clad polymer melts may be the same or different. The first to sixth feed ports 710 to 760 are respectively communicated with the first, second, third, fourth, fifth and sixth layer flow passages 711, 712, 713, 714, 715 and 716. The layers of polymer melt are sequentially fed in order of arrangement from the first feed port 710 to the sixth feed port 760. The feeding flow of each layer of runner is strictly controllable.

In some embodiments, the first through fifth inlets input the same first polymeric material; the sixth feed inlet is fed with a second polymeric material, the first polymeric material being of a different type than the second polymeric material. The second polymeric material is a high toughness polymeric material, such as a polyester-based polymer. The end of the die main body, which is far away from the fiber outlet, is provided with an air chamber with controllable air pressure, and the temperature in the air chamber of the die can be changed by adjusting the local temperature of the end of the die main body, which is close to the air chamber, so that the air chamber has different air pressures; the pressure difference is used for guiding the gas into the optical fiber along the axial hollow column (namely, the arrow in the figure) so as to protect the cavity structure. The final fiber-out direction represents the direction in which the fiber is drawn after extrusion from the die.

In other embodiments, the gas pressure may also or alternatively be controlled, for example, by controlling the flow of gas into the innermost annular member lumen 780 and the hollow column 770 lumen.

As shown in fig. 12, after each layer of raw material enters the extrusion die, the raw material can advance in the die and is attached to the next layer of material to form a structure of the polymer ring-cavity-next layer of polymer ring until all the stacked structures and the coating layers are attached to the middle layer of the die and are extruded from the die. The first material layer to the fifth material layer are made of polymer materials, the sixth material layer is made of coating materials, and the high-toughness polymer materials are selected according to requirements.

In the embodiment of the application, the annular cavity polymer optical fiber is produced by adopting a layered coextrusion technology, so that the complicated step of manufacturing the prefabricated rod is avoided, and meanwhile, the stack structural design of each layer is more controllable. The layering co-extrusion technology carries out layering feeding on each layering stack structure, reduces the internal stress of the material when the melt flows, and avoids the deformation of the layering stack structures caused by irregular bubbles generated during extrusion traction or extrusion cavity structures. The front end of the extrusion die is introduced with a temperature-controllable air chamber, the air pressure is adjusted by controlling the temperature of the air chamber, the air is continuously input into an axially extending hollow column by utilizing the pressure difference, the internal pressure is utilized to support the cavity structure, the internal stress of the material generated when the melt raw material is pulled to flow is counteracted, the cavity is extruded, and the size change is caused. The feeding flow of each layer is controlled by a metering pump, so that each laminated stack structure is ensured not to leak materials to generate bubbles or overflow materials to extrude the cavity structure.

The design of the layering co-extrusion die and the extrusion process ensure that each layering stack structure is tightly attached when being covered in the aspects of feeding flow, air pressure, temperature and die structure design, and no bubbles or gaps exist between interlayers. According to principle deduction, the annular cavity polymer optical fibers with different cavity size structures are designed, and the working wavelength window of the annular cavity polymer optical fibers can be changed. In production, the cavity size structure of the die is designed and processed differently, so that the annular cavity polymer optical fiber with the working wavelength in different windows can be produced.

The embodiment of the application provides a domestic and foreign unprecedented photonic band gap polymer optical fiber or Bragg polymer optical fiber layering co-extrusion die and a process thereof, which are used for analyzing two special polymer optical fibers from an optical fiber structure according to a photonic band gap principle and a Bragg reflection principle, establishing an annular cavity polymer optical fiber concept by combining with actual production and equipment conditions, and providing a layering co-extrusion production process aiming at the optical fiber with the novel structure.

According to the embodiment of the application, continuous extrusion production of the annular cavity polymer optical fiber can be realized, the annular cavity polymer optical fiber with excellent performance and stable structure is prepared, complicated and difficult process steps in a preform drawing production mode are avoided, the production difficulty is reduced, and the production efficiency is improved. Extrusion production does not need to process the prefabricated rod, and continuous extrusion production can be realized only by designing and processing a layered co-extrusion die. The layering coextrusion technology can monitor the stack structure in the fiber cladding in real time, adjust the technological parameters in time, and the production process is flexible and controllable.

The layered coextrusion die is used for realizing continuous extrusion type industrialized production of the annular cavity polymer optical fiber. In some embodiments, the optical fiber cladding has a stack structure with a periodically changing refractive index, and according to the photonic band gap theory and the bragg reflection principle, the optical fiber cladding can bind the light of a specific mode with a specific frequency to the central refractive index defect layer, namely the hollow core layer for propagation. From the photonic band gap theory and the Bragg reflection theory, the optical fibers with different stack structure sizes in the cladding can be applied to different working wavelengths. Therefore, the annular cavity polymer optical fiber with different structures can be produced by designing different moulds, so that the optical fiber has excellent light guide performance in the visible light wave band or even in the micro wave.

In some embodiments, according to the above theory, the annular cavity polymer optical fiber produced by the process provided by the application can radially bind the light with a specific frequency in the central hollow layer, reduce the absorption loss of the material and the nonlinear effect of the optical fiber, and has good light guiding performance in various wavelength working bands.

The layering co-extrusion process can realize continuous extrusion production of the annular cavity polymer optical fiber, ensure the stability of the structure and performance of the product, greatly improve the production efficiency and improve the price competitiveness of the product. The step of manufacturing the prefabricated rod is omitted, so that the optical fiber has more controllability in the production process, defects in the production process can be timely found and timely modified, and the production accident rate and the product reject ratio are reduced.

The embodiment of the application also provides a preparation method of the optical cable, which comprises the following steps: preparing a polymer optical fiber according to the method provided in the above examples; a protective jacket is disposed over the outer surface of the at least one polymer optical fiber to provide an optical cable. The optical fiber must be covered by several layers of protection structures before use, and the covered cable is called an optical cable.

Finally, it should be noted that: the above embodiments are only for illustrating the technical solution of the present invention, and are not limiting; the technical features of the above embodiments or in the different embodiments may also be combined within the idea of the invention, the steps may be implemented in any order, and there are many other variations of the different aspects of the invention as described above, which are not provided in detail for the sake of brevity; although the invention has been described in detail with reference to the foregoing embodiments, it will be understood by those of ordinary skill in the art that: the technical scheme described in the foregoing embodiments can be modified or some technical features thereof can be replaced by equivalents; such modifications and substitutions do not depart from the spirit of the invention.

Claims

1. The preparation method of the polymer optical fiber is characterized in that the polymer optical fiber comprises a core layer and a cladding layer, wherein the cladding layer comprises a plurality of layers of annular stack structures which are sequentially arranged from inside to outside along the radial direction of the optical fiber, and a plurality of cavities which are distributed at intervals are formed by stacking at least two layers of adjacent stack structures in the plurality of layers of stack structures;

the method comprises the following steps:

extruding a prefabricated stack structure corresponding to each layer of the stack structure layer by adopting a layered co-extrusion process, so as to obtain an optical fiber prefabricated member with a prefabricated cavity;

and drawing the optical fiber prefabricated member so that the prefabricated cavity corresponds to the cavity for forming the polymer optical fiber, thereby obtaining the polymer optical fiber.

2. The method of claim 1, wherein the core layer is a hollow core layer, the hollow core layer being void, the optical fiber preform further having a preformed hollow core layer;

the step of drawing the optical fiber preform so that the preform cavity corresponds to a cavity in which the polymer optical fiber is formed, thereby obtaining the polymer optical fiber specifically includes:

and drawing the optical fiber prefabricated member so that the prefabricated cavity and the prefabricated hollow layer respectively form a cavity and a hollow layer of the polymer optical fiber, thereby obtaining the polymer optical fiber.

3. The method of claim 1, wherein extruding each layer of the multilayer stack structure layer-by-layer using a layered co-extrusion process comprises:

and extruding each layer of the stack structure in the plurality of layers layer by layer according to the sequence from inside to outside by adopting a layered coextrusion process to obtain a prefabricated stack structure corresponding to the stack structure.

4. The method of claim 1, wherein the multilayer stack structure comprises an nth stack structure and an n+1 stack structure, wherein N is greater than or equal to 1 and N is a positive integer, the n+1 stack structure comprises an annular polymer layer and a plurality of support bars distributed on a side of the annular polymer layer adjacent to the nth stack structure, the cavity being disposed between two adjacent support bars;

the step of extruding each layer of the stack structure in the multilayer stack structure layer by adopting a layered coextrusion process according to the sequence from inside to outside comprises the following steps of:

when the Nth layer polymer melt enters an Nth layer runner of the layering co-extrusion die, an Nth layer prefabricated stack structure is formed;

When the Nth layer of prefabricated stacking structure moves to a feeding area of the N+1 layer of polymer melt along the fiber outlet direction, under the action of the layering coextrusion die, part of the N+1 layer of polymer melt covers the Nth layer of prefabricated stacking structure to form a plurality of supporting strips, and part of the N+1 layer of polymer forms an N+1 layer of annular polymer on one side of the supporting strips, which is far away from the Nth layer of prefabricated stacking structure;

the feeding area of the (N+1) th layer polymer melt is positioned at the front end of the fiber outlet direction relative to the feeding area of the (N) th layer polymer melt.

5. The method according to claim 1, wherein the method further comprises:

controlling the flow rate of each layer of polymer melt entering each runner of the layered co-extrusion die through a metering pump in the layered co-extrusion process;

wherein the flow rate of the polymer melt of each layer is positively correlated with the cross-sectional area of the annular stack structure of the corresponding layer.

6. The method of claim 1, wherein the optical fiber preform further comprises a coating layer disposed on a side of the cladding layer remote from the hollow core layer;

before the drawing process of the optical fiber preform, the method further comprises:

When the cladding layer moves to a feeding area of the coating layer polymer melt along the fiber outlet direction, the coating layer polymer melt forms the coating layer on the surface of the side, far away from the core layer, of the cladding layer;

the feeding area of the coating layer polymer melt is positioned at the front end of the fiber outlet direction relative to the feeding area of the cladding layer.

7. The method according to any one of claims 2-6, further comprising:

inputting a first gas into the prefabricated cavity in the process of drawing the optical fiber prefabricated member, and controlling the first air pressure of the first gas to be within a first preset air pressure range; and/or the number of the groups of groups,

and in the process of drawing the optical fiber prefabricated member, inputting a second gas into the hollow layer of the optical fiber prefabricated member, and controlling the second gas pressure of the second gas to be within a second preset gas pressure range.

8. The method according to claim 7, characterized in that it comprises in particular:

inputting a first gas into the prefabricated cavity in the process of drawing the optical fiber prefabricated member, 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 the number of the groups of groups,

And in the process of drawing the optical fiber prefabricated member, inputting a second gas into the hollow layer of the optical fiber prefabricated member, and adjusting the second air pressure by adjusting the temperature of the second gas so as to enable the second air pressure to be within a second preset air pressure range.

9. The method according to claim 8, characterized in that it comprises in particular:

adjusting the temperature of the first gas by adjusting the temperature of the layered coextrusion die, so that the first gas pressure is controlled within a first preset pressure range; and/or the number of the groups of groups,

and adjusting the temperature of the second gas by adjusting the temperature of the layered coextrusion die, so that the second gas pressure is controlled within a second preset pressure range.

10. A method of making an optical cable, the method comprising:

preparing a polymer optical fiber according to the method of any one of claims 1-9;

and arranging a protective sleeve on the outer surface of at least one polymer optical fiber to obtain the optical cable.