Device and method for preparing optical fiber preform

Abstract

The invention relates to the technical field of optical fibers, in particular to a preparation device and method of an optical fiber preform. The preparation device of the optical fiber preform comprises a heating piece and a pressure regulating structure, wherein the heating piece is used for heating the sleeve. The pressure regulating structure comprises an air supply assembly and an exhaust assembly, the air supply assembly is used for communicating with the first end of the sleeve, and the exhaust assembly is used for communicating with the second end of the sleeve; the air supply assembly and the exhaust assembly are used for adjusting the pressure value in the sleeve together so as to adjust the inner diameter of the sleeve together with the heating piece. According to the preparation device and method of the optical fiber preform, the inner diameter of the sleeve can be changed to control the gap between the sleeve and the core rod, so that the quality of the optical fiber preform is improved.

Description

Technical Field

[0001] This application relates to the field of optical fiber technology, and in particular to an apparatus and method for preparing optical fiber preforms. Background Technology

[0002] An optical fiber preform is a high-purity glass rod made of high-purity silicon dioxide and doped with other materials to adjust its optical properties. The optical fiber preform is the "matrix" for manufacturing optical fibers; by heating and stretching the preform, optical fibers as thin as a hair can be drawn out.

[0003] In related technologies, during the fabrication of optical fiber preforms, a core rod is inserted into a sleeve, and both the core rod and the sleeve are heated to cause the sleeve to collapse inward and enclose the core rod, thus forming a solid optical fiber preform. To meet the needs of different optical fiber applications, core rods of different diameters are used.

[0004] However, since the dimensions of the ferrule are relatively fixed, if the diameter of the core rod is too small, the gap between the inner wall of the ferrule and the core rod will be large, leading to eccentricity issues after the ferrule is fused together. Conversely, if the diameter of the core rod is too large, the gap between the inner wall of the ferrule and the core rod will be small, making it easier to scratch the core rod. This, in turn, affects the quality of the optical fiber preform. Summary of the Invention

[0005] This application provides an apparatus and method for preparing optical fiber preforms, which can change the inner diameter of the sleeve to control the gap between the sleeve and the core rod, thereby improving the quality of the optical fiber preforms.

[0006] In a first aspect, this application provides an apparatus for preparing an optical fiber preform, including a heating element and a voltage regulating structure, wherein the heating element is used to heat the sleeve.

[0007] The pressure regulating structure includes an air supply component and an exhaust component. The air supply component is used to connect to the first end of the sleeve, and the exhaust component is used to connect to the second end of the sleeve. The air supply component and the exhaust component are used together to regulate the internal pressure value of the sleeve, so as to adjust the inner diameter of the sleeve together with the heating element.

[0008] In one possible implementation, the optical fiber preform fabrication apparatus provided in this application includes an air supply component comprising an air supply element and an air supply pipe, wherein the air supply element is connected to a first end via the air supply pipe for supplying air to the sleeve.

[0009] The exhaust assembly includes an exhaust pump and an exhaust pipe, the exhaust pump being connected to the second end via the exhaust pipe for supplying exhaust gas to the sleeve.

[0010] In one possible implementation, the optical fiber preform fabrication apparatus provided in this application further includes an air supply valve in the air supply component, the air supply valve being connected to the air supply pipe and the first end.

[0011] The exhaust assembly also includes an exhaust valve, which connects the exhaust pipe to the second end.

[0012] In one possible implementation, the optical fiber preform fabrication apparatus provided in this application further includes a first pressure measuring element connected to a gas supply valve to detect the pressure value of the gas supply valve.

[0013] The exhaust assembly also includes a second pressure sensor, which is connected to the exhaust valve to detect the pressure value of the exhaust valve.

[0014] In one possible implementation, the optical fiber preform fabrication apparatus provided in this application further includes an insulation cavity and a detection component. The insulation cavity is used to place the sleeve, and the heating element is slidably disposed within the insulation cavity.

[0015] The detection assembly includes a first detection element and a second detection element, both of which are disposed within the insulation cavity.

[0016] The first testing element is used to detect the inner diameter of the sleeve, and the second testing element is used to detect the temperature inside the insulation cavity.

[0017] In one possible implementation, the optical fiber preform fabrication apparatus provided in this application further includes a sliding assembly, which includes a guide rail and at least one base slidably disposed on the guide rail.

[0018] The guide rail is set inside the insulation cavity, and the first detection element, the second detection element, and the heating element are all set on the base.

[0019] In one possible implementation, the optical fiber preform fabrication apparatus provided in this application further includes a clamping member disposed within an insulation cavity, the clamping member being used to clamp the sleeve.

[0020] Secondly, this application also provides a method for preparing an optical fiber preform, using any of the optical fiber preform preparation apparatuses provided in the first aspect above. The optical fiber preform preparation apparatus includes a heating element and a voltage regulating structure.

[0021] Methods for preparing optical fiber preforms include:

[0022] A heating element is used to heat the sleeve, and a pressure regulating structure is used for the air supply and exhaust components to jointly regulate the internal pressure of the sleeve, so as to adjust the inner diameter of the sleeve together with the heating element.

[0023] In one possible implementation, the fiber optic preform fabrication method provided in this application employs a pressure-regulating gas supply assembly and an exhaust assembly to jointly adjust the internal pressure value of the sleeve, thereby adjusting the inner diameter of the sleeve in conjunction with the heating element, including:

[0024] When the positive difference between the inner diameter of the sleeve and the diameter of the mandrel to be inserted is greater than the first preset value, the air supply and exhaust components with the pressure regulating structure reduce the internal pressure value of the sleeve by the first preset pressure difference reduction, so as to reduce the inner diameter of the sleeve by the first preset reduction amount.

[0025] When the inner diameter of the casing is reduced by a first preset reduction amount, the internal pressure value of the casing is reduced by a second preset pressure difference decrease, so that the inner diameter of the casing is reduced by a second preset reduction amount.

[0026] Alternatively, when the positive difference between the inner diameter of the sleeve and the diameter of the mandrel to be inserted is less than the second preset value, the air supply and exhaust components with the pressure regulating structure are used to increase the internal pressure value of the sleeve by the first preset pressure difference increase, so as to expand the inner diameter of the sleeve by the first preset expansion amount.

[0027] When the inner diameter of the casing is increased by the first preset expansion amount, the internal pressure value of the casing is increased by the second preset pressure difference increase, so that the inner diameter of the casing is increased by the second preset expansion amount.

[0028] In one possible implementation, the fiber preform fabrication method provided in this application has a first preset differential pressure drop greater than or equal to 2 MPa and less than or equal to 5 MPa.

[0029] The second preset differential pressure drop is greater than or equal to 6 MPa and less than or equal to 10 MPa.

[0030] The first preset pressure difference increase is greater than or equal to 6 MPa and less than or equal to 10 MPa.

[0031] The second preset pressure difference increase is greater than or equal to 2 MPa and less than or equal to 5 MPa.

[0032] This application provides an apparatus and method for fabricating optical fiber preforms. The apparatus includes a heating element and a pressure regulating structure. The heating element heats the sleeve. The pressure regulating structure includes a gas supply component and a gas exhaust component. The gas supply component is connected to a first end of the sleeve, and the gas exhaust component is connected to a second end of the sleeve. The gas supply component and the gas exhaust component work together to regulate the internal pressure of the sleeve, thereby adjusting the inner diameter of the sleeve in conjunction with the heating element. This controls the gap between the sleeve and the core rod, improving the quality of the optical fiber preform. Attached Figure Description

[0033] To more clearly illustrate the technical solutions in the embodiments of this application or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are some embodiments of this application. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0034] Figure 1 A schematic diagram of the structure of the optical fiber preform fabrication apparatus provided in the embodiments of this application;

[0035] Figure 2 The axial distribution diagram of the cladding / core ratio of the optical fiber preform prepared in Example 4;

[0036] Figure 3 The axial distribution of the zero-dispersion wavelength of the optical fiber preform prepared in Example 4 is shown.

[0037] Figure 4 This is a graph showing the changing trends of pressure and rod diameter during the fabrication of the optical fiber preform in Example 4.

[0038] Figure 5 The axial distribution diagram of the cladding / core ratio of the optical fiber preform prepared in Example 5;

[0039] Figure 6 The axial distribution diagram of the eccentricity of the optical fiber preform prepared in Example 5 is shown.

[0040] Figure 7 The axial distribution of the zero-dispersion wavelength of the optical fiber preform prepared in Example 5 is shown.

[0041] Figure 8 A diagram showing the cladding / core ratio axial distribution of the optical fiber preforms prepared in Example 1 and Comparative Example 1;

[0042] Figure 9 The image shows the cladding / core ratio axial distribution of the optical fiber preforms prepared in Example 3 and Comparative Example 3.

[0043] Explanation of reference numerals in the attached figures:

[0044] 10-Sleeve; 11-First end; 12-Second end;

[0045] 100 - Insulated cavity;

[0046] 200 - Heating element; 210 - Induction furnace; 220 - Blowtorch;

[0047] 300-Voltage Regulating Structure;

[0048] 310 - Gas supply assembly; 311 - Gas supply component; 312 - Gas supply pipe fitting; 313 - Gas supply valve; 314 - First pressure measuring component;

[0049] 320 - Exhaust assembly; 321 - Exhaust pump; 322 - Exhaust pipe fitting; 323 - Exhaust valve; 324 - Second pressure measuring element;

[0050] 400 - Detection component; 410 - First detection element; 420 - Second detection element;

[0051] 500 - Sliding assembly; 510 - Guide rail; 520 - Base;

[0052] 600-Clamping component;

[0053] 700 - Transfer Platform.

[0054] The accompanying drawings illustrate specific embodiments of this application, which will be described in more detail below. These drawings and descriptions are not intended to limit the scope of the concept in any way, but rather to illustrate the concept of this application to those skilled in the art through reference to particular embodiments. Detailed Implementation

[0055] First, those skilled in the art should understand that these embodiments are merely for explaining the technical principles of this application and are not intended to limit the scope of protection of this application. Those skilled in the art can make adjustments as needed to adapt to specific application scenarios.

[0056] Secondly, it should be noted that, in the description of this application, unless otherwise expressly specified and limited, the terms "installation," "connection," and "linking" should be interpreted broadly. For example, they can refer to a fixed connection, an indirect connection through an intermediate medium, or the internal communication of two components or the interaction between two components. Those skilled in the art can understand the specific meaning of the above terms in this application according to the specific circumstances.

[0057] Furthermore, it should be noted that in the description of this application, the terms "upper," "lower," "front," "back," "vertical," "horizontal," "top," "bottom," "inner," and "outer," etc., indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings. They are used only for the convenience of describing this application and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation. Therefore, they should not be construed as limitations on this application.

[0058] Furthermore, the terms "first" and "second" are used for descriptive purposes only and should not be construed as indicating or implying relative importance or implicitly specifying the number of technical features indicated. Thus, a feature defined as "first" or "second" may explicitly or implicitly include one or more of that feature. In the description of this application, unless otherwise stated, "a plurality of" means two or more.

[0059] As illustrated in the background section, existing technologies employ core rods of varying diameters to meet the demands of different optical fiber applications. Since producing ferrules of different sizes increases process complexity and management costs, the ferrule dimensions are relatively fixed. If the core rod diameter is too small, the gap between the inner wall of the ferrule and the core rod is large, leading to eccentricity issues after the ferrule is fused together. Conversely, if the core rod diameter is too large, the gap between the inner wall of the ferrule and the core rod is small, making it easier to scratch the core rod. This, in turn, affects the quality of the optical fiber preform.

[0060] Based on this, the optical fiber preform fabrication apparatus and method provided in this application include a heating element and a pressure regulating structure. The heating element is used to heat the sleeve. The pressure regulating structure includes a gas supply component and a gas exhaust component. The gas supply component is connected to a first end of the sleeve, and the gas exhaust component is connected to a second end of the sleeve. The gas supply component and the gas exhaust component are used to jointly regulate the internal pressure value of the sleeve, thereby adjusting the inner diameter of the sleeve in conjunction with the heating element, thus controlling the gap between the sleeve and the core rod and improving the quality of the optical fiber preform.

[0061] To make the objectives, technical solutions, and advantages of this application clearer, the technical solutions in the embodiments of this application will be described in more detail below with reference to the accompanying drawings. In the drawings, the same or similar reference numerals denote the same or similar components or components having the same or similar functions throughout. The described embodiments are some, but not all, of the embodiments of this application. The embodiments described below with reference to the accompanying drawings are exemplary and intended to explain this application, and should not be construed as limiting this application. All other embodiments obtained by those skilled in the art based on the embodiments of this application without creative effort are within the scope of protection of this application.

[0062] Reference Figure 1 As shown, this application provides an apparatus for preparing an optical fiber preform, including a heating element 200 and a voltage regulating structure 300, wherein the heating element 200 is used to heat the sleeve 10.

[0063] The pressure regulating structure 300 includes an air supply component 310 and an exhaust component 320. The air supply component 310 is used to communicate with the first end 11 of the sleeve 10, and the exhaust component 320 is used to communicate with the second end 12 of the sleeve 10. The air supply component 310 and the exhaust component 320 are used to jointly regulate the internal pressure value of the sleeve 10, so as to jointly regulate the inner diameter of the sleeve 10 with the heating element 200.

[0064] For example, the heating element 200 can be a graphite furnace (not shown in the figure), an induction furnace 210, or a blowtorch 220 (i.e., an oxyhydrogen flame lamp or a methane flame lamp), and this application embodiment does not impose too many restrictions on this.

[0065] It should be noted that the sleeve 10 is made of high-purity quartz. Quartz will change from a rigid solid state to a viscoelastic state (i.e., a softened state) at high temperatures. At this time, the material fluidity is enhanced, and it is easy to undergo plastic deformation under the action of pressure difference.

[0066] The air supply assembly 310 is connected to the first end 11 of the sleeve 10 and is used to supply air to the sleeve 10. The exhaust assembly 320 is connected to the second end 12 of the sleeve 10 and is used to exhaust air from the sleeve 10. Therefore, by controlling the air supply volume of the air supply assembly 310 and the exhaust volume of the exhaust assembly 320, the internal pressure of the sleeve 10 can be adjusted. Since the external pressure of the sleeve 10 is equal to atmospheric pressure, meaning the external pressure of the sleeve 10 remains constant, changing the internal pressure of the sleeve 10 changes the pressure difference between the inside and outside of the sleeve 10. This pressure difference causes the sleeve 10, which softens at high temperatures, to deform, thereby changing the inner and outer diameters of the sleeve 10.

[0067] When the gap between the inner wall of the sleeve 10 and the mandrel to be inserted is large, by controlling the air supply of the air supply component 310 to be less than the exhaust of the exhaust component 320, the internal pressure of the sleeve 10 can be reduced. Thus, the internal pressure of the sleeve 10 is less than the external pressure of the sleeve 10. The external pressure squeezes the sleeve 10, causing its diameter to shrink and its wall thickness to increase, thereby achieving tube shrinkage and reducing the problem of eccentricity.

[0068] When the gap between the inner wall of the sleeve 10 and the mandrel to be inserted is small, by controlling the air supply volume of the air supply component 310 to be greater than the exhaust volume of the exhaust component 320, the internal pressure value of the sleeve 10 is increased. The internal pressure value of the sleeve 10 is greater than the external pressure value of the sleeve 10. The internal pressure pushes the inner wall of the sleeve 10 outward, resulting in an increase in the diameter of the sleeve 10 and a decrease in the wall thickness, thereby expanding the tube and reducing the possibility of mandrel scratches.

[0069] Thus, the optical fiber preform fabrication apparatus provided in this application embodiment can change the inner diameter of the sleeve 10 to control the gap between the sleeve 10 and the core rod, thereby improving the quality of the optical fiber preform.

[0070] It should be noted that by controlling the amount of gas supplied by the gas supply component 310 and the amount of gas discharged by the exhaust component 320, the gas supply component 310 and the exhaust component 320 can jointly adjust the internal pressure value of the sleeve 10. Compared with the gas supply component 310 or the exhaust component 320 adjusting the internal pressure value of the sleeve 10 alone, the continuous injection and discharge of gas into the sleeve 10 can make the sleeve 10 more uniformly stressed and reduce the possibility of geometric non-uniformity in the sleeve 10.

[0071] It should also be noted that when the diameter of the core rod is larger than the inner diameter of the sleeve 10, the core rod cannot be inserted into the sleeve 10. In the prior art, a drill bit is required to enlarge the inner diameter of the sleeve 10, which results in low work efficiency. The optical fiber preform fabrication apparatus provided in this application embodiment can change the inner diameter of the sleeve 10 so that the inner diameter of the sleeve 10 is larger than the diameter of the core rod, thereby improving work efficiency.

[0072] In some embodiments, refer to Figure 1 As shown, the gas supply assembly 310 includes a gas supply component 311 and a gas supply pipe 312. The gas supply component 311 is connected to the first end 11 through the gas supply pipe 312 for supplying gas to the sleeve 10.

[0073] The exhaust assembly 320 includes an exhaust pump 321 and an exhaust pipe 322. The exhaust pump 321 is connected to the second end 12 through the exhaust pipe 322 for supplying exhaust to the sleeve 10.

[0074] Specifically, one end of the gas supply pipe 312 is connected to the gas supply component 311, and the other end of the gas supply pipe 312 is connected to the first end 11 of the sleeve 10. The gas supply component 311 injects gas into the sleeve 10 through the gas supply pipe 312. One end of the exhaust pipe 322 is connected to the second end 12 of the sleeve 10, and the other end of the exhaust pipe 322 is connected to the exhaust pump 321. The gas inside the sleeve 10 is discharged by the exhaust pump 321 through the exhaust pipe 322. In this way, by controlling the gas supply volume of the gas supply component 311 and the exhaust volume of the exhaust pump 321, the internal pressure value of the sleeve 10 can be adjusted.

[0075] For example, the air supply component 311 can be an air cylinder, an air compressor or a booster pump, and the air supply pipe 312 and the exhaust pipe 322 can both be metal pipes or pipes of other materials. This application embodiment does not impose too many restrictions on this.

[0076] In some embodiments, refer to Figure 1 As shown, the gas supply assembly 310 also includes a gas supply valve 313, which connects the gas supply pipe 312 to the first end 11.

[0077] The exhaust assembly 320 also includes an exhaust valve 323, which connects the exhaust pipe 322 to the second end 12.

[0078] It should be noted that by setting the air supply valve 313 and the exhaust valve 323, the air supply valve 313 can control the air supply of the sleeve 10, and the exhaust valve 323 can control the exhaust of the sleeve 10. Thus, the air supply valve 313 and the exhaust valve 323 jointly regulate the internal pressure value of the sleeve 10.

[0079] It should also be noted that the air supply valve 313 and the air exhaust valve 323 can gradually reduce or increase the internal pressure value of the sleeve 10, thereby achieving gradual pressure reduction or increase, that is, staged pressure regulation. This can avoid local stress concentration, reduce the shape deviation of the sleeve 10, and reduce the possibility of geometric inhomogeneity in the sleeve 10.

[0080] For example, both the air supply valve 313 and the exhaust valve 323 can be solenoid valves or manual ball valves, and this application embodiment does not impose too many restrictions on this.

[0081] In some embodiments, refer to Figure 1 As shown, the air supply assembly 310 also includes a first pressure measuring element 314, which is connected to the air supply valve 313 to detect the pressure value of the air supply valve 313.

[0082] The exhaust assembly 320 also includes a second pressure measuring element 324, which is connected to the exhaust valve 323 to detect the pressure value of the exhaust valve 323.

[0083] Specifically, the pressure of the air supply valve 313 is monitored in real time by the first pressure measuring element 314, and the pressure of the exhaust valve 323 is detected synchronously by the second pressure measuring element 324. The first pressure measuring element 314 and the second pressure measuring element 324 work together to accurately adjust the internal pressure value of the sleeve 10, thereby ensuring accurate adjustment of the inner diameter of the sleeve 10.

[0084] For example, the first pressure measuring element 314 and the second pressure measuring element 324 can both be connected to a negative pressure gauge.

[0085] In some embodiments, refer to Figure 1 As shown, the optical fiber preform fabrication device also includes a heat insulation cavity 100 and a detection component 400. The heat insulation cavity 100 is used to place the sleeve 10, and the heating element 200 is slidably disposed in the heat insulation cavity 100.

[0086] The detection component 400 includes a first detection element 410 and a second detection element 420, both of which are disposed within the heat-insulating cavity 100.

[0087] The first detection element 410 is used to detect the inner diameter of the sleeve 10, and the second detection element 420 is used to detect the temperature inside the insulation cavity 100.

[0088] Understandably, the insulation cavity 100 is used to maintain a stable temperature environment, ensuring that the sleeve 10 is heated evenly during the heating process, reducing heat loss, thereby improving process accuracy and manufacturing efficiency. For example, through holes can be provided on opposite sides of the insulation cavity 100, through which the sleeve 10 is inserted into the insulation cavity 100, and a sealing ring can be provided between the sleeve 10 and the through hole for sealing.

[0089] The heating element 200 adopts a sliding design, which can improve the uniformity of heating and prevent stress concentration caused by uneven heat conduction.

[0090] Specifically, the first detection element 410 monitors the changes in the inner and outer diameters of the sleeve 10 in real time to ensure that the dimensions of the shrinking or expanding tube meet the process requirements. The second detection element 420 monitors the actual temperature of the insulation cavity 100 to ensure the uniformity of heating and prevent local overheating or underheating.

[0091] For example, the first detection element 410 can be an infrared diameter gauge, and the second detection element 420 can be an infrared thermometer.

[0092] In some embodiments, refer to Figure 1 As shown, the optical fiber preform fabrication apparatus further includes a sliding component 500, which includes a guide rail 510 and at least one base 520 slidably disposed on the guide rail 510.

[0093] The guide rail 510 is set inside the insulation cavity 100, and the first detection element 410, the second detection element 420 and the heating element 200 are all set on the base 520.

[0094] It should be noted that during the heating process, the heating temperature and deformation may vary at different locations of the sleeve 10. The base 520 drives the first detection element 410, the second detection element 420, and the heating element 200 to slide relative to the guide rail 510, achieving segmented and precise control. Specifically, the first detection element 410 monitors the inner diameter of the sleeve 10 in real time, the second detection element 420 provides feedback on local temperature, and the heating element 200 ensures that each segment of the sleeve 10 is heated uniformly and meets dimensional standards. At the same time, it eliminates blind spots in fixed detection, improving process consistency and production efficiency.

[0095] For example, a groove matching the guide rail 510 can be provided on the base 520, and the base 520 is slidably connected to the guide rail 510 through the groove. The first detection element 410, the second detection element 420 and the heating element 200 can be connected to the base 520 by welding, bolting or other means, and the embodiments of this application do not impose too many restrictions on this.

[0096] In some embodiments, refer to Figure 1 As shown, the optical fiber preform preparation device also includes a clamping member 600, which is disposed in the heat insulation cavity 100 and is used to clamp the sleeve 10.

[0097] Understandably, the clamping member 600 clamps the sleeve 10, which can fix the sleeve 10 and ensure that it maintains accurate positioning during the shrinking or expanding process, preventing the sleeve 10 from shifting.

[0098] In a specific implementation, the clamping component 600 can be a chuck. The chuck can be connected to the inner wall of the insulation cavity 100 via a flange. The chuck clamps the sleeve 10 and can apply torque to the sleeve 10 to make the sleeve 10 rotate along its own axis, thereby making the sleeve 10 more evenly heated. It should be noted that the chuck is a technology well known to those skilled in the art and will not be described in detail here.

[0099] Reference Figure 1 As shown, this application also provides a method for preparing an optical fiber preform, using the above-mentioned optical fiber preform preparation apparatus, which includes a heating element 200 and a voltage regulating structure 300.

[0100] Methods for preparing optical fiber preforms include:

[0101] The heating element 200 is used to heat the sleeve 10, and the air supply component 310 and the exhaust component 320 of the pressure regulating structure 300 are used to jointly adjust the internal pressure value of the sleeve 10, so as to adjust the inner diameter of the sleeve 10 together with the heating element 200.

[0102] It should be noted that the sleeve 10 can be placed inside the insulation cavity 100, and the sleeve 10 can be fixed by the clamping member 600 to prevent the sleeve 10 from shifting during processing and to ensure the geometric symmetry of the optical fiber preform.

[0103] Dry and purified gas can be introduced into the sleeve 10, and the sleeve 10 can be preheated by a heating element 200 at a first preset temperature greater than or equal to 300°C and less than or equal to 500°C. The moving speed of the heating element 200 along the axial direction of the sleeve 10 is greater than or equal to 30 mm / min and less than or equal to 100 mm / min. It should be noted that introducing dry and purified gas (such as high-purity nitrogen or argon) into the sleeve 10 can remove impurities inside the sleeve 10, and preheating the sleeve 10 can remove residual moisture inside the sleeve 10. This prevents moisture and impurities from reacting with the quartz glass at high temperatures to produce hydroxyl groups or bubbles, thereby reducing the transmission loss of the optical fiber. A first preset temperature greater than or equal to 300°C can ensure that the sleeve 10 is fully heated and remove residual moisture inside the sleeve 10. A first preset temperature less than or equal to 500°C can prevent the sleeve 10 from softening prematurely during preheating. The moving speed of the heating element 200 is greater than or equal to 30 mm / min, which ensures that the quartz sleeve 10 is heated evenly and avoids local overheating that could lead to material volatilization or deformation. The moving speed of the heating element 200 is less than or equal to 100 mm / min, which can prevent insufficient heating and avoid thermal stress cracks in the sleeve 10 due to excessive temperature gradient.

[0104] Next, the sleeve 10 can be heated by the heating element 200 at a second preset temperature, which is greater than or equal to 1800°C and less than or equal to 2000°C. The moving speed of the heating element 200 along the axial direction of the sleeve 10 is greater than or equal to 3 mm / min and less than or equal to 20 mm / min.

[0105] It should be noted that a second preset temperature greater than or equal to 1800°C can soften the sleeve 10, allowing it to undergo effective plastic flow. A second preset temperature less than or equal to 2000°C can prevent the decomposition and volatilization of the quartz material in the sleeve 10. Exemplarily, the second preset temperature can be 1800°C, 1900°C, or 2000°C, or any temperature between 1800°C and 2000°C; this application embodiment does not impose excessive limitations on this.

[0106] The moving speed of the heating element 200 determines the residence time of the sleeve 10 in the high-temperature zone. A moving speed of the heating element 200 greater than or equal to 3 mm / min can prevent local overheating and material decomposition. A moving speed of the heating element 200 less than or equal to 20 mm / min can ensure the softening of the quartz material in the sleeve 10.

[0107] It should be noted that the sleeve 10 changes from a rigid solid to a viscoelastic state at high temperatures. At this point, the material's fluidity increases, making it prone to plastic deformation under pressure differential. Furthermore, since the external pressure of the sleeve 10 is equal to atmospheric pressure, meaning the external pressure of the sleeve 10 remains constant, the pressure difference between the inside and outside of the sleeve 10 can be changed by jointly adjusting the internal pressure value of the sleeve 10 through the air supply assembly 310 and the exhaust assembly 320. This pressure difference drives the softened sleeve 10 at high temperatures to deform, thereby changing the outer and inner diameters of the sleeve 10.

[0108] Thus, the fiber optic preform preparation method provided in this application embodiment can change the size of the sleeve 10 to control the gap between the sleeve 10 and the core rod, thereby improving the quality of the fiber optic preform.

[0109] In some embodiments, refer to Figure 1 As shown, the air supply assembly 310 and exhaust assembly 320 of the pressure regulating structure 300 jointly regulate the internal pressure value of the sleeve 10, so as to jointly regulate the inner diameter of the sleeve 10 with the heating element 200, including:

[0110] When the positive difference between the inner diameter of the sleeve 10 and the diameter of the mandrel to be inserted is greater than the first preset value, the air supply component 310 and the exhaust component 320 of the pressure regulating structure 300 are used to reduce the internal pressure value of the sleeve 10 by the first preset pressure difference reduction, so as to reduce the inner diameter of the sleeve 10 by the first preset reduction amount.

[0111] When the inner diameter of the sleeve 10 is reduced by a first preset reduction amount, the pressure value inside the sleeve 10 is reduced by a second preset pressure difference reduction amount, so that the inner diameter of the sleeve 10 is reduced by a second preset reduction amount.

[0112] Alternatively, when the positive difference between the inner diameter of the sleeve 10 and the diameter of the mandrel to be inserted is less than the second preset value, the air supply component 310 and the exhaust component 320 of the pressure regulating structure 300 are used to increase the internal pressure value of the sleeve 10 by the first preset pressure difference increase, so as to expand the inner diameter of the sleeve 10 by the first preset expansion amount.

[0113] When the inner diameter of the sleeve 10 is increased by the first preset expansion amount, the internal pressure value of the sleeve 10 is increased by the second preset pressure difference increase, so that the inner diameter of the sleeve 10 is increased by the second preset expansion amount.

[0114] It should be noted that, in the initial state, the pressure inside the sleeve 10 is equal to the pressure outside, both of which are equal to atmospheric pressure.

[0115] When the positive difference between the inner diameter of the sleeve 10 and the diameter of the mandrel to be inserted is greater than a first preset value, that is, when the gap between the inner wall of the sleeve 10 and the mandrel is large, the pressure inside the sleeve 10 is reduced so that the pressure inside the sleeve 10 is less than the pressure outside the sleeve 10. The external pressure squeezes the sleeve 10, causing its diameter to shrink and its wall thickness to increase, thereby achieving tube shrinkage. This ensures that the positive difference between the inner diameter of the sleeve 10 and the diameter of the mandrel to be inserted is less than or equal to the first preset value (and greater than or equal to a second preset value). For example, the first preset value can be 3 mm. When the positive difference between the inner diameter of the sleeve 10 and the diameter of the mandrel to be inserted is less than or equal to the first preset value, that is, when the mandrel is inserted into the sleeve 10, the gap between the inner wall of the sleeve 10 and the mandrel is less than or equal to 1.5 mm, which can reduce the problem of eccentricity.

[0116] During the tube shrinking process, the initial wall of the sleeve 10 is relatively thin, making it more susceptible to plastic deformation. A smaller pressure differential reduction allows the sleeve 10 to shrink evenly and slowly, avoiding wrinkles or uneven wall thickness caused by localized stress concentration. When the inner diameter of the sleeve 10 decreases by a first preset reduction amount, the wall thickness of the sleeve 10 increases. Increasing the pressure differential reduction overcomes the deformation resistance caused by the increased wall thickness, ensuring uniform overall deformation. This staged pressure differential control method balances material flowability and forming force, reducing geometric inhomogeneities (such as localized depressions or bulges) caused by sudden changes in deformation rate, thereby ensuring that the shrunken sleeve 10 has consistent wall thickness and roundness. If the sum of the first preset reduction amount and the second preset reduction amount is the total preset reduction amount, for example, the first preset reduction amount can be 25% to 50% of the total preset reduction amount.

[0117] When the positive difference between the inner diameter of the sleeve 10 and the diameter of the mandrel to be inserted is less than a second preset value, that is, the gap between the inner wall of the sleeve 10 and the mandrel is small. Increasing the internal pressure value of the sleeve 10, making the internal pressure value of the sleeve 10 greater than the external pressure value of the sleeve 10, the internal pressure pushes the inner wall of the sleeve 10 outward, causing the diameter of the sleeve 10 to increase and the wall thickness to decrease, thereby expanding the tube so that the positive difference between the inner diameter of the sleeve 10 and the diameter of the mandrel to be inserted is greater than or equal to the second preset value. For example, the second preset value can be 1 mm. The positive difference between the inner diameter of the sleeve 10 and the diameter of the mandrel to be inserted is greater than or equal to the second preset value (and less than or equal to the first preset value), that is, when the mandrel is inserted into the sleeve 10, the gap between the inner wall of the sleeve 10 and the mandrel is greater than or equal to 0.5 mm, which can reduce the possibility of mandrel scratching.

[0118] During the expansion process, the initial wall thickness of the sleeve 10 is relatively thick, requiring a larger pressure differential reduction to overcome the initial yield strength of the material, enabling the sleeve 10 to quickly enter the plastic deformation stage and avoiding uneven expansion due to insufficient local deformation. When the inner diameter of the sleeve 10 increases by the first preset expansion amount, the wall thickness of the sleeve 10 decreases. Reducing the pressure differential reduction can prevent excessive deformation or cracking caused by the decrease in material strength due to wall thinning. This staged pressure differential control method can balance the deformation rate and stability of the material, reduce geometric defects (such as local bulging or necking) caused by uneven stress distribution, thereby ensuring that the sleeve 10 has a uniform wall thickness and regular shape after expansion. If the sum of the first preset expansion amount and the second preset expansion amount is the total preset expansion amount, for example, the first preset expansion amount can be 50% to 75% of the total preset expansion amount.

[0119] In some embodiments, the first preset differential pressure drop is greater than or equal to 2 MPa and less than or equal to 5 MPa.

[0120] The second preset differential pressure drop is greater than or equal to 6 MPa and less than or equal to 10 MPa.

[0121] The first preset pressure difference increase is greater than or equal to 6 MPa and less than or equal to 10 MPa.

[0122] The second preset pressure difference increase is greater than or equal to 2 MPa and less than or equal to 5 MPa.

[0123] It should be noted that a first preset pressure difference reduction greater than or equal to 2 MPa can ensure that the sleeve 10 deforms slowly and uniformly during the initial shrinkage; a first preset pressure difference reduction less than or equal to 5 MPa can prevent stress concentration or cracks from occurring in the sleeve 10 due to excessively rapid deformation.

[0124] The second preset pressure differential drop is greater than or equal to 6 MPa, which can ensure sufficient pressure to overcome the deformation resistance caused by the increase in wall thickness and allow the tube shrinkage to continue; the second preset pressure differential drop is less than or equal to 10 MPa, which can avoid excessive thinning or rupture of the tube wall due to a sudden increase in pressure.

[0125] It should also be noted that a first preset pressure difference increase of 6 MPa ensures sufficient pressure in the initial stage of expansion to allow the casing 10 to uniformly enter the plastic deformation stage, avoiding local deformation lag or uneven expansion due to insufficient pressure. A first preset pressure difference increase of 10 MPa prevents excessive pressure from causing the material to flow too quickly, leading to excessive thinning or rupture in some areas.

[0126] A second preset pressure differential increase of 2 MPa or more can maintain a stable deformation rate and prevent tube expansion from stalling or rebounding due to a sudden drop in pressure. A second preset pressure differential increase of 5 MPa or less can prevent material instability or fracture caused by excessive pressure when the wall thickness is thin.

[0127] In some embodiments, after heating the sleeve 10 with the heating element 200 and adjusting the internal pressure value of the sleeve 10 together with the gas supply component 310 and the exhaust component 320 of the pressure regulating structure 300 to adjust the inner diameter of the sleeve 10 together with the heating element 200, the method for preparing the optical fiber preform further includes:

[0128] Insert the mandrel to be inserted into the sleeve 10 and close the sleeve 10 and the mandrel together.

[0129] Specifically, a vacuum is drawn into the gap between the mandrel and the sleeve 10, and a heating element 200 is used to close the sleeve 10 and the mandrel together at a third preset temperature, which is greater than or equal to 1900°C and less than or equal to 2100°C.

[0130] The moving speed of the heating element 200 along the axial direction of the sleeve 10 is greater than or equal to 3 mm / min and less than or equal to 10 mm / min.

[0131] It should be noted that the optical fiber preform fabrication apparatus provided in this application may further include a transfer platform 700, with a gas supply assembly 310 mounted on the transfer platform 700. After adjusting the inner diameter of the sleeve 10, the gas supply assembly 310 can be moved using the transfer platform 700 to expose the first end 11 of the sleeve 10. The core rod is then inserted into the center of the sleeve 10 through the first end 11. A sealing element can be used to seal the gap between the first end 11 of the sleeve 10 and the end of the core rod, ensuring that the core rod and the sleeve 10 are coaxial during sealing. Then, a vacuum is drawn into the gap between the core rod and the sleeve 10 to completely eliminate the gas between the core rod and the sleeve 10, allowing the sleeve 10 and the core rod to fuse tightly.

[0132] It should be noted that during the fusion of the sleeve 10, the sleeve 10 contracts inward under the action of surface tension, closely fitting with the core rod, thus fusing together with the core rod as one unit. The core rod (high refractive index, such as germanium-doped quartz) and the sleeve 10 (low refractive index, such as pure quartz or fluorine-doped quartz) are combined, with the core rod inserted into the sleeve 10 to form the refractive index difference required for optical fiber transmission of optical signals.

[0133] Understandably, a third preset temperature greater than or equal to 1900°C ensures that the sleeve 10 reaches a viscoelastic state. A third preset temperature less than or equal to 2100°C prevents quartz volatilization. Exemplarily, the third preset temperature can be 1900°C, 2000°C, or 2100°C, or any temperature between 1900°C and 2100°C; this application embodiment does not impose excessive limitations on this.

[0134] It should also be noted that the moving speed of the heating element 200 is greater than or equal to 3 mm / min, which can avoid local overheating and material degradation, and prevent residual stress concentration. The moving speed of the heating element 200 is less than or equal to 2100℃, which can ensure that the sleeve 10 is fully melted and fully bonded to the mandrel.

[0135] In some embodiments, after inserting the core rod to be inserted into the sleeve 10 and closing the sleeve 10 and the core rod together, the method for preparing the optical fiber preform further includes:

[0136] The mandrel and sleeve 10, which are fused together, are heated and annealed using a heating element 200 at a fourth preset temperature, which is greater than or equal to 1000℃ and less than or equal to 1200℃.

[0137] The moving speed of the heating element 200 along the axial direction of the sleeve 10 is greater than or equal to 2 mm / min and less than or equal to 5 mm / min.

[0138] It should be noted that after the sleeve 10 melts, it is in a high-temperature plastic state. If it is cooled directly and rapidly, the temperature difference will cause the thermal stress to be "frozen" in the solid sleeve 10. Therefore, after the sleeve 10 and the mandrel are melted and closed together, the mandrel and sleeve 10 that have been melted and closed together are immediately annealed, which can release the stress in advance while the material still has a high mobility.

[0139] During the melting process, there may be a local temperature gradient at the interface between the mandrel and the sleeve 10. After the sleeve 10 and the mandrel are melted together, heating the melted mandrel and sleeve 10 can homogenize the overall temperature field through high-temperature homogenization, preventing stress caused by asynchronous thermal contraction during subsequent cooling.

[0140] Understandably, a fourth preset temperature greater than or equal to 1000℃ ensures that the quartz material achieves sufficiently high atomic activity, allowing residual stress to be fully released through plastic deformation or diffusion. A fourth preset temperature less than or equal to 1200℃ prevents overheating of the material, which could lead to grain coarsening, deformation, or even melting, thus affecting the performance of the optical fiber preform.

[0141] The moving speed of the heating element 200 is less than or equal to 5 mm / min, which can prevent thermal stress concentration caused by excessive temperature gradient, thereby preventing cracking or deformation of the sleeve 10. The moving speed of the heating element 200 is greater than or equal to 2 mm / min, which can ensure that the optical fiber preform stays in the high-temperature zone for a sufficient time, allowing for sufficient atomic diffusion and recombination, and completely eliminating residual stress.

[0142] It should be noted that, in order to verify the fabrication effect of the optical fiber preform fabrication apparatus and method provided in this application, the following embodiments use core rods of different diameters and sleeves 10 of similar size. Although the size of the sleeve 10 is similar to that of the corresponding core rod, there is still a problem that the gap between the inner wall of the sleeve 10 and the core rod is too large or too small. Therefore, the sleeve 10 is subjected to shrinking or expanding treatment so that the sleeve 10 can be used to fit the core rod. This can reduce the variety of sleeve 10 specifications in the process production, and reduce the process complexity and management costs.

[0143] Example 1:

[0144] A sleeve 10 with an outer diameter of 35 mm, an inner diameter of 20 mm, and a refractive index of -0.3% is used, along with a mandrel with a diameter of 10 mm to be inserted. The sleeve 10 is placed inside the insulation cavity 100, and a chuck secures it. The first end 11 and the second end 12 of the sleeve 10 are connected to a gas supply assembly 310 and an exhaust assembly 320, respectively. The gas supply assembly 310 introduces dry and purified gas (N2) into the sleeve 10. The oxyhydrogen flame lamp is activated and moved back and forth along the axial direction of the sleeve 10 for preheating. The temperature is monitored using an infrared thermometer to ensure that the preheating temperature reaches 300°C. The moving speed of the oxyhydrogen flame lamp is 100 mm / min, and the back-and-forth movement is repeated 3 times.

[0145] The tube shrinkage operation is carried out based on the target gap of 0.5mm between the sleeve 10 and the mandrel to be inserted. Combining the dimensions of the sleeve 10 and the mandrel, the outer diameter of the sleeve 10 should be shrunk to 33.94mm. A step-by-step tube pressure control is adopted. The first stage: reaching the set mandrel diameter shrinkage of 25%. During this process, the pressure difference decreases by 2Pa each time, gradually decreasing from the initial pressure difference value of 0Pa. When the expected mandrel diameter is reached, the first stage stops, at which point the negative pressure value inside the sleeve 10 is -20Pa.

[0146] After completing the first stage, the second stage begins: the differential pressure drop is adjusted to 6 Pa for each cycle, and the differential pressure value is gradually reduced. Throughout the tube shrinking process, infrared temperature monitoring is used, the temperature at the oxyhydrogen flame lamp is controlled at 1800℃, the moving speed is 20 mm / min, and the inner and outer diameters of the sleeve 10 are measured after each tube shrinking cycle using an infrared diameter gauge to predict whether the target shrinkage amount and target gap value have been achieved.

[0147] After multiple heating and shrinking operations, once the inner diameter of the sleeve 10 and the diameter of the mandrel reach the desired gap, the gas supply assembly 310 is removed, and the mandrel is inserted into the sleeve 10. After sealing the end of the sleeve 10, a vacuum is activated, with the internal pressure at -0.092 bar. The heating temperature is controlled at 1900℃, and the moving speed is 10 mm / min, until melting is complete. Simultaneously, after the initial end has melted, the induction furnace 210 is simultaneously activated for online annealing at 1000℃, with a moving speed of 5 mm / min, to remove residual stress after melting.

[0148] In Example 1, the optical fiber preform was tested at 10 points along the axial direction using an optical fiber preform analyzer. Three angles were measured at each point. The average of the cladding / core ratio and eccentricity obtained at different angles at each point was taken as the cladding / core ratio and eccentricity at that location. The difference between the maximum and minimum cladding / core ratios at different axial positions was taken as the axial fluctuation value, and the maximum eccentricity data at different axial positions was taken as the eccentricity value of the optical fiber preform. The prepared optical fiber preform was then drawn into fibers. The difference between the maximum and minimum zero-dispersion wavelengths of a single preform was taken as the fluctuation value of the zero-dispersion wavelength, and the ratio of the number of screenings per preform to the drawing length was taken as the fiber breakage rate.

[0149] The implementation steps of Examples 2 to 4 are the same as those of Example 1, and the corresponding process parameters are shown in Table 1. The axial distribution of the cladding / core ratio, the axial distribution of the zero-dispersion wavelength during fiber drawing, and the trends of pressure and diameter changes during the fiber preform preparation process are described in reference to... Figures 2 to 4 As shown.

[0150] Table 1. Process parameters and test results for examples 1-4 of the tube shrinking process.

[0151]

[0152] Example 5:

[0153] A sleeve 10 with an outer diameter of 35 mm, an inner diameter of 15 mm, and a refractive index of 0.15% is used, along with a mandrel with a diameter of 20 mm to be inserted. The sleeve 10 is placed inside the insulation cavity 100, and a chuck secures it. The first end 11 and the second end 12 of the sleeve 10 are connected to a gas supply assembly 310 and an exhaust assembly 320, respectively. The gas supply assembly 310 introduces dry and purified gas (N2 and O2) into the sleeve 10 at a gas flow ratio of 1:1. The graphite furnace is started and moved back and forth along the axial direction of the sleeve 10 for preheating. The temperature is monitored using an infrared thermometer to ensure that the preheating temperature reaches 360°C. The graphite furnace moves at a speed of 80 mm / min, and the process is repeated 4 times.

[0154] The expansion work is carried out based on the target gap of 1.5mm between the sleeve 10 and the mandrel to be inserted. Combining the dimensions of the sleeve 10 and the mandrel, the outer diameter of the sleeve 10 should be expanded to 36.99mm. A step-by-step tube pressure control technology is adopted. The first stage: reaching the set mandrel diameter expansion amount of 50%. During this process, the pressure difference increases by 6Pa each time, starting from the initial pressure difference value of 0Pa and gradually increasing. When the expected mandrel diameter is reached, the first stage is stopped, at which point the negative pressure value inside the sleeve 10 is 36Pa.

[0155] After completing the first stage, the second stage begins: the differential pressure increase is adjusted to 2 Pa per cycle, with the differential pressure gradually increasing and the increasing trend slowing down. Throughout the tube expansion process, infrared temperature monitoring is used, with the heating temperature controlled at 1850℃ and the moving speed at 9 mm / min. An infrared diameter gauge is used to test the inner and outer diameters of the sleeve 10 after each expansion cycle to predict whether the target expansion amount and target gap value have been achieved.

[0156] After multiple heating and expansion operations, once the inner diameter of the sleeve 10 and the diameter of the mandrel reach the desired gap, the gas supply assembly 310 is removed, and the mandrel is inserted into the sleeve 10. After sealing the end of the sleeve 10, a vacuum is activated, with the internal pressure at -0.09 bar. The heating temperature is controlled at 1960℃, and the moving speed is 8 mm / min until melting is complete. Simultaneously, after the initial melting is complete, the induction furnace 210 is simultaneously activated for online annealing at 1100℃, with a moving speed of 4 mm / min, to remove residual stress after melting.

[0157] Reference Figures 5 to 7As shown, in Example 5, the optical fiber preform was tested at 10 points along the axial direction using an optical fiber preform analyzer. Three angles were measured at each point. The average of the cladding / core ratio and eccentricity obtained at different angles at each point was taken as the cladding / core ratio and eccentricity at that location. The difference between the maximum and minimum cladding / core ratios at different axial positions was taken as the axial fluctuation value, and the maximum eccentricity data at different axial positions was taken as the eccentricity value of the optical fiber preform. The prepared optical fiber preform was then drawn into fibers. The difference between the maximum and minimum zero-dispersion wavelengths of a single preform was taken as the fluctuation value of the zero-dispersion wavelength, and the ratio of the number of screenings per preform to the drawing length was taken as the fiber breakage rate.

[0158] The implementation steps of Examples 6 and 7 are the same as those of Example 5, and the corresponding process parameters are shown in Table 2.

[0159] Table 2. Process parameters and test results for tube expansion processes corresponding to Examples 5-7.

[0160]

[0161] Comparative Example 1:

[0162] A sleeve 10 with an outer diameter of 35 mm, an inner diameter of 20 mm, and a refractive index of -0.3% is used, along with a mandrel with a diameter of 10 mm to be inserted. The sleeve 10 is placed inside the insulation cavity 100, and a chuck is used to fix the sleeve 10 in place. The mandrel is then inserted into the sleeve 10, and the end of the sleeve 10 is sealed. The oxyhydrogen flame lamp is activated to directly perform the melting and closure process.

[0163] Vacuuming is initiated, with the internal pressure at -0.092 bar. The heating temperature is controlled at 1900℃, and the moving speed is 10 mm / min until melting is complete. Simultaneously, after the initial end has melted, induction furnace 210 is simultaneously activated for online annealing at 1250℃, with a moving speed of 8 mm / min, to remove residual stress after melting.

[0164] The optical fiber preform prepared in Comparative Example 1 was tested at 10 points uniformly along the axial direction using an optical fiber preform analyzer. Three angles were measured at each point. The average of the cladding / core ratio and eccentricity obtained at different angles at each point was taken as the cladding / core ratio and eccentricity at that location. The difference between the maximum and minimum cladding / core ratios at different axial positions was taken as the axial fluctuation value, and the maximum eccentricity data at different axial positions was taken as the eccentricity value of the optical fiber preform. The prepared optical fiber preform was then drawn into fibers. The difference between the maximum and minimum zero-dispersion wavelengths of a single preform was taken as the fluctuation value of the zero-dispersion wavelength, and the ratio of the number of screenings per preform to the drawing length was taken as the fiber breakage rate.

[0165] The implementation steps for Comparative Examples 2 and 3 are the same as those for Comparative Example 1, and the corresponding process parameters are shown in Table 3.

[0166] The implementation steps for Comparative Examples 4 and 5 are the same as those for Example 1, and the corresponding process parameters are shown in Table 3.

[0167] Table 3. Process parameters and test results of tube shrinking process in Comparative Examples 1 to 5

[0168]

[0169]

[0170] Reference Figure 8 As shown in Comparative Example 1, due to the lack of pretreatment and step-by-step compression tube stages, the gap between the core rod and the sleeve 10 is large, resulting in poor uniform heating inside the sleeve 10. This leads to a large cladding / core ratio in the fiber preform and an increase in the axial fluctuation of the zero-dispersion wavelength during fiber preform drawing. Simultaneously, due to the high temperature and fast movement speed during the annealing stage, residual stress remains after cooling, resulting in insignificant improvement in fiber strength and potentially increasing residual stress, thus affecting strength.

[0171] In Comparative Example 2, due to the lack of pretreatment and step-by-step compression tube stage, the gap between the core rod and the sleeve 10 is large, and the heating inside the sleeve 10 is not uniform, resulting in a large cladding / core ratio of the optical fiber preform and an increase in the axial fluctuation of the zero-dispersion wavelength of the optical fiber preform drawing.

[0172] Reference Figure 9 As shown in Comparative Example 3, due to the lack of pretreatment and step-by-step compression tube process, the gap between the core rod and the sleeve 10 is large, the melting temperature is high, and the moving speed is fast, which aggravates the poor heating uniformity inside the sleeve 10, increases the cladding / core ratio of the optical fiber preform, and increases the fluctuation of the zero-dispersion wavelength. At the same time, after melting and cooling, there is a large amount of residual stress inside the optical fiber preform, which affects the strength of the optical fiber.

[0173] In Comparative Example 4, the low melting temperature and insufficient vacuum resulted in poor melting effect, which affected the strength of the optical fiber.

[0174] In Comparative Example 5, during the step-by-step compression tube stage, the diameter shrinkage in the first stage is relatively small, and the gap is still relatively large, which significantly increases the negative pressure value inside the sleeve 10, causing uneven shrinkage of the sleeve 10, which will also increase the eccentricity and core ratio fluctuation value.

[0175] Those skilled in the art will understand that the optical fiber preform fabrication apparatus and method provided in this application include an insulating cavity 100, a heating element 200, and a pressure regulating structure 300. The insulating cavity 100 is used to house the sleeve 10. The heating element 200 is slidably disposed within the insulating cavity 100 and is used to heat the sleeve 10. The pressure regulating structure 300 includes a gas supply component 310 and a gas exhaust component 320. The gas supply component 310 is connected to the first end 11 of the sleeve 10, and the gas exhaust component 320 is connected to the second end 12 of the sleeve 10. The gas supply component 310 and the gas exhaust component 320 are used to jointly regulate the internal pressure value of the sleeve 10, thereby adjusting the inner diameter of the sleeve 10 together with the heating element 200, controlling the gap between the sleeve 10 and the core rod, and improving the quality of the optical fiber preform.

[0176] In the description of this specification, the references to terms such as "one embodiment," "some embodiments," "illustrative embodiment," "example," "specific example," or "some examples," etc., indicate that a specific feature, structure, material, or characteristic described in connection with that embodiment or example is included in at least one embodiment or example of this application. In this specification, the illustrative expressions of the above terms do not necessarily refer to the same embodiment or example. Furthermore, the specific features, structures, materials, or characteristics described may be combined in any suitable manner in one or more embodiments or examples.

[0177] It is understood that the various numerical designations used in the embodiments of this application are merely for descriptive convenience and are not intended to limit the scope of the embodiments of this application.

[0178] The technical solutions of this application have been described above with reference to the preferred embodiments shown in the accompanying drawings. However, it will be readily understood by those skilled in the art that the scope of protection of this application is obviously not limited to these specific embodiments. Without departing from the principles of this application, those skilled in the art can make equivalent changes or substitutions to the relevant technical features, and the technical solutions after these changes or substitutions will all fall within the scope of protection of this application.

Claims

1. An apparatus for preparing optical fiber preforms, characterized in that, include: A heating element (200) is used to heat the sleeve (10); A pressure regulating structure (300) includes an air supply assembly (310) and an exhaust assembly (320). The air supply assembly (310) is used to communicate with the first end (11) of the sleeve (10), and the exhaust assembly (320) is used to communicate with the second end (12) of the sleeve (10). The gas supply assembly (310) and the exhaust assembly (320) are used to jointly adjust the internal pressure value of the sleeve (10) so as to adjust the inner diameter of the sleeve (10) together with the heating element (200).

2. The apparatus for preparing optical fiber preforms according to claim 1, characterized in that, The gas supply assembly (310) includes a gas supply component (311) and a gas supply pipe (312). The gas supply component (311) is connected to the first end (11) through the gas supply pipe (312) for supplying gas to the sleeve (10). The exhaust assembly (320) includes an exhaust pump (321) and an exhaust pipe (322), wherein the exhaust pump (321) is connected to the second end (12) through the exhaust pipe (322) for supplying exhaust to the sleeve (10).

3. The apparatus for preparing optical fiber preforms according to claim 2, characterized in that, The gas supply assembly (310) also includes a gas supply valve (313), which connects the gas supply pipe (312) to the first end (11). The exhaust assembly (320) also includes an exhaust valve (323) that connects the exhaust pipe (322) to the second end (12).

4. The apparatus for preparing optical fiber preforms according to claim 3, characterized in that, The gas supply assembly (310) further includes a first pressure measuring element (314), which is connected to the gas supply valve (313) to detect the pressure value of the gas supply valve (313); The exhaust assembly (320) further includes a second pressure measuring element (324), which is connected to the exhaust valve (323) to detect the pressure value of the exhaust valve (323).

5. The apparatus for preparing optical fiber preforms according to any one of claims 1 to 4, characterized in that, It also includes a heat-insulating cavity (100) and a detection component (400), wherein the heat-insulating cavity (100) is used to place the sleeve (10), and the heating element (200) is slidably disposed within the heat-insulating cavity (100); The detection component (400) includes a first detection element (410) and a second detection element (420), both of which are disposed within the heat-insulating cavity (100); The first detection element (410) is used to detect the inner diameter of the sleeve (10), and the second detection element (420) is used to detect the temperature inside the insulation cavity (100).

6. The apparatus for preparing optical fiber preforms according to claim 5, characterized in that, It also includes a sliding assembly (500), which includes a guide rail (510) and at least one base (520) slidably disposed on the guide rail (510). The guide rail (510) is disposed inside the heat preservation cavity (100), and the first detection element (410), the second detection element (420) and the heating element (200) are all disposed on the base (520).

7. The apparatus for preparing optical fiber preforms according to claim 6, characterized in that, It also includes a clamping member (600), which is disposed in the insulation cavity (100) and is used to clamp the sleeve (10).

8. A method for preparing an optical fiber preform, characterized in that, The optical fiber preform fabrication apparatus according to any one of claims 1 to 7 comprises a heating element (200) and a voltage regulating structure (300). The method for preparing the optical fiber preform includes: The heating element (200) is used to heat the sleeve (10), and the air supply component (310) and exhaust component (320) of the pressure regulating structure (300) are used to jointly adjust the internal pressure value of the sleeve (10) so as to adjust the inner diameter of the sleeve (10) together with the heating element (200).

9. The method for preparing an optical fiber preform according to claim 8, characterized in that, The gas supply assembly (310) and the exhaust assembly (320) employing the pressure regulating structure (300) jointly regulate the pressure value inside the sleeve (10) to jointly regulate the inner diameter of the sleeve (10) with the heating element (200), including: When the positive difference between the inner diameter of the sleeve (10) and the diameter of the mandrel to be inserted is greater than a first preset value, the air supply component (310) and the exhaust component (320) of the pressure regulating structure (300) reduce the pressure value inside the sleeve (10) by a first preset pressure difference reduction, so that the inner diameter of the sleeve (10) is reduced by a first preset reduction amount; When the inner diameter of the sleeve (10) is reduced by the first preset reduction amount, the pressure value inside the sleeve (10) is reduced by the second preset pressure difference reduction amount, so that the inner diameter of the sleeve (10) is reduced by the second preset reduction amount. Alternatively, when the positive difference between the inner diameter of the sleeve (10) and the diameter of the mandrel to be inserted is less than a second preset value, the air supply component (310) and the exhaust component (320) of the pressure regulating structure (300) are used to increase the pressure value inside the sleeve (10) by a first preset pressure difference increase, so that the inner diameter of the sleeve (10) is expanded by a first preset expansion amount; When the inner diameter of the sleeve (10) is increased by the first preset expansion amount, the pressure value inside the sleeve (10) is increased by the second preset pressure difference increase, so that the inner diameter of the sleeve (10) is increased by the second preset expansion amount.

10. The method for preparing an optical fiber preform according to claim 9, characterized in that, The first preset differential pressure drop is greater than or equal to 2 MPa and less than or equal to 5 MPa; The second preset differential pressure drop is greater than or equal to 6 MPa and less than or equal to 10 MPa; The first preset pressure difference increase is greater than or equal to 6 MPa and less than or equal to 10 MPa; The second preset differential pressure increase is greater than or equal to 2 MPa and less than or equal to 5 MPa.

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