Method for manufacturing an optical fiber preform

Abstract

The application provides a fiber preform preparation method, and belongs to the technical field of fiber preform processing. The fiber preform preparation method comprises a reaction tube, a heating device, a gas inlet pipe, a driving assembly and a controller. The gas outlet end of the reaction tube is communicated with a negative pressure source. The heating device has a heating source which moves along the axial direction of the reaction tube. The gas inlet end of the gas inlet pipe is communicated with a gas supplement source. The gas outlet end of the gas inlet pipe extends into the reaction tube from the gas inlet end of the reaction tube and is close to the heating point of the heating source on the reaction tube. The driving assembly is connected with the part of the gas inlet pipe which is outside the reaction tube. The driving assembly is used to drive the extending end of the gas inlet pipe to extend and retract along the axial direction of the reaction tube. The controller is in communication connection with the driving assembly and the heating device. The controller is used to control the extending end of the gas inlet pipe to move synchronously with the heating source through the driving assembly. The fiber preform preparation method provided by the application can realize accurate gas supplement for the shrinkage position, is beneficial to accurate pressure control for the shrinkage position and can improve the roundness of the fiber preform.

Description

Technical Field

[0001] This application belongs to the field of optical fiber preform processing technology, and more specifically, relates to a method for preparing optical fiber preforms. Background Technology

[0002] After the optical fiber preform is deposited by MCVD or PCVD, the reaction tube needs to be heated by a heating device. The heating point of the heating device is moved along the direction of the reaction tube, which allows the optical fiber preform to melt and shrink at high temperature, i.e., melting and shrinking. After melting and shrinking, further compaction is carried out until a complete optical fiber preform is formed.

[0003] In existing technologies, gas is often supplied to the reaction tube during the melting and shrinking process using a gas supply device. Since the reaction tube itself has a certain length, the supplied gas needs to travel a certain distance within the tube before reaching the melting and shrinking position. Therefore, there is a gas loss between the actual gas supply volume at the melting and shrinking position and the actual gas delivery volume through the gas supply inlet pipe. This is detrimental to pressure control at the melting and shrinking position, resulting in low roundness and poor quality of the fabricated optical fiber preform. Summary of the Invention

[0004] The purpose of this application is to provide a method for preparing optical fiber preforms, which aims to solve the technical problem in existing optical fiber preform preparations where there is a deviation between the actual gas replenishment volume and the actual gas delivery volume of the gas replenishment inlet pipe during the melting and shrinking process, which affects the roundness of the optical fiber preform.

[0005] To achieve the above objectives, the technical solution adopted in this application is as follows:

[0006] In a first aspect, an optical fiber preform melting and shrinking device is provided, comprising:

[0007] The gas outlet of the reaction tube is connected to a negative pressure source.

[0008] The heating device has a heating source that moves axially along the reaction tube;

[0009] An air inlet pipe has an air inlet end connected to a supplementary air source; the air outlet end of the air inlet pipe extends into the reaction tube from the air inlet end of the reaction tube and is close to the heating point of the heating source on the reaction tube.

[0010] A drive assembly is connected to the portion of the intake pipe located outside the reaction tube; the drive assembly is used to drive the extended end of the intake pipe to extend or retract axially along the reaction tube; and

[0011] The controller is communicatively connected to the drive assembly and the heating device;

[0012] The controller is used to control the extension end of the air intake pipe to move synchronously with the heating source through the drive component, so that the extension end of the air intake pipe changes with the shrinkage position.

[0013] Compared with the prior art, the solution shown in this application embodiment melts and shrinks at the heating point of the heating source. When the heating source moves along the axial direction of the reaction tube, the melting and shrinking position also changes continuously along the axial direction of the reaction tube. The outlet end of the gas inlet pipe in this application extends into the reaction tube, which can directly input the supplemented gas into the reaction tube, shortening the intermediate transport path of the gas in the reaction tube.

[0014] Furthermore, when the heating device moves, the controller can control the drive component to make the extension end of the air inlet pipe move synchronously with the heating source, so that the air replenishment position changes in real time with the melting and shrinking position, thereby achieving precise air replenishment at the melting and shrinking position. Therefore, it can be ensured that the actual air replenishment amount at the melting and shrinking position matches the preset air replenishment amount, which is conducive to achieving precise pressure control at the melting and shrinking position, improving the roundness of the optical fiber preform, and thus improving the quality of the optical fiber preform.

[0015] Therefore, the optical fiber preform melting and shrinking device provided in this application can achieve precise gas replenishment at the melting and shrinking position, which is conducive to achieving pressure control at the melting and shrinking position, improving the roundness of the optical fiber preform, and ensuring product quality.

[0016] In conjunction with the first aspect, in one possible implementation, the intake pipe is provided with a pressure monitoring device at its insertion end; the controller is communicatively connected to both the air supply source and the pressure monitoring device.

[0017] The controller is used to control the air supply volume of the air source after receiving the pressure signal from the pressure monitoring device.

[0018] By installing a pressure monitoring device at the insertion end of the air inlet pipe, and by allowing the insertion end of the air inlet pipe to move synchronously with the heating source, the pressure monitoring device can achieve real-time pressure measurement of the melting and shrinking position. This allows the controller to promptly control the gas supply source to replenish gas or reduce the amount of gas supplied, which helps to keep the gas pressure at the melting and shrinking position within the preset pressure range.

[0019] In conjunction with the first aspect, in one possible implementation, the extension end of the intake pipe near the heating point of the heating source on the reaction tube includes:

[0020] During the remaining melting and shrinking process, the insertion end of the air inlet pipe corresponds to the position of the heating point in the axial direction of the reaction tube;

[0021] During the final melting and shrinking process, the inlet end of the air inlet pipe and the heating point are offset from each other along the axial direction of the reaction tube.

[0022] During the melting and shrinking process, in order to ensure precise pressure control and gas replenishment at the melting and shrinking position by the inlet pipe extension end, the inlet pipe extension end should be as close as possible to the melting and shrinking position point. However, during the last melting and shrinking process, the optical fiber preform will be compacted at the heating point of the heating source, causing the reaction tube to close. Therefore, by setting the inlet pipe extension end and the heating point to be staggered in the axial direction of the reaction tube, interference between the inlet pipe extension end and the compaction part can be avoided, ensuring the smooth progress of the melting and shrinking process.

[0023] In conjunction with the first aspect, in one possible implementation, the intake pipe includes:

[0024] The first connecting pipe has its air inlet end connected to the air supply source;

[0025] The intermediate tube has an air inlet end connected to the air outlet end of the first connecting tube; the intermediate tube is a retractable flexible tube.

[0026] The second connecting pipe has an inlet end connected to the outlet end of the intermediate pipe, and the outlet end extends into the reaction tube; the portion of the second connecting pipe outside the reaction tube is connected to the drive assembly.

[0027] The first connecting tube is used to introduce supplementary gas, that is, to introduce it into the air inlet pipe; the second connecting tube is used to export supplementary gas, that is, to export it into the reaction pipe; the intermediate tube is set as a telescopic hose structure, which can realize the telescopic extension and retraction of the air inlet pipe, thereby facilitating the telescopic extension and retraction of the second connecting tube along the axial direction of the reaction pipe, and meeting the telescopic extension and retraction requirements of the air inlet pipe extension end.

[0028] In conjunction with the first aspect, in one possible implementation, the driving component includes:

[0029] The drive motor is communicatively connected to the controller.

[0030] The transmission assembly has its power input end connected to the output shaft of the drive motor; the power output end of the transmission assembly has a degree of freedom to move along the axial direction of the reaction tube.

[0031] The connecting block is fixed on the part of the air intake pipe located outside the reaction pipe and is fixedly connected to the power output end of the transmission assembly;

[0032] The drive motor is used to drive the connecting block to extend and retract axially along the reaction tube via the transmission assembly.

[0033] The drive motor is used to drive the connecting block to extend and retract along the axial direction of the reaction tube, so that the extension end of the air inlet pipe moves accordingly, thereby enabling the supplementary gas to move with the change of melting and shrinking position; the controller is connected to the drive motor, and the controller can control the opening and closing of the drive motor to realize the movement and stopping of the extension end of the air inlet pipe.

[0034] In some embodiments, the transmission assembly includes:

[0035] A rotating lead screw extends axially along the reaction tube; the rotating lead screw is poweredly connected to the output shaft to form the power input end of the transmission assembly;

[0036] The movable nut is screwed onto the rotating lead screw and fixedly connected to the connecting block;

[0037] When the drive motor drives the rotating lead screw to rotate, the movable nut is used to drive the connecting block to move on the rotating lead screw to form the power output end of the transmission assembly.

[0038] The rotating screw is connected to the output shaft, which can transmit the rotation of the drive motor to the rotating screw. When the rotating screw rotates, the movable nut can move on the rotating screw to realize power output, thereby driving the connecting block to move along the axis of the rotating screw.

[0039] Secondly, this application also provides a preparation method using the aforementioned optical fiber preform melting and shrinking device; the preparation method includes the following steps:

[0040] Determine the various process parameters of the optical fiber preform to be processed;

[0041] The insertion end of the air intake pipe is brought close to the heating point of the heating source;

[0042] The drive assembly and the heating device are activated; the heating source reciprocates along the axial direction of the reaction tube, and the extension end of the air inlet pipe moves synchronously with the heating source until the inner diameter of the reaction tube after melting and shrinking reaches a preset value; the drive assembly and the heating device are deactivated.

[0043] Define the end of the melting and shrinking stroke closest to the gas outlet of the reaction tube as the starting point of compaction and the other end as the ending point of compaction; adjust the relative position of the extension end of the gas inlet pipe and the heating point of the heating source in the axial direction of the reaction tube;

[0044] The drive assembly and the heating device are activated; the heating source moves from the starting point of the collection to the ending point of the collection, and the extension end of the air inlet pipe moves synchronously with the heating source until the inner diameter of the reaction tube in the collection section is zero, at which point the drive assembly and the heating device are deactivated.

[0045] The preparation method provided in this application, by using the aforementioned optical fiber preform melting and shrinking device, possesses all the beneficial effects of the aforementioned optical fiber preform melting and shrinking device. It can achieve precise gas replenishment and precise pressure control at the melting and shrinking position, which is beneficial to improving the roundness of the optical fiber preform and thus ensuring the quality of the optical fiber preform.

[0046] In conjunction with the second aspect, in one possible implementation, the determination of the various process parameters for the optical fiber preform to be processed includes:

[0047] Determine the type of gas to be supplied and the initial ventilation rate;

[0048] Determine the preset pressure value inside the reaction tube during melting and shrinkage;

[0049] Determine the melting and shrinkage stroke and the number of passes required for the melting and shrinkage process;

[0050] Determine the moving speed of the heating source and the moving speed of the intake pipe extension end.

[0051] By pre-determining the type of supplementary gas and the initial gas flow rate, the type of supplementary gas is made to match the composition of the optical fiber preform; by determining the number of melting passes, melting stroke, and the moving speed of the heating source and the inlet pipe extension end, clear control instructions are generated in the controller, and the various parameters of the melting process are defined.

[0052] In some embodiments, a pressure monitoring device is provided at the insertion end of the air intake pipe before the preparation method begins;

[0053] During the melting and shrinking process, the controller is used to adjust the air supply of the air source so that the pressure value monitored by the pressure monitoring device reaches the preset pressure value.

[0054] By setting up a pressure monitoring device, the pressure at the inlet pipe extension end can be monitored in real time to ensure that the pressure value at the melting and shrinking position reaches the preset pressure value during the melting and shrinking process, thereby improving the roundness of the optical fiber preform.

[0055] For example, bringing the extension end of the air inlet pipe close to the heating point of the heating source specifically means aligning the heating point of the heating device with the extension end of the air inlet pipe along the axial direction of the reaction tube.

[0056] The adjustment of the relative position of the inlet end of the air inlet pipe and the heating point of the heating source in the axial direction of the reaction tube is specifically as follows: the heating source is placed at the starting point of the shrinkage, the inlet end of the air inlet pipe is placed within the shrinkage stroke, and there is a preset distance between them and the heating point of the heating source, the preset distance being 20-40mm.

[0057] During the shrinking process, by aligning the heating point and the insertion end of the gas inlet pipe along the axial direction of the reaction tube, the supplementary gas can be directly introduced into the shrinking position. Furthermore, after the shrinking tube diameter reaches the preset value, a final shrinking process is performed to shrink the optical fiber preform inside the reaction tube until the aperture is zero, thereby forming a complete optical fiber preform. During the shrinking process, the gas inlet pipe and the heating point of the heating source are staggered to avoid interference between them and the insertion end of the gas inlet pipe, ensuring the smooth progress of the shrinking process. Attached Figure Description

[0058] To more clearly illustrate the technical solutions in the embodiments of this application, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of this application. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0059] Figure 1 Schematic diagram of the optical fiber preform melting and shrinking device provided in the embodiments of this application Figure 1 ;

[0060] Figure 2 Schematic diagram of the optical fiber preform melting and shrinking device provided in the embodiments of this application Figure 2 .

[0061] In the diagram: 1. Reaction tube; 2. Heating source; 3. Inlet pipe; 31. First connecting pipe; 32. Intermediate pipe; 33. Second connecting pipe; 4. Drive assembly; 41. Drive motor; 42. Transmission assembly; 421. Rotating lead screw; 422. Moving nut; 43. Connecting block; 5. Pressure monitoring device; 6. Negative pressure source; 7. Air supply source; 8. Rotary sealing structure; 9. Outlet pipe. Detailed Implementation

[0062] To make the technical problems, technical solutions, and beneficial effects to be solved by this application clearer, the following detailed description is provided in conjunction with the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are merely illustrative and are not intended to limit the scope of this application.

[0063] It should be noted that when an element is referred to as being "set on" another element, it can be directly on or indirectly on that other element. It should be understood that the terms "length," "width," "upper," "lower," "front," "rear," "top," "bottom," "inner," and "outer," etc., indicating orientation or positional relationships, are based on the orientation or positional relationships shown in the accompanying drawings and are used only for the convenience of describing this application and simplifying the description, and are not intended to indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation, and therefore should not be construed as a limitation of this application.

[0064] 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. Therefore, a feature defined as "first" or "second" may explicitly or implicitly include one or more of that feature. In the description of this application, "multiple" means two or more, unless otherwise explicitly specified.

[0065] It should be noted that fiber preform melting and shrinking is a crucial step in the fiber manufacturing process. This involves melting and shrinking the fiber preform at high temperatures to form a rod-shaped material suitable for subsequent fiber drawing. During melting and shrinking, the aperture within the reaction tube 1 continuously decreases. After several melting and shrinking cycles, the translation speed of the heating source 2 is reduced, and concentrated heating is applied to a single location within the reaction tube 1. This causes the single point to solidify prematurely, and the solidified point moves with the heat source until the entire reaction tube 1 is completely solidified into a fiber preform—this is the solidification process. After solidification, the aperture within the reaction tube 1 is zero, and a complete fiber preform can be formed.

[0066] In addition, during the melting and shrinking process, the pressure inside reaction tube 1 is controlled by supplementing nitrogen, and the core is filled by supplementing pure oxygen or an oxygen-containing mixture of core-filling materials. During melting and shrinking, some elements in the core layer, such as Ge and P, are prone to volatilization at high temperatures, leading to problems such as refractive index dips in the fiber preform core. To reduce volatilization, a mixture of reactants from the core layer elements and oxygen is introduced into the tube during melting and shrinking for core filling. Furthermore, a certain slight positive pressure needs to be maintained inside reaction tube 1 during melting and shrinking. In traditional technology, when the gas pressure is low, nitrogen or other gases are also introduced into reaction tube 1 to maintain positive pressure.

[0067] Please refer to the following: Figures 1 to 2The fiber optic preform fabrication method provided in this application is described below. The fiber optic preform melting and shrinking device includes a reaction tube 1, a heating device, an inlet pipe 3, a drive assembly 4, and a controller; the outlet end of the reaction tube 1 is connected to a negative pressure source 6; the heating device has a heating source 2 that moves along the axial direction of the reaction tube 1; the inlet end of the inlet pipe 3 is connected to a supplementary gas source 7; the outlet end of the inlet pipe 3 extends into the reaction tube 1 from the inlet end of the reaction tube 1 and is close to the heating point of the heating source 2 on the reaction tube 1; the drive assembly 4 is connected to the portion of the inlet pipe 3 that is outside the reaction tube 1; the drive assembly 4 is used to drive the extended end of the inlet pipe 3 to extend and retract along the axial direction of the reaction tube 1; the controller is communicatively connected to the drive assembly 4 and the heating device; wherein, the controller is used to control the extended end of the inlet pipe 3 to move synchronously with the heating source 2 through the drive assembly 4, so that the extended end of the inlet pipe 3 changes with the melting and shrinking position.

[0068] For example, a rotary sealing structure 8 is provided at both the inlet and outlet ends of the reaction tube 1. The rotary sealing structure 8 is used to prevent gas leakage from the reaction tube 1 and affecting the pressure inside the reaction tube 1. Furthermore, at the inlet end of the reaction tube 1, the extension end of the inlet pipe 3 passes through the rotary sealing structure 8 and is placed inside the reaction tube 1. During the extension and retraction of the inlet pipe 3, the rotary sealing structure 8 does not affect the extension and retraction sliding of the inlet pipe 3.

[0069] Specifically, the rotary sealing structure 8 can be one or more of a sealing ring or a rubber ring, and the specific arrangement and working principle of the rotary sealing structure 8 are existing technologies and will not be described in detail here. Furthermore, high-temperature resistant sealing grease will be used to seal the rotary sealing structure 8 between the intake pipe 3 and the intake end of the reaction pipe 1, and the sealing effect will not be affected when the intake pipe 3 extends or retracts.

[0070] In addition, the gas outlet of the reaction tube 1 is connected to the negative pressure source 6. Specifically, the gas outlet of the reaction tube 1 is provided with a gas outlet pipe 9. One end of the gas outlet pipe 9 is connected to the gas outlet of the reaction tube 1 through a rotary sealing structure 8, and the other end is connected to the negative pressure source 6.

[0071] The heating device includes a heating source 2 and a telescopic drive mechanism that drives the heating source 2 to move axially along the reaction tube 1. This telescopic drive mechanism can be one or more of a telescopic cylinder, a telescopic hydraulic cylinder, or an electric push rod. Alternatively, it can be a method where a drive motor 41 drives a lead screw nut to move the heating source 2, or a method where the drive motor 41 is coupled with belt or chain drive. The movement method and specific structure of the heating source 2 are existing technologies. Optionally, the telescopic drive mechanism of the heating source 2 has the same structure as the drive assembly 4 of the air inlet pipe 3.

[0072] For example, the heating source 2 is one or more of the following high-temperature heat sources: oxyhydrogen flame lamp, graphite resistance furnace, plasma flame, etc., which can heat a specified position of the reaction tube 1, so that the reaction tube 1 melts and shrinks at the heating point of the heating source 2.

[0073] The controller is communicatively connected to the drive assembly 4 and the heating device. The controller can control the start and relationship of the drive assembly 4 to move the air inlet end. The controller can control the movement of the heating source 2 by controlling the heating device. Furthermore, the controller can control the drive assembly 4 and the heating device to make the heating source 2 and the air inlet end of the air inlet pipe 3 move synchronously.

[0074] It should be noted that in this application, the heating source 2 and the extension end of the air intake pipe 3 move synchronously, which can be understood as the heating source 2 and the extension end of the air intake pipe 3 moving in the same direction and at the same speed.

[0075] Optionally, to achieve synchronous movement of the heating source 2 and the extension end of the air intake pipe 3, this application also provides a first sensor and a second sensor. The first sensor and the second sensor each include one or more of a speed sensor and a position sensor. The first sensor is used to sense the position and speed signals of the heating source 2, and the second sensor is used to sense the position and speed signals of the extension end of the air intake pipe 3. The controller is used to control the synchronous movement of the heating source 2 and the extension end of the air intake pipe 3 after receiving the sensing signals from the first sensor and the second sensor.

[0076] Optionally, the heating source 2 and the extension end of the air intake pipe 3 can adopt the same structure of the drive component 4. The controller is used to control the simultaneous start and stop of the two sets of drive components 4 so that the extension ends of the heating source 2 and the air intake pipe 3 move synchronously.

[0077] Compared with the prior art, the optical fiber preform melting and shrinking device provided in this application melts and shrinks at the heating point of the heating source 2 in the reaction tube 1. When the heating source 2 moves along the axial direction of the reaction tube 1, the melting and shrinking position also changes continuously in the axial direction of the reaction tube 1. The outlet end of the gas inlet pipe 3 in this application extends into the reaction tube 1, which can directly input the supplemented gas into the reaction tube 1, shortening the intermediate transport path of the gas in the reaction tube 1.

[0078] Furthermore, when the heating device moves, the controller can control the drive component 4 to make the extension end of the air inlet pipe 3 move synchronously with the heating source 2, so that the gas replenishment position changes in real time with the melting and shrinking position, thereby achieving precise gas replenishment at the melting and shrinking position. Therefore, it can be ensured that the actual gas replenishment amount at the melting and shrinking position matches the preset gas replenishment amount, which is conducive to achieving precise pressure control at the melting and shrinking position, improving the roundness of the optical fiber preform, and thus improving the quality of the optical fiber preform.

[0079] Therefore, the optical fiber preform melting and shrinking device provided in this application can achieve precise gas replenishment at the melting and shrinking position, which is conducive to achieving pressure control at the melting and shrinking position, improving the roundness of the optical fiber preform, and ensuring product quality.

[0080] It is important to understand that, in order to ensure the roundness of the preform, a slight positive pressure is generally maintained inside the reaction tube 1. However, there is a pressure gradient inside the reaction tube 1 in the direction near and away from the gas outlet. In traditional technology, the gas inlet tube 3 can often only replenish gas to a specific location, resulting in uneven actual pressure at different locations inside the reaction tube 1. Therefore, during the melting and shrinking process, the melting and shrinking location changes continuously, and the pressure at each melting and shrinking location is not equal. As a result, the prepared optical fiber preform has low roundness and poor quality.

[0081] Please see Figure 1 In some possible embodiments, the intake pipe 3 is provided with a pressure monitoring device 5 at its extension end; the controller is communicatively connected to the air supply source 7 and the pressure monitoring device 5; wherein, the controller is used to control the air supply volume of the air supply source 7 after receiving the pressure signal from the pressure monitoring device 5.

[0082] Specifically, the pressure monitoring component 5 can be a pressure sensor to achieve real-time monitoring of the pressure at the melting point.

[0083] Optionally, the gas supply source 7 includes a gas supply system and a control valve located on the inlet pipe 3 or at the outlet of the gas supply system. The controller controls the flow rate of the gas supply by controlling the opening and closing degree of the control valve, thereby realizing gas supply and pressure control at the melting and shrinking position.

[0084] By setting a pressure monitoring device 5 at the insertion end of the air inlet pipe 3, and the insertion end of the air inlet pipe 3 can move synchronously with the heating source 2, the pressure monitoring device 5 can realize real-time pressure measurement of the melting and shrinking position, so that the controller can timely control the gas supply source 7 to supplement gas or reduce the gas supply amount, which is beneficial to keep the gas pressure at the melting and shrinking position within the preset pressure value range.

[0085] It should be understood that when replenishing gas is required, replenishing gas can be introduced into the reaction tube 1 through the gas supply source 7. When replenishing gas is not required and the pressure in the reaction tube 1 is insufficient, nitrogen can be introduced to increase the pressure at the melting point in the reaction tube 1.

[0086] Please see Figure 1 and Figure 2 In some possible embodiments, the fact that the extension end of the air inlet pipe 3 is close to the heating point of the heating source 2 on the reaction tube 1 can be understood as follows: during the remaining melting and shrinking process, the extension end of the air inlet pipe 3 and the heating point are positioned axially in the reaction tube 1; during the last melting and shrinking process, the extension end of the air inlet pipe 3 and the heating point are staggered axially in the reaction tube 1.

[0087] During the initial melting and shrinking process, the insertion end of the air inlet pipe 3 needs to be as close as possible to the heating point of the heating source 2, so that the insertion end of the air inlet pipe 3 is as close as possible to the melting and shrinking position, so as to ensure that the supplementary gas is directly introduced into the melting and shrinking position through the insertion end of the air inlet pipe 3, thereby ensuring the accurate input of the core gas; or the insertion end of the air inlet pipe 3 can directly introduce the pressurized gas into the melting and shrinking position, thereby achieving precise pressure control at the insertion end of the air inlet pipe 3.

[0088] During the melting and shrinking process, in order to ensure precise pressure control and gas replenishment at the melting and shrinking position by the insertion end of the air inlet pipe 3, the insertion end of the air inlet pipe 3 should be as close as possible to the melting and shrinking position. However, during the last melting and shrinking process, the optical fiber preform will be compacted at the heating point of the heating source 2, causing the reaction tube 1 to close. Therefore, by setting the insertion end of the air inlet pipe 3 and the heating point to be staggered in the axial direction of the reaction tube 1, interference between the insertion end of the air inlet pipe 3 and the compacted part can be avoided, ensuring the smooth progress of the melting and shrinking process.

[0089] It should be noted that during the final fusion shrinking process, the optical fiber preform needs to be packed into the reaction tube 1 to reduce the inner diameter of the reaction tube 1 to zero. If the inserted end of the reaction tube 1 is still in the fusion shrinking position during this process, it will affect the packing process at the fusion shrinking position. Therefore, in this application, it is set to a staggered form.

[0090] It should be noted that the offset distance between the inlet end of the air inlet pipe 3 and the heating point in the axial direction of the reaction tube 1 should not be too large, so that the core filling gas or pressurizing gas is as close as possible to the compaction point.

[0091] Please see Figure 1 In some possible embodiments, the air intake pipe 3 includes a first connecting pipe 31, an intermediate pipe 32, and a second connecting pipe 33; the air intake end of the first connecting pipe 31 is connected to the air supply source 7; the air intake end of the intermediate pipe 32 is connected to the air outlet end of the first connecting pipe 31; the intermediate pipe 32 is a retractable flexible hose; the air intake end of the second connecting pipe 33 is connected to the air outlet end of the intermediate pipe 32, and the air outlet end extends into the reaction pipe 1; the portion of the second connecting pipe 33 outside the reaction pipe 1 is connected to the drive assembly 4.

[0092] The first connecting pipe 31 is used to introduce supplementary gas, that is, to introduce it into the air inlet pipe 3; the second connecting pipe 33 is used to export supplementary gas, that is, to export it into the reaction pipe 1; the intermediate pipe 32 is set as a telescopic hose structure, which can realize the telescopic extension of the air inlet pipe 3, thereby facilitating the extension and retraction of the second connecting pipe 33 along the axial direction of the reaction pipe 1, and meeting the telescopic extension requirements of the extension end of the air inlet pipe 3.

[0093] The pressurizing gas or core-filling gas enters the reaction tube 1 sequentially through the first connecting pipe 31, the intermediate pipe 32, and the second connecting pipe 33, and is directly introduced into the melting and shrinking position through the extension end of the second connecting pipe 33. The first connecting pipe 31 and the second connecting pipe 33 are used to guide the gas flow and can be set as rigid pipes to communicate with the gas supply source 7 or the reaction tube 1.

[0094] Optionally, the intermediate tube 32 can also be configured as a telescopic tube assembly, which enables the extension and retraction of the intake tube 3 at the insertion end through the telescopic sleeve and the inner tube; specifically, the structure and principle of the telescopic tube assembly are existing technologies.

[0095] Optionally, the intermediate tube 32 is a telescopic flexible hose. Specifically, the outer wall of the hose is provided with pleats. When the intermediate tube 32 is stretched, the distance between two adjacent pleats increases, the pleats unfold, so that the intermediate tube 32 extends and the second connecting tube 33 extends. Conversely, the pleats contract and the intermediate tube 32 contracts.

[0096] Please see Figure 1 In some possible embodiments, the drive assembly 4 includes a drive motor 41, a transmission assembly 42, and a connecting block 43; the drive motor 41 is communicatively connected to the controller; the power input end of the transmission assembly 42 is poweredly connected to the output shaft of the drive motor 41; the power output end of the transmission assembly 42 has a degree of freedom to move along the axial direction of the reaction tube 1; the connecting block 43 is fixed on the portion of the air inlet pipe 3 located outside the reaction tube 1 and is fixedly connected to the power output end of the transmission assembly 42; wherein, the drive motor 41 is used to drive the connecting block 43 to extend and retract along the axial direction of the reaction tube 1 through the transmission assembly 42.

[0097] The drive motor 41 is used to drive the connecting block 43 to extend and retract along the axial direction of the reaction tube 1, so that the extension end of the air inlet pipe 3 moves accordingly, thereby realizing that the supplementary gas moves with the change of melting and shrinking position; the controller is connected to the drive motor 41, and the controller can control the opening and closing of the drive motor 41 to realize the movement and stopping of the extension end of the air inlet pipe 3.

[0098] Optionally, the transmission component 42 can also be a belt transmission component 42 or a chain transmission component 42.

[0099] Specifically, the connecting block 43 is fixed on the second connecting tube 33. When the drive motor 41 drives the connecting block 43 to extend or retract through the transmission assembly 42, the connecting block 43 drives the second connecting tube 33 to extend or retract, so as to adjust the length of the second connecting tube 33 extending into the reaction tube 1, thereby adapting to the change in the melting and shrinking position.

[0100] Specifically, the communication connection between the controller and the drive motor 41 enables the controller to control the opening and closing of the drive motor 41, as well as adjust the speed of the drive motor 41. This connection method and control principle are existing technologies and will not be described in detail here.

[0101] For example, in order to guide the second connecting pipe 33 during extension and retraction, a guide rail structure can be provided below the second connecting pipe 33, and the connecting pipe can move on the guide rail to prevent the second connecting pipe 33 from deviating from the preset direction during extension and retraction.

[0102] Please see Figure 1 In some embodiments, the transmission assembly 42 includes a rotating lead screw 421 and a movable nut 422; the rotating lead screw 421 extends axially along the reaction tube 1; the rotating lead screw 421 is poweredly connected to the output shaft to form the power input end of the transmission assembly 42; the movable nut 422 is screwed onto the rotating lead screw 421 and is fixedly connected to the connecting block 43; wherein, when the drive motor 41 drives the rotating lead screw 421 to rotate, the movable nut 422 is used to drive the connecting block 43 to move on the rotating lead screw 421 to form the power output end of the transmission assembly 42.

[0103] The movable nut 422 is screwed to the rotating screw 421. Therefore, when the rotating screw 421 rotates, the movable nut 422 moves along the axial direction of the rotating screw 421. The movable nut 422 is fixedly connected to the connecting block 43, which can drive the connecting block 43 to move.

[0104] Specifically, the movable nut 422 is welded to the connecting block 43, or the movable nut 422 is fixedly connected to the connecting block 43 by bolts or screws.

[0105] The rotating lead screw 421 is connected to the output shaft for power transmission. The rotation of the drive motor 41 can be transmitted to the rotating lead screw 421. When the rotating lead screw 421 rotates, the movable nut 422 can move on the rotating lead screw 421 to achieve power output, thereby driving the connecting block 43 to move axially along the rotating lead screw 421.

[0106] Based on the same inventive concept, this application also provides a preparation method using the aforementioned optical fiber preform melting and shrinking device. The preparation method includes the following steps: First, determine the various process parameters of the optical fiber preform to be processed; Second, bring the extension end of the air inlet pipe 3 close to the heating point of the heating source 2; Third, start the drive assembly 4 and the heating device; the heating source 2 moves back and forth along the axial direction of the reaction tube 1, and the extension end of the air inlet pipe 3 moves synchronously with the heating source 2 until the inner diameter of the reaction tube 1 after melting and shrinking reaches a preset value; the drive assembly 4 and the heating device are turned off; Fourth, define one end of the melting and shrinking stroke closest to the outlet end of the reaction tube 1 as the starting point of compaction and the other end as the ending point of compaction; adjust the relative position of the extension end of the air inlet pipe 3 and the heating point of the heating source 2 in the axial direction of the reaction tube 1; Fifth, start the drive assembly 4 and the heating device; the heating source 2 moves from the starting point of compaction to the ending point of compaction, and the extension end of the air inlet pipe 3 moves synchronously with the heating source 2 until the inner diameter of the reaction tube 1 in the compaction section is zero, and the drive assembly 4 and the heating device are turned off.

[0107] It should be noted that the melting and shrinking stroke of reaction tube 1 is not the entire length of reaction tube 1 from the gas inlet to the gas outlet. The length of reaction tube 1 after deposition is often only a part of reaction tube 1. Therefore, the melting and shrinking stroke is not the entire length of reaction tube 1, but a distance on reaction tube 1. The starting point of the melting and shrinking stroke is the melting and shrinking start point, and the ending point of the melting and shrinking stroke is the melting and shrinking end point.

[0108] In the third step of the melting and shrinking process, optionally, the heating point can start from the melting and shrinking starting point and move towards the melting and shrinking ending point, and then start again from the melting and shrinking starting point and move to the melting and shrinking ending point to achieve cyclic movement.

[0109] Optionally, the heating point can start from the beginning of the melting and shrinking stroke, move towards the end of the melting and shrinking stroke, and then move back to the beginning of the melting and shrinking stroke to achieve reciprocating movement.

[0110] Optionally, the heating point can start from any point in the melting and shrinking stroke and move back and forth between the starting point and the ending point of the melting and shrinking stroke to achieve melting and shrinking of the entire melting and shrinking stroke on the reaction tube 1.

[0111] In addition, in the third step, the inner diameter of the reaction tube 1 after melting and shrinking reaches a preset value, and the diameter of the preset value is not less than the diameter of the inlet end of the air inlet pipe 3, so as to ensure that there is no interference between the inlet end of the air inlet pipe 3 during the melting and shrinking process.

[0112] After the inner diameter of the reaction tube 1 in the solidification section is zero, it indicates that the solidification process is complete. The optical fiber preform in the reaction tube 1 is solidified into a solid cylindrical structure, and at this time the last melting and shrinking process is completed.

[0113] During the melting and shrinking process, the end closest to the gas outlet of reaction tube 1 is the starting point for compaction. During the compaction process, the inside of reaction tube 1 is gradually sealed. Therefore, it is necessary to compact from the gas outlet side of reaction tube 1 to the gas inlet side, that is, to melt and shrink from the compaction starting point to the compaction ending point.

[0114] It should be noted that the compaction process is also a step in the melting and shrinking process, and it is the last melting and shrinking process in the optical fiber preform melting and shrinking process.

[0115] The preparation method provided in this application, by using the aforementioned optical fiber preform melting and shrinking device, possesses all the beneficial effects of the aforementioned optical fiber preform melting and shrinking device. It can achieve precise gas replenishment and precise pressure control at the melting and shrinking position, which is beneficial to improving the roundness of the optical fiber preform and thus ensuring the quality of the optical fiber preform.

[0116] In some possible embodiments, determining the various process parameters of the optical fiber preform to be processed includes: first, determining the type of gas supplied by the gas supply source 7 and the initial gas flow rate according to the process requirements; determining the preset pressure value in the reaction tube 1 during melting and shrinking; determining the melting and shrinking stroke and the number of passes in the melting and shrinking process; and determining the moving speed of the heating source 2 and the moving speed of the inlet pipe 3.

[0117] By pre-determining the type of supplementary gas and the initial gas flow rate, the type of supplementary gas is made to match the composition of the optical fiber preform; by determining the number of melting passes, melting stroke, and the moving speed of the heating source 2 and the inlet pipe 3, clear control instructions are generated in the controller, and the various parameters of the melting process are defined.

[0118] Since the entire length of reaction tube 1 after deposition is not an effective portion, the melting and shrinking stroke needs to be determined before melting and shrinking. The two ends of the melting and shrinking stroke are the starting point and the ending point of melting and shrinking, respectively. The melting and shrinking stroke and the number of passes in the melting and shrinking process are related to the diameter of the optical fiber preform to be prepared and the manufacturing process.

[0119] Since the moving speed of the intake pipe 3 extension end is synchronized with the moving speed of the heating source 2, after determining the moving speed and direction of the heating source 2, the moving speed and direction of the intake pipe 3 extension end can be obtained based on the moving speed of the heating source 2.

[0120] In some embodiments, a pressure monitoring element 5 is installed at the insertion end of the air inlet pipe 3 before the preparation method begins; during the melting and shrinking process, the controller adjusts the air supply volume of the air supply source 7 so that the pressure value monitored by the pressure monitoring element 5 reaches the preset pressure value.

[0121] By setting pressure monitoring device 5, the pressure at the inlet end of air inlet pipe 3 can be monitored in real time to ensure that the pressure value at the melting and shrinking position reaches the preset pressure value during the melting and shrinking process, thereby improving the roundness of the optical fiber preform.

[0122] Specifically, the pressure monitoring component 5 is a pressure sensor. When it detects that the pressure at the inlet end of the air inlet pipe 3 is insufficient, the controller controls the air supply source 7 to increase the air flow to improve the air flow at the inlet end of the air inlet pipe 3, so that the pressure at the shrinkage position increases to the preset pressure value.

[0123] In addition, the increased ventilation volume can be made up with pressurized gas, core-filling gas, or a mixture of both. The specific gas composition can be selectively set according to actual needs.

[0124] Please see Figure 1 and Figure 2 For example, in the second step, bringing the extension end of the air inlet pipe 3 close to the heating point of the heating source 2 specifically means aligning the heating point of the heating device with the extension end of the air inlet pipe 3 in the axial direction of the reaction tube 1; in the fourth step, adjusting the relative position of the extension end of the air inlet pipe 3 and the heating point of the heating source 2 in the axial direction of the reaction tube 1 specifically means placing the heating source 2 at the starting point of the shrinkage, placing the extension end of the air inlet pipe 3 within the shrinkage stroke, and offsetting it from the heating point of the heating source 2 by a preset distance, the preset distance being 20-40mm.

[0125] During the shrinking process, by aligning the heating point and the extension end of the air inlet pipe 3 along the axial direction of the reaction tube 1, the supplemented gas can be directly introduced into the shrinking position. Furthermore, after the shrinking tube diameter reaches the preset value, a final shrinking process is performed to shrink the optical fiber preform in the reaction tube 1 until the aperture is zero, thereby forming a complete optical fiber preform. During the shrinking process, the air inlet pipe 3 and the heating point of the heating source 2 are staggered to avoid interference between them and the extension end of the air inlet pipe 3, ensuring the smooth progress of the shrinking process.

[0126] For ease of description, the appendix is ​​used in this application. Figure 2 The "L" in the designation indicates the preset distance; the specific preset distance value depends on the type of fiber preform and the inner diameter before fusion shrinkage, with a common value of 20-40mm. When the misalignment distance is 20-40mm, it ensures that the supplementary gas is introduced directly to the fusion shrinkage position as much as possible while avoiding interference, so as to facilitate the smooth progress of the fusion shrinkage process.

[0127] It is important to understand that the final melting and shrinking process uses reverse shrinking. At this time, the position of the inlet pipe 3 needs to be at a certain distance from the heating point of the heating source 2. This is because the reaction tube 1 in a certain length area directly above the heating source 2 will close during the shrinking process, and this area needs to be made available.

[0128] It should be noted that in the fourth step, if the extension end of the intake pipe 3 is not placed within the melting and shrinking stroke, but exceeds the melting and shrinking stroke and is misaligned with the heating point in another direction, interference will also occur at the melting and shrinking position. Therefore, the extension end of the intake pipe 3 needs to be placed within the melting and shrinking stroke, and as the melting and shrinking process continues, the extension end of the intake pipe 3 gradually exits the melting and shrinking stroke, and the melting and shrinking position gradually moves to the end point of compaction.

[0129] The above description is merely a preferred embodiment of this application and is not intended to limit this application. Any modifications, equivalent substitutions, and improvements made within the spirit and principles of this application should be included within the protection scope of this application.

Claims

1. A method for preparing optical fiber preforms, characterized in that, The optical fiber preform is fabricated using an optical fiber preform melting and shrinking device, which includes: The gas outlet of the reaction tube (1) is connected to the negative pressure source (6); The heating device has a heating source (2) that moves axially along the reaction tube (1); The air inlet pipe (3) is connected to the air supply source (7) at the air inlet end and extends into the reaction pipe (1) from the air inlet end of the reaction pipe (1) and is close to the heating point of the heating source (2) on the reaction pipe (1); A drive assembly (4) is connected to the portion of the intake pipe (3) located outside the reaction tube (1); the drive assembly (4) is used to drive the extension end of the intake pipe (3) to extend and retract axially along the reaction tube (1); and The controller is communicatively connected to the drive assembly (4) and the heating device; The controller is used to control the extension end of the air inlet pipe (3) to move synchronously with the heating source (2) through the drive component (4), so that the extension end of the air inlet pipe (3) changes with the melting position. The preparation method includes the following steps: Determine the various process parameters of the optical fiber preform to be processed; Make the extension end of the air inlet pipe (3) close to the heating point of the heating source (2); The drive assembly (4) and the heating device are started; the heating source (2) moves back and forth along the axial direction of the reaction tube (1), and the extension end of the air inlet pipe (3) moves synchronously with the heating source (2) until the inner diameter of the reaction tube (1) after melting and shrinking reaches the preset value; the drive assembly (4) and the heating device are turned off. Define the end of the melting and shrinking process closest to the gas outlet of the reaction tube (1) as the starting point of the compaction and the other end as the ending point of the compaction; adjust the relative position of the extension end of the gas inlet pipe (3) and the heating point of the heating source (2) in the axial direction of the reaction tube (1); The driving component (4) and the heating device are started; the heating source (2) moves from the starting point of the collection to the ending point of the collection, and the extension end of the air inlet pipe (3) moves synchronously with the heating source (2) until the inner diameter of the reaction tube (1) in the collection section is zero, and the driving component (4) and the heating device are turned off.

2. The method for preparing optical fiber preforms as described in claim 1, characterized in that, The intake pipe (3) is provided with a pressure monitoring device (5) at its insertion end; the controller is communicatively connected to the air supply source (7) and the pressure monitoring device (5); The controller is used to control the air supply volume of the air source (7) after receiving the pressure signal from the pressure monitoring device (5).

3. The method for preparing optical fiber preforms as described in claim 1, characterized in that, The heating points on the reaction tube (1) near the heating source (2) at the insertion end of the air inlet pipe (3) include: During the remaining melting and shrinking process, the insertion end of the air inlet pipe (3) corresponds to the position of the heating point in the axial direction of the reaction tube (1); During the final melting and shrinking process, the inlet end of the air inlet pipe (3) and the heating point are staggered in the axial direction of the reaction tube (1).

4. The method for preparing optical fiber preforms as described in claim 1, characterized in that, The intake pipe (3) includes: The first connecting pipe (31) is connected to the air supply source (7) at its air inlet end; The intermediate tube (32) has an air inlet end connected to the air outlet end of the first connecting tube (31); the intermediate tube (32) is a retractable flexible tube. The second connecting pipe (33) has an air inlet end connected to the air outlet end of the intermediate pipe (32), and the air outlet end extends into the reaction pipe (1); the part of the second connecting pipe (33) placed outside the reaction pipe (1) is connected to the drive assembly (4).

5. The method for preparing optical fiber preforms as described in claim 1, characterized in that, The driving component (4) includes: The drive motor (41) is communicatively connected to the controller; The transmission assembly (42) has its power input end connected to the output shaft of the drive motor (41); the power output end of the transmission assembly (42) has the degree of freedom to move along the axial direction of the reaction tube (1); The connecting block (43) is fixed on the part of the air inlet pipe (3) located outside the reaction pipe (1) and is fixedly connected to the power output end of the transmission assembly (42); The drive motor (41) is used to drive the connecting block (43) to extend and retract axially along the reaction tube (1) via the transmission assembly (42).

6. The method for preparing optical fiber preforms as described in claim 5, characterized in that, The transmission assembly (42) includes: A rotating lead screw (421) is provided to extend axially along the reaction tube (1); the rotating lead screw (421) is poweredly connected to the output shaft to form the power input end of the transmission assembly (42); The movable nut (422) is screwed onto the rotating lead screw (421) and fixedly connected to the connecting block (43); When the drive motor (41) drives the rotating lead screw (421) to rotate, the movable nut (422) is used to drive the connecting block (43) to move on the rotating lead screw (421) to form the power output end of the transmission assembly (42).

7. The preparation method according to claim 1, characterized in that, The process parameters for determining the optical fiber preform to be processed include: Determine the type of gas and initial ventilation rate of the supplementary gas source (7); Determine the preset pressure value inside the reaction tube (1) during melting and shrinkage; Determine the melting and shrinkage stroke and the number of passes required for the melting and shrinkage process; Determine the moving speed of the heating source (2) and the moving speed of the inlet pipe (3) extension end.

8. The preparation method according to claim 7, characterized in that, Before the preparation method begins, a pressure monitoring device (5) is installed at the insertion end of the air inlet pipe (3); During the melting and shrinking process, the controller is used to adjust the air supply of the air source (7) so that the pressure value monitored by the pressure monitoring device (5) reaches the preset pressure value.

9. The preparation method according to claim 1, characterized in that, The specific meaning of bringing the extension end of the air inlet pipe (3) close to the heating point of the heating source (2) is: aligning the heating point of the heating device with the extension end of the air inlet pipe (3) in the axial direction of the reaction tube (1). The adjustment of the relative position of the extension end of the air inlet pipe (3) and the heating point of the heating source (2) in the axial direction of the reaction tube (1) is specifically as follows: the heating source (2) is placed at the starting point of the shrinkage, the extension end of the air inlet pipe (3) is placed within the shrinkage stroke, and there is a preset distance between it and the heating point of the heating source (2), the preset distance being 20-40mm.

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