A manufacturing equipment for optical fiber preforms based on OVD technology

Abstract

This invention discloses a manufacturing equipment for optical fiber preforms based on OVD (Optical Vapor Deposition) technology, including a rotating frame, a deposition torch assembly, a flow guide tube holder, and a pick-and-place device. The rotating frame clamps a horizontally placed core rod and drives it to rotate coaxially. The deposition torch assembly has a deposition torch that can reciprocate below the core rod to form a powder rod on the outer periphery of the core rod. The nozzle of the deposition torch faces upward and is equipped with a flow guide tube. The flow guide tube holder and the pick-and-place device are located next to the rotating frame. The flow guide tube holder stores various sizes of flow guide tubes. The pick-and-place device is used to retrieve flow guide tubes from the deposition torch and place them in the flow guide tube holder, and then retrieve a flow guide tube from the flow guide tube holder and install it at the nozzle of the deposition torch to replace the flow guide tube on the deposition torch. This allows for convenient replacement of the flow guide tubes on the deposition torch during the operation of the deposition torch assembly, resulting in a lower stress in the final optical fiber preform and reduced production costs.

Description

Technical Field

[0001] This utility model belongs to the field of optical fiber preparation technology, and in particular relates to a manufacturing equipment for optical fiber preforms based on OVD process. Background Technology

[0002] During the OVD process for fabricating optical fiber preforms, the core rod rotates coaxially while a deposition torch moves back and forth along its length below the core rod to uniformly deposit the powder (SiO2) generated in the flame onto the outer periphery of the core rod, forming a powder rod body. One round trip of the deposition torch can be considered as one deposition cycle (i.e., one deposition is completed). Each time the deposition torch completes one deposition, a new powder rod layer can be added to the periphery of the core rod (the powder rod body is formed by stacking powder rod layers one by one, and there is no obvious boundary between adjacent powder rod layers).

[0003] During the fabrication of optical fiber preforms, the entire deposition process takes tens of hours, during which the outer diameter of the powder rod gradually grows to several hundred millimeters. This results in differences in important parameters such as powder temperature, density, and material stress between the early and later stages of deposition. In the early stage of deposition, the powder has a small outer diameter, high temperature, and high density, which can lead to anomalies such as opacity and significant attenuation at 1383nm in the optical fiber during subsequent dehydration and sintering. In the later stage of deposition, the powder has a large outer diameter, low temperature, and low density, which can cause anomalies such as cracking during the deposition process.

[0004] Currently, the method to eliminate or reduce the temperature difference, density difference, and stress difference of powder between the early and late stages of deposition is to adjust the flow rate of gases such as hydrogen and oxygen during the early and late stages of deposition. However, this introduces other problems. For example, reducing the flow rate of hydrogen and oxygen in the early stage of deposition leads to a decrease in the utilization rate of raw materials; while increasing the flow rate of hydrogen and oxygen in the late stage of deposition leads to a shortening of the lifespan of the deposition torch. Utility Model Content

[0005] To address the aforementioned technical problems, the present invention aims to provide a simple manufacturing equipment for optical fiber preforms based on the OVD process, which allows for the replacement of the guide tube on the deposition torch as needed. This equipment can prepare low-stress optical fiber preforms by gradually reducing the length and / or inner diameter of the guide tube during the deposition process.

[0006] To achieve the above objectives, the technical solution of this utility model is as follows: A manufacturing equipment for optical fiber preforms based on OVD process includes a rotating frame, a deposition torch assembly, a flow guide tube rack, and a pick-and-place device. The rotating frame is used to clamp a horizontally placed core rod and drive the core rod to rotate coaxially. The deposition torch assembly has a deposition torch that can reciprocate below the core rod to generate powder rods on the outer periphery of the core rod. The nozzle of the deposition torch faces upward and is equipped with a flow guide tube. The flow guide tube rack and the pick-and-place device are arranged next to the rotating frame. The flow guide tube rack is used to store various flow guide tubes of different specifications. The pick-and-place device is used to pick up the flow guide tubes on the deposition torch and store them on the flow guide tube rack, and pick up one flow guide tube from the flow guide tube rack and install it at the nozzle of the deposition torch to replace the flow guide tubes on the deposition torch.

[0007] The beneficial effects of the above technical solution are as follows: during the deposition torch assembly operation, the pick-and-place component can automatically replace the guide tube on the deposition torch, thereby allowing the powder rod to independently and repeatedly reduce the length and / or inner diameter of the guide tube during the deposition process to adjust the temperature distribution and orientation of the flame, thereby reducing the stress difference, density difference and temperature difference of the powder rod in the radial direction, and ultimately producing an optical fiber preform with lower stress, while reducing production costs.

[0008] The rotating frame described in the above technical solution includes a support frame, a rotating drive component, a weighing component, and two rotating chucks. Both rotating chucks are rotatably mounted on the support frame and are horizontally distributed relative to each other. The rotating drive component is mounted on the support frame, and its drive end is connected to one of the rotating chucks. The mandrel is horizontally placed between the two rotating chucks, and both ends of the mandrel are detachably clamped by the two rotating chucks. The rotating drive component drives the rotating chucks to rotate the mandrel coaxially. The support frame is mounted on the weighing end of the weighing component, which is used to weigh the powder rod.

[0009] The beneficial effect of the above technical solution is that the weight change of the powder rod during the deposition process can be conveniently known through the weighing device.

[0010] The weighing component described in the above technical solution is an electronic platform scale, or the weighing component includes a base and multiple weighing feet, the base is horizontally arranged, and the support frame is installed on the upper end of the base through the multiple weighing feet.

[0011] The advantages of the above technical solution are that it has a simple structure, good stability, and high weighing sensitivity.

[0012] In the above technical solution, the support frame is a U-shaped frame, and the two rotating chucks are respectively installed at both ends of the support frame. The rotating drive component is installed at one end of the support frame and is connected to the corresponding rotating chuck for transmission.

[0013] The advantages of the above technical solution are: its structure is simple, so that when the mandrel is clamped on two rotating chucks, there is enough space below the mandrel to install the deposition torch assembly.

[0014] The above technical solution also includes a controller, and the rotating frame, the deposition torch assembly, and the pick-and-place device are all electrically connected to the controller.

[0015] The beneficial effect of the above technical solution is that it makes the entire manufacturing equipment highly automated.

[0016] The above technical solution also includes a temperature probe electrically connected to the controller. The temperature probe is located next to the core rod, and the detection part of the temperature probe faces the middle part corresponding to the length direction of the core rod. It is used to measure the temperature of the outer side of the powder rod.

[0017] The beneficial effects of the above technical solution are as follows: the temperature probe can know the temperature of the outer periphery of the powder rod in real time, so as to determine whether the guide tube needs to be replaced by the temperature value. If it needs to be replaced, the controller controls the pick-and-place device to replace the guide tube on the deposition torch according to the preset replacement strategy.

[0018] The above technical solution also includes a ranging probe electrically connected to the controller. The ranging probes are all located next to the core rod. The detection part of the ranging probe is perpendicular to the middle part of the core rod along its length direction. The ranging probe is used to measure the outer diameter of the corresponding part of the powder rod.

[0019] The beneficial effect of the above technical solution is that the ranging probe can know the change in the radial thickness of the powder rod in real time during each deposition, so as to determine whether the guide tube needs to be replaced based on the change in radial thickness of each deposition. If replacement is required, the controller controls the pick-and-place device to replace the guide tube on the deposition torch according to the preset replacement strategy.

[0020] The picking and holding device described in the above technical solution includes a robotic arm and a mechanical gripper. The robotic arm is located next to the flow guide tube frame, and the mechanical gripper is located at the drive end of the robotic arm. The robotic arm drives the mechanical gripper to move between the deposition torch and the flow guide tube frame to pick up and place the flow guide tube.

[0021] The beneficial effect of the above technical solution is that when the guide tube on the deposition torch needs to be replaced, the mechanical arm drives the mechanical gripper to remove the guide tube from the deposition torch and place it on the guide tube rack. Then, the guide tube of the required specification is taken out from the guide tube rack and installed at the nozzle of the deposition torch.

[0022] The above technical solution describes a flow guide tube rack with multiple horizontally arranged and stepped support platforms. Each support platform has multiple placement parts spaced apart along its length, and each placement part is used to place one flow guide tube.

[0023] The beneficial effect of the above technical solution is that it allows multiple guide tubes to be placed in an orderly manner on the guide tube rack, and at the same time, they can be easily picked up and put away by the pick-up and drop-off device.

[0024] The placement part described in the above technical solution is a groove or protrusion provided on the support platform.

[0025] The advantages of the above technical solution are: its structure is simple and it provides a good limiting effect for the guide tube at the placement part. Attached Figure Description

[0026] Figure 1 This is a side view of the optical fiber preform. Figure 2 for Figure 1 Sectional view at point AA; Figure 3 This is a top view of the manufacturing equipment described in an embodiment of the present utility model; Figure 4 This is a schematic diagram of the deposition torch assembly and the rotating frame described in this embodiment of the present invention; Figure 5 This is another structural schematic diagram of the weighing component described in this embodiment of the present utility model; Figure 6 This is one of the elevation views of the flow guide frame described in this utility model embodiment; Figure 7 This is one of the schematic diagrams showing the cooperation between the guide tube and the placement part in an embodiment of this utility model; Figure 8 This is a second elevation view of the flow guide frame described in this embodiment of the utility model; Figure 9 This is the second schematic diagram of the cooperation between the guide tube and the placement part in the embodiment of this utility model.

[0027] In the diagram: 1. Rotating frame; 11. Support frame; 12. Rotation drive component; 13. Weighing component; 131. Base; 132. Weighing foot; 14. Rotating chuck; 2. Deposition torch assembly; 21. Deposition torch; 22. Guide tube; 23. Reciprocating drive component; 3. Guide tube frame; 31. Support platform; 32. Placement part; 4. Picking and picking component; 41. Robotic arm; 42. Mechanical gripper; 5. Controller; 6. Temperature probe; 7. Distance probe; 8. Fiber optic preform; 81. Core rod; 82. Powder rod body; 821. Powder rod layer. Detailed Implementation

[0028] To facilitate understanding of this application, a more complete description will be provided below with reference to the accompanying drawings, which illustrate embodiments of the present application. However, the present application can be implemented in many different forms and is not limited to the embodiments described herein. Rather, these embodiments are provided so that the disclosure of this application will be thorough and complete.

[0029] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this application belongs. The terminology used herein is for the purpose of describing particular embodiments only and is not intended to be limiting of the application.

[0030] It is understood that spatial relation terms such as “below,” “under,” “below,” “below,” “above,” “above,” etc., can be used here to describe the relationship between one element or feature shown in the figure and other elements or features. It should be understood that, in addition to the orientation shown in the figure, spatial relation terms also include different orientations of the device in use and operation. For example, if the device in the figure is flipped, the element or feature described as “below,” “below,” or “below” will be oriented “above” the other element or feature. Therefore, the exemplary terms “below” and “under” can include both upper and lower orientations. Furthermore, the device may also include other orientations (e.g., rotated 90 degrees or other orientations), and the spatial descriptive terms used herein will be interpreted accordingly.

[0031] It should be noted that when one element is considered to be "connected" to another element, it can be directly connected to the other element or connected to the other element through an intermediary element. In the following embodiments, "connection" should be understood as "electrical connection," "communication connection," etc., if the connected circuits, modules, units, etc., have the transmission of electrical signals or data between them.

[0032] When used herein, the singular forms of “a,” “an,” and “the” may also include the plural forms unless the context clearly indicates otherwise. It should also be understood that the terms “comprising,” “including,” or “having,” etc., specify the presence of the stated feature, whole, step, operation, component, part, or combination thereof, but do not preclude the possibility of the presence or addition of one or more other features, wholes, steps, operations, components, parts, or combinations thereof.

[0033] like Figure 1 and Figure 2 As shown, for the optical fiber preform 8, its center is the core rod 81, and the middle part of the core rod 81 is deposited to form a powder rod body 82. The powder rod body 82 is obtained by stacking powder rod layers 821 deposited layer by layer. The OVD (external vapor deposition) manufacturing process of the optical fiber preform 8 is an existing technology.

[0034] like Figure 3 As shown, this embodiment provides a manufacturing apparatus for an optical fiber preform 8 based on OVD technology, including a rotating frame 1, a deposition torch assembly 2, a flow guide frame 3, and a pick-and-place component 4. The rotating frame 1 is used to clamp the horizontally placed core rod 81 and drive the core rod 81 to rotate coaxially. The deposition torch assembly 2 has a deposition torch 21 that can reciprocate below the core rod 81 to generate powder rods 82 on the outer periphery of the core rod 81. The nozzle of the deposition torch 21 faces... A guide tube 22 is installed on the rotating frame 1. The guide tube rack 3 and the pick-up piece 4 are located next to the rotating frame 1. The guide tube rack 3 is used to store guide tubes 22 of various specifications. The pick-up piece 4 is used to pick up the guide tubes 22 on the deposition torch 21 and store them on the guide tube rack 3. It also picks up one guide tube 22 from the guide tube rack 3 and installs it at the nozzle of the deposition torch 21 to replace the guide tubes 22 on the deposition torch 21. In this way, when the deposition torch assembly 2 is in operation, the pick-up piece 4 can automatically complete the replacement of the guide tubes 22 on the deposition torch 21. This allows the length and / or inner diameter of the guide tube 22 to be adjusted independently and repeatedly during the deposition process of the powder rod 82, so as to adjust the temperature distribution and orientation of the flame. This reduces the radial stress difference, density difference and temperature difference of the powder rod 82, and ultimately produces an optical fiber preform 8 with lower stress, while reducing production costs.

[0035] like Figure 4 As shown, the deposition torch assembly 2 in this embodiment also has a reciprocating drive 23 disposed below the mandrel 81. The deposition torch 21 is installed on the drive end of the reciprocating drive 23. The reciprocating drive 23 can be a linear drive module. The deposition torch assembly 2 is a prior art. Other parts not described in detail can be understood according to the prior art and will not be elaborated here.

[0036] like Figure 3 As shown, the manufacturing equipment in this embodiment also includes a controller 5. The rotating frame 1, the deposition torch assembly 2, and the pick-and-place component 4 are all electrically connected to the controller 5. This results in a high degree of automation for the entire manufacturing equipment. In this embodiment, the controller 5 can be an ARM series microcontroller or PLC controller. The controller 5 can be housed in a control cabinet, which can be placed near the guide tube frame 3 or the pick-and-place component 4. Figure 3 The dashed line in the middle represents the electrical connection line of controller 5.

[0037] For the deposition torch assembly 2, both the deposition torch 21 and the reciprocating drive 23 can be electrically connected to the controller 5.

[0038] like Figure 4 and Figure 5 As shown, in this embodiment, the rotating frame 1 includes a support frame 11, a rotating drive component 12, a weighing component 13, and two rotating chucks 14. Both rotating chucks 14 are rotatably mounted on the support frame 11 and are horizontally distributed relative to each other. The rotating drive component 12 is mounted on the support frame 11, and its driving end is connected to one of the rotating chucks 14. The mandrel 81 is horizontally placed between the two rotating chucks 14, and both ends of the mandrel 81 are detachably clamped by the two rotating chucks 14. The rotating drive component 12 drives the rotating chucks 14 to rotate the mandrel 81 coaxially. The support frame 11 is mounted on the weighing end of the weighing component 13, which is used to weigh the powder rod 82. Thus, the weight change of the powder rod 82 during the deposition process can be conveniently known through the weighing component 13. In this embodiment, the rotary drive 12 can be a servo motor. During the deposition of the powder rod 82, the deposition torch 21 moves slowly, while the mandrel 81 rotates at a suitable speed under the drive of the rotary drive 12, so as to ensure that the powder rod 82 around the mandrel 81 completes one deposition (forming a new powder rod layer 821). For the same powder rod layer 821, its thickness is relatively uniform at all points.

[0039] In this embodiment, the rotary drive 12 and the weighing component 13 are both electrically connected to the controller 5. The controller 5 controls the rotary drive 12 to operate synchronously with the deposition torch 21, while the weighing component 13 monitors the weight of each powder rod layer 821 in real time. It can also determine whether the guide tube 22 needs to be replaced based on the weight change of the powder rod layer 821 during each deposition. If replacement is required, the controller 5 controls the pick-and-place component 4 to replace the guide tube 22 on the deposition torch 21 according to a pre-set replacement strategy.

[0040] like Figure 4As shown, the weighing component 13 in this embodiment is an electronic platform scale; or as... Figure 5 As shown, the weighing component 13 includes a base 131 and multiple weighing feet 132. The base 131 is horizontally arranged, and the support frame 11 is mounted on the upper end of the base 131 via the multiple weighing feet 132 (preferably, two weighing feet are sufficient, and the two weighing feet are spaced apart along the length of the bottom of the support frame 11). Its structure is simple, has good stability, and high weighing sensitivity.

[0041] Compared with the prior art, the only improvement of the rotating frame 1 in this embodiment is the addition of a weighing component. Other aspects not described in detail can be understood according to the prior art and will not be elaborated here.

[0042] like Figure 4 and Figure 5 As shown, in this embodiment, the support frame 11 is a U-shaped frame (at this time, the deposition torch assembly 2 is located inside the support frame 11; note that the deposition torch 21 does not contact the support frame 11, so as not to affect the accuracy of the weighing component). The two rotating chucks 14 are respectively installed at both ends of the support frame 11, and the rotating drive component 12 is installed at one end of the support frame 11 and is connected to the corresponding rotating chuck 14 for transmission. Its structure is simple, so that when the mandrel 81 is clamped on the two rotating chucks 14, there is enough space below the mandrel 81 to install the deposition torch assembly 2.

[0043] like Figure 3 As shown, the manufacturing equipment in this embodiment also includes a temperature probe 6 electrically connected to the controller 5. The temperature probe 6 is located next to the mandrel 81, with its detection part facing the middle of the mandrel 81 along its length. It is used to measure the temperature of the outer side of the powder rod 82. This allows the temperature probe 6 to know the temperature of the outer periphery of the powder rod 82 in real time, enabling the determination of whether the guide tube 22 needs to be replaced based on the temperature value. If replacement is required, the controller 5 controls the pick-and-place component 4 to replace the guide tube 22 on the deposition torch 21 according to a pre-set replacement strategy.

[0044] like Figure 3As shown, the manufacturing equipment in this embodiment also includes a ranging probe 7 electrically connected to the controller 5. The ranging probes 7 are all located beside the mandrel 81, with the detection portion of the ranging probe 7 perpendicularly facing the middle of the mandrel 81 along its length. The ranging probe 7 is used to measure the outer diameter of the powder rod 82 at the corresponding location. Thus, the ranging probe 7 can monitor the radial thickness change of the powder rod 82 in real time during each deposition, allowing for a determination of whether the guide tube 22 needs to be replaced based on the radial thickness change during each deposition. If replacement is required, the controller 5 controls the pick-and-place component 4 to replace the guide tube 22 on the deposition torch 21 according to a pre-set replacement strategy.

[0045] In this embodiment, the ranging probe 7 can determine the radial thickness of the powder rod layer 821 deposited each time based on the radial thickness change of the powder rod body 82 before and after each deposition (when the length of the powder rod layer 821 is relatively fixed). Based on this, the volume of each powder rod layer 821 can be easily calculated. When the weight of each powder rod layer 821 is known, the density of each powder rod layer 821 can be easily calculated. At this time, the density difference between two adjacent powder rod layers 821 can also be used to determine whether the guide tube 22 needs to be replaced. If it needs to be replaced, the controller 5 controls the pick-and-place component 4 to replace the guide tube 22 on the deposition torch 21 according to the preset replacement strategy.

[0046] like Figure 3 As shown, in this embodiment, the picking device 4 includes a robotic arm 41 and a mechanical gripper 42. The robotic arm 41 is positioned next to the flow guide tube frame 3, and the mechanical gripper 42 is positioned at the drive end of the robotic arm 41. The robotic arm 41 drives the mechanical gripper 42 to move between the deposition torch 21 and the flow guide tube frame 3 to pick up and place the flow guide tube 22. This allows the robotic arm 41 to drive the mechanical gripper 42 to remove the flow guide tube 22 from the deposition torch 21 when it needs to be replaced, placing it on the flow guide tube frame 3. Then, a flow guide tube 22 of the required size is taken from the flow guide tube frame 3 and installed at the nozzle of the deposition torch 21. Both the robotic arm 41 and the mechanical gripper 42 are electrically connected to the controller 5.

[0047] In this embodiment, the robotic arm 41 can be a six-degree-of-freedom robotic arm. In this embodiment, the end of the moving trajectory of the deposition torch 21 can be used as the starting point and the other end as the ending point. After the deposition torch 21 completes one round trip cycle during operation (in each round trip cycle, the deposition nozzle sprays flames to perform deposition operations during the movement from the starting point to the ending point, and the flame can be reduced during the return process from the ending point to the starting point, during which no deposition operations are performed), if it is necessary to replace the guide tube 22, it can stop briefly at the starting point to replace the guide tube 22.

[0048] like Figures 6-9 As shown, in this embodiment, the guide tube rack 3 has multiple horizontally arranged and stepped support platforms 31. Each support platform 31 has multiple placement portions 32 spaced apart along its length, each placement portion 32 for placing one guide tube 22. This allows multiple guide tubes 22 to be placed orderly on the guide tube rack 3, while also facilitating easy placement and removal by the picking member 4. Preferably, in this embodiment, the placement portion 32 is a groove provided on the support platform 31 (e.g.,...). Figure 6 and Figure 7 (as shown) or protrusions (such as) Figure 8 and Figure 9 (As shown). Its structure is simple and provides good positioning of the guide tube 22 at the placement part 32. When the placement part 32 is a groove, the lower end of the guide tube 22 is simply inserted into the placement part 32. When the placement part 32 is a protrusion, the guide tube 22 is simply sleeved over the placement part 32. Preferably, the multiple placement parts 32 on two adjacent supports 31 can be staggered, which makes it more convenient for the pick-and-place member 4 to pick up and place the guide tube 22 on the guide tube frame 3.

[0049] In this embodiment, the multiple placement parts 32 on the guide tube frame 3 can be numbered and correspond to the guide tubes 22 of the corresponding specifications. At the same time, the number of each placement part 32 and the specifications of the corresponding guide tube 22 can also be entered into the controller 5. When the take-up piece 4 removes the guide tube 22 from the deposition torch 21, it can be placed in the placement part 32 with the corresponding number, and the required guide tube 22 can be taken out from the guide tube frame 3 and installed at the nozzle of the deposition torch 21 (that is, there is always one placement part 32 on the guide tube frame 3 that is empty and corresponds to the guide tube 22 currently installed on the deposition torch 21).

[0050] Since the position of the starting point of the deposition torch 21 and the positions of the multiple placement parts 32 are fixed relative to the position of the pick-up part 4, the movement trajectory of the mechanical gripper 42 can be preset in the controller 5, so that the pick-up part 4 can accurately pick up and place the guide tube 22.

[0051] Specifically, in this embodiment, the rotating frame 1 can be arranged in the left-right direction, while the flow guide frame 3 can be arranged behind the rotating frame 1. The pick-and-place component 4 is arranged between the flow guide frame 3 and the rotating frame 1, and the temperature probe 6 and the distance probe 7 can be arranged in the middle of the front of the rotating frame 1 (the temperature probe 6 and the distance probe 7 can be installed on a support column arranged vertically in front of the rotating frame 1, and the support column will not be described here). In this embodiment, the distance probe 7 can be an infrared distance probe, and the temperature probe 6 can be an infrared temperature probe. Both of them are existing technologies, so they will not be described in detail here.

[0052] Principle introduction Stress generation mechanism of optical fiber preform 8 during OVD deposition: Thermal stress: During the OVD deposition process, the temperature of the optical fiber preform 8 will change significantly with the deposition process. When the optical fiber preform 8 is heated from room temperature to the high temperature required for deposition, the material will generate stress due to thermal expansion. If the heating or cooling process is uneven, it will lead to uneven stress distribution inside the optical fiber preform 8, thereby generating thermal stress.

[0053] Chemical stress: During the deposition process, silica particles generated by the chemical reaction will be deposited on the surface of the optical fiber preform 8 to form a porous powder rod 82. These particles may chemically bond with the surface of the optical fiber preform 8 during the deposition process, resulting in local stress. In addition, by-products generated during the deposition process (such as HCl) may chemically corrode the surface of the preform, further affecting the stress distribution.

[0054] Mechanical stress: During the deposition process, the optical fiber preform 8 needs to be rotated above the deposition torch assembly 2 to ensure the uniformity of deposition. This mechanical movement may apply additional mechanical stress to the preform, especially when the preform is long or thin, stress concentration is more likely to occur.

[0055] In this embodiment, the manufacturing equipment for the optical fiber preform 8 based on the OVD process mainly reduces the stress difference by gradually reducing the length and / or inner diameter of the guide tube 22 as needed during the deposition process to control the temperature difference, density difference, and thickness difference between adjacent powder rod layers 821 during the deposition of the powder rod body 82.

[0056] The main characteristic of the early stage of deposition is that the temperature of the powder rod 82 is high, but the powder rod 82 is thin and far from the deposition torch 21, resulting in low silica particle deposition efficiency. Based on this, When the inner diameter of the guide tube 22 is large: The large flame distribution area results in a large heating area for the powder rod 82, which in turn leads to a large deposition area for silicon dioxide particles. This means that more silicon dioxide particles are deposited on the powder rod 82, resulting in a smaller density difference (i.e., a smaller stress difference) between adjacent powder rod layers 821 in the radial direction.

[0057] When the length of the guide tube 22 is large: The silica particles generated by the reaction of the escorting raw materials travel a long distance, that is, more silica particles are deposited on the powder rod 82. In this way, the density difference between two adjacent powder rod layers 821 in the radial direction is small, that is, the stress difference is small.

[0058] The main characteristic of the later stage of deposition is that the coarse powder rod 82 is close to the deposition torch 21, but the low temperature leads to low silica particle deposition efficiency. Based on this, When the inner diameter of the guide tube is 22, The small flame distribution area results in a high temperature concentration, which increases the temperature of the powder rod 82, allowing more silica particles to be deposited on the powder rod 82. This results in a small density difference between two adjacent powder rod layers 821 in the radial direction, i.e., a small stress difference.

[0059] When the length of the guide tube is 22, The silica particles generated by the reaction of the escorting raw materials have a large diffusion area, that is, more silica particles are deposited on the powder rod 82. In this way, the density difference between two adjacent powder rod layers 821 in the radial direction is small, that is, the stress difference is small.

[0060] The main objective of this embodiment is to maximize the deposition efficiency of silica particles in the early and late stages of deposition, while avoiding excessive stress differences between layers (i.e., minimizing the density difference between adjacent powder rod layers 821).

[0061] If the existing technology is followed without replacing the flow guide 22 or adjusting the supply flow rate of hydrogen and oxygen in the deposition torch 21 during the deposition process, the deposition efficiency will be low and the density will be high in the early stage of deposition, which will cause abnormalities such as opaque appearance and large attenuation of the 1383nm fiber during the subsequent dehydration and sintering of the powder rod 82. In the later stage of deposition, the deposition efficiency will be low and the density will be low, which will cause abnormalities such as cracking of the powder rod 82 during the deposition process. At the same time, the stress difference between the two adjacent powder rod layers 821 will be large, and the generated micro-defects will directly increase the bending loss of the optical fiber and reduce the strength of the optical fiber.

[0062] Example Introduction Taking a total of 55 depositions as an example, the entire deposition process can be divided into a preheating period and a deposition period. The deposition period is further divided into five stages: the first deposition stage, the second deposition stage, the third deposition stage, the fourth deposition stage, and the fifth deposition stage. In the preheating period and the first deposition stage, the specifications of the guide pipe 22 remain unchanged. However, starting from the second deposition stage, the length and / or inner diameter of the guide pipe 22 can be adjusted as needed. The number of depositions and the reference specifications of the guide pipe 22 for each stage of the deposition process are shown in Table 1. The first and second deposition stages can be considered as the early deposition stage, while the third to fifth deposition stages can be considered as the late deposition stage.

[0063] Table 1. Specifications of the guide tubes during the preheating and deposition periods, and reference conditions for continued deposition.

[0064] In the second to fifth deposition stages, at least one of the length and inner diameter of the guide tube 22 needs to be reduced [only the length of the guide tube 22 can be reduced, or only the inner diameter of the guide tube 22 can be reduced, or both the length and inner diameter of the guide tube 22 can be reduced (the length and inner diameter can be reduced sequentially or simultaneously)]. The strategy of replacing the guide tube 22 in each deposition stage is not the focus of this embodiment, so it will not be elaborated here. The optical fiber produced by the optical fiber preform 8 prepared according to this process has the characteristics of low stress and good bending resistance.

[0065] According to Table 1, the guide tube 22 in this embodiment is provided with 25 specifications for selection, which are divided into the following according to the length / inner diameter (in mm): 200 / 60, 200 / 58, 200 / 56, 200 / 54, 200 / 52, 190 / 60, 190 / 58, 190 / 56, 190 / 54, 190 / 52, 180 / 60, 180 / 58, 180 / 56, 180 / 54, 180 / 52, 170 / 60, 170 / 58, 170 / 56, 170 / 54, 170 / 52, 160 / 60, 160 / 58, 160 / 56, 160 / 54, 160 / 52.

[0066] The above description is only a preferred embodiment of the present utility model and is not intended to limit the present utility model. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present utility model should be included within the protection scope of the present utility model.

Claims

1. A manufacturing apparatus for optical fiber preforms based on OVD technology, comprising a rotating frame (1) and a deposition torch assembly (2), wherein the rotating frame (1) is used to clamp a horizontally placed core rod (81) and drive the core rod (81) to rotate coaxially, and the deposition torch assembly (2) has a deposition torch (21) capable of reciprocating below the core rod (81) to generate powder rods (82) on the outer periphery of the core rod (81), wherein the nozzle of the deposition torch (21) faces upward and is equipped with a guide tube (22), characterized in that, It also includes a guide tube rack (3) and a pick-up piece (4), which are located next to the rotating frame (1). The guide tube rack (3) is used to store various guide tubes (22) of different specifications. The pick-up piece (4) is used to pick up the guide tubes (22) on the deposition torch (21) and store them on the guide tube rack (3). It also picks up one guide tube (22) from the guide tube rack (3) and installs it at the nozzle of the deposition torch (21) to replace the guide tubes (22) on the deposition torch (21).

2. The optical fiber preform manufacturing equipment based on OVD process according to claim 1, characterized in that, The rotating frame (1) includes a support frame (11), a rotating drive (12), a weighing component (13), and two rotating chucks (14). The two rotating chucks (14) are rotatably mounted on the support frame (11) and are distributed relative to each other in the horizontal direction. The rotating drive (12) is mounted on the support frame (11) and its driving end is connected to one of the rotating chucks (14). The mandrel (81) is placed horizontally between the two rotating chucks (14) and both ends of the mandrel (81) are detachably clamped by the two rotating chucks (14). The rotating drive (12) drives the rotating chucks (14) to rotate the mandrel (81) coaxially. The support frame (11) is mounted on the weighing end of the weighing component (13) and the weighing component (13) is used to weigh the powder rod (82).

3. The optical fiber preform manufacturing equipment based on OVD process according to claim 2, characterized in that, The weighing component (13) is an electronic platform scale, or the weighing component (13) includes a base (131) and multiple weighing feet (132). The base (131) is horizontally arranged, and the support frame (11) is installed on the upper end of the base (131) through the multiple weighing feet (132).

4. The optical fiber preform manufacturing equipment based on OVD process according to claim 2 or 3, characterized in that, The support frame (11) is a U-shaped frame, and the two rotating chucks (14) are respectively installed at both ends of the support frame (11). The rotating drive (12) is installed at one end of the support frame (11) and is connected to the corresponding rotating chuck (14) in a transmission connection.

5. The manufacturing equipment for optical fiber preforms based on OVD process according to any one of claims 1-3, characterized in that, It also includes a controller (5), and the rotating frame (1), the deposition torch assembly (2) and the pick-up piece (4) are all electrically connected to the controller (5).

6. The optical fiber preform manufacturing equipment based on OVD process according to claim 5, characterized in that, It also includes a temperature probe (6) electrically connected to the controller (5). The temperature probe (6) is located next to the core rod (81). The detection part of the temperature probe (6) faces the middle part corresponding to the length direction of the core rod (81). It is used to measure the temperature of the outside of the powder rod (82).

7. The optical fiber preform manufacturing equipment based on OVD process according to claim 5, characterized in that, It also includes a ranging probe (7) electrically connected to the controller (5). The ranging probe (7) is located next to the core rod (81). The detection part of the ranging probe (7) is perpendicular to the middle part of the core rod (81) in the length direction. The ranging probe (7) is used to measure the outer diameter of the corresponding part of the powder rod (82).

8. The manufacturing equipment for optical fiber preforms based on OVD process according to any one of claims 1-3, characterized in that, The picking device (4) includes a robotic arm (41) and a mechanical gripper (42). The robotic arm (41) is located next to the flow guide tube frame (3), and the mechanical gripper (42) is located at the drive end of the robotic arm (41). The robotic arm (41) drives the mechanical gripper (42) to move between the deposition torch (21) and the flow guide tube frame (3) to pick up and place the flow guide tube (22).

9. The manufacturing equipment for optical fiber preforms based on OVD process according to any one of claims 1-3, characterized in that, The guide tube rack (3) has multiple horizontally arranged and stepped support platforms (31), and the support platforms (31) have multiple placement parts (32) spaced apart along their length direction, each placement part (32) being used to place one guide tube (22).

10. The manufacturing equipment for optical fiber preforms based on OVD process according to claim 9, characterized in that, The placement part (32) is a groove or protrusion provided on the support (31).

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