Rod feeding device and wire drawing method for panda type polarization maintaining optical fiber

Abstract

The invention provides a rod feeding device and a wire drawing method of a panda type polarization maintaining optical fiber, the rod feeding device comprises a preform rod and a rod feeding assembly, the preform rod comprises a fiber core mold rod, two stress rods and two extension rods, the two stress rods are respectively embedded in the fiber core mold rod, and the upper end surface of each stress rod is higher than the upper end surface of the fiber core mold rod; the two extension rods are respectively connected to the upper ends of the two stress rods; and the rod feeding assembly is connected with the upper end of the extension rod and is used for pushing the stress rod downwards when the preform rod is drawn. According to the rod feeding device of the panda type polarization maintaining optical fiber, the part, higher than the fiber core mold rod, of the stress rod is pushed into the stress area position of the preform rod at the preset speed through the rod feeding assembly, volume shrinkage of the stress rod is compensated in real time, and the problem that the diameter of the stress area is reduced is fundamentally solved; the uniformity of the diameter of the stress area in the whole wire drawing process is ensured, the consistency and the stability of the performance of the panda type polarization maintaining optical fiber are improved, and the requirement of high-precision application is met.

Description

Technical Field

[0001] This invention belongs to the field of polarization-maintaining fiber manufacturing technology, specifically relating to a rod feeding device and drawing method for a panda-type polarization-maintaining fiber. Background Technology

[0002] Panda-type polarization-maintaining fiber, as one of the most widely used types of polarization-maintaining fiber, can stably transmit linearly polarized light and effectively suppress polarization state coupling, playing an important role in devices such as fiber optic gyroscopes and fiber optic hydrophones. Figure 1 As shown, the center of the panda-type polarization-maintaining fiber is a circular core doped with germanium, and the outer side is a low-refractive-index quartz glass cladding. Stress regions are symmetrically distributed on both sides of the core inside the cladding. The stress regions are generally stress bars doped with boron. By utilizing the difference in the coefficient of thermal expansion between the stress bars and the cladding material, a stable birefringence effect is formed inside the fiber, thereby realizing long-distance, low-loss transmission of linearly polarized light.

[0003] In the manufacturing process of panda-type polarization-maintaining optical fiber, a preform assembly and drawing method is usually adopted. First, two boron-doped stress rods are inserted into the stress regions on both sides of the fiber core to complete the assembly of the preform. Then, the assembled preform is sent into the drawing furnace, where it forms a continuous fiber under the action of high temperature and gravity.

[0004] However, during the high-temperature melting process, the volume of the boron-doped stress bar shrinks. As the fiber drawing process continues, the effective volume of the stress bar decreases, leading to a corresponding reduction in the diameter of the stress region in the subsequently formed fiber. This affects the fiber's consistency and performance stability. Especially in the winding of high-precision fiber optic gyroscopes, where the continuous length of the fiber can reach tens of kilometers, the unevenness of the stress region diameter causes differences in the fiber's birefringence effect across different sections, resulting in fluctuations in the polarization transmission characteristics and severely impacting the gyroscope's measurement accuracy and stability. Summary of the Invention

[0005] The present invention provides a rod feeding device and drawing method for a panda-type polarization-maintaining optical fiber, which can solve the technical problem of uneven diameter of the stress zone during the drawing process of panda-type polarization-maintaining optical fiber in the prior art.

[0006] To achieve the above objectives, the technical solution adopted by the present invention is as follows: Firstly, a rod feeding device for a panda-type polarization-maintaining optical fiber is provided, comprising: A preform includes a core die, two stress bars, and two extension bars. The two stress bars are respectively embedded in the core die, with their upper surfaces higher than the upper surfaces of the core die. The two extension bars are connected one-to-one to the upper ends of the two stress bars. The preform can be connected to the rod-hanging platform of a wire drawing device. The rod feeding assembly, connected to the upper end of the extension rod, is used to push the stress rod downwards when the preform rod is being drawn.

[0007] In conjunction with the first aspect, in one possible implementation, the preform also includes: A tail tube, connected to the upper end of the fiber core mold rod, the upper end of the tail tube being sealed with a cap; and The two extension rods extend upward through the cover and are connected to the rod feeding assembly.

[0008] In some embodiments, the cap has a sealing post inserted into the tailpipe, and a first sealing ring is fitted on the outer peripheral wall of the sealing post, the first sealing ring being used to press against the inner peripheral wall of the tailpipe.

[0009] In some embodiments, the upper surface of the cap is provided with two second sealing rings, and the two second sealing rings are fitted one-to-one on the outer periphery of the two extension rods; The cover is also threaded with two compression sleeves, which are fitted one-to-one on the outer periphery of the two extension rods, with the lower end face of the compression sleeve abutting against the corresponding second sealing ring.

[0010] In some embodiments, the rod feeding assembly includes: A pusher, connected to the wire drawing equipment, and having a lifting end; and A push plate is connected to the lifting end, and the upper ends of the two extension rods are respectively connected to the push plate by fasteners.

[0011] In some embodiments, the pusher includes: A rotary drive component is connected to the wire drawing equipment; The lead screw is connected at its upper end to the drive end of the rotary drive component and at its lower end to the cover component. A lead nut, threadedly fitted onto the outer circumference of the lead screw, the lead nut serving as the lifting end, and the push plate connected to the lead nut; and A guide rod is connected to the wire drawing equipment and extends in the vertical direction; the push plate is slidably connected to the guide rod.

[0012] The beneficial effects of the panda-type polarization-maintaining fiber feeding device provided by this invention are as follows: Compared with the prior art, the panda-type polarization-maintaining fiber feeding device of this invention utilizes the extra length of the stress bar exceeding the core mold rod to reserve a material foundation for the subsequent pushing of the stress bar by the feeding assembly; during the fiber drawing process, when the high temperature inside the drawing furnace melts the stress bar and its volume gradually shrinks, the feeding assembly pushes the stress bar downward through the extension rod, gradually pushing the portion of the stress bar above the core mold rod into the stress zone position of the preform rod at a preset speed, compensating for the volume shrinkage of the stress bar in real time, fundamentally solving the problem of the shrinkage of the stress zone diameter of the polarization-maintaining fiber, ensuring the uniformity of the stress zone diameter throughout the entire drawing process, thereby improving the consistency and stability of the performance of the panda-type polarization-maintaining fiber and meeting the requirements of high-precision applications.

[0013] Secondly, embodiments of the present invention also provide a method for drawing a panda-shaped polarization-maintaining fiber, based on the aforementioned panda-shaped polarization-maintaining fiber feeding device, the method for drawing the panda-shaped polarization-maintaining fiber includes the following steps: S1. Insert the two stress bars into the fiber core mold rod respectively, and make the upper end face of the stress bar higher than the upper end face of the fiber core mold rod. Connect the two extension rods one-to-one to the upper ends of the two stress bars to assemble the preform rod. S2. Connect the preformed rod to the rod hanging platform of the wire drawing equipment, so that the rod feeding assembly and the upper end of the extension rod are connected; S3. The preform rod is drawn into wires using the wire drawing equipment, and at the same time, the stress rod is pushed downwards at a first preset speed using the rod feeding assembly; S4. When it is determined that the stress bar has reached the rapid contraction condition, the bar feeding assembly pushes the stress bar downward at a second preset speed, the second preset speed being greater than the first preset speed; S5. Pulled into a panda-shaped polarization-maintaining fiber.

[0014] In conjunction with the second aspect, in one possible implementation, prior to step S3, the preform is further evacuated using a vacuum device until the vacuum pressure inside the preform reaches a first pressure value.

[0015] In some embodiments, when the effective length of the fiber core rod reaches a first preset value, nitrogen gas is supplied into the preform using a nitrogen pipeline to reduce the vacuum pressure to a second pressure value.

[0016] In conjunction with the second aspect, in one possible implementation, in step S4, determining whether the stress bar has reached the rapid contraction condition specifically includes: Determine whether the effective length of the fiber core rod has reached the second preset value; If the effective length of the fiber core rod reaches the second preset value, it is determined that the stress rod has reached the condition of rapid contraction.

[0017] The beneficial effects of the panda-type polarization-maintaining fiber drawing method provided by this invention are as follows: Compared with the prior art, the panda-type polarization-maintaining fiber drawing method of this invention, by making the upper end face of the stress bar higher than the upper end face of the fiber core mold rod, reserves length for subsequent supplementation of stress bar material; while drawing, the rod feeding assembly pushes the stress bar downward by extending the rod, and when the stress bar shrinks rapidly, the speed at which the rod feeding assembly pushes the stress bar downward is accelerated to compensate for the volume shrinkage of the stress bar caused by high temperature melting at different stages in real time, avoiding the problem of the stress region diameter gradually shrinking in the same batch of fiber. Finally, the uniformity of the stress region diameter of the drawn panda-type polarization-maintaining fiber is significantly improved, ensuring the consistency and stability of the performance of the panda-type polarization-maintaining fiber and meeting the requirements of high-precision applications. Attached Figure Description

[0018] To more clearly illustrate the technical solutions in the embodiments of the present invention, 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 the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0019] Figure 1 This is a schematic diagram of the cross-sectional structure of a panda-type polarization-maintaining fiber in the prior art; Figure 2 A schematic diagram of a rod feeding device for a panda-type polarization-maintaining optical fiber provided in an embodiment of the present invention; Figure 3 This is an embodiment of the present invention. Figure 2 Enlarged schematic diagram of the middle section; Figure 4 This is a schematic diagram of the structure of the preform provided in an embodiment of the present invention.

[0020] The following are the labeling elements in the figure: 1. Precast rod; 11. Core rod; 12. Stress rod; 13. Tail tube; 14. Extension rod; 15. Core rod; 2. Cover; 21. Sealing column; 22. First sealing ring; 23. Second sealing ring; 24. Pressing sleeve; 3. Rod feeding assembly; 31. Pushing component; 311. Rotary drive component; 312. Lead screw; 313. Lead nut; 314. Guide rod; 32. Pushing plate; 33. Fastener; 4. Vacuum pipeline; 5. Nitrogen pipeline; 10. Fiber drawing equipment; 101. Rod hanging platform; 20. Cladding; 201. Core; 30. Stress zone. Detailed Implementation

[0021] To make the technical problems to be solved, the technical solutions, and the beneficial effects of the present invention clearer, the present invention will be further described in detail below with reference to the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are merely illustrative of the present invention and are not intended to limit the present invention.

[0022] It should be noted that when an element is referred to as being "set on" another element, it can be directly on the other element or indirectly on the 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 only for the convenience of describing the invention 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 the invention.

[0023] The terms "first" and "second" are used for descriptive purposes only and should not be construed as indicating or implying relative importance or implicitly specifying the number of technical features indicated. Thus, a feature defined as "first" or "second" may explicitly or implicitly include one or more of that feature. In the description of this invention, "a number" means two or more, unless otherwise explicitly specified.

[0024] Please refer to the following: Figures 1 to 4 The present invention will now describe a panda-type polarization-maintaining optical fiber feeding device and a drawing method. The panda-type polarization-maintaining optical fiber feeding device includes a preform 1 and a feeding assembly 3. The preform 1 includes a core mold 11, two stress rods 12, and two extension rods 14. The two stress rods 12 are respectively embedded in the core mold 11, and the upper end surface of the stress rods 12 is higher than the upper end surface of the core mold 11. The two extension rods 14 are connected one-to-one to the upper ends of the two stress rods 12. The preform 1 can be connected to the rod hanging platform 101 of the drawing equipment 10. The feeding assembly 3 is connected to the upper end of the extension rods 14 and is used to push the stress rods 12 downwards during the drawing of the preform 1.

[0025] This embodiment provides a panda-type polarization-maintaining fiber feeding device. Compared with the prior art, it utilizes the extra length of the stress rod 12 that extends beyond the core mold rod 11, reserving a material foundation for the subsequent pushing of the stress rod 12 by the feeding assembly 3. During the fiber drawing process, when the high temperature inside the furnace of the fiber drawing equipment 10 melts the stress rod 12 and its volume gradually shrinks, the feeding assembly 3 pushes the stress rod 12 downward through the extension rod 14, gradually pushing the portion of the stress rod 12 that extends beyond the core mold rod 11 into the stress zone 30 position of the preform rod 1 at a preset speed. This compensates for the volume shrinkage of the stress rod 12 in real time, fundamentally solving the problem of the shrinkage of the diameter of the stress zone 30 of the polarization-maintaining fiber. This ensures the uniformity of the diameter of the stress zone 30 throughout the fiber drawing process, thereby improving the consistency and stability of the panda-type polarization-maintaining fiber performance and meeting the requirements of high-precision applications.

[0026] For ease of description, the vertical direction in this application is defined as follows: Figure 2 The state of the preform 1 shown is defined based on the state during the wire drawing process.

[0027] In this embodiment, see Figure 4 The fiber core mold 11 is prefabricated from the core rod 15 and quartz glass, and its lower end is equipped with a quartz cone. When assembling the prefabricated rod 1, mounting holes are first made on the fiber core mold 11 to pre-set insertion positions for the two stress rods 12. The two mounting holes must be symmetrically located on both sides of the core rod 15, ensuring that the centers of the two mounting holes and the center of the core rod 15 are collinear. Furthermore, the diameter of the mounting holes is slightly larger than the diameter of the stress rods 12 to facilitate the subsequent formation of a vacuum environment between the stress rods 12 and the fiber core mold 11, meeting the process requirements for drawing the prefabricated rod 1.

[0028] The stress rod 12 is a boron-doped quartz glass rod. The length, diameter, and boron doping concentration of the two stress rods 12 must be consistent to ensure the consistency of the two stress regions 30 in the subsequently formed polarization-maintaining fiber. The stress rod 12 is inserted into the mounting hole pre-set on the fiber core mold 11, with the upper end face of the stress rod 12 protruding above the upper end face of the fiber core mold 11 by a distance h1 of 20mm-50mm, ensuring sufficient material foundation for subsequent addition of stress rods 12.

[0029] The extension rod 14 is welded to the upper end of the corresponding stress rod 12, which is equivalent to extending the stress rod 12. This makes it easier for the rod feeding assembly 3 to push the stress rod 12 through the extension rod 14, while ensuring the effective reserved supply length of the stress rod 12.

[0030] Specifically, the extension rod 14 is made of quartz glass, which facilitates its welding connection with the stress rod 12. On the other hand, the extension rod 14 mainly serves to connect the stress rod 12 and the rod feeding assembly 3. It does not require the addition of boron, thus saving the manufacturing cost of the preform rod 1.

[0031] The pushing speed of the stress bar 12 by the bar feeding assembly 3 needs to match the contraction rate of the stress bar 12 during the wire drawing process. Furthermore, the bar feeding assembly 3 needs to push two stress bars 12 simultaneously, ensuring their synchronous movement and the symmetry of the two stress zones 30. Specifically, the bar feeding assembly 3 can employ a servo motor and ball screw structure, achieving precise control of the pushing speed by controlling the servo motor's rotational speed; alternatively, it can employ an electronically controlled valve and hydraulic cylinder structure, controlling the hydraulic oil flow rate through the electronically controlled valve to reliably control the hydraulic cylinder's pushing speed.

[0032] The process of drawing the preform 1 using the wire drawing equipment 10 is existing technology and will not be described in detail here.

[0033] In some possible implementations, the aforementioned preform 1 adopts the following... Figure 3 and Figure 4 The structure shown. See also Figure 3 and Figure 4 The preform 1 also includes a tail tube 13, which is connected to the upper end of the fiber core mold 11. The upper end of the tail tube 13 is sealed with a cap 2. Two extension rods 14 pass through the cap 2 upwards and are connected to the rod feeding assembly 3.

[0034] In this embodiment, the tail tube 13 is welded to the upper end of the fiber core mold rod 11. The tail tube 13 facilitates the clamping and assembly of the preform rod 1 and the hanging rod platform 101, avoiding affecting the effective drawing length of the preform rod 1. The extension rod 14 extends upward through the cover member 2, facilitating the connection between the stress rod 12 and the rod feeding assembly 3.

[0035] Since the extension rod 14 needs to extend upward through the cap 2 and be adapted to connect with the rod feeding assembly 3, the extension rod 14 needs to have sufficient length. For example, when assembling the preformed rod 1, the distance h2 between the upper end of the extension rod 14 and the upper end face of the tail tube 13 is 100-200mm.

[0036] It is important to understand that when drawing the preform 1 of the panda-type polarization-maintaining fiber, the preform 1 needs to be evacuated to remove the gas inside the preform 1 and put the inside of the preform 1 under negative pressure. This can prevent the quartz cladding 20 from collapsing due to the pressure difference between the inside and outside at high temperatures, reduce the generation of interface cavities, and thus ensure the geometric shape and dimensional accuracy of the polarization-maintaining fiber, and ensure the stability of its polarization-maintaining performance.

[0037] Based on this, the sealing member 2 acts as a "plug" to seal the upper end of the preform 1, ensuring a vacuum environment inside the preform 1. Specifically, the sealing member 2 integrates a vacuum pipeline 4, which is connected to the interior of the preform 1 and is connected to a vacuum device (such as a vacuum pump). The vacuum pressure inside the preform 1 is controlled by controlling the vacuum device. In addition, the sealing member 2 provides a stable bearing foundation for the connection between the rod feeding assembly 3 and the stress rod 12, avoiding additional problems such as stress rod 12 displacement and preform 1 deformation during the jacking process, and ensuring the effectiveness of subsequent jacking operations.

[0038] In some embodiments, see Figure 3 The cover 2 has a sealing post 21 that is inserted into the tail tube 13. A first sealing ring 22 is sleeved on the outer peripheral wall of the sealing post 21. The first sealing ring 22 is used to press against the inner peripheral wall of the tail tube 13.

[0039] The tail tube 13 provides a dedicated channel for vacuuming during the wire drawing process. To ensure the sealing of this channel, the sealing post 21 of the cover 2 is inserted into the tail tube 13, and the first sealing ring 22 is tightly pressed against the inner circumferential wall of the tail tube 13. This effectively prevents air from seeping into the preform 1 from the connection between the cover 2 and the tail tube 13, ensuring that the negative pressure value inside the preform 1 is stably maintained within the process requirement range after vacuuming, thus ensuring the stable progress of the wire drawing process.

[0040] In this embodiment, an annular groove is pre-set on the outer peripheral wall of the sealing post 21, and the first sealing ring 22 is disposed in the annular groove. The outer diameter of the first sealing ring 22 in its natural state is larger than the outer diameter of the sealing post 21. When the sealing post 21 is inserted into the tail tube 13, the first sealing ring 22 is squeezed and deformed, and an interference fit is formed between it and the inner peripheral wall of the tail tube 13, thereby realizing the sealing connection between the cover 2 and the tail tube 13.

[0041] Specifically, there are three first sealing rings 22, which are arranged at intervals along the axial direction of the tail pipe 13, further increasing the reliability of the seal.

[0042] Among some possible implementations, see [link to relevant documentation]. Figure 3 The upper surface of the cover 2 is provided with two second sealing rings 23, which are fitted one-to-one on the outer periphery of the two extension rods 14; the cover 2 is also threaded with two clamping sleeves 24, which are fitted one-to-one on the outer periphery of the two extension rods 14, and the lower end face of the clamping sleeve 24 abuts against the corresponding second sealing ring 23.

[0043] To ensure that the feeding assembly 3 smoothly drives the stress rod 12 downward, the cover 2 and the extension rod 14 are in clearance fit, and the gap between them is less than 2mm. At this time, in order to avoid the gap affecting the vacuum environment inside the preform rod 1, the gap needs to be sealed.

[0044] In this embodiment, by tightening the clamping sleeve 24, its lower end face abuts against the second sealing ring 23. The axial pressure causes the second sealing ring 23 to undergo elastic deformation and tightly adhere to the outer periphery of the extension rod 14 and the surface of the cover 2, effectively preventing air from seeping into the interior of the preformed rod 1 from the gap between the extension rod 14 and the cover 2. Together with the first sealing ring 22 on the outer periphery of the sealing column 21, a double sealing system is formed, further ensuring the negative pressure stability of the internal vacuum.

[0045] In addition, during the process of the feeding assembly 3 pushing the stress rod 12 downward through the extension rod 14, the second sealing ring 23 always maintains dynamic sealing contact with the outer periphery of the extension rod 14. The continuous pressure of the clamping sleeve 24 ensures that the sealing effect will not be weakened due to the movement of the extension rod 14, thereby maintaining a stable negative pressure environment throughout the entire wire drawing cycle and improving the overall reliability of the device.

[0046] Specifically, the upper surface of the cover 2 has two threaded sleeves. The clamping sleeve 24 is threadedly engaged with the threaded sleeves, and the inner diameter of the threaded sleeve is larger than the outer diameter of the second sealing ring 23. After the clamping sleeve 24 is screwed into the threaded sleeve, the lower end face of the clamping sleeve 24 presses against the second sealing ring 23. When the second sealing ring 23 is damaged and needs to be replaced, the clamping sleeve 24 can be removed to easily replace the second sealing ring 23, which improves the convenience of device maintenance. In addition, the inner hole of the clamping sleeve 24 can also play a certain guiding role for the extension rod 14, ensuring the stability of the stress rod 12 during the downward movement process.

[0047] In some possible implementations, the aforementioned rod feeding component 3 adopts, for example... Figure 3 The structure shown. See also Figure 3 The bar feeding assembly 3 includes a pusher 31 and a pusher plate 32. The pusher 31 is connected to the wire drawing equipment 10 and has a lifting end. The pusher plate 32 is connected to the lifting end. The upper ends of the two extension bars 14 are respectively connected to the pusher plate 32 by fasteners 33.

[0048] The upper ends of the two extension rods 14 are connected to the same push plate 32 by fasteners 33. When the lifting end of the pusher 31 drives the push plate 32 to rise and fall smoothly, the push plate 32 can transmit the force to the two stress rods 12 synchronously, avoiding tilting and displacement caused by uneven force on a single stress rod 12. This ensures that the stress rods 12 are always symmetrically distributed on both sides of the fiber core mold rod 11 when replenishing, thus ensuring the accuracy of the position of the fiber stress zone 30.

[0049] Specifically, the fastener 33 is a set screw. When connecting, the upper end face of the extension rod 14 is first made to fit against the lower surface of the push plate 32. Then, the fastener 33 is inserted from top to bottom through the push plate 32 and screwed into the upper end of the extension rod 14 to achieve a reliable connection between the extension rod 14 and the push plate 32.

[0050] In some possible implementations, the aforementioned pusher 31 adopts, for example... Figure 3 The structure shown. See also Figure 3 The pusher 31 includes a rotary drive 311, a lead screw 312, a lead screw nut 313, and a guide rod 314. The rotary drive 311 is connected to the wire drawing equipment 10. The upper end of the lead screw 312 is connected to the drive end of the rotary drive 311, and the lower end is rotatably connected to the cover 2. The lead screw nut 313 is threaded on the outer circumference of the lead screw 312. The lead screw nut 313 is the lifting end, and the pusher plate 32 is connected to the lead screw nut 313. The guide rod 314 is connected to the wire drawing equipment 10 and extends in the vertical direction. The pusher plate 32 is slidably connected to the guide rod 314.

[0051] In this embodiment, the rotary drive 311 uses a servo motor to ensure a stable and adjustable output speed. By driving the lead screw 312 to rotate, the rotary motion is converted into the linear lifting motion of the lead nut 313. The downward speed of the lead nut 313 can be precisely adjusted according to the wire drawing speed and the volume shrinkage rate of the stress bar 12, ensuring that the pushing speed is matched with the consumption speed and shrinkage rate of the stress bar 12 in real time. Moreover, the transmission method of the lead screw 312 and the lead nut 313 has a self-locking characteristic, which can prevent the push plate 32 from sliding on its own and ensure the stability of the wire drawing process.

[0052] Specifically, there are two guide rods 314, and the push plate 32 can be a long strip-shaped component with its two ends slidably connected to the two guide rods 314 respectively, forming a double guide constraint on the push plate 32, so that the push plate 32 always rises and falls in a horizontal state, avoiding uneven force on the two stress rods 12 due to tilting, ensuring the synchronicity of the push of the two stress rods 12, and ensuring that the stress zone 30 is symmetrically distributed on both sides of the fiber core mold rod 11.

[0053] Specifically, the upper end of the lead screw 312 is rotatably connected to the wire drawing device 10 via a bearing and is also connected to the drive end of the rotary drive component 311. The lower end of the lead screw 312 is rotatably connected to the cover component 2 via a bearing, ensuring the stability of the lead screw 312 during rotation. The upper ends of the two guide rods 314 are connected to the wire drawing device 10, and the lower ends can be inserted into the cover component 2 to ensure the reliability of the guiding function of the guide rods 314.

[0054] Based on the same inventive concept, this application also provides a method for drawing a panda-shaped polarization-maintaining fiber. Based on the aforementioned panda-shaped polarization-maintaining fiber feeding device, the method for drawing the panda-shaped polarization-maintaining fiber includes the following steps: S1. Insert two stress rods 12 into the core mold rod 11 respectively, and make the upper end face of the stress rod 12 higher than the upper end face of the core mold rod 11. Connect two extension rods 14 one-to-one to the upper end of the two stress rods 12 to assemble the preform rod 1. S2. Connect the preformed rod 1 to the rod hanging platform 101 of the wire drawing equipment 10, so that the upper end of the rod feeding assembly 3 and the extension rod 14 are connected. S3. The preform 1 is drawn into wire using the wire drawing equipment 10, and at the same time, the stress rod 12 is pushed downward at a first preset speed using the rod feeding assembly 3. S4. When it is determined that the stress rod 12 has reached the rapid contraction condition, the rod feeding assembly 3 pushes the stress rod 12 downward at a second preset speed, the second preset speed being greater than the first preset speed. S5. Pulled into a panda-shaped polarization-maintaining fiber.

[0055] This embodiment provides a method for drawing panda-type polarization-maintaining fiber. Compared with the prior art, by making the upper end face of the stress rod 12 higher than the upper end face of the core mold rod 11, the length of the stress rod 12 material is reserved for subsequent supplementation. At the same time as drawing, the rod feeding assembly 3 pushes the stress rod 12 downward through the extension rod 14. When the stress rod 12 shrinks rapidly, the speed at which the rod feeding assembly 3 pushes the stress rod 12 downward is accelerated to compensate for the volume shrinkage of the stress rod 12 caused by high temperature melting at different stages in real time. This avoids the problem of the stress region 30 diameter of the same batch of fiber gradually shrinking. Finally, the uniformity of the diameter of the stress region 30 of the drawn panda-type polarization-maintaining fiber is significantly improved, ensuring the consistency and stability of the performance of the panda-type polarization-maintaining fiber and meeting the requirements of high-precision applications.

[0056] Furthermore, during the assembly of the preform 1, a tail tube 13 is connected to the upper end of the core die 11, and a cap 2 is placed over the upper end of the tail tube 13. Simultaneously, an extension rod 14 is connected to the upper end of the stress rod 12, allowing the extension rod 14 to pass upwards through the cap 2. The assembled preform 1 ensures a reliable internal sealing environment to guarantee its internal vacuum effect, while also establishing a precise transmission path for the pushing of the stress rod 12, thus enhancing the overall structural stability of the preform 1.

[0057] In some embodiments, before step S3, the preform 1 is evacuated using a vacuum device until the vacuum pressure inside the preform 1 reaches a first pressure value, which may be -80 kPa to -90 kPa.

[0058] Vacuum line 4 is installed through the cap 2 and maintains an interference fit with the cap 2 to ensure the airtightness of the preform 1. By using vacuum equipment and vacuum line 4 to evacuate the interior of the preform 1 to a vacuum pressure of -80kPa to -90kPa, the gas inside the preform 1 can be effectively removed, maintaining a stable negative pressure inside. This prevents the quartz cladding 20 from collapsing due to the pressure difference between the inside and outside at high temperatures, reduces the generation of interface cavities, ensures the geometric shape and dimensional accuracy of the optical fiber, and ensures the stable performance of the panda-type polarization-maintaining optical fiber.

[0059] In some embodiments, see Figure 2 When the effective length L of the fiber core mold rod 11 reaches the first preset value, nitrogen is supplied into the preform rod 1 through the nitrogen pipeline 5, so that the vacuum pressure drops to the second pressure value, which can be -20kPa to -30kPa.

[0060] The first preset value can be 50mm-70mm, and in some specific embodiments it can be 60mm. When the effective length L of the fiber core mold 11 is less than or equal to the first preset value, it indicates that the fiber drawing process has entered the later stage of tail cone formation. The diameter of the tail cone gradually decreases, and the overall structure becomes more fragile. At this time, the vacuum pressure is reduced to -20kPa to -30kPa. The pressure difference between the inside and outside of the preform 1 can be significantly reduced by actively reducing the pressure, preventing the tail cone from melting and shrinking too quickly due to excessive negative pressure at high temperature. This avoids deformation of the stress zone 30 and ensures the structural stability of the stress zone 30 of the drawn optical fiber from the main body to the tail end, meeting the stringent requirements of high-precision applications for the performance consistency of the entire length of the optical fiber.

[0061] Based on this, if the vacuum pressure inside the preform 1 is reduced simply by adjusting the valve of the vacuum equipment, it will inevitably lead to gas backflow. However, in this embodiment, the pressure is actively reduced by supplying nitrogen into the preform 1, which can replace air to fill the internal gap of the preform 1 and prevent unclean gas from flowing back into the fiber core mold 11 during the pressure reduction process, causing impurities to melt into the fiber. At the same time, it can prevent moisture (hydroxyl ions) in the air from invading the interior of the preform 1 and affecting the loss performance of the 1380 band.

[0062] Furthermore, during the adjustment of the vacuum pressure from the first pressure value (-80 kPa to -90 kPa) to the second pressure value (-20 kPa to -30 kPa), strict control of the adjustment accuracy is required. However, the valves of the vacuum equipment can only achieve coarse pressure adjustment and cannot meet the pressure control precision requirements. In this embodiment, a mass flow meter can be installed on the nitrogen pipeline 5 to precisely control the nitrogen flow rate, thereby ensuring a precise negative pressure range.

[0063] Specifically, the nitrogen pipeline 5 passes through the sealing member 2 and maintains an interference fit with the sealing member 2 to ensure the airtightness of the preform 1.

[0064] In some embodiments, in step S4, determining whether the stress bar 12 has reached the rapid contraction condition specifically includes: determining whether the effective length L of the core mold rod 11 has reached a second preset value; if the effective length L of the core mold rod 11 has reached the second preset value, then it is determined that the stress bar 12 has reached the rapid contraction condition.

[0065] In this embodiment, the second preset value can be 70mm-100mm, and in some specific embodiments it can be 90mm. During the fiber drawing process, when the effective length L of the core die 11 is greater than the second preset value, it is the initial stage of fiber drawing, and the overall length is relatively long. At this time, the volume shrinkage rate of the stress rod 12 after melting is relatively slow. The rod feeding assembly 3 pushes the stress rod 12 downward at a first preset speed. The first preset speed can be 0.1-0.2mm / min, which can avoid excessive replenishment of the stress rod 12, resulting in an excessively large diameter of the stress zone 30. When the effective length L of the core die 11 is less than or equal to the second preset value, it enters the middle and later stages of fiber drawing, and the volume shrinkage rate of the stress rod 12 at high temperature accelerates. At this time, the rod feeding assembly 3 pushes the stress rod 12 downward at a second preset speed. The second preset speed can be 0.4-0.6 mm / min. This can make up for the accelerated shrinkage of the stress rod 12 material in time and prevent the diameter of the stress zone 30 from shrinking. By dynamically adjusting the preset speed of the rod feeding assembly 3 according to the effective length L of the fiber core mold rod 11, the amount of stress rod 12 replenishment and shrinkage can be accurately matched throughout the entire drawing cycle. This avoids fluctuations in the diameter of the stress zone 30 at different stages and ensures the consistency and stability of the polarization-maintaining performance of the panda-type polarization-maintaining fiber product.

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

Claims

1. A rod feeding device for a panda-type polarization-maintaining optical fiber, characterized in that, include: The preform (1) includes a core mold rod (11), two stress rods (12) and two extension rods (14). The two stress rods (12) are respectively embedded in the core mold rod (11), and the upper end surface of the stress rod (12) is higher than the upper end surface of the core mold rod (11). The two extension rods (14) are connected to the upper ends of the two stress rods (12) in a one-to-one correspondence. The preform (1) can be connected to the rod hanging platform (101) of the drawing equipment (10). as well as The rod feeding assembly (3) is connected to the upper end of the extension rod (14) and is used to push the stress rod (12) downward when the preform rod (1) is pulled.

2. The rod feeding device for a panda-type polarization-maintaining optical fiber as described in claim 1, characterized in that, The preform (1) also includes: Tail tube (13) is connected to the upper end of the fiber core mold rod (11), and the upper end of the tail tube (13) is sealed with a cap (2); The two extension rods (14) extend upward through the cover (2) and are connected to the rod feeding assembly (3).

3. The rod feeding device for a panda-type polarization-maintaining optical fiber as described in claim 2, characterized in that, The cover (2) has a sealing post (21) inserted into the tail tube (13), and a first sealing ring (22) is sleeved on the outer peripheral wall of the sealing post (21). The first sealing ring (22) is used to press against the inner peripheral wall of the tail tube (13).

4. The rod feeding device for a panda-type polarization-maintaining optical fiber as described in claim 2, characterized in that, The upper surface of the cover (2) is provided with two second sealing rings (23), and the two second sealing rings (23) are fitted one-to-one on the outer periphery of the two extension rods (14); The cover (2) is also threaded with two compression sleeves (24), which are fitted one-to-one on the outer periphery of the two extension rods (14), and the lower end face of the compression sleeve (24) abuts against the corresponding second sealing ring (23).

5. The rod feeding device for a panda-type polarization-maintaining optical fiber as described in claim 2, characterized in that, The rod feeding assembly (3) includes: A pusher (31) is connected to the wire drawing device (10) and has a lifting end; and The push plate (32) is connected to the lifting end, and the upper ends of the two extension rods (14) are respectively connected to the push plate (32) by fasteners (33).

6. The rod feeding device for a panda-type polarization-maintaining optical fiber as described in claim 5, characterized in that, The pusher (31) includes: A rotary drive (311) is connected to the wire drawing device (10); The lead screw (312) is connected at its upper end to the drive end of the rotary drive (311) and at its lower end to the cover (2) in a rotating manner. A nut (313) is threaded onto the outer periphery of the lead screw (312), the nut (313) is the lifting end, and the push plate (32) is connected to the nut (313); and The guide rod (314) is connected to the wire drawing device (10) and extends in the vertical direction. The push plate (32) is slidably connected to the guide rod (314).

7. A method for drawing panda-type polarization-maintaining optical fiber, characterized in that, Based on the panda-type polarization-maintaining fiber feeding device as described in any one of claims 1-6, the fiber drawing method of the panda-type polarization-maintaining fiber includes the following steps: S1. Insert the two stress rods (12) into the core mold rod (11) respectively, and make the upper end face of the stress rod (12) higher than the upper end face of the core mold rod (11). Connect the two extension rods (14) one by one to the upper end of the two stress rods (12) to assemble the preform rod (1). S2. Connect the preformed rod (1) to the rod hanging platform (101) of the wire drawing equipment (10) so that the upper end of the rod feeding assembly (3) and the extension rod (14) are connected; S3. The preform (1) is drawn using the drawing device (10), and the stress rod (12) is pushed downwards at a first preset speed using the rod feeding assembly (3). S4. When it is determined that the stress rod (12) has reached the rapid contraction condition, the rod feeding assembly (3) pushes the stress rod (12) downward at a second preset speed, the second preset speed being greater than the first preset speed; S5. Pulled into a panda-shaped polarization-maintaining fiber.

8. The method for drawing a panda-type polarization-maintaining optical fiber as described in claim 7, characterized in that, Before step S3, the preform (1) is evacuated using a vacuum device until the vacuum pressure inside the preform (1) reaches a first pressure value.

9. The method for drawing a panda-type polarization-maintaining optical fiber as described in claim 8, characterized in that, When the effective length of the fiber core mold rod (11) reaches the first preset value, nitrogen gas is supplied to the preform rod (1) through the nitrogen pipeline (5) to reduce the vacuum pressure to the second pressure value.

10. The method for drawing a panda-type polarization-maintaining optical fiber as described in claim 7, characterized in that, In step S4, determining whether the stress rod (12) has reached the rapid contraction condition specifically includes: Determine whether the effective length of the fiber core mold (11) reaches the second preset value; If the effective length of the core mold rod (11) reaches the second preset value, it is determined that the stress rod (12) has reached the condition of rapid contraction.

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