A panda polarized optical fiber rod feeding device and a drawing method

Abstract

The application provides a panda type polarization maintaining optical fiber rod feeding device and a drawing method, which comprises a preform rod and a rod feeding assembly. The preform rod comprises a core mold rod, two stress rods and two extension rods. The two stress rods are embedded in the core mold rod respectively, and the upper end surface of the stress rod is higher than the upper end surface of the core mold rod. The two extension rods are connected to the upper end of the two stress rods respectively. The rod feeding assembly is connected to the upper end of the extension rod, and is used for pushing the stress rod downward when the preform rod is drawn. The rod feeding assembly of the panda type polarization maintaining optical fiber rod feeding device pushes the part of the stress rod which is higher than the core mold rod into the stress area position of the preform rod at a preset speed, compensates the volume shrinkage of the stress rod in real time, solves the problem of the diameter reduction of the stress area from the root, ensures the uniformity of the diameter of the stress area in the whole drawing process, improves the consistency and stability of the performance of the panda type polarization maintaining optical fiber, and meets the demand of high-precision application.

Description

TECHNICAL FIELD

[0001] The application belongs to the technical field of polarization maintaining optical fiber manufacturing, and particularly relates to a panda polarization maintaining optical fiber rod feeding device and a drawing method. BACKGROUND

[0002] As one of the most widely used types of polarization maintaining optical fibers, panda polarization maintaining optical fibers can stably transmit linearly polarized light and effectively suppress polarization state coupling, and thus play an important role in devices such as fiber-optic gyroscopes and fiber-optic hydrophones. Figure 1 As shown in the figure, the center of the panda polarization maintaining optical fiber is a circular core doped with germanium elements, and the outside is a low-refractive quartz glass cladding layer. Two stress regions are symmetrically distributed on both sides of the core in the cladding layer. The stress regions are generally stress rods doped with boron elements. By utilizing the difference in the thermal expansion coefficients between the stress rods and the cladding material, a stable birefringence effect is formed in the optical fiber, thereby realizing long-distance low-loss transmission of linearly polarized light.

[0003] In the manufacturing process of panda polarization maintaining optical fibers, a preform rod assembly drawing method is usually adopted. First, two stress rods doped with boron elements are inserted into the stress regions on both sides of the core, and the assembly of the preform rod is completed. Then, the assembled preform rod is fed into a drawing furnace to form a continuous fiber under the action of high temperature and gravity.

[0004] However, the volume of the stress rod doped with boron elements will shrink during the high-temperature melting process. As the drawing process continues, the effective volume of the stress rod continuously decreases, which leads to a corresponding reduction in the diameter of the stress region of the subsequently formed optical fiber, thereby affecting the consistency and performance stability of the optical fiber. Especially in the ring winding of high-precision fiber-optic gyroscopes, the continuous length of the optical fiber can reach tens of kilometers. The uneven diameter of the stress region will cause differences in the birefringence effect of the optical fiber in different sections, thereby causing fluctuations in the polarization light transmission characteristics, which seriously affects the measurement accuracy and stability of the gyroscope. SUMMARY

[0005] The panda polarization maintaining optical fiber rod feeding device and the drawing method provided by the embodiments of the present application can solve the technical problem of uneven diameter of the stress region in the drawing process of the panda polarization maintaining optical fiber in the prior art.

[0006] To achieve the above-mentioned purpose, the technical solution adopted by the present application is as follows: in the first aspect, a panda polarization maintaining optical fiber rod feeding device is provided, which comprises:

[0007] a preform rod, two stress rods and two extension rods, the two stress rods are respectively embedded in the core rod, and the upper end surface of the stress rod is higher than the upper end surface of the core rod, and the two extension rods are respectively connected to the upper end of the two stress rods; the preform rod can be connected with the rod hanging platform of the drawing equipment; and

[0008] A pushing assembly is connected to the upper end of the elongated rod for pushing the stress rod downward when the preform rod is drawn.

[0009] In combination with the first aspect, in a possible implementation manner, the preform rod further comprises:

[0010] A tail pipe is connected to the upper end of the core mold rod, and the upper end of the tail pipe is blocked by a cover piece; and

[0011] The two elongated rods respectively pass through the cover piece upward and are connected to the pushing assembly.

[0012] In some embodiments, the cover piece has a sealing column inserted into the tail pipe, and a first sealing ring is sleeved on the outer peripheral wall of the sealing column, and the first sealing ring is used for abutting against the inner peripheral wall of the tail pipe.

[0013] In some embodiments, the upper surface of the cover piece is provided with two second sealing rings, and the two second sealing rings are respectively sleeved on the outer periphery of the two elongated rods.

[0014] The cover piece is further provided with two pressing sleeves which are respectively sleeved on the outer periphery of the two elongated rods, and the lower end surface of the pressing sleeve abuts against the corresponding second sealing ring.

[0015] In some embodiments, the pushing assembly comprises:

[0016] A pushing piece is connected to the wire drawing equipment and has a lifting end; and

[0017] A pushing plate is connected to the lifting end, and the upper ends of the two elongated rods are respectively connected to the pushing plate through fasteners.

[0018] In some embodiments, the pushing piece comprises:

[0019] A rotating driving piece is connected to the wire drawing equipment;

[0020] A lead screw is connected to the driving end of the rotating driving piece at the upper end and is rotationally connected to the cover piece at the lower end;

[0021] A lead nut is threadedly sleeved on the outer periphery of the lead screw, the lead nut is the lifting end, and the pushing plate is connected to the lead nut; and

[0022] A guide rod is connected to the wire drawing equipment and extends in the up-down direction, and the pushing plate is slidingly connected to the guide rod.

[0023] The beneficial effects of the panda type polarization maintaining optical fiber rod feeding device provided by the application are as follows: compared with the prior art, the panda type polarization maintaining optical fiber rod feeding device reserves a material basis for the subsequent pushing of the stress rod by the rod feeding assembly, by virtue of the extra length of the stress rod above the core rod; in the drawing process, when the high temperature in the furnace of the drawing equipment causes the stress rod to melt and gradually shrink, the rod feeding assembly pushes the stress rod downward by the extension rod, and gradually pushes the part of the stress rod above the core rod into the stress area position of the preform rod at a preset speed, so as to compensate for the volume shrinkage of the stress rod in real time, solve the problem of the diameter reduction of the stress area of the polarization maintaining optical fiber from the root, ensure the uniformity of the diameter of the stress area in the whole drawing process, and further improve the consistency and stability of the performance of the panda type polarization maintaining optical fiber, thereby meeting the needs of high-precision applications.

[0024] In a second aspect, the embodiments of the application also provide a drawing method of a panda type polarization maintaining optical fiber, based on the aforementioned panda type polarization maintaining optical fiber rod feeding device, the drawing method of the panda type polarization maintaining optical fiber comprises the following steps:

[0025] S1. Embedding two stress rods into the core rod respectively, and making the upper end face of the stress rod higher than the upper end face of the core rod, and connecting two extension rods to the upper end of the two stress rods one by one to form the preform rod;

[0026] S2. Connecting the preform rod to the rod hanging platform of the drawing equipment, and connecting the upper end of the rod feeding assembly and the extension rod;

[0027] S3. Drawing the preform rod by using the drawing equipment, and simultaneously pushing the stress rod downward by the rod feeding assembly at a first preset speed;

[0028] S4. When it is judged that the stress rod reaches the rapid shrinkage condition, the rod feeding assembly pushes the stress rod downward at a second preset speed, and the second preset speed is greater than the first preset speed;

[0029] S5. Drawing a panda type polarization maintaining optical fiber.

[0030] In combination with the second aspect, in a possible implementation manner, before step S3, the method further comprises vacuumizing the preform rod by using a vacuum device, until the vacuum pressure in the preform rod reaches a first pressure value.

[0031] In some embodiments, when the effective length of the core rod reaches a first preset value, nitrogen gas is supplied into the preform rod by using a nitrogen gas pipeline, so that the vacuum pressure is reduced to a second pressure value.

[0032] With reference to the second aspect, in a possible implementation manner, in step S4, determining whether the stress rod reaches the fast shrinkage condition specifically includes:

[0033] determining whether the effective length of the core rod reaches a second preset value;

[0034] if the effective length of the core rod reaches the second preset value, it is determined that the stress rod reaches the fast shrinkage condition.

[0035] The panda-type polarization maintaining optical fiber drawing method provided by the application has the beneficial effects that, compared with the prior art, the panda-type polarization maintaining optical fiber drawing method reserves the length of the stress rod by making the upper end face of the stress rod higher than the upper end face of the core rod, and the length of the stress rod material is reserved for subsequent supplement; the push rod assembly pushes the stress rod downward while drawing, and when the stress rod shrinks rapidly, the speed of the push rod assembly pushing the stress rod downward is accelerated to compensate for the volume shrinkage of the stress rod caused by high-temperature melting in real time, thereby avoiding the problem that the diameters of the stress regions of the optical fibers in the same batch gradually decrease, and the uniformity of the diameters of the stress regions of the panda-type polarization maintaining optical fibers drawn finally is significantly improved, the consistency and stability of the performance of the panda-type polarization maintaining optical fibers are ensured, and the demand of high-precision applications is met. BRIEF DESCRIPTION OF DRAWINGS

[0036] In order to more clearly illustrate the technical solutions in the embodiments of the present application, the following will briefly introduce the drawings needed to be used in the embodiments or the prior art description. Obviously, the drawings in the following description are only some embodiments of the present application, and other drawings can be obtained by those skilled in the art without creative labor.

[0037] Figure 1 It is a cross-sectional structure schematic diagram of the panda-type polarization maintaining optical fiber in the prior art.

[0038] Figure 2 It is a structure schematic diagram of the push rod device of the panda-type polarization maintaining optical fiber provided by the embodiment of the present application.

[0039] Figure 3 It is a partial enlarged structure schematic diagram in the embodiment of the present application. Figure 2

[0040] Figure 4 It is a structure schematic diagram of the preform provided by the embodiment of the present application.

[0041] In the drawings, various reference signs represent:

[0042] ​1, preform; 11, core rod; 12, stress rod; 13, tail pipe; 14, extension rod; 15, core rod; 2, cover; 21, sealing column; 22, first sealing ring; 23, second sealing ring; 24, compression sleeve; 3, rod feeding assembly; 31, pushing piece; 311, rotary driving piece; 312, lead screw; 313, nut; 314, guide rod; 32, pushing plate; 33, fastener; 4, vacuum pipeline; 5, nitrogen pipeline; 10, drawing equipment; 101, rod hanging platform; 20, cladding; 201, core; 30, stress zone. DETAILED DESCRIPTION

[0043] In order to make the technical problems to be solved by the present application, technical solutions and beneficial effects clearer, the present application will be further described in detail below in combination with the drawings and embodiments. It should be understood that the specific embodiments described herein are only used to explain the present application and not used to limit the present application.

[0044] It should be noted that when an element is referred to as being "disposed 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", "back", "top", "bottom", "inner", "outer" and the like indicate the orientation or positional relationship based on the orientation or positional relationship shown in the drawings, and are only used to facilitate the description of the present application and simplify the description, and therefore cannot be understood as indicating or implying that the device or element referred to must have a particular orientation, be constructed and operated in a particular orientation, and therefore cannot be understood as limiting the present application.

[0045] The terms "first", "second" are only used for descriptive purposes and cannot be understood as indicating or implying relative importance or implicitly indicating the number of the technical features indicated. Therefore, the features defined with "first", "second" can explicitly or implicitly include one or several of the features. In the description of the present application, the meaning of "several" is two or more, unless otherwise explicitly and specifically limited.

[0046] Please refer to Figures 1 to 4 , a panda type polarization maintaining optical fiber rod feeding device and drawing method provided by the present application will be described. The panda type polarization maintaining optical fiber rod feeding device comprises a preform 1 and a rod feeding assembly 3, the preform 1 comprises a core rod 11, two stress rods 12 and two extension rods 14, the two stress rods 12 are respectively embedded in the core rod 11, and the upper end surface of the stress rod 12 is higher than the upper end surface of the core rod 11, and the two extension rods 14 are connected to the upper end of the two stress rods 12 one by one; the preform 1 can be connected with the rod hanging platform 101 of the drawing equipment 10; the rod feeding assembly 3 is connected with the upper end of the extension rod 14, and is used for pushing down the stress rod 12 when the preform 1 is drawn.

[0047] Compared with the prior art, the stress rod 12 is higher than the core rod 11 by an extra length, which reserves a material basis for the subsequent pushing of the stress rod 12 by the push rod assembly 3. During the drawing process, when the high temperature in the furnace of the drawing equipment 10 melts the stress rod 12 and the volume of the stress rod 12 gradually shrinks, the push rod assembly 3 pushes the stress rod 12 downward through the extension rod 14, and gradually pushes the part of the stress rod 12 that is higher than the core rod 11 into the stress area 30 of the preform rod 1 at a preset speed, which compensates for the volume shrinkage of the stress rod 12 in real time, solves the problem of the diameter reduction of the stress area 30 of the polarization maintaining optical fiber from the root, ensures the uniformity of the diameter of the stress area 30 during the entire drawing process, and further improves the consistency and stability of the performance of the panda-type polarization maintaining optical fiber, thereby meeting the needs of high-precision applications.

[0048] For ease of description, the up-down direction in the present application is defined with reference to the state of the preform rod 1 in the drawing process as shown in the drawings. Figure 2 The up-down direction in the present application is defined with reference to the state of the preform rod 1 in the drawing process as shown in the drawings.

[0049] In the embodiment, referring to Figure 4 , the core rod 11 is made of a core rod 15 and quartz glass, and a quartz cone head is arranged at the lower end of the core rod 11. When assembling the preform rod 1, the installation holes are first formed on the core rod 11 to preset the insertion positions of the two stress rods 12. The two installation holes are symmetrically arranged on the two sides of the core rod 15 to ensure that the centers of the two installation holes and the center of the core rod 15 are in a collinear state. Moreover, the diameter of the installation hole is slightly larger than the diameter of the stress rod 12, so as to facilitate the formation of a vacuum environment between the stress rod 12 and the core rod 11 in the subsequent process, and meet the process requirements of the preform rod 1 drawing.

[0050] The stress rod 12 is a quartz glass rod doped with boron elements, and the length, diameter and boron element doping concentration of the two stress rods 12 need to be consistent to ensure the consistency of the two stress areas 30 of the polarization maintaining optical fiber formed subsequently. The stress rod 12 is inserted into the installation hole preset on the core rod 11, and the upper end surface of the stress rod 12 is higher than the upper end surface of the core rod 11. The distance h1 by which the upper end surface of the stress rod 12 is higher than the upper end surface of the core rod 11 is 20mm-50mm, which ensures that sufficient material basis is reserved for the subsequent stress rod 12.

[0051] 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, facilitating the push rod assembly 3 to push the stress rod 12 through the extension rod 14, and ensuring the effective reserved supply length of the stress rod 12.

[0052] Specifically, the extension rod 14 is made of quartz glass, which is convenient for welding connection with the stress rod 12, and the extension rod 14 mainly plays a role in connecting the stress rod 12 and the push rod assembly 3, so it does not need to be doped with boron elements, thereby saving the manufacturing cost of the preform rod 1.

[0053] 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.

[0054] The process of drawing the preform 1 using the wire drawing equipment 10 is existing technology and will not be described in detail here.

[0055] 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.

[0056] 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.

[0057] 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.

[0058] 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.

[0059] On this basis, the setting of the cover piece 2 is equivalent to a "plug" to block the upper end of the preform rod 1, ensuring the vacuum environment inside the preform rod 1. Specifically, the cover piece 2 is integrated with a vacuum pipeline 4, which communicates with the inside of the preform rod 1, and the vacuum pipeline 4 is connected with a vacuum device (such as a vacuum pump), and the control of the vacuum device realizes the control of the vacuum pressure inside the preform rod 1. In addition, the cover piece 2 provides a stable bearing basis for the connection of the rod feeding assembly 3 and the stress rod 12, avoiding additional problems such as the offset of the stress rod 12 and the deformation of the preform rod 1 during the pushing process, and ensuring the effectiveness of the subsequent pushing action.

[0060] In some embodiments, referring to Figure 3 , the cover piece 2 has a sealing column 21 inserted into the tail pipe 13, and a first sealing ring 22 is sleeved on the outer peripheral wall of the sealing column 21, and the first sealing ring 22 is used to abut against the inner peripheral wall of the tail pipe 13.

[0061] The setting of the tail pipe 13 provides a special channel for vacuumizing in the drawing process, and at this time, in order to ensure the sealing of the channel, the sealing column 21 of the cover piece 2 is inserted into the tail pipe 13, and at the same time the first sealing ring 22 is tightly abutted to the inner peripheral wall of the tail pipe 13, effectively blocking the air from the connection part of the cover piece 2 and the tail pipe 13 into the preform rod 1, ensuring that the negative pressure value of the preform rod 1 after vacuumizing is stably maintained in the process requirement interval, and ensuring the stable progress of the drawing process.

[0062] In this embodiment, an annular groove is pre-set on the outer peripheral wall of the sealing column 21, and the first sealing ring 22 is arranged in the annular groove, and the outer diameter of the first sealing ring 22 in the natural state is greater than the outer diameter of the sealing column 21. When the sealing column 21 is inserted into the tail pipe 13, the first sealing ring 22 is deformed by extrusion, and an interference fit is formed between the first sealing ring 22 and the inner peripheral wall of the tail pipe 13, thereby realizing the sealed connection of the cover piece 2 and the tail pipe 13.

[0063] Specifically, the first sealing ring 22 is provided with three, and the three first sealing rings 22 are arranged in the axial direction of the tail pipe 13, further increasing the reliability of the sealing.

[0064] In some possible implementations, referring to Figure 3 , the upper surface of the cover piece 2 is provided with two second sealing rings 23, and the two second sealing rings 23 are correspondingly sleeved on the outer periphery of the two extension rods 14; the cover piece 2 is also threadedly connected with two compression sleeves 24, and the two compression sleeves 24 are correspondingly sleeved 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.

[0065] To ensure the smooth driving of the rod feeding assembly 3 downward, the gap between the cover 2 and the extension rod 14 is less than 2 mm, and the gap needs to be sealed to avoid affecting the vacuum environment inside the preform rod 1.

[0066] In this embodiment, the lower end surface of the compression sleeve 24 abuts against the second sealing ring 23, and the axial pressure of the compression sleeve 24 causes the second sealing ring 23 to elastically deform and tightly fit the outer periphery of the extension rod 14 and the surface of the cover 2, effectively blocking air from entering the inside of the preform rod 1 through the gap between the extension rod 14 and the cover 2. The first sealing ring 22 on the outer periphery of the sealing column 21 forms a double sealing system, further ensuring the stability of the negative pressure in the internal vacuum.

[0067] In addition, during the process of the rod feeding assembly 3 pushing the stress rod 12 downward through the extension rod 14, the second sealing ring 23 is always in dynamic sealing contact with the outer periphery of the extension rod 14, and the continuous pressure of the compression 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 during the entire wire drawing period and improving the overall reliability of the device.

[0068] Specifically, the upper surface of the cover 2 has two threaded sleeves, the compression sleeve 24 is in threaded cooperation with the threaded sleeves, and the inner diameter of the threaded sleeves is greater than the outer diameter of the second sealing ring 23. After the compression sleeve 24 is screwed into the threaded sleeves, the lower end surface of the compression sleeve 24 abuts against the second sealing ring 23. When the second sealing ring 23 needs to be replaced due to damage, the compression sleeve 24 can be easily removed to facilitate the replacement of the second sealing ring 23, improving the convenience of device maintenance. In addition, the inner hole of the compression sleeve 24 can also guide the extension rod 14 to a certain extent, ensuring the stability of the stress rod 12 during the downward movement.

[0069] In some possible implementations, the rod feeding assembly 3 has a structure as shown in Figure 3 . Referring to Figure 3 , the rod feeding assembly 3 includes a pushing piece 31 and a pushing plate 32. The pushing piece 31 is connected to the wire drawing equipment 10 and has a lifting end. The pushing plate 32 is connected to the lifting end, and the upper ends of the two extension rods 14 are connected to the pushing plate 32 through fasteners 33 respectively.

[0070] By connecting the upper ends of the two extension rods 14 to the same pushing plate 32 through the fasteners 33, when the lifting end of the pushing piece 31 stably lifts the pushing plate 32, the pushing plate 32 can synchronously transmit the force to the two stress rods 12, avoiding the inclination and deviation of a single stress rod 12 due to uneven force, ensuring that the stress rods 12 are always symmetrically distributed on both sides of the core mold rod 11 when being replenished, and ensuring the accuracy of the position of the optical fiber stress area 30.

[0071] Specifically, the fastener 33 is a tightening screw, and when connected, the upper end surface of the extension rod 14 is first attached to the lower surface of the pushing plate 32, and then the fastener 33 is inserted from top to bottom through the pushing plate 32 and screwed into the upper end of the extension rod 14, thereby achieving reliable connection between the extension rod 14 and the pushing plate 32.

[0072] In some possible implementation manners, the pushing piece 31 has a structure as shown in Figure 3 Figure 3 The pushing piece 31 comprises a rotary driving piece 311, a lead screw 312, a nut 313, and a guide rod 314. The rotary driving piece 311 is connected to the wire drawing equipment 10. The upper end of the lead screw 312 is connected to the driving end of the rotary driving piece 311, and the lower end is rotationally connected to the cover piece 2. The nut 313 is threadedly sleeved on the outer periphery of the lead screw 312. The nut 313 is a lifting end, and the pushing plate 32 is connected to the nut 313. The guide rod 314 is connected to the wire drawing equipment 10 and extends in the up-down direction. The pushing plate 32 is slidingly connected to the guide rod 314.

[0073] In this embodiment, the rotary driving piece 311 is a servo motor, which ensures stable and adjustable rotation speed. The rotary motion is converted into linear lifting motion of the nut 313 by driving the lead screw 312 to rotate. The descending speed of the nut 313 can be accurately adjusted according to the wire drawing speed and the volume shrinkage rate of the stress rod 12, so as to ensure that the pushing speed is real-time matched with the consumption speed and shrinkage rate of the stress rod 12. The transmission mode of the lead screw 312 and the nut 313 has self-locking characteristics, which can avoid the sliding of the pushing plate 32 by itself, and ensure the stability of the wire drawing process.

[0074] Specifically, the guide rod 314 is provided with two guide rods, and the pushing plate 32 can be a long strip-shaped member, the two ends of which are slidingly connected to the two guide rods 314, respectively, to form double-guide constraints on the pushing plate 32, so that the pushing plate 32 always lifts in a horizontal state, avoids uneven force on the two stress rods 12 due to inclination, ensures the synchronization of the pushing of the two stress rods 12, and ensures the symmetrical distribution of the stress area 30 on both sides of the core mold rod 11.

[0075] Specifically, the upper end of the lead screw 312 is rotationally connected to the wire drawing equipment 10 through a bearing and connected to the driving end of the rotary driving piece 311. The lower end of the lead screw 312 is rotationally connected to the cover piece 2 through a bearing, which ensures the stability of the lead screw 312 when rotating. The upper ends of the two guide rods 314 are connected to the wire drawing equipment 10, and the lower ends can be inserted into the cover piece 2, so as to ensure the reliability of the guiding effect of the guide rods 314.

[0076] Based on the same inventive concept, the embodiments of the present application also provide a panda-type polarization maintaining optical fiber drawing method based on the foregoing rod feeding device. The panda-type polarization maintaining optical fiber drawing method comprises the following steps:

[0077] ​S1. Embedding two stress rods 12 into the core mold rod 11 respectively, and making the upper end face of the stress rod 12 higher than the upper end face of the core mold rod 11, connecting two extension rods 14 to the upper end of the two stress rods 12 respectively, and assembling to form the preform rod 1;

[0078] S2. Connecting the preform rod 1 to the hanging rod platform 101 of the drawing equipment 10, and connecting the feeding rod assembly 3 and the upper end of the extension rod 14;

[0079] S3. Drawing the preform rod 1 by using the drawing equipment 10, and pushing the stress rod 12 downward at a first preset speed by using the feeding rod assembly 3;

[0080] S4. When it is judged that the stress rod 12 reaches the rapid shrinkage condition, pushing the stress rod 12 downward at a second preset speed by using the feeding rod assembly 3, and the second preset speed is greater than the first preset speed;

[0081] S5. Drawing the panda type polarization maintaining optical fiber.

[0082] Compared with the prior art, the panda type polarization maintaining optical fiber drawing method provided by the embodiment reserves the length of the stress rod 12 by making the upper end face of the stress rod 12 higher than the upper end face of the core mold rod 11, and the feeding rod assembly 3 pushes the stress rod 12 downward through the extension rod 14 while drawing, and when the stress rod 12 rapidly shrinks, the speed of the feeding rod assembly 3 pushing the stress rod 12 downward is increased to compensate for the volume shrinkage of the stress rod 12 caused by high temperature melting in real time, thereby avoiding the problem that the diameter of the stress area 30 of the same batch of optical fibers gradually shrinks, and the uniformity of the diameter of the stress area 30 of the finally drawn panda type polarization maintaining optical fiber is significantly improved, thereby ensuring the consistency and stability of the performance of the panda type polarization maintaining optical fiber, and meeting the needs of high-precision applications.

[0083] Further, when assembling the preform rod 1, the tail pipe 13 is connected to the upper end of the core mold rod 11, the cover 2 is sealed to the upper port of the tail pipe 13, and the extension rod 14 is connected to the upper end of the stress rod 12, and the extension rod 14 passes through the cover 2 upward. The preform rod 1 after assembly ensures a reliable sealing environment inside to ensure the vacuum effect inside, and establishes a precise transmission path for the pushing of the stress rod 12, thereby strengthening the overall structural stability of the preform rod 1.

[0084] In some embodiments, before step S3, the method further includes vacuumizing the preform rod 1 by using a vacuum device until the vacuum pressure in the preform rod 1 reaches a first pressure value, and the first pressure value can be specifically -80kPa to -90kPa.

[0085] The vacuum pipeline 4 is arranged through the cover 2 and is in interference fit with the cover 2 to ensure the sealing of the inside of the preform 1. The inside of the preform 1 is extracted to a vacuum pressure of -80 kPa to -90 kPa through the vacuum device and the vacuum pipeline 4, which can effectively remove the gas in the inside of the preform 1, maintain a stable negative pressure in the inside, prevent the quartz cladding 20 from collapsing due to the pressure difference between the inside and the outside at high temperature, reduce the interface cavity, ensure the geometric shape and size precision of the optical fiber, and ensure the performance stability of the panda polarization maintaining optical fiber.

[0086] In some embodiments, referring to Figure 2 When the effective length L of the core rod 11 reaches the first preset value, nitrogen is supplied into the preform 1 through the nitrogen pipeline 5 to reduce the vacuum pressure to a second pressure value, which can be -20 kPa to -30 kPa.

[0087] The first preset value can be 50 mm to 70 mm, and in some specific embodiments, can be 60 mm. When the effective length L of the core rod 11 is less than or equal to the first preset value, it indicates that the drawing process has entered the tail cone forming stage, the diameter of the tail cone part gradually decreases, and the overall structure is more fragile. At this time, the vacuum pressure is reduced to -20 kPa to -30 kPa, which can significantly reduce the pressure difference between the inside and the outside of the preform 1 by actively reducing the pressure, prevent the tail cone part from melting and shrinking too fast at high temperature due to excessive negative pressure, and further avoid the deformation of the stress area 30, ensure the stable structure of the stress area 30 of the drawn optical fiber from the main body to the tail end, and meet the strict requirements of high-precision applications on the performance consistency of the full length of the optical fiber.

[0088] On this basis, if the vacuum pressure in the preform 1 is only reduced by adjusting the valve of the vacuum device, it will inevitably lead to gas backflow. In the embodiment, the nitrogen is actively supplied into the preform 1 to reduce the pressure, which can replace the air to fill the internal gap of the preform 1, avoid the non-clean gas backflow into the core rod 11 during the pressure reduction process, and cause impurities to melt into the inside of the optical fiber; and at the same time, it can avoid the moisture (hydroxyl) in the air from invading the inside of the preform 1 to affect the loss performance of the 1380 wave band.

[0089] In addition, during the process of adjusting the vacuum pressure from the first pressure value (-80 kPa to -90 kPa) to the second pressure value (-20 kPa to -30 kPa), the adjustment accuracy needs to be strictly controlled, and the valve of the vacuum device can only realize rough pressure adjustment and cannot meet the control accuracy of the pressure. In the embodiment, a mass flow meter can be arranged on the nitrogen pipeline 5 to accurately control the flow of nitrogen, thereby ensuring the accurate negative pressure range.

[0090] Specifically, the nitrogen pipeline 5 is arranged through the cover 2 and is in interference fit with the cover 2 to ensure the sealing of the inside of the preform 1.

[0091] In some embodiments, in step S4, determining whether the stress rod 12 reaches the fast shrinkage condition specifically includes: determining whether the effective length L of the core rod 11 reaches a second preset value; if the effective length L of the core rod 11 reaches the second preset value, it is determined that the stress rod 12 reaches the fast shrinkage condition.

[0092] In the embodiment, the second preset value can be 70mm-100mm, and in some specific embodiments, it can be 90mm. In the drawing process, when the effective length L of the core rod 11 is greater than the second preset value, it is the initial stage of drawing, and the overall length is relatively long. At this time, the volume shrinkage rate of the stress rod 12 after melting is relatively flat, and the rod feeding assembly 3 pushes the stress rod 12 downward at a first preset speed for feeding the rod, and the first preset speed can be specifically 0.1-0.2mm / min, which can avoid that the stress rod 12 is over-supplied to cause the diameter of the stress zone 30 to be too large; when the effective length L of the core rod 11 is less than or equal to the second preset value, it enters the later stage of drawing, and the volume shrinkage rate of the stress rod 12 under high temperature is accelerated. At this time, the rod feeding assembly 3 pushes the stress rod 12 downward at a second preset speed for feeding the rod, and the second preset speed can be specifically 0.4-0.6mm / min, which can compensate the material of the stress rod 12 that shrinks at an accelerated rate in time, and prevent the diameter of the stress zone 30 from being reduced; by dynamically adjusting the preset speed of the rod feeding assembly 3 according to the effective length L of the core rod 11, the accurate matching of the stress rod 12 supply amount and the shrinkage amount in the whole drawing period can be realized, the diameter fluctuation of the stress zone 30 in different stages is avoided, and the consistency and polarization performance stability of the panda-type polarization maintaining optical fiber product are ensured.

[0093] The above only describes the preferred embodiments of the present application and is not intended to limit the present application. Any modification, equivalent replacement and improvement within the spirit and principle of the present application shall be included in the protection scope of the present application.

Claims

1. A panda polarization maintaining optical fiber rod feeding device, characterized in that, The application relates to a panda-type polarization maintaining optical fiber rod feeding device and a panda-type polarization maintaining optical fiber rod drawing method. The panda-type polarization maintaining optical fiber rod feeding device comprises a preform rod (1) and a rod feeding assembly (3). The preform rod (1) comprises a core rod (11), two stress rods (12) and two extension rods (14). The two stress rods (12) are embedded in the core rod (11) respectively, and the upper end surface of the stress rod (12) is higher than the upper end surface of the core rod (11). The two extension rods (14) are connected to the upper ends of the two stress rods (12) respectively. The rod feeding assembly (3) is connected to the upper ends of the extension rods (14) and is used for pushing the stress rods (12) downward when the preform rod (1) is drawn. The rod feeding assembly (3) comprises a pushing piece (31) and a pushing plate (32). The pushing piece (31) is connected to the drawing equipment (10) and has a lifting end.

2. A panda polarisation maintaining optical fibre rod delivery device as claimed in claim 1, wherein, The pushing plate (32) is connected to the lifting end, and the upper ends of the two extension rods (14) are connected to the pushing plate (32) through fasteners (33) respectively. The preform rod (1) further comprises a tail pipe (13) and a cover piece (2). The tail pipe (13) is connected to the upper end of the core rod (11), and the upper end of the tail pipe (13) is blocked by the cover piece (2).

3. A panda polarisation maintaining optical fibre rod delivery device as claimed in claim 2, wherein, The two extension rods (14) penetrate the cover piece (2) upward and are connected to the rod feeding assembly (3).

4. A panda polarisation maintaining optical fibre rod delivery device as claimed in claim 2, wherein, The cover piece (2) has a sealing column (21) inserted into the tail pipe (13). A first sealing ring (22) is sleeved on the outer peripheral wall of the sealing column (21) and is used for abutting against the inner peripheral wall of the tail pipe (13).

5. The panda polarized optical fiber rod feeding device according to claim 2, wherein, The upper surface of the cover piece (2) is provided with two second sealing rings (23) which are sleeved on the outer peripheries of the two extension rods (14) respectively. Two pressing sleeves (24) are threadedly connected to the cover piece (2) and are sleeved on the outer peripheries of the two extension rods (14) respectively. The lower end surface of the pressing sleeve (24) abuts against the corresponding second sealing ring (23). The pushing piece (31) comprises a rotary driving piece (311), a lead screw (312), a lead nut (313) and a guide rod (314). The rotary driving piece (311) is connected to the drawing equipment (10).

6. A method of drawing a panda polarisation maintaining optical fibre, characterised in that, The upper end of the lead screw (312) is connected to the driving end of the rotary driving piece (311), and the lower end is rotationally connected to the cover piece (2). The lead nut (313) is threadedly sleeved on the outer periphery of the lead screw (312). The guide rod (314) is connected to the drawing equipment (10) and extends in the up-down direction. The lifting end of the pushing plate (32) is connected to the lead nut (313). The lifting end of the pushing plate (32) is slidably connected to the guide rod (314). The panda-type polarization maintaining optical fiber rod drawing method comprises the following steps: S1. Inserting two stress rods (12) into the core mold rod (11) respectively, and making the upper end face of the stress rod (12) higher than the upper end face of the core mold rod (11), connecting two extension rods (14) to the upper end of the two stress rods (12) one by one, and assembling to form the preform rod (1); S2. Connecting the preform rod (1) to the hanging rod platform (101) of the drawing equipment (10), and connecting the rod feeding assembly (3) and the upper end of the extension rod (14); S3. Drawing the preform rod (1) by using the drawing equipment (10), and pushing the stress rod (12) downward at a first preset speed by using the rod feeding assembly (3); S4. When it is determined that the stress rod (12) reaches the rapid shrinkage condition, pushing the stress rod (12) downward at a second preset speed by using the rod feeding assembly (3), and the second preset speed is greater than the first preset speed; S5. Drawing a panda-shaped polarization maintaining optical fiber.

7. A method of drawing a panda polarisation maintaining optical fibre as claimed in claim 6, characterised in that, Before step S3, it further includes using a vacuum device to vacuum the preform rod (1) until the vacuum pressure in the preform rod (1) reaches a first pressure value.

8. A method of drawing a panda polarisation maintaining optical fibre as claimed in claim 7, characterised in that, When the effective length of the core mold rod (11) reaches a first preset value, nitrogen is supplied into the preform rod (1) by using a nitrogen pipeline (5), so that the vacuum pressure is reduced to a second pressure value.

9. The method of drawing a panda polarisation maintaining optical fibre as claimed in claim 6, wherein, In step S4, determining whether the stress rod (12) reaches the rapid shrinkage condition specifically includes: Determining whether the effective length of the core mold rod (11) reaches a 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) reaches the rapid shrinkage condition.

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