A sintering apparatus and sintering method for optical fiber preforms

Abstract

The application discloses a sintering device and a sintering method for optical fiber preform loose bodies, and belongs to the technical field of optical fiber production. The sintering device for optical fiber preform loose bodies comprises a rod feeding mechanism, a quartz furnace tube, a sealing assembly, a first heating assembly, a second heating assembly and a gas inlet assembly. The sealing assembly is arranged on the top of the quartz furnace tube and seals the quartz furnace tube. The gas inlet assembly is arranged on the bottom of the quartz furnace tube. The rod feeding mechanism is arranged on the upper portion of the quartz furnace tube and is in transmission connection with the powder preform rod placed in the quartz furnace tube. The rod feeding mechanism drives the powder preform rod to move up and down and rotate in the quartz furnace tube. The first heating assembly for dehydration and the second heating assembly for sintering are arranged on the outer side of the quartz furnace tube from top to bottom.

Description

Technical Field

[0001] This invention relates to the field of optical fiber production technology, specifically to a sintering apparatus and sintering method for optical fiber preforms. Background Technology

[0002] The main methods currently used for manufacturing optical fiber preforms include VAD (vapor axial deposition), OVD (external vapor deposition), PCVD (plasma chemical vapor deposition), and MCVD (modified chemical vapor deposition). Among them, VAD and OVD are known as external deposition methods, which are suitable for manufacturing larger-sized optical fiber preforms and have advantages in terms of high production efficiency and low cost.

[0003] Both VAD and OVD methods involve two main steps: deposition and sintering. During deposition, a white, porous cylinder composed of silica and germanium dioxide particles is first formed. Next, in a high-temperature sintering furnace, a highly oxidizing gas (such as chlorine) is introduced to remove moisture and metallic impurities from the porous body. Simultaneously, an inert gas is introduced to maintain the stability of the gas flow and temperature distribution, ultimately sintering the porous body into a transparent, moisture-free, dense glass preform.

[0004] The sintering process of the preform directly affects its internal hydroxyl content, dopant concentration, and internal stress level, all of which further influence the attenuation characteristics of the optical fiber. Therefore, the sintering process conditions and the stability of the sintering furnace system are crucial to the quality of the preform. Factors affecting the stability of the sintering furnace system include temperature control accuracy, temperature distribution uniformity, and furnace sealing performance.

[0005] Traditional sintering furnaces typically have only one heating zone, relying on graphite resistance thermometers or silicon molybdenum rods for heating. In this process, the porous material first undergoes dehydration in this zone, and then passes through the same zone again for sintering. This single-zone heating design prolongs the process time and reduces the overall efficiency of the equipment. Furthermore, since dehydration and sintering require different temperature settings, this repeated switching can shorten the lifespan of the heating elements. The sealing of the quartz furnace body is also crucial, as the chlorine gas used in the dehydration process is toxic, and leaks pose serious safety risks. Poor sealing can also allow outside air to enter the furnace, affecting the dehydration effect of the porous material.

[0006] Therefore, the applicant designed a sintering apparatus and sintering method for optical fiber preforms. Summary of the Invention

[0007] The purpose of this invention is to provide a sintering apparatus and sintering method for optical fiber preforms to solve the technical problems mentioned in the background art.

[0008] The technical solution to achieve the objective of this invention is: a sintering device for porous optical fiber preforms, comprising a rod feeding mechanism, a quartz furnace tube, a sealing assembly, a first heating assembly, a second heating assembly, and an air inlet assembly; the sealing assembly is disposed at the top of the quartz furnace tube to seal the quartz furnace tube; the air inlet assembly is disposed at the bottom of the quartz furnace tube; the rod feeding mechanism is disposed at the upper part of the quartz furnace tube, and the rod feeding mechanism is connected to the powder preform placed inside the quartz furnace tube, the rod feeding mechanism driving the powder preform to move up and down and rotate inside the quartz furnace tube; the outer side of the quartz furnace tube is provided with a first heating assembly for dehydration and a second heating assembly for sintering from top to bottom.

[0009] Furthermore, the first heating component uses silicon carbide rod heating; the first heating component adopts a three-stage heating system, including a first heating furnace, a second heating furnace, and a third heating furnace from top to bottom.

[0010] Furthermore, the second heating component uses a silicon molybdenum rod for heating.

[0011] Furthermore, a layer of silicon dioxide powder is provided between the second heating component and the quartz furnace tube.

[0012] Furthermore, the rod feeding mechanism is connected to the powder preform via a guide rod. One end of the guide rod is connected to the rod feeding mechanism, and the other end of the guide rod passes through the sealing assembly and extends into the quartz furnace tube to connect with the powder preform.

[0013] Furthermore, the guide rod is connected to the powder preform rod via an adapter.

[0014] Furthermore, the top of the powder preform is provided with a target rod, and the powder preform is connected to the rod feeding mechanism through the target rod. A quartz ring is held on the target rod.

[0015] Furthermore, the sealing assembly comprises, from top to bottom, a top sealing system, a middle sealing system, and a lower sealing system; the top sealing system is connected to the exhaust gas treatment system; and both the middle sealing system and the lower sealing system are provided with a second pipe through which inert gas flows.

[0016] Furthermore, the internal pressure of the top sealing system is negative, while the internal pressures of the middle sealing system, the lower sealing system, and the quartz furnace tube are all slightly positive. The internal pressures of the middle sealing system and the lower sealing system are lower than the internal pressure of the quartz furnace tube, preventing chlorine gas inside the furnace tube from overflowing into the workshop and affecting the dehydration effect of the powder preform and the safety of workshop personnel.

[0017] Furthermore, the top sealing system is also equipped with an air inlet.

[0018] Furthermore, the air intake assembly includes an inverted conical tube and an air intake pipe; the inverted conical tube is disposed inside the quartz furnace tube, and the air intake pipe passes through the tube wall at the bottom of the quartz furnace tube to reach the interior of the quartz furnace tube and communicates with the bottom of the inverted conical tube. Gas enters the interior of the quartz furnace tube sequentially through the air intake pipe and the inverted conical tube; the top of the inverted conical tube is provided with a plurality of centrally symmetrically arranged air holes, the number of which is set to 9, 16 or 25.

[0019] The present invention also provides a sintering method based on the aforementioned sintering apparatus for optical fiber preform powder preforms, comprising the following steps:

[0020] S1. Connect the powder preform after deposition to the guide rod. The rod feeding mechanism drives the guide rod to descend, thereby driving the powder preform to descend into the quartz furnace tube. When the upper part of the powder preform is level with the temperature zone of the first heating component, it is taken as the starting position. At this time, the quartz discs hanging on the guide rod sit on the steps of the quartz furnace tube in sequence to form a sealing system.

[0021] S2. Chlorine, oxygen and helium are introduced into the quartz furnace tube through the air inlet assembly. The first heating assembly is heated to the dehydration temperature. The powder preform remains at the starting position to carry out the dehydration process. At this time, the inside of the quartz furnace tube maintains a slight positive pressure, and the top sealing system maintains a negative pressure.

[0022] S3. After the dehydration time reaches the set time, the second heating component is turned on and the temperature is raised to the sintering temperature. The rod feeding mechanism slowly descends at a certain speed and chlorine and helium gas for the sintering process are introduced to carry out the sintering process. At this time, the inside of the quartz furnace tube still maintains a slight positive pressure and the top sealing system still maintains a negative pressure.

[0023] S4. After the powder preform rod passes through the heating component to form a glass preform rod, the rod feeding mechanism is raised to the starting position. After the second heating component cools down to the standby temperature, the sintering process of the powder preform rod is completed.

[0024] Furthermore, the standby temperature of the first heating component is controlled at 1000-1050℃, and the dehydration temperature is controlled at 1100-1150℃; the standby temperature of the second heating component is controlled at 1100-1200℃, and the sintering temperature is controlled at 1400-1450℃.

[0025] Furthermore, the internal pressure of the top sealing system is -150 to -100 Pa, and the middle and lower sealing systems are 0 to 30 Pa; the internal pressure of the quartz furnace tube is 0 to 50 Pa.

[0026] Furthermore, the flow rate of chlorine is controlled at 0.5–1 L / min, the flow rate of helium is controlled at 10–15 L / min, and the flow rate of oxygen is controlled at 0.5–0.8 L / min.

[0027] By adopting the above technical solution, the present invention has the following beneficial effects:

[0028] (1) This invention relates to a sintering apparatus for optical fiber preform powder preforms. The apparatus is equipped with a first heating component for dehydration and a second heating component for sintering, arranged sequentially from top to bottom on the outside of a quartz furnace tube. During operation, the feeding mechanism slowly lowers the powder preform. First, the powder preform undergoes dehydration via the first heating component. After dehydration, the first heating component enters a standby state, while the second heating component is activated to raise its temperature to the required sintering temperature. Subsequently, the feeding mechanism continues to lower the dehydrated powder preform into the second heating zone for sintering. After sintering to obtain the optical fiber preform, the feeding mechanism raises the powder preform back to the starting position, and the second heating component cools and enters a standby state. In the next cycle, this integrated design combining dehydration and sintering significantly shortens the sintering process time, improves production efficiency, and solves the problem of shortened lifespan of graphite resistors or silicon molybdenum rods caused by frequent switching between dehydration and sintering temperatures in traditional sintering furnaces. It also reduces the risk of cracking that may occur during the up-and-down movement of the powder preform. In addition, to further enhance the safety and reliability of the device, a sealing component is added to the top of the quartz furnace tube. This not only effectively prevents chlorine leakage and ensures the safety of the optical fiber preform powder preform sintering process, but also prevents the infiltration of external gases, avoiding the situation where the powder preform is not fully dehydrated.

[0029] (2) A silicon dioxide powder layer is provided between the second heating component of the present invention and the quartz furnace tube. During sintering, the high-temperature silicon dioxide powder layer is used for microcrystallization treatment to form a microcrystallized surface layer on the outer wall of the quartz furnace tube, which reduces the crystallization defects of the quartz furnace tube itself, avoids uneven stress distribution in the high-temperature zone of the quartz furnace tube, improves the service life and thermal stability of the quartz furnace tube, and thus ensures the product quality of the preform.

[0030] (3) The upper target rod of the powder preform of the present invention holds a quartz ring, which increases the dehydration effect of the loose body of the powder preform and also avoids the deformation of the guide rod and the adapter due to high temperature.

[0031] (4) The quartz furnace tube of the present invention is provided with a triple sealing system consisting of a top sealing system, a middle sealing system and a lower sealing system, which can prevent chlorine gas from leaking out during the dehydration stage, so that the loose body of the powder preform is completely dehydrated and the optical fiber water peak can reach 0.27 to 0.28 dB / km after the optical fiber preform is drawn.

[0032] (5) The top sealing system of the present invention is also provided with an air inlet, which can further suppress the overflow of chlorine gas in the furnace tube.

[0033] (6) The top of the inverted conical tube of the present invention is provided with a plurality of centrally symmetrically arranged air holes. The number of air holes is set to 9, 16 or 25. Gas enters through the air holes of the inverted conical tube, which homogenizes the gas flow in the quartz furnace tube. The gas contacts the powder preform better, and can carry out the dehydration reaction more fully, reducing the hydroxyl content of the preform and reducing the consumption of chlorine and helium resources. Attached Figure Description

[0034] To make the content of this invention easier to understand, the invention will be further described in detail below with reference to specific embodiments and accompanying drawings, wherein...

[0035] Figure 1 This is a schematic diagram of the structure of a sintering apparatus for an optical fiber preform according to an embodiment of the present invention.

[0036] Figure 2 This is a schematic diagram of the structure of a sealing assembly according to an embodiment of the present invention;

[0037] Figure 3 This is a top view of an inverted conical tube according to an embodiment of the present invention.

[0038] The labels in the attached diagram are as follows: Top sealing system 1, Middle sealing system 2, Lower sealing system 3, Exhaust pipe 4, Air 5, Second pipe 6, Exhaust gas treatment system 7, Guide rod 8, Adapter 9, Powder preform 10, First heating component 11, Silica powder layer 12, Second heating component 13, Quartz furnace tube 14, Inverted conical tube 15. Detailed Implementation

[0039] To better understand the above technical solutions, the following will provide a detailed explanation of the technical solutions in conjunction with the accompanying drawings and specific implementation methods.

[0040] To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, the technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. The components of the embodiments of the present invention described and shown in the accompanying drawings can generally be arranged and designed in various different configurations.

[0041] Therefore, the following detailed description of the embodiments of the invention provided in the accompanying drawings is not intended to limit the scope of the claimed invention, but merely to illustrate selected embodiments of the invention. All other embodiments obtained by those skilled in the art based on the embodiments of the invention without inventive effort are within the scope of protection of the invention.

[0042] It should be noted that similar labels and letters in the following figures indicate similar items. Therefore, once an item is defined in one figure, it does not need to be further defined and explained in subsequent figures.

[0043] In the description of the embodiments of the present invention, it should be understood that the terms "center", "upper", "lower", "left", "right", "vertical", "horizontal", "inner", "outer", etc., indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings, or the orientation or positional relationship commonly used when the product of the invention is in use, or the orientation or positional relationship commonly understood by those skilled in the art. They are only used to facilitate the description of the present invention and to simplify 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. Therefore, they should not be construed as limitations on the present invention.

[0044] In the description of the embodiments of the present invention, it should also be noted that, unless otherwise explicitly specified and limited, the terms "set," "install," "connect," and "link" should be interpreted broadly. For example, they can refer to a fixed connection, a detachable connection, or an integral connection; they can refer to a direct connection or an indirect connection through an intermediate medium; and they can refer to the internal communication between two components. Those skilled in the art can understand the specific meaning of the above terms in the present invention based on the specific circumstances. The present invention will be further described below with reference to the accompanying drawings. The following embodiments are only used to more clearly illustrate the technical solutions of the present invention and should not be used to limit the scope of protection of the present invention.

[0045] (Example 1)

[0046] See Figures 1-2 A sintering apparatus for porous optical fiber preforms includes a rod feeding mechanism, a quartz furnace tube 14, a sealing assembly, a first heating assembly 11, a second heating assembly 13, and an air inlet assembly. The sealing assembly is located at the top of the quartz furnace tube 14 to seal the quartz furnace tube. The air inlet assembly is located at the bottom of the quartz furnace tube 14. The rod feeding mechanism is located at the upper part of the quartz furnace tube 14 and is connected to the powder preform 10 placed inside the quartz furnace tube 14. The rod feeding mechanism drives the powder preform 10 to move up and down and rotate inside the quartz furnace tube 14. The outer side of the quartz furnace tube 14 is provided with a first heating assembly 11 for dehydration and a second heating assembly 13 for sintering, arranged sequentially from top to bottom.

[0047] The diameter of the quartz furnace tube is 320 mm.

[0048] The first heating component 11 uses silicon carbide rod heating; the first heating component 11 adopts three-stage heating, including a first heating furnace, a second heating furnace, and a third heating furnace from top to bottom.

[0049] The second heating component 13 uses a silicon molybdenum rod for heating.

[0050] A silicon dioxide powder layer 12 is provided between the second heating component 13 and the quartz furnace tube 14.

[0051] The feeding mechanism is connected to the powder preform 10 via a guide rod 8. One end of the guide rod 8 is connected to the feeding mechanism, and the other end of the guide rod 8 passes through the sealing assembly and extends into the quartz furnace tube 14 to connect with the powder preform 10.

[0052] The guide rod 8 is connected to the powder preform 10 via an adapter 9.

[0053] The powder preform 10 is provided with a target rod at its top. The powder preform 10 is connected to the rod feeding mechanism via the target rod, and a quartz ring is held on the target rod.

[0054] The sealing assembly forms three sealing systems through a quartz ring and a step at the top of the quartz furnace tube. The contact surface between the quartz ring and the step is a frosted surface, which can further increase the sealing performance.

[0055] The sealing assembly comprises, from top to bottom, a top sealing system 1, a middle sealing system 2, and a lower sealing system 3; the top sealing system 1 is connected to the exhaust gas treatment system 7; the middle sealing system 2 and the lower sealing system 3 are each provided with a second pipe 6 through which inert gas flows.

[0056] The internal pressure of the top sealing system 1 is negative, while the internal pressures of the middle sealing system 2, the lower sealing system 3, and the quartz furnace tube 14 are all slightly positive. Furthermore, the internal pressures of the middle sealing system 2 and the lower sealing system 3 are lower than the internal pressure of the quartz furnace tube 14.

[0057] The top sealing system 1 is also equipped with an air inlet, which is positioned opposite to the exhaust pipe. This effectively strengthens the seal of the middle sealing system and prevents airflow from leaking out from the gap between the quartz disc and the guide rod.

[0058] The air intake assembly includes an inverted conical tube 15 and an air intake pipe. The inverted conical tube 15 is disposed inside the quartz furnace tube 14. The air intake pipe passes through the tube wall at the bottom of the quartz furnace tube 14 and reaches the interior of the quartz furnace tube 14, communicating with the bottom of the inverted conical tube 15. Gas enters the interior of the quartz furnace tube 14 sequentially through the air intake pipe and the inverted conical tube 15. The top of the inverted conical tube 15 is provided with a plurality of centrally symmetrically arranged air holes, the number of which is set to 9, 16 or 25.

[0059] A sintering method based on the aforementioned sintering apparatus for optical fiber preform powder preforms includes the following steps:

[0060] S1. Connect the powder preform after deposition to the guide rod. The rod feeding mechanism drives the guide rod to descend, thereby driving the powder preform to descend into the quartz furnace tube. When the upper part of the powder preform is level with the temperature zone of the first heating component 11, it is taken as the starting position. At this time, the quartz discs hanging on the guide rod are placed on the steps of the quartz furnace tube in sequence to form a sealing system.

[0061] S2. Chlorine, oxygen and helium are introduced into the quartz furnace tube through the air inlet assembly. The first heating assembly 11 is heated to the dehydration temperature. The powder preform stays at the starting position to carry out the dehydration process. At this time, the inside of the quartz furnace tube maintains a slight positive pressure, and the top sealing system maintains a negative pressure.

[0062] S3. After the dehydration time reaches the set time, the second heating component 13 is turned on and the temperature is raised to the sintering temperature. The rod feeding mechanism slowly descends at a certain speed and chlorine and helium gas for the sintering process are introduced to carry out the sintering process. At this time, the inside of the quartz furnace tube still maintains a slight positive pressure and the top sealing system still maintains a negative pressure.

[0063] S4. After the powder preform rod passes through the heating component to form a glass preform rod, the rod feeding mechanism is raised to the starting position. After the second heating component 13 cools down to the standby temperature, the sintering process of the powder preform rod is completed.

[0064] The standby temperature of the first heating component 11 is controlled at 1000-1050℃, and the dehydration temperature is controlled at 1100-1150℃. In this embodiment, the preferred dehydration temperature is 1100℃. The standby temperature of the second heating component 13 is controlled at 1100-1200℃, and the sintering temperature is controlled at 1400-1450℃. In this embodiment, the preferred sintering temperature is 1450℃.

[0065] The internal pressure of the top sealing system 1 is -150 to -100 Pa, while that of the middle sealing system 2 and the lower sealing system 3 is 0 to 30 Pa; the internal pressure of the quartz furnace tube 14 is 0 to 50 Pa.

[0066] The flow rate of chlorine is controlled at 0.5–1 L / min, the flow rate of helium is controlled at 10–15 L / min, and the flow rate of oxygen is controlled at 0.5–0.8 L / min.

[0067] The rotational speed of the bar feeding mechanism is 3 r / min, and the bar feeding speed is 3 mm / min.

[0068] (Example 2)

[0069] See Figure 2The only difference between Example 2 and Example 1 is that the inverted conical tube of the sintering device for the optical fiber preform powder preform has nine pores. The powder preform 10 in this example is prepared by the VAD process, with a length of 2000 mm and a diameter of 220 mm. During the dehydration stage, the flow rate of chlorine is controlled at 1 L / min, the flow rate of helium is controlled at 15 L / min, and the flow rate of oxygen is controlled at 0.6 L / min. During the sintering stage, the flow rate of chlorine is controlled at 0.6 L / min and the flow rate of helium is controlled at 15 L / min. The structure of the sintering device for the optical fiber preform powder preform and the sintering method steps are the same.

[0070] The glass preform prepared in this embodiment was directly used for optical fiber drawing, and the average attenuation of the optical fiber at 1383nm reached 0.286dB / km.

[0071] (Example 3)

[0072] The only difference between Example 2 and Example 1 is that the inverted conical tube of the sintering apparatus for the optical fiber preform powder preform has 16 pores; the powder preform 10 is prepared by OVD process, with a length of 2000mm and a diameter of 300mm; the flow rate of chlorine gas in the dehydration stage is controlled at 0.6L / min, the flow rate of helium gas is controlled at 12L / min, and the flow rate of oxygen gas is controlled at 0.6L / min; the flow rate of chlorine gas in the sintering stage is controlled at 0.6L / min, and the flow rate of helium gas is controlled at 10L / min. The structure of the sintering apparatus for the optical fiber preform powder preform and the sintering method steps are the same.

[0073] The glass preform prepared in this embodiment was directly used for optical fiber drawing, and the average attenuation of the optical fiber at 1383nm reached 0.275dB / km.

[0074] (Example 4)

[0075] The only difference between Example 2 and Example 1 is that the inverted conical tube of the sintering device for the optical fiber preform powder preform has 25 pores; the powder preform 10 is prepared by the VAD process, with a length of 1500 mm and a diameter of 240 mm; the flow rate of chlorine gas in the dehydration stage is controlled at 1 L / min, the flow rate of helium gas is controlled at 15 L / min, and the flow rate of oxygen gas is controlled at 0.6 L / min; the flow rate of chlorine gas in the sintering stage is controlled at 0.6 L / min, and the flow rate of helium gas is controlled at 10 L / min. The structure of the sintering device for the optical fiber preform powder preform and the sintering method steps are the same.

[0076] The glass preform prepared in this embodiment was directly used for optical fiber drawing, and the average attenuation of the optical fiber at 1383nm reached 0.264dB / km.

[0077] The specific embodiments described above further illustrate the purpose, technical solution, and beneficial effects of the present invention. It should be understood that the above descriptions are merely specific embodiments of the present invention and are not intended to limit the present invention. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the protection scope of the present invention.

Claims

1. An apparatus for sintering an optical fiber preform loose body, characterized by comprising: The device comprises a rod feeding mechanism, a quartz furnace tube (14), a sealing assembly, a first heating assembly (11), a second heating assembly (13), and an air inlet assembly. The sealing assembly is arranged on the top of the quartz furnace tube (14) to seal the quartz furnace tube. The air inlet assembly is arranged on the bottom of the quartz furnace tube (14). The rod feeding mechanism is arranged on the upper part of the quartz furnace tube (14) and is in driving connection with a powder preform rod (10) arranged in the quartz furnace tube (14). The rod feeding mechanism drives the powder preform rod (10) to move up and down and rotate in the quartz furnace tube (14). The outer side of the quartz furnace tube (14) is sequentially provided from top to bottom with the first heating assembly (11) for dehydration and the second heating assembly (13) for sintering. The sealing assembly sequentially comprises a top sealing system (1), a middle sealing system (2), and a lower sealing system (3) from top to bottom. The top sealing system (1) is in communication with a waste gas treatment system (7). The middle sealing system (2) and the lower sealing system (3) are both provided with a second pipeline through which inert gas passes. The internal pressure of the top sealing system (1) is negative pressure. The internal pressure of the middle sealing system (2), the lower sealing system (3), and the quartz furnace tube (14) is micro-positive pressure. The internal pressure of the middle sealing system (2) and the lower sealing system (3) is lower than the internal pressure of the quartz furnace tube (14).

2. The sintering apparatus for optical fiber preform loose bodies according to claim 1, characterized in that, The second heating assembly (13) and the quartz furnace tube (14) are provided with a silicon dioxide powder layer (12) therebetween.

3. The sintering apparatus for optical fiber preform loose bodies according to claim 1, characterized in that, The rod feeding mechanism is in driving connection with the powder preform rod (10) through a guide rod (8). One end of the guide rod (8) is in driving connection with the rod feeding mechanism, and the other end of the guide rod (8) penetrates through the sealing assembly and extends into the quartz furnace tube (14) to be connected with the powder preform rod (10).

4. The sintering apparatus for optical fiber preform loose bodies according to claim 3, characterized in that, The top of the powder preform rod (10) is provided with a target rod. The powder preform rod (10) is in driving connection with the rod feeding mechanism through the target rod. A quartz ring is clamped on the target rod.

5. The sintering apparatus for optical fiber preform loose body according to claim 1, wherein The top sealing system (1) is further provided with an air supplementing opening.

6. The sintering apparatus for optical fiber preform loose body according to claim 1, wherein The air inlet assembly comprises an inverted conical tube (15) and an air inlet pipe. The inverted conical tube (15) is arranged inside the quartz furnace tube (14). The air inlet pipe penetrates through the pipe wall of the bottom of the quartz furnace tube (14) to reach the inside of the quartz furnace tube (14) and is in communication with the bottom of the inverted conical tube (15). Gas enters the inside of the quartz furnace tube (14) through the air inlet pipe and the inverted conical tube (15) in sequence. The top of the inverted conical tube (15) is provided with a plurality of gas holes arranged in central symmetry. The number of the gas holes is 9, 16, or 25.

7. A sintering method based on the sintering device for the powder preform rod of an optical fiber preform rod according to any one of claims 1-6, comprising the following steps: S1. connecting the powder preform rod at the end of deposition to a guide rod, and driving the guide rod to descend by the rod feeding mechanism, so as to drive the powder preform rod to descend into the quartz furnace tube. When the upper part of the powder preform rod is flush with the temperature zone of the first heating assembly (11) as the starting position, the quartz disc hung on the guide rod is sequentially seated on the steps of the quartz furnace tube to form a sealing system. S2. Through the gas inlet assembly, chlorine, oxygen and helium are introduced into the quartz furnace tube, the first heating assembly (11) is heated to a dehydration temperature, the powder preform rod stays at the starting position for dehydration process, at this time, the quartz furnace tube is maintained at a slight positive pressure, and the top sealing system is maintained at a negative pressure; S3. After the dehydration time reaches the set time, the second heating assembly (13) is started, heated to a sintering temperature, the rod feeding mechanism slowly descends at a certain speed, and chlorine and helium for sintering process are introduced for sintering process, at this time, the quartz furnace tube is still maintained at a slight positive pressure, and the top sealing system is still maintained at a negative pressure; S4. After the powder preform rod forms a glass preform rod by passing through the heating assembly, the rod feeding mechanism is lifted to the starting position, and after the second heating assembly (13) is cooled to standby temperature, the sintering process of the powder preform rod is completed.

8. The sintering method of a fiber preform loose body according to claim 7, characterized by, The standby temperature of the first heating assembly (11) is controlled at 1000-1050℃, and the dehydration temperature is controlled at 1100-1150℃; the standby temperature of the second heating assembly (13) is controlled at 1100-1200℃, and the sintering temperature is controlled at 1400-1450℃.

9. The sintering method of a fiber preform loose body according to claim 7, characterized by, The internal pressure of the top sealing system (1) is -150 to -100 Pa, the internal pressure of the middle sealing system (2) and the lower sealing system (3) is 0-30 Pa, and the internal pressure of the quartz furnace tube (14) is 0-50 Pa.

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