WO2021184713A1

WO2021184713A1 - Sintering device and sintering method for optical fiber preform soot body

Info

Publication number: WO2021184713A1
Application number: PCT/CN2020/115863
Authority: WO
Inventors: 崔东明; 孔明; 伍淑坚
Original assignee: 烽火通信科技股份有限公司; 武汉烽火锐拓科技有限公司
Priority date: 2020-03-17
Filing date: 2020-09-17
Publication date: 2021-09-23
Also published as: CN111423106A

Abstract

The present application relates to a sintering device and a sintering method for an optical fiber preform soot body. The sintering device comprises a sintering box, a furnace core tube, a heating assembly, a lead rod, a preform feeding mechanism, a first pipe group, and a second pipe group. The furnace core tube and the heating assembly are arranged in the sintering box, the heating assembly forming a heating zone. The lead rod extends into the furnace core tube and is used to connect a preform soot body. The preform feeding mechanism is connected to the lead rod to drive the lead rod to move so that the preform soot body is heated in the heating zone. The first pipe group runs through the walls of the sintering box and the furnace core tube and communicates with an inner cavity of the furnace core tube, and comprises a first intake pipe and a first exhaust pipe. The second pipe group runs through the wall of the sintering box and communicates with an internal cavity of the sintering box, and comprises a second intake pipe and a second exhaust pipe. The present application integrates dehydroxylation, vitrification sintering, and deuteration, and can effectively eliminate a residual gas inside an optical fiber preform, reduce the amount of He used, and eliminate structural defects from the source of optical fiber preform manufacturing, thereby reducing the hydrogen sensitivity of an optical fiber.

Description

Sintering device and method for loose body of optical fiber preform

Technical field

The application relates to the field of optical fiber preform preparation, and in particular to a sintering device and method for the loose body of an optical fiber preform.

Background technique

External vapor deposition (OVD) and axial vapor deposition (VAD) have become the mainstream rod making technology in the industry due to their high cost performance. First _{, large-size optical fiber preforms are prepared through the high-temperature hydrolysis reaction of SiCl 4} and other raw materials and the principle of thermophoresis. Rod loose body, and then through dehydration-sintering process to obtain low water peak, dense and defect-free transparent glass body.

Since the loose body of the optical fiber preform will inevitably contain free water and silanol (Si-OH) during the deposition process, it is necessary to pass oxidizing gas such as Cl ₂ and O ₂ for high temperature dehydroxylation treatment before vitrification and sintering , And then pass in a large flow of He to replace Cl ₂ and O ₂ in the pores of the loose body, but this method is difficult to completely remove Cl ₂ and O ₂ so that a small amount of gas may remain in the sintered glass Bubble defects are formed in the transformed light rod.

In addition, the above-mentioned conventional dehydration-sintering process needs to use a large amount of He, and the high price of He makes the cost of rod making high. At the same time, part of He will remain in the glass body during the sintering and densification process. Patent CN1174820A introduces a method for degassing the sintered optical fiber preform in a high-temperature furnace using the principle of gas thermal diffusion, but this method requires additional special degassing equipment, and the degassing time is long, thereby increasing The equipment investment has reduced the production cost and efficiency of the optical fiber preform.

Compared with the conventional sintering process, negative pressure sintering is a sintering method with higher sintering efficiency. Due to the good sealing of the equipment, the vitrification process is carried out under negative pressure, so that there is basically no gas residue in the sintered densified glass body. No additional degassing process is required, and in addition, the amount of He used can be effectively reduced. However, the design of conventional sintering equipment cannot meet the requirements of high temperature and negative pressure conditions, and the existing negative pressure sintering adopts a long temperature zone, which means that the entire loose body mother rod is placed in a heating furnace and integrated sintered under negative pressure conditions. The actual forming process It is difficult to control and is only suitable for the sintering of core rods and mother rods with smaller dimensions.

In addition, some optical fiber preforms have a large number of structural defects during the manufacturing process, which leads to the deuteration of the produced optical fiber for a long time to achieve the purpose of reducing the hydrogen sensitivity, which increases the optical fiber production cycle. Patent CN101838114A describes a method for optical fiber deuterium treatment. This method optimizes the deuterium treatment time, but only from the perspective of optical fiber processing, and does not solve this problem from the source of optical fiber preform manufacturing.

Summary of the invention

The embodiments of the application provide a sintering device and method for loose bodies of optical fiber preforms, which integrate dehydroxylation, vitrification sintering and deuteration, which can effectively eliminate the residual gas in the optical fiber preforms and reduce the amount of He in sintering. The optical fiber preform eliminates structural defects at the source of manufacturing, thereby reducing the optical fiber's hydrogen sensitivity.

In the first aspect, a sintering device for the loose body of an optical fiber preform is provided, which includes:

Sintered box;

Furnace core tube, which is assembled in the sintering box;

A heating assembly, which is assembled in the sintering box and located outside the furnace core tube, and the heating assembly forms a heating zone in a partial space of the furnace core tube;

A lead rod, the bottom end of the lead rod extends into the furnace core tube and is used to connect the loose body of the preform;

A rod-feeding mechanism, which is connected with the lead rod, and the rod-delivery mechanism is used to drive the lead rod to move in a vertical direction, so that the loose body of the preform is heated in the heating zone;

The first tube group, which penetrates the walls of the sintering box and the furnace core tube and communicates with the inner cavity of the furnace core tube, and includes a first air inlet tube and a first exhaust tube;

The second tube group penetrates the wall surface of the sintering box body and communicates with the inner cavity of the sintering box, and includes a second air inlet pipe and a second exhaust pipe.

In some embodiments, the sintering device further includes a negative pressure mechanism connected to the second exhaust pipe and the first exhaust pipe.

In some embodiments, the sintering device further includes:

A pressure measuring mechanism, which is used to measure the pressure in the furnace core tube and the pressure in the sintering box;

A control system, which is used to control the rod feeding mechanism to drive the movement of the lead rod, control the opening and closing of the heating assembly, control the pressure measurement mechanism to measure pressure, control the opening and closing of the negative pressure mechanism, and control the on and off of the first tube group and the second tube group .

In some embodiments, an opening and closing valve is provided on the second air inlet pipe, the opening and closing valve is used to connect a second gas source, and the second gas source is used to provide Ar;

The first air inlet pipe is provided with a multi-way valve, the multi-way valve is used to connect to a first gas source, and the first gas source is used to provide Cl ₂ , O ₂ , He, D ₂ and/or Ar;

The control system is connected to the opening and closing valve and the multi-way valve, and is used to control the opening and closing valve to control Ar to enter the second intake pipe, and to control the multi-way valve to control the access to the first intake pipe. Type of gas.

In some embodiments, the pressure measurement mechanism includes:

The first pressure sensor and the second pressure sensor are separately arranged on the first air inlet pipe and the second air inlet pipe. State the pressure in the furnace core tube and the sintering box;

And, a third pressure sensor and a fourth pressure sensor are separately arranged on the first exhaust pipe and the second exhaust pipe, the third pressure sensor and the fourth pressure sensor are respectively used to measure the furnace core tube and the sintering box The pressure in the furnace core tube and the sintering box during vacuuming.

In a second aspect, a method for sintering a loose body of an optical fiber preform is provided, which includes the following steps:

Provide a sintering device as described in any one of the above, and connect the loose body of the preform to the lead rod;

Through the negative pressure mechanism, the furnace core tube is pumped to the preset first negative pressure through the first exhaust pipe, and the sintering box is pumped to the preset first negative pressure through the second exhaust pipe. Within the first pressure range;

The heating assembly is heated to a preset dehydroxylation temperature, Cl ₂ , O ₂ and He are introduced into the furnace core tube through the first air inlet pipe, and into the sintering box body through the second air inlet pipe Enter Ar, and make the pressure difference between the inside and outside of the furnace core tube within the preset second pressure range;

Move the preform loose body so that the preform loose body gradually passes through the heating zone, and complete the dehydroxylation of the entire preform loose body;

Pumping the furnace core tube to a preset second negative pressure, and at the same time pumping the sintering box body until the pressure difference between the inside and outside of the furnace core tube is within the preset third pressure range, to remove the residual gas in the preform rod;

Heating the heating assembly to a preset vitrification and sintering temperature, and moving the loose body of the preform under the second negative pressure until the sintering of the loose body of the entire preform is completed;

Cool down to a preset temperature, pass D ₂ and Ar into the furnace core tube until the third negative pressure is reached, and pass Ar into the sintering box at the same time, until the pressure difference between the inside and outside of the furnace core tube is at the preset fourth Deuterium treatment is performed within the pressure range to obtain an optical fiber preform.

In some embodiments, it further includes the following steps:

_{Drain the D 2} and Ar in the furnace core tube and the Ar in the sintering box;

Pour Ar into the furnace core tube and the sintering box until the pressure reaches atmospheric pressure, then take out the optical fiber preform.

In some embodiments, before raising the temperature to the preset dehydroxylation temperature, the following steps are further included:

The lead rod is driven so that the top or bottom end of the loose body of the preform is located in the heating zone.

In some embodiments, the _{flow rates of Cl 2} , O ₂ and He are 0.5 to 1.5 L/min, 0.6 to 1.2 L/min, and 15 to 25 L/min.

In some embodiments, the first pressure range, the second pressure range, the third pressure range, and the fourth pressure range are all -1 to 1 mbar.

The beneficial effects brought about by the technical solution provided by this application include:

The sintering device provided in this application has two sealing systems, one of which is a sealing system composed of a furnace core tube, which can be used for dehydroxylation, negative pressure removal of residual gas, negative pressure vitrification sintering and negative pressure deuteration treatment; second It is a sealing system composed of a sintering box, which is synchronized with the furnace core tube by gas or pumped into a negative pressure to balance the pressure difference between the inside and outside of the furnace core tube to protect the furnace core tube.

Compared with the replacement by a large flow of He, when the sintering device provided in this application is used, the furnace core tube is first pumped to a negative pressure after the dehydroxylation is completed. Under negative pressure, the loose body of the preform can be removed more completely The residual Cl ₂ and O ₂ in the carbon dioxide can reduce defects such as bubbles.

With this application, the vitrification sintering is performed under negative pressure without the use of He. Compared with the traditional sintering method, the amount of He is greatly reduced, which effectively reduces the cost of manufacturing the polished rod. At the same time, there is no residual He in the glass body and no additional need Carry out high temperature degassing treatment.

Using this application, the optical fiber preform is deuterated under negative pressure during the cooling time in the furnace core tube, and high temperature conditions are used to accelerate the diffusion of deuterium molecules, so that the structural defects formed in the optical rod are combined with deuterium in advance, thereby reducing its hydrogen Sensitivity and difficulty of subsequent optical fiber deuteration without affecting the overall optical rod manufacturing efficiency.

Using this application to manufacture preforms under negative pressure conditions can avoid _{the leakage of gases such as Cl 2} and O ₂ and reduce the probability of heating components being oxidized.

Description of the drawings

In order to more clearly describe the technical solutions in the embodiments of the present application, the following will briefly introduce the drawings that need to be used in the description of the embodiments. Obviously, the drawings in the following description are only some embodiments of the present application. For those of ordinary skill in the art, other drawings can be obtained based on these drawings without creative work.

Fig. 1 is a schematic diagram of a sintering device for a loose body of an optical fiber preform provided by an embodiment of the application.

In the figure: A, heating zone; 1. sintering box; 2. furnace core tube; 20, second insulation layer; 21, furnace core tube cover plate; 3. heating assembly; 30, first insulation layer; 31, heating body; 32. Muffle tube; 4. Lead rod; 5. Preform loose body; 6. Rod feeding mechanism; 60. Frame body; 61. Slide arm; 7. First intake pipe; 8. First exhaust pipe; 9. 10. Second intake pipe; 10. Second exhaust pipe; 11. Negative pressure mechanism; 12. Dynamic sealing mechanism; 13. Quartz adapter; 14. Pressure measuring mechanism; 140. First pressure sensor; 141. Second pressure Sensor; 142, the third pressure sensor; 143, the fourth pressure sensor.

Detailed ways

In order to make the purpose, technical solutions and advantages of the embodiments of the present application clearer, the technical solutions in the embodiments of the present application will be described clearly and completely in conjunction with the accompanying drawings in the embodiments of the present application. Obviously, the described embodiments These are a part of the embodiments of the present application, but not all of the embodiments. Based on the embodiments in this application, all other embodiments obtained by those of ordinary skill in the art without creative work shall fall within the protection scope of this application.

The embodiment of the application provides a sintering device for the loose body of an optical fiber preform, which integrates dehydroxylation, vitrification, sintering and deuteration. It can effectively eliminate the residual gas in the optical fiber preform and reduce the amount of He in sintering. Eliminate structural defects at the source of the preform manufacturing, thereby reducing the fiber's hydrogen sensitivity.

Referring to Figure 1, the optical fiber preform loose body sintering device provided by the embodiment of the present application includes a sintering box body 1, a furnace core tube 2, a heating assembly 3, a lead rod 4, a rod feeding mechanism 6, a first tube group, and a second tube. Two tube groups; among them, the sintering box body 1 adopts a sealed box structure; the furnace core tube 2 is set in the sintering box body 1, the furnace core tube 2 includes the tube body and the furnace core tube cover 21 on the top, the tube body and the furnace core tube on the top The cover plate 21 constitutes a sealed furnace core tube 2. The heating assembly 3 is assembled in the sintering box 1 and located outside the furnace core tube 2. The heating assembly 3 forms a heating zone A in a part of the furnace core tube 2; the bottom end of the lead rod 4 extends into the furnace core tube 2 and is used to connect the prefabricated The rod loose body 5 and the lead rod 4 are sealed at the position where the sintering box body 1 and the furnace core tube 2 penetrate, so as to avoid the sintering box body 1 and the furnace core tube 2 from communicating.

The rod feeding mechanism 6 is connected with the lead rod 4, and the rod feeding mechanism 6 is used to drive the lead rod 4 to move in the vertical direction, so that the preform loose body 5 is heated in the heating zone A;

The first tube group penetrates the walls of the sintering box 1 and the furnace core tube 2 and communicates with the inner cavity of the furnace core tube 2, which includes a first air inlet pipe 7 and a first exhaust pipe 8, a first air inlet pipe 7 and a first exhaust pipe 8 Seal at the junction with the wall surface of the sintering box 1 and the furnace core tube 2; the second tube group penetrates the wall of the sintering box 1 and communicates with the inner cavity of the sintering box 1, which includes a second air inlet pipe 9 and a second The exhaust pipe 10, the second intake pipe 9 and the second exhaust pipe 10 are sealed at the joint with the wall surface of the sintering box 1. The first air inlet pipe 7 and the second air inlet pipe 9 are used to connect corresponding air sources.

In some preferred embodiments, as shown in FIG. 1, along the vertical direction, the length of the heating zone A is less than the length of the preform loose body 5, so that during the heating process, the preform loose body 5 needs to be in the rod feeding mechanism 6 It moves in the vertical direction under the drive of, to complete the heating of the entire preform loose body 5. The length of the heating zone in this application is less than the length of the preform loose body. Compared with the sintering method using a long temperature zone, this application moves up and down The loose body of the preform can complete the treatment of the whole rod, the forming process is easy to control, the temperature field is more uniform, and the sintering quality of the loose body can be improved.

In some preferred embodiments, the heating assembly 3 is configured such that when the preform loose body 5 is connected to the lead 4, the bottom or top end of the preform loose body 5 is located in the heating zone A, so that the preform can be moved The loose body 5 facilitates sintering from one end to the other.

In some preferred embodiments, as shown in FIG. 1, the rod feeding mechanism 6 includes a frame body 60 and a sliding arm 61. The sliding arm 61 is movably arranged on the frame body 60 in the vertical direction, and the lead rod 4 is connected to the frame body 60. On the sliding arm 61, the rod feeding mechanism 6 is simple in structure and low in cost, and can realize the lifting and lowering of the loose body 5 of the preform. Of course, in some preferred embodiments, the lead 4 is rotatably arranged on the sliding arm 61, Thereby, the loose body 5 of the preform can be driven to rotate around its own axis.

In some preferred embodiments, as shown in FIG. 1, the heating assembly 3 includes a first insulation layer 30, a heating body 31, and a muffle tube 32 all in a ring shape, and the first insulation layer 30, the heating body 31 and the horse The flange tubes 32 are sequentially arranged at intervals from the sintering box body 1 toward the furnace core tube 2. In this embodiment, the heating body adopts a graphite heating body. The use of a muffle tube can make the temperature field of the heating zone more stable and uniform, and at the same time isolate and protect the graphite heating body. In addition, the graphite heating body directly heats the muffle tube at high temperature. The volatilized carbon on the graphite heating body avoids damage to the furnace core tube due to the existence of the muffle furnace.

In some preferred embodiments, as shown in FIG. 1, the sintering device further includes a negative pressure mechanism 11, which is connected to the second exhaust pipe 10 and the first exhaust pipe 8, and is realized by a negative pressure mechanism 11. Vacuuming the furnace core tube and the sintering box body saves the number of equipment, and the negative pressure mechanism 11 can adopt a vacuum pump.

In the actual arrangement, in order to better perform exhaust and intake, as shown in Figure 1, the first intake pipe 7 penetrates one of the upper and lower portions of the furnace core tube 2, and the first exhaust pipe 8 penetrates the furnace core tube The other of the upper part and the lower part of 2; and in order to facilitate the connection through a negative pressure mechanism 11, the second exhaust pipe 10 is arranged close to the first exhaust pipe 8;

In some preferred embodiments, as shown in FIG. 1, a second insulation layer 20 is provided on the outer wall of the furnace core tube 2 located outside the heating assembly. The lead rod 4 and the furnace core tube 2 are connected with a dynamic sealing mechanism 12. The dynamic sealing mechanism 12 seals the lead rod 4 and the furnace core tube 2 by means of packing or oil seal. The bottom end of the lead rod 4 is provided with Quartz adapter 13 to which the loose body 5 of the preform is connected.

In some preferred embodiments, the second air inlet pipe 9 is provided with an opening and closing valve, which is connected to the second air source, and the second air source is used to provide Ar; the first air inlet pipe 7 is provided with a multi-pass Valve, multi-way valve is used to connect the first gas source, the first gas source is used to provide Cl ₂ , O ₂ , He, D ₂ and/or Ar, where D ₂ and Ar are usually mixed gas, the control system and the start The closing valve and the multi-way valve are connected. The opening and closing valve is controlled by the control system to control Ar to enter the second air inlet pipe 9, thereby venting or shutting off the sintering box 1, and the multi-way valve is controlled by the control system to control the entry into the first air inlet pipe. The gas types of 7, for example, allow Cl ₂ , O ₂ , and He to enter the furnace core tube 2 at the same time, or D ₂ and Ar enter the furnace core tube 2, or allow Ar to enter the furnace core tube 2, so as to realize the ventilation and cut-off of the furnace core tube 2.

As shown in Fig. 1, in some preferred embodiments, the sintering device further includes a pressure measuring mechanism 14 and a control system. The pressure measuring mechanism 14 can be used to measure the pressure in the furnace core tube 2 and the pressure in the sintering box 1. The first intake pipe 7 is provided with a multi-way valve, and the second intake pipe 9, the first exhaust pipe 8 and the second exhaust pipe 10 are provided with opening and closing valves; The measuring mechanism 14, the heating assembly 3, the rod feeding mechanism 6, and the negative pressure mechanism 11 are connected. The control system is used to control the rod feeding mechanism 6 to drive the guide rod 4 to move to make the preform loose body 5 move up and down, and to control the heating assembly 3 to open and close. Perform heating or stop heating, control the opening and closing valves and multi-way valves to open and close the first tube group and the second tube group, and control the opening and closing of the negative pressure mechanism 11 so that the pressure in the furnace core tube is at the first negative pressure and the first negative pressure. The second negative pressure or the third negative pressure, the pressure measuring mechanism 14 is controlled to perform pressure measurement to ensure that the pressure in the furnace core tube is at the first negative pressure, the second negative pressure or the third negative pressure, and the pressure difference between the inside and outside of the furnace core tube is at a preset The first pressure range, the second pressure range, the third pressure range, or the fourth pressure range.

Referring to Figure 1, in some preferred embodiments, the first air inlet pipe 7 penetrates one of the upper and lower portions of the furnace core tube 2, and the first exhaust pipe 8 penetrates the other of the upper and lower portions of the furnace core tube 2. One; and the second intake pipe 9 is located close to the first intake pipe 7, and the second exhaust pipe 10 is located close to the first exhaust pipe 8; the pressure measuring mechanism 14 includes: separately located in the first intake pipe 7 and the second intake pipe 9 The first pressure sensor 140 and the second pressure sensor 141, the first pressure sensor 140 and the second pressure sensor 141 are respectively used to measure the furnace core tube 2 and the sintering box 1 when the furnace core tube 2 and the sintering box 1 Pressure; and, a third pressure sensor 142 and a fourth pressure sensor 143 separately provided on the first exhaust pipe 8 and the second exhaust pipe 10, the third pressure sensor 142 and the fourth pressure sensor 143 are used to measure the furnace core tube 2 and the pressure in the furnace core tube 2 and the sintering box 1 when the sintering box 1 is vacuumed.

The advantage of using the above four pressure sensors for the layout is that the furnace core tube 2 is usually very long, and there are some differences in the pressure at the upper and lower ends of the furnace core tube 2 during ventilation or vacuuming. Therefore, the first pressure sensor 140 and the second pressure sensor 140 are used for air intake. The second pressure sensor 141 performs measurement, and the third pressure sensor 142 and the fourth pressure sensor 143 are used to measure when vacuuming, to ensure that the measured pressure is more accurate.

As shown in Figure 1, in some preferred embodiments, a method for sintering the loose body of an optical fiber preform is also provided, which includes the following steps:

S1: Provide any one of the above-mentioned sintering devices, and connect the loose body 5 of the preform to the lead 4;

S2: Through the negative pressure mechanism 11, the furnace core tube 2 is pumped to the preset first negative pressure through the first exhaust pipe 8, and the sintering box 1 is pumped to the furnace core tube 2 through the second exhaust pipe 10 until the pressure difference between the inside and the outside of the furnace core tube 2 is located Within the preset first pressure range; in this step, the first negative pressure is 10-100 mbar;

S3: The heating assembly 3 is heated to the preset dehydroxylation temperature, Cl ₂ , O ₂ and He are introduced into the furnace core tube 2 through the first air inlet pipe 7, and into the sintering box 1 through the second air inlet pipe 9 Ar, the pressure difference between the inside and outside of the furnace core tube 2 is within the preset second pressure range; in this step, the heating element 3 has a heating rate of 25-50°C/min, and a dehydroxylation temperature of 1100-1250°C.

S4: Move the preform loose body 5 until the dehydroxylation of the entire preform loose body 5 is completed in the heating zone A; in this step, the moving speed of the preform loose body 5 is 10-30 mm/min.

S5: Pump the furnace core tube 2 to the preset second negative pressure, and at the same time pump the sintering box 1 until the pressure difference between the inside and outside of the furnace core tube 2 is within the preset third pressure range, and keep it for 15-30 minutes to remove the loose body of the preform 5 Residual gas; in this step, the second negative pressure is 5-10mbar;

S6: The heating assembly 3 is heated to the preset vitrification and sintering temperature, and under the second negative pressure, the preform loose body 5 is moved until the sintering of the entire preform loose body 5 is completed; in this step, the vitrification and sintering temperature is 1500-1600°C, the heating speed of the heating assembly 3 is 25-50°C/min, and the moving speed of the preform loose body 5 is 3-8mm/min.

It should be noted that in step S5, the second negative pressure has been pumped, and in step S6, when the temperature is raised, on the one hand, since the second negative pressure is close to vacuum and there is less gas, the temperature rise pressure changes little, step S6 The pressure in S6 is basically under the second negative pressure. On the other hand, if the internal pressure of S6 deviates from the second negative pressure due to the increase in temperature, it can be adjusted by the negative pressure mechanism so that the pressure is at the second negative pressure. Down.

_{S7: Cool down to a preset temperature, pass D 2} and Ar into the furnace core tube 2 through the first air inlet pipe 7, where the _{volume concentration of D 2} is 1% to 3%, until the third negative pressure is reached, and pass through the second air inlet pipe 9 Simultaneously pour Ar into the sintering box 1 until the pressure difference between the inside and outside of the furnace core tube 2 is within the preset fourth pressure range, and perform the deuteration treatment, which ends after 1 to 3 hours, and the optical fiber preform is obtained. In this step, the preset temperature is 800-1000°C, the third negative pressure is 0.5-0.8 bar,

_{S8: Drain the D 2} and Ar in the furnace core tube 2 and the Ar in the sintering box 1; pour Ar into the furnace core tube 2 and the sintering box 1 until the pressure in the furnace core tube 2 and the sintering box 1 reaches atmospheric pressure When, take out the optical fiber preform.

In some preferred embodiments, before the temperature is raised to the preset dehydroxylation temperature, the following step is further included: driving the lead 4 so that the top or bottom end of the loose body 5 of the preform is located in the heating zone A.

In some preferred embodiments, _{the flow rates of Cl 2} , O ₂ and He are 0.5 to 1.5 L/min, 0.6 to 1.2 L/min, and 15 to 25 L/min.

In some preferred embodiments, the first pressure range, the second pressure range, the third pressure range, and the fourth pressure range are all -1 to 1 mbar.

Specific embodiment:

Place the large-size preform loose body 5 with a density of 0.3-0.5 g/cm ³ produced by the OVD outer coating deposition process into the furnace core tube 2 and lower it so that the bottom end of the preform loose body 5 is positioned in the middle of the heating zone. As the starting position for dehydroxylation and vitrification and sintering, the vacuum pump is turned on to pump the inside and outside of the furnace core tube 2 to 20 mbar to discharge the air in the tube, and the heating body 31 is heated to 1200 °C at a heating rate of 25 °C/min, and the furnace core tube 2 is passed through Into _{1slm Cl 2} , 0.8slm O ₂ and 15slm He, turn on the rod feeding mechanism 6 to make the preform loose body 5 move downwards at a speed of 15mm/min for dehydroxylation. After the top of the preform loose body 5 reaches the heating zone, stop the flow Into the gas and lift the preform loose body 5 to the starting position, turn on the vacuum pump to simultaneously pump the pressure in the furnace core tube 2 and the sintering box 1 to 10mbar, and keep it for 30 minutes to make the remaining Cl ₂ , O ₂ and He are completely escaped and removed from the porous structure, and then the heating body 31 is heated to 1550 ℃ at a heating rate of 25 ℃/min, and the rod feeding mechanism 6 is turned on to make the preform loose body 5 under a negative pressure environment. The speed of 4mm/min is gradually sintered from bottom to top to be transparent. After the top of the preform loose body 5 reaches the hot zone, the vitrification and sintering is finished, the heating body 31 enters the cooling stage, the vacuum pump is turned off, and the _{volume D 2} is introduced into the furnace core tube 2 _{The D 2} /Ar mixture with a concentration of 1.5% and Ar is introduced into the sintering box 1, when the pressure in the furnace core tube 2 reaches 0.6 bar, the ventilation is stopped and the deuteration is maintained for 3 hours, and then the vacuum pump is turned on to reduce the D _{2 in the furnace core tube 2} The /Ar mixed gas and Ar in the sintering box 1 are removed, and then a large flow of Ar is passed into the quartz furnace core tube. When the pressure reaches 1 bar, the rising rod feeding mechanism lifts the sintered optical fiber preform out of the furnace core tube. There are no obvious bubbles in the sintered transparent optical fiber preform. The typical attenuation of the drawn optical fiber at 1383nm is 0.275db/km. _{Deuterium treatment at 1.5% D 2} volume concentration can effectively reduce its hydrogen sensitivity. .

In the description of this application, it should be noted that the orientation or positional relationship indicated by the terms "upper", "lower", etc. is based on the orientation or positional relationship shown in the drawings, and is only for the convenience of describing the application and simplifying the description. It does not indicate or imply that the pointed device or element must have a specific orientation, be constructed and operated in a specific orientation, and therefore cannot be understood as a limitation of the present application. Unless otherwise clearly specified and limited, the terms "installation", "connection" and "connection" should be understood in a broad sense. For example, it can be a fixed connection, a detachable connection, or an integral connection; it can be a mechanical connection, It can also be an electrical connection; it can be directly connected, or indirectly connected through an intermediate medium, and it can be the internal communication between two components. For those of ordinary skill in the art, the specific meanings of the above-mentioned terms in this application can be understood according to specific circumstances.

It should be noted that in this application, relational terms such as "first" and "second" are only used to distinguish one entity or operation from another entity or operation, and do not necessarily require or imply There is any such actual relationship or sequence between these entities or operations. Moreover, the terms "include", "include" or any other variants thereof are intended to cover non-exclusive inclusion, so that a process, method, article or device including a series of elements not only includes those elements, but also includes those that are not explicitly listed Other elements of, or also include elements inherent to this process, method, article or equipment. If there are no more restrictions, the element defined by the sentence "including a..." does not exclude the existence of other identical elements in the process, method, article, or equipment that includes the element.

The above are only specific implementations of the application, so that those skilled in the art can understand or implement the application. Various modifications to these embodiments will be obvious to those skilled in the art, and the general principles defined herein can be implemented in other embodiments without departing from the spirit or scope of the application. Therefore, this application will not be limited to the embodiments shown in this document, but should conform to the widest scope consistent with the principles and novel features applied in this document.

Claims

A sintering device for a loose body of an optical fiber preform, which is characterized in that it comprises:

Sintering box (1);

Furnace core tube (2), which is assembled in the sintering box (1);

The heating component (3) is assembled in the sintering box (1) and located outside the furnace core tube (2), and the heating component (3) is formed in a partial space of the furnace core tube (2) Heating zone (A);

A lead rod (4), the bottom end of the lead rod (4) extends into the furnace core tube (2) and is used to connect the preform loose body (5);

The rod feeding mechanism (6) is connected with the lead rod (4), and the rod feeding mechanism (6) is used to drive the lead rod (4) to move in the vertical direction so that the preform loose body (5) is in the Heating in the heating zone (A);

The first tube group, which penetrates the walls of the sintering box (1) and the furnace core tube (2) and communicates with the inner cavity of the furnace core tube (2), and includes a first air inlet tube (7) and a first exhaust tube ( 8);

The second tube group penetrates the wall surface of the sintering box (1) and communicates with the inner cavity of the sintering box (1), and includes a second air inlet pipe (9) and a second exhaust pipe (10).
The sintering device for the loose body of the optical fiber preform according to claim 1, wherein the sintering device further comprises a negative pressure mechanism (11), the negative pressure mechanism (11) and the second exhaust pipe ( 10) Connect with the first exhaust pipe (8).
The sintering device for the loose body of the optical fiber preform according to claim 2, wherein the sintering device further comprises:

A pressure measuring mechanism (14), which is used to measure the pressure in the furnace core tube (2) and the pressure in the sintering box (1);

A control system, which is used to control the rod feeding mechanism (6) to drive the lead rod (4) to move, to control the opening and closing of the heating assembly (3), to control the pressure measuring mechanism (14) to measure pressure, and to control the negative pressure mechanism (11) to start Close, control the on and off of the first tube group and the second tube group.
The sintering device for the loose body of the optical fiber preform according to claim 3, wherein:

The second air inlet pipe (9) is provided with an opening and closing valve, the opening and closing valve is used to connect a second air source, and the second air source is used to provide Ar;

The first air inlet pipe (7) is provided with a multi-way valve, the multi-way valve is used to connect a first air source, and the first air source is used to provide Cl 2 , O 2 , He, D 2 and/ Or Ar;

The control system is connected to the opening and closing valve and the multi-way valve, and is used to control the opening and closing valve to control Ar to enter the second intake pipe (9), and to control the multi-way valve to control the access to the first intake pipe (9). The gas type of the intake pipe (7).
The sintering device for the loose body of the optical fiber preform according to claim 3, wherein the pressure measuring mechanism (14) comprises:

The first pressure sensor (140) and the second pressure sensor (141) are separately arranged on the first intake pipe (7) and the second intake pipe (9). The first pressure sensor (140) and the second pressure sensor ( 141) respectively used to measure the pressure in the furnace core tube (2) and the sintering box body (1) when the furnace core tube (2) and the sintering box body (1) are fed;

And, a third pressure sensor (142) and a fourth pressure sensor (143) separately provided on the first exhaust pipe (8) and the second exhaust pipe (10), the third pressure sensor (142) and the second Four pressure sensors (143) are respectively used to measure the pressure in the furnace core tube (2) and the sintering box (1) when the furnace core tube (2) and the sintering box (1) are evacuated.
A method for sintering a loose body of an optical fiber preform, which is characterized in that it comprises the following steps:

Provide a sintering device according to any one of claims 1 to 5, and connect the preform loose body (5) to the lead rod (4);

Through the negative pressure mechanism (11), the furnace core tube (2) is pumped to a preset first negative pressure through the first exhaust pipe (8), and the sintered tube is sintered through the second exhaust pipe (10). The box body (1) is pumped to the furnace core tube (2) where the pressure difference between inside and outside is within the preset first pressure range;

The heating assembly (3) is heated to a preset dehydroxylation temperature, and Cl 2 , O 2 and He are introduced into the furnace core tube (2) through the first air inlet pipe (7), and pass through the first gas inlet pipe (7). Two air inlet pipes (9) pass Ar into the sintering box (1), and make the pressure difference between the inside and outside of the furnace core pipe (2) be within a preset second pressure range;

Move the preform loose body (5) so that the preform loose body (5) gradually passes through the heating zone (A), and completes the dehydroxylation of the entire preform loose body (5);

The furnace core tube (2) is pumped to the preset second negative pressure, while the sintering box (1) is pumped to the furnace core tube (2) where the pressure difference between the inside and outside of the furnace core tube (2) is within the preset third pressure range, and the preform is removed Residual gas in the loose body (5);

The heating assembly (3) is heated to a preset vitrification and sintering temperature, and the preform loose body (5) is moved under the second negative pressure until the sintering of the entire preform loose body (5) is completed;

Cool down to a preset temperature, pass D 2 and Ar into the furnace core tube (2) until the third negative pressure is reached, and at the same time pass Ar into the sintering box (1) until the furnace core tube ( 2) The internal and external pressure difference is within the preset fourth pressure range, and the deuteration process is performed to obtain the optical fiber preform.
The method for sintering the loose body of the optical fiber preform according to claim 6, further comprising the following steps:

Drain the D 2 and Ar in the furnace core tube (2) and the Ar in the sintering box (1);

Ar is introduced into the furnace core tube (2) and the sintering box (1) until the pressure reaches the atmospheric pressure, and then the optical fiber preform is taken out.
7. The method for sintering the loose body of the optical fiber preform according to claim 6, characterized in that, before raising the temperature to the preset dehydroxylation temperature, the method further comprises the following steps:

The leading rod (4) is driven to make the top or bottom end of the preform loose body (5) located in the heating zone (A).
The method for sintering the loose body of an optical fiber preform according to claim 6, wherein the flow rates of Cl 2 , O 2 and He are 0.5 to 1.5 L/min, 0.6 to 1.2 L/min, and 15 to 25 L, respectively. /min.
The method for sintering the loose body of the optical fiber preform according to claim 6, wherein the first pressure range, the second pressure range, the third pressure range and the fourth pressure range are all -1 to 1 mbar.