WO2018036142A1 - Sintering device with casing tube for optical fibre preform rod and sintering method therefor - Google Patents

Abstract

A sintering device with a casing tube for an optical fibre preform rod, comprising a casing tube, an upper fixing means, a lower fixing means and a heating furnace, wherein the casing tube is installed vertically in a heating furnace by means of the upper fixing means and the lower fixing means, and a loose body of the optical fibre preform is arranged in the casing tube and connected to the upper fixing means; and an exhaust mechanism is arranged on the upper fixing means, the exhaust mechanism being connected to an exhaust system and a vacuum pump through a valve switch, and a gas inlet mechanism is arranged on the lower fixing means. A sintering method comprises sintering a loose body of the optical fibre preform using a casing tube evacuation method, with the use of furnace core tubes that are expensive and easy to be damaged being avoided, and can prepare a large-size loose body.

Description

Optical fiber preform sleeve sintering device and sintering method thereof Technical field

The present invention relates to the field of optical fiber preform manufacturing, and in particular to an optical fiber preform sleeve sintering device and a sintering method thereof.

Background technique

The large-scale optical fiber preform production process in the field is mainly deposited by VAD and OVD processes to form a loose body. The so-called VAD, OVD process, that is, the preform is made by vapor deposition. The SiO ₂ granules are produced in the combustion chamber by introducing the raw materials into a flame, and are deposited on a preset target rod or a middle rod to form a loose body. After the loose body is formed by the VAD and OVD processes, it is placed in a sintering furnace and sintered under high temperature to form a vitrified preform. The finished preform is drawn to obtain a finished fiber or melt-shrinked using a quartz sleeve of the same grade as the fiber material to produce a larger-sized optical fiber preform.

For loose bodies made by VAD, OVD or VAD and OVD mixing processes, the sintering process must prevent moisture and other impurities such as various metallic impurities from entering the preform. In general, if more than 1 ppb of moisture or metal impurities enter the optical fiber preform during the sintering process, the attenuation of the optical fiber made by the preform in a large wavelength range will greatly increase, resulting in product failure. In order to prevent the moisture contained in the loose body from adversely affecting the quality of the product, the loose body must be dehydrated before the loose body is vitrified to form a transparent preform. A common method of dehydration is to remove the hydroxyl and moisture in the loose body by physical and chemical action by heating the loose body to a high temperature of 1100 ° C to 1300 ° C in an inert gas atmosphere containing Cl ₂ or other chlorine-based desiccant. .

After the loose body is dehydrated, it is placed in an inert gas atmosphere such as He or Ar, and heated to 1450 ° C or higher. Under these conditions, the loose body vitrified to form a transparent quartz preform.

Obviously, in the process of dewatering and sintering of loose bodies, the loose process must be placed in a closed environment to provide a corresponding atmosphere for dehydration and complete transparency, while avoiding Foreign matter enters it. The sealing environment is generally provided by installing a furnace tube in a heating furnace, and the loose body is placed in the furnace core tube, and various process gases are introduced under high temperature conditions for dehydration and sintering.

Chinese patent CN101426742B "Method for manufacturing optical fiber preform" invents a loose body sintering method. The loose body is suspended in a furnace tube having a heating zone. The loose body is passed through the heating zone from bottom to top, and a chlorine-based gas and an inert gas are introduced for dehydration. After the dehydration is finished, the loose body is moved to the lower side of the heating zone, the heating zone is heated to the sintering temperature, and an inert gas is introduced, and then the loose body passes through the heating zone from bottom to top to completely transparently vitrify.

This method is similar to other conventional methods in that a furnace tube made of quartz material is used. Its originality is mainly to improve the uniformity of product quality, to avoid the impurities in the furnace core tube from entering the interior of the preform during the dehydration and sintering process, and to take the loose body from the bottom to the top through the heating zone during the dehydration and sintering process. According to this method, a dehydration atmosphere is provided by 10% chlorine gas and 90% helium gas, 100% helium gas provides a sintering atmosphere, and an optical fiber made of an optical fiber preform manufactured at a suitable dehydration temperature and a sintering temperature has good attenuation. Level.

Chinese Patent CN102992611B "Method for Producing Glass Base Material" invents a manufacturing method for providing a closed environment by a furnace tube made of carbon material. The optical fiber produced by this method shows good attenuation performance.

For example, the above method is to increase the necessity of dehydration and sintering conditions by adding a high-purity material furnace tube to the sintering furnace.

High purity material grade requirements result in expensive material costs. The larger the size of the furnace tube, the more difficult it is to process, and the processing equipment is more complicated, which greatly increases the manufacturing cost.

The residual stress of the quartz material furnace tube during the heat treatment process is prone to cracking during the processing, transportation, storage and use, resulting in scrapping. In addition, due to the unique material characteristics of the quartz itself, once the furnace tube is heated to above 1100 °C, the furnace tube is devitrified, and if the temperature is restored to a low temperature, cracking will occur.

The carbon material furnace tube itself is easily contaminated by external conditions. If it is in contact with the atmosphere, the furnace tube itself Will be oxidized. Higher requirements are placed on the airtightness of the equipment. In addition, when the loose body is placed from the atmospheric environment into the furnace tube, oxygen is inevitably entered into it, and long-term use will inevitably lead to aging of the furnace tube and affect product performance.

Another crucial shortcoming is that due to the limitations of the material of the quartz tube, such as quartz and carbon, the traditional process generally fixes the furnace tube and the heating zone and uses the loose body to complete the heating zone. sintering. As a result, the length of the furnace tube is generally greater than twice the length of the loose body. Obviously, this not only greatly increases the complexity of the equipment, the size of the equipment, but also achieves the perfect dehydration, completely transparent atmosphere conditions, greatly increasing the various process gases, especially the very expensive, non-renewable resources. The amount of helium used, which greatly increases the manufacturing cost of the optical fiber preform.

Therefore, the inventors of the present invention need to conceive a new technique to improve the problem.

Summary of the invention

The invention aims to provide an optical fiber preform sleeve sintering device and a sintering method thereof, which can effectively reduce equipment complexity, reduce equipment space occupation, reduce production cost, and facilitate large-scale mass production.

In order to solve the above technical problem, the technical solution of the present invention is:

An optical fiber preform sleeve sintering device comprising a sleeve, an upper fixing device, a lower fixing device, and a heating furnace, wherein the sleeve is vertically mounted on the heating by the upper fixing device and the lower fixing device In the furnace, an optical fiber preform loose body is disposed in the sleeve and connected to the upper fixing device; the upper fixing device is provided with an exhaust mechanism, and the exhaust mechanism passes through the valve switch and the exhaust system and A vacuum pump is connected, and the lower fixing device is provided with an air inlet mechanism.

Preferably, the upper fixing device and the lower fixing device are driven by a rotating mechanism, and the two are synchronously rotatable.

Preferably, the optical fiber preform loose body is connected to the upper fixing device through a connecting mechanism.

Preferably, the furnace consists of one or more heating elements disposed on the casing The outside.

Preferably, the sleeve is a quartz sleeve.

The sintering method of the optical fiber preform sleeve sintering device according to the above, comprising the following steps:

S1: installing the sleeve in the heating furnace through the upper fixing device and the lower fixing device in a vertical manner;

S2: disposing the optical fiber preform loose body in the sleeve and connecting with the upper fixing device;

S3: removing the hydroxyl group introduced by the production process in the bulk of the optical fiber preform by the temperature rise and movement of the heating furnace;

S4: moving the heating furnace to the bottom of the optical fiber preform loose body, heating up to above 1450 ° C, and forming a temperature gradient distribution;

S5: under a certain sintering temperature condition, the lower end portion of the loose portion of the optical fiber preform is vitrified;

S6: connecting the exhaust mechanism with the vacuum pump through the valve switch to form a negative pressure inside the sleeve; adjusting the temperature distribution of the heating furnace to melt and shrink the lower end of the sleeve, and merging with the vitrified optical fiber preform;

S7: After the bottom fusion is completed, the heating furnace moves upward at a certain moving speed, and the optical fiber preform loose partition is vitrified.

Preferably, the step S3 specifically includes:

Heating the furnace to 1100 ° C ~ 1300 ° C, and moving back and forth 1 or more times in the vertical direction;

At the same time, the desiccant and the process gas are introduced into the casing by the air inlet mechanism; the passage of the exhaust system and the exhaust mechanism is opened through the valve switch, and the pressure in the casing is maintained at an appropriate level to provide a dehydration atmosphere environment.

Preferably, the process gas is one or more of chlorine gas, helium gas and nitrogen gas.

Preferably, the sleeve is a quartz sleeve.

With the above technical solutions, the present invention at least includes the following beneficial effects:

The optical fiber preform sleeve sintering device and the sintering method thereof of the invention use the casing vacuum method to sinter the optical fiber preform loose body, thereby avoiding the use of expensive and easy to damage furnace core tube, which can be manufactured Large size loose body. At the same time, the vacuum environment is beneficial to improve the quality of the preform, speed up the sintering and increase the production efficiency. At the same time, the furnace-free tube sintering method is adopted to reduce the production cost, reduce the complexity of the equipment, reduce the space occupation of the equipment, and is advantageous for mass production.

DRAWINGS

1 is a schematic structural view of an optical fiber preform sleeve sintering device according to the present invention;

2 is a schematic view showing the process of sintering and shrinking the upper portion of the optical fiber preform sleeve sintering device according to the present invention.

Figure 3 is a temperature distribution diagram of the center of the heating furnace;

Figure 4 is a temperature distribution diagram of the center of the furnace in the melting stage.

Among them: 1. upper fixing device, 2. exhausting mechanism, 3. casing, 4. optical fiber preform loose body, 5. heating furnace, 6. lower fixing device, 7. air intake mechanism, 8. connecting mechanism.

detailed description

The technical solutions in the embodiments of the present invention are clearly and completely described in the following with reference to the accompanying drawings in the embodiments of the present invention. It is obvious that the described embodiments are only a part of the embodiments of the present invention, but not all embodiments. All other embodiments obtained by those skilled in the art based on the embodiments of the present invention without creative efforts are within the scope of the present invention.

Example 1

As shown in FIG. 1 to FIG. 2, an optical fiber preform sleeve sintering device according to the embodiment includes a sleeve 3, an upper fixing device 1, a lower fixing device 6, and a heating furnace 5, wherein the sleeve 3 Installed in the heating furnace 5 in a vertical manner by the upper fixing device 1 and the lower fixing device 6, an optical fiber preform loose body 4 is disposed in the sleeve 3 and realized with the upper fixing device 1 The upper fixing device 1 is provided with an exhausting mechanism 2, and the exhausting mechanism 2 is connected to the exhaust system and the vacuum pump through a valve switch, and the lower fixing device 6 is provided with an air intake mechanism 7.

Preferably, the upper fixing device 1 and the lower fixing device 6 are driven by a rotating mechanism, Can rotate synchronously.

Preferably, the optical fiber preform loose body 4 is connected to the upper fixing device 1 via a connecting mechanism 8.

Preferably, the furnace 5 consists of one or more heating elements which are arranged outside the sleeve 3.

Preferably, the sleeve 3 is a quartz sleeve 3.

The sintering device uses the casing 3 vacuuming method to sinter the optical fiber preform loose body 4, thereby avoiding the use of expensive and easily damaged furnace core tubes, and can prepare large-sized loose bodies. At the same time, the vacuum environment is beneficial to improve the quality of the preform, speed up the sintering and increase the production efficiency.

Example 2

The sintering method of the optical fiber preform sleeve sintering device according to Embodiment 1 includes the following steps:

S1: the sleeve 3 is vertically installed in the heating furnace 5 through the upper fixing device 1 and the lower fixing device 6;

S2: disposing the optical fiber preform loose body 4 in the sleeve 3 and connecting with the upper fixing device 1;

S3: removing the hydroxyl group introduced by the production process in the optical fiber preform loose body 4 by the temperature rise and movement of the heating furnace 5;

S4: moving the heating furnace 5 to the bottom of the optical fiber preform loose body 4, raising the temperature to above 1450 ° C, and forming a temperature gradient distribution, the temperature distribution is shown in FIG. 3;

S5: at a sintering temperature of 1450 ° C to 1550 ° C, the lower end portion of the optical fiber preform loose body 4 is vitrified;

S6: connecting the exhaust mechanism 2 and the vacuum pump through the valve switch to form a negative pressure inside the sleeve 3; adjusting the temperature distribution of the heating furnace 5 to melt and contract the lower end of the sleeve 3, and the vitrified optical fiber preform loose body 4 Fusion, temperature distribution is shown in Figure 4;

S7: After the bottom fusion is completed, the heating furnace 5 moves upward at a speed of 3 mm/min to 8 mm/min. The optical fiber preform loose body 4 is vitrified. After the bottom is fused, the upper part of the sintering and melting process is shown in Fig. 2.

Preferably, the step S3 specifically includes:

Heating the furnace 5 to 1100 ° C ~ 1300 ° C, and moving back and forth 1 or more times in the vertical direction;

At the same time, the desiccant and the process gas are introduced into the casing 3 by the air inlet mechanism 7; the passage of the exhaust system and the exhaust mechanism 2 is opened through the valve switch, and the pressure in the casing 3 is maintained within a range of 10 to 40 Pa to provide dehydration. Atmosphere.

Preferably, the process gas is one or more of chlorine gas, helium gas and nitrogen gas.

Preferably, the sleeve 3 is a quartz sleeve 3.

The improvement of the present invention is that:

1 Sintered with casing 3, without quartz furnace core tube. Significantly simplifies equipment complexity. And avoid the product quality risk caused by the pollution of the furnace tube itself and aging.

2 The method of moving the heating furnace 5 greatly reduces the size of the equipment, reduces the amount of gas, and reduces the production cost.

3 When vacuuming the inside of the casing 3 during sintering, it is advantageous to eliminate air bubbles and improve production efficiency.

4 When sintering, the sleeve 3 is melted to form a part of the product, and the preform size is increased, which is advantageous for improving production efficiency.

The furnaceless tube sintering method is adopted to reduce the production cost, and a large-sized loose body can be prepared. Reducing the complexity of the equipment and reducing the space occupied by the equipment is conducive to large-scale mass production. Sintering the loose body under vacuuming conditions is advantageous for eliminating bubbles, speeding up the sintering speed, and improving the sintering efficiency. The above description of the disclosed embodiments enables those skilled in the art to make or use the invention. It will be apparent to those skilled in the art that various modifications of the embodiments may be made without departing from the spirit or scope of the invention. It is implemented in its embodiment. Therefore, the present invention is not to be limited to the embodiments shown herein, but the scope of the invention is to be accorded

Claims (9)

1. An optical fiber preform sleeve sintering device, comprising: a sleeve, an upper fixing device, a lower fixing device, and a heating furnace, wherein the sleeve is vertically installed by the upper fixing device and the lower fixing device In the heating furnace, an optical fiber preform loose body is disposed in the sleeve and connected to the upper fixing device; the upper fixing device is provided with an exhaust mechanism, and the exhaust mechanism passes through a valve switch The exhaust system is connected to a vacuum pump, and the lower fixing device is provided with an air intake mechanism.
2. The optical fiber preform sleeve sintering apparatus according to claim 1, wherein said upper fixing means and said lower fixing means are driven by a rotating mechanism, and both of them are synchronously rotatable.
3. The optical fiber preform sleeve sintering apparatus according to claim 1 or 2, wherein said optical fiber preform loose body is connected to said upper fixing means via a connecting mechanism.
4. The optical fiber preform sleeve sintering apparatus according to any one of claims 1 to 3, wherein the heating furnace is composed of one or more heating elements disposed outside the sleeve.
5. The optical fiber preform sleeve sintering apparatus according to any one of claims 1 to 4, wherein the sleeve is a quartz sleeve.
6. A sintering method for an optical fiber preform sleeve sintering apparatus according to any one of claims 1 to 5, characterized in that it comprises the following steps:

   S1: installing the sleeve in the heating furnace through the upper fixing device and the lower fixing device in a vertical manner;

   S2: disposing the optical fiber preform loose body in the sleeve and connecting with the upper fixing device;

   S3: removing the hydroxyl group introduced by the production process in the bulk of the optical fiber preform by the temperature rise and movement of the heating furnace;

   S4: moving the heating furnace to the bottom of the optical fiber preform loose body, heating up to above 1450 ° C, and forming a temperature gradient distribution;

   S5: under a certain sintering temperature condition, the lower end portion of the loose portion of the optical fiber preform is vitrified;

   S6: the exhaust mechanism is connected with the vacuum pump through a valve switch to form a negative pressure inside the sleeve; at the same time, the temperature distribution of the heating furnace is adjusted, so that the lower end of the sleeve is melted and shrunk, and the vitrified optical fiber preform is loosened. Loose body fusion;

   S7: After the bottom fusion is completed, the heating furnace moves upward at a certain moving speed, and the optical fiber preform loose partition is vitrified.
7. The method for sintering an optical fiber preform sleeve according to claim 6, wherein the step S3 specifically comprises:

   Heating the furnace to 1100 ° C ~ 1300 ° C, and moving back and forth 1 or more times in the vertical direction;

   At the same time, the desiccant and the process gas are introduced into the casing by the air inlet mechanism; the passage of the exhaust system and the exhaust mechanism is opened through the valve switch, and the pressure in the casing is maintained at an appropriate level to provide a dehydration atmosphere environment.
8. The method for sintering an optical fiber preform sleeve according to claim 7, wherein the process gas is one or more of chlorine gas, helium gas and nitrogen gas.
9. The method for sintering an optical fiber preform sleeve according to any one of claims 6 to 8, wherein the sleeve is a quartz sleeve.

Images