Apparatus and method for producing fluorine-based glass optical fiber preform clad hollow tube

Abstract

The application relates to a device and a method for preparing a fluorine-based glass optical fiber preform rod cladding hollow tube. In the device, by reducing the air pressure in a closed crucible environment and assisting with a constant rotation rate, dissolved gas in the glass liquid can be effectively removed, and a fluorine-based glass preform rod cladding hollow tube without bubbles, high uniformity and high interface quality can be automatically / semi-automatically prepared. The method has a short preparation period and is expected to be applied to the preparation of a fluorine-based optical fiber preform rod with a high-quality core-cladding structure.

Description

Technical Field

[0001] This invention relates to fluorine-based glass fiber cladding hollow tubes, and in particular to an apparatus and method for preparing fluorine-based glass fiber preform cladding hollow tubes. It is especially suitable for preparing cladding of multimode power transfer and gain fiber preforms with core-cladding structures. The hollow tubes have the advantages of good internal surface quality, no bubbles, and high uniformity. Background Technology

[0002] Near- and mid-infrared energy transfer and laser generation hold significant research value in numerous fields, including global communications, microdevice fabrication, medical surgery, gas detection, and infrared countermeasures in national defense. Among these, energy transfer and gain fibers used for ultra-long-distance signal transmission, high-power energy transmission, and high-power laser generation have sparked a research boom. As an excellent mid-infrared material, fluorine-based glass is widely used in the manufacture of near- and mid-infrared lasers, amplifiers, and energy transfer fibers due to its low phonon energy, ultra-low theoretical mid-infrared loss, high infrared transmittance, and far infrared cutoff edge. However, the preparation of high-quality fluorine-based optical fiber preforms often encounters several problems, such as core-cladding eccentricity, bubbles, and crystallization, posing challenges to the industrial-scale fabrication of optical fiber preforms. Traditional optical fiber preform fabrication involves the transfer of molten glass from a crucible to a mold, leading to increased internal stress in the glass, difficulty in eliminating bubbles, and low reproducibility. Therefore, a novel fabrication device and process are urgently needed. We have designed a closed-loop low-pressure spin-casting fabrication device and process technology that can effectively remove bubbles within the glass, enabling automated / semi-automated optical fiber preform fabrication. Summary of the Invention

[0003] The objective of this invention is to provide an apparatus and method for preparing fluorine-based glass fiber preform cladding hollow tubes. Compared with previous preparation methods and apparatus, this invention can prepare bubble-free fluorine-based glass fiber preform cladding hollow tubes with high uniformity and high interface quality.

[0004] The technical solution of the present invention is as follows:

[0005] A fabrication apparatus for fluorine-based glass optical fiber preform cladding hollow tubes includes a vertically placed high-temperature heating furnace and a lifting platform for glass melting, and a parallelly placed annealing furnace and a parallel moving connector for glass tube forming and annealing. Its features are as follows:

[0006] It also includes a top controller for controlling the device to rotate from vertical to horizontal, a rotator for controlling the device to rotate at high speed, a clamp for clamping and fixing, a crucible container for glass melting and spinning, and a hollow connector for sealing the crucible container and providing a low-pressure environment.

[0007] The rotator consists of a controller and a rotating rod. The lower end of the rotating rod is connected to the clamp, and a top controller is provided above the controller.

[0008] The crucible container is a hollow cylindrical tube, which is made up of two identical semi-circular cylindrical tubes joined together. The bottom is closed and the top is open. The hollow connector is set on the top of the crucible container to completely fix and close the crucible container.

[0009] The hollow connector has a small opening at the bottom to connect the hollow connector with the gas inside the crucible container. The hollow connector has an opening at the top, and a clamp is provided above the hollow connector to fix and close the hollow connector.

[0010] The gripper is equipped with a rotator above it, and the gripper has a pipe inside. The lower part of the pipe is connected to the opening above the hollow connector. A shut-off switch is provided in the center of the pipe, and an opening is provided at the right end of the pipe. The opening is connected to an air pressure pump to reduce the air pressure inside the device and stabilize the air pressure inside the device through the shut-off switch.

[0011] The top controller is used to control the overall device to change from a vertical to a horizontal position.

[0012] The crucible container is made of heavy metals such as platinum and gold. The interior of the crucible container is mirror-polished, and the opening at the top is frosted.

[0013] The hollow connector is made of stainless steel, and the part at the bottom that closes the crucible container and the opening at the top that connects to the clamp are frosted.

[0014] The method for preparing fluorine-based glass fiber preform cladding hollow tubes using the above-mentioned apparatus includes the following steps:

[0015] 1) Add the proportioned glass raw material into the assembled crucible container, fix the crucible container on the hollow connector, use a clamp to fix the hollow connector, and connect the top of the clamp to the rotating rod. Keep the device vertical, use the lifting platform to raise the high-temperature heating furnace, so that the crucible container is in the high-temperature heating furnace, and keep the crucible container suspended.

[0016] 2) After the glass raw material melts, the temperature of the high-temperature heating furnace is reduced, and the gas pressure inside the clamp, hollow connector and crucible container is reduced. The internal gas pressure is isolated and stabilized by the closed switch inside the clamp. The rotator is turned on and the clamp, hollow connector and crucible container are slowly rotated at a certain speed to promote the gas in the glass melt to escape.

[0017] 3) Stop rotating, lower the high-temperature heating furnace, change the device from vertical to horizontal placement using the top controller, and move the annealing furnace to the left using the parallel movement connector so that the crucible container is placed in the annealing furnace and the crucible container is suspended. Then turn on the controller to rotate the clamp, hollow connector and crucible container at a certain speed, so that the glass liquid in the crucible container forms a hollow tube of uniform thickness under the action of centrifugal force.

[0018] 4) Once the hollow tube is formed and the temperature is stable, the clamp, hollow connector, and crucible container stop rotating and are then annealed in the annealing furnace.

[0019] Compared with the prior art, the beneficial effects of the present invention are as follows:

[0020] 1. This invention effectively promotes the escape of gas from the molten glass by providing a closed low-pressure environment and rotational disturbance, and eliminates the manual casting process, thereby improving the feasibility and repeatability of preparation. At the same time, the closed environment effectively isolates the external atmosphere and effectively prevents contamination by impurity particles during the preparation process.

[0021] 2. The obtained fluorine-based glass optical fiber preform has high-quality internal interface, uniform wall thickness, and no air bubbles in the cladding hollow tube. The preparation method is simple and can be automated, with a short preparation cycle. It is expected to be applied to the preparation of high-quality core-cladding structure fluorine-based optical fiber preforms. Attached Figure Description

[0022] Figure 1 A schematic diagram of an apparatus for preparing hollow tubes clad with fluorine-based glass optical fiber preforms;

[0023] Figure 2 This is a cross-sectional schematic diagram of a crucible container part;

[0024] Figure 3 This is a cross-sectional schematic diagram of a hollow connector;

[0025] Figure 4 This is a schematic diagram of the glass optical fiber preform cladding hollow tube obtained in Embodiment 1 of the present invention;

[0026] Figure 5 This is a schematic diagram of the glass fiber preform cladding hollow tube obtained in Comparative Example 1. Detailed Implementation

[0027] The following specific embodiments are provided to illustrate the present invention and help to further understand the present invention. However, the specific details of the embodiments are only for illustrating the present invention and do not represent all the technical solutions under the concept of the present invention. Therefore, they should not be construed as limiting the overall technical solution of the present invention. Some non-substantial additions and modifications that do not deviate from the concept of the present invention in the view of those skilled in the art, such as simple substitution or replacement of technical features with the same or similar technical effects, are all within the protection scope of the present invention.

[0028] Figure 1 This is a schematic diagram of a device for preparing fluorine-based glass fiber preform cladding hollow tubes. As shown in the figure, the device for preparing fluorine-based glass fiber preform cladding hollow tubes of the present invention includes a vertically placed high-temperature heating furnace 7 for glass melting and a lifting platform 8, a parallelly placed annealing furnace 9 for glass tube forming and annealing and a parallel moving connector 10. Its features are: it also includes a top controller 1 for controlling the device to rotate from vertical to parallel, a rotator for controlling the device to rotate at high speed, a clamp 4 for clamping and fixing, a crucible container 6 for glass melting and tube forming, and a hollow connector 5 for sealing the crucible container 6 and providing a low-pressure environment.

[0029] The rotator consists of a controller 2 and a rotating rod 3. The lower end of the rotating rod 3 is connected to the clamp 4. The top controller 1 is located above the controller 2.

[0030] The crucible container 6 is a hollow cylindrical tube. Please refer to [link / reference]. Figure 2 It is composed of two identical semi-circular cylindrical tubes joined together, with a closed bottom and an opening at the top. The hollow connector 5 is set above the crucible container 6 to completely fix and seal the crucible container 6.

[0031] Please see Figure 3 The hollow connector 5 has a small hole opening at its lower part to connect the hollow connector 5 with the gas inside the crucible container 6. The hollow connector 5 has an opening at its upper part, and the clamp 4 is provided above the hollow connector 5. The clamp 4 is used to fix and close the hollow connector 5.

[0032] The rotator is provided above the clamp 4. The clamp 4 has a pipe inside. The lower part of the pipe is connected to the opening above the hollow connector 5. A shut-off switch is provided in the center of the pipe. An opening is provided at the right end of the pipe. The opening is connected to an air pressure pump to reduce the air pressure inside the device and stabilize the air pressure inside the device through the shut-off switch.

[0033] The top controller 1 is used to control the overall device to change from vertical to horizontal placement.

[0034] The crucible container 6 is made of heavy metals such as platinum and gold. The interior of the crucible container 6 is mirror-polished, and the upper opening is frosted.

[0035] The hollow connector 5 is made of stainless steel, and the part of its bottom that closes the crucible container 6 and the opening above that connects to the clamp 4 are frosted.

[0036] The method for preparing fluorine-based glass fiber preform cladding hollow tubes using the above-mentioned apparatus includes the following steps:

[0037] 1) Add the proportioned glass raw materials into the assembled crucible container 6, fix the crucible container 6 onto the hollow connector 5, use the clamp 4 to fix the hollow connector 5, and connect the top of the clamp 4 to the rotating rod 3. Keep the device vertical, use the lifting platform 8 to raise the high temperature furnace 7, so that the crucible container 6 is in the high temperature furnace 7 heated to 900℃~1000℃, and keep the crucible container 6 suspended.

[0038] 2) After the glass raw material melts, the temperature of the high-temperature heating furnace 7 is reduced to 600°C. At the same time, a pneumatic pump is connected through the right opening of the clamp 4 to reduce the gas pressure in the clamp 4, hollow connector 5 and crucible container 6 to 0.3 to 0.5 times the atmospheric pressure. The sealing switch in the clamp 4 is closed, and the controller 2 is turned on, so that the clamp 4, hollow connector 5 and crucible container 6 rotate slowly at a speed of 100 to 150 r / min, causing the gas in the glass melt to escape.

[0039] 3) Stop rotating, adjust the lifting platform 8 to lower the high-temperature heating furnace 7, adjust the top controller 1 to change the device from vertical to horizontal placement, and move the annealing furnace 9 to the left through the parallel movement connector 10 so that the crucible container 6 is placed in the annealing furnace 9 heated to 210-240°C, keeping the crucible container 6 suspended. Then turn on the controller 2 to rotate the clamp 4, hollow connector 5 and crucible container 6 at a speed of 1000-1600 r / min, so that the glass liquid in the crucible container 6 forms a hollow tube of uniform thickness under the action of centrifugal force.

[0040] 4) After the hollow tube is formed and the temperature is stable, the clamp 4, hollow connector 5 and crucible container 6 stop rotating, and the temperature of the annealing furnace (9) is changed to 220-240°C. The glass tube is kept in the annealing furnace 9 for annealing treatment for 240 minutes. Then the annealing furnace 9 is turned off and gradually cooled to room temperature. The crucible container 6 is removed and the finished product is taken out.

[0041] Table 1 is a parameter table for each embodiment of the present invention.

[0042] Example 1

[0043] The apparatus for preparing fluorine-based glass optical fiber preforms with cladding hollow tubes is as follows: Figure 1 As shown, the assembled crucible container is used. The prepared glass raw material is added to the crucible container through the opening at the top. The crucible container is then fixed to the hollow connector with screws. After heating the high-temperature furnace to the melting temperature set at #1 in Table 1, the crucible container is placed in the furnace, suspended in mid-air. Once the raw material has fully melted, the temperature of the high-temperature furnace is reduced to 600℃. Simultaneously, the gas pressure inside the hollow connector and crucible container is reduced to the gas pressure parameter set at #1 in Table 1. The clamp, hollow connector, and crucible container are then slowly rotated at the slow rotation speed set at #1 in Table 1 to allow gas to escape from the molten glass. After the temperature stabilizes, rotation continues for 10 minutes. Then, rotation is stopped, and the crucible container is quickly transferred to an annealing furnace heated to the casting temperature set at #1 in Table 1, suspended in mid-air. The clamp, hollow connector, and crucible container are then rotated at a high rotation speed set at #1 in Table 1, causing the molten glass in the crucible container to form a hollow tube of uniform thickness under centrifugal force. After the hollow tube has formed and the temperature has stabilized, stop rotating and set the temperature of the annealing furnace to the annealing temperature of 1# in Table 1. Keep the glass tube in the annealing furnace for 240 minutes, then turn off the annealing furnace and gradually cool it to room temperature. Remove the crucible container and take out the finished product.

[0044] The obtained glass fiber preform cladding hollow tube, such as Figure 4 As shown, no obvious bubbles were observed.

[0045] Comparative Example 1

[0046] The prepared glass raw materials were added to a platinum crucible and fully melted at 900°C to obtain a clear and transparent molten glass, which was then held at 600°C. A platinum tube with the same structure as the crucible container in Example 1 was placed in an annealing furnace at 180°C for preheating. After the temperature stabilized, the molten glass was slowly poured into the platinum tube. The platinum tube was then sealed and placed in the annealing furnace and rotated at a high speed of 1000 r / min to obtain a hollow glass tube. The temperature of the annealing furnace was raised to 220°C and held for 240 minutes. After that, the annealing furnace was closed and allowed to cool naturally to room temperature.

[0047] The glass fiber preform cladding hollow tube obtained in Comparative Example 1 is as follows: Figure 5 As shown, bubbles of various sizes appear on the surface and inside the tube wall.

[0048] Table 1:

[0049]

Claims

1. A fabrication apparatus for cladding hollow tubes of fluorine-based glass optical fiber preforms, comprising a vertically placed high-temperature heating furnace (7) for glass melting and a lifting platform (8), a parallelly placed annealing furnace (9) for glass tube forming and annealing, and a parallel moving connector (10), characterized in that: It also includes a top controller (1) for controlling the device to rotate from vertical to horizontal, a rotator for controlling the device to rotate at high speed, a clamp (4) for clamping and fixing, a crucible container (6) for glass melting and spinning, and a hollow connector (5) for sealing the crucible container (6) and providing a low-pressure environment; the rotator is composed of a controller (2) and a rotating rod (3), the lower end of the rotating rod (3) is connected to the clamp (4), and the top controller (1) is located above the controller (2); The crucible container (6) is a hollow cylindrical tube, and is made of two identical semi-circular cylindrical tubes joined together. The bottom is closed and the top is open. The hollow connector (5) is set on the top of the crucible container (6) to completely fix and close the crucible container (6). The hollow connector (5) has a small hole opening at the bottom to connect the hollow connector (5) with the gas inside the crucible container (6). The hollow connector (5) has an opening at the top, and the clamp (4) is set at the top of the hollow connector (5) to fix and close the hollow connector (5). The clamp (4) is provided with a rotator above it. The clamp (4) is provided with a pipe inside. The lower part of the pipe is connected to the opening above the hollow connector (5). The pipe is provided with a sealing switch in the center. The pipe is provided with an opening at the right end. The opening is connected to an air pressure pump to reduce the internal air pressure of the device to 0.3~0.5 times the atmospheric pressure. The sealing switch stabilizes the internal air pressure of the device.

2. The apparatus for preparing fluorine-based glass optical fiber preform cladding hollow tubes according to claim 1, characterized in that, The crucible container (6) is made of platinum or gold. The interior of the crucible container (6) is mirror polished, and the opening at the top is frosted.

3. The apparatus for preparing fluorine-based glass optical fiber preform cladding hollow tubes according to claim 1, characterized in that, The hollow connector (5) is made of stainless steel, and the part at the bottom that closes the crucible container (6) and the opening at the top that connects to the clamp (4) are frosted.

4. A method for preparing a fluorine-based glass fiber preform cladding hollow tube using the apparatus for preparing a fluorine-based glass fiber preform cladding hollow tube according to any one of claims 1-3, characterized in that, The method includes the following steps: 1) Add the prepared glass raw materials into the assembled crucible container (6), fix the crucible container (6) on the hollow connector (5), use the clamp (4) to fix the hollow connector (5), and connect the top of the clamp (4) to the rotating rod (3). Keep the device vertical, use the lifting platform (8) to raise the high temperature furnace (7), so that the crucible container (6) is in the high temperature furnace (7) and the crucible container (6) is suspended. 2) After the glass raw material melts, the temperature of the high-temperature heating furnace (7) is reduced, and the gas pressure in the clamp (4), hollow connector (5) and crucible container (6) is reduced. The internal gas pressure is isolated and stabilized by the closed switch inside the clamp (4). The rotator is turned on and the clamp (4), hollow connector (5) and crucible container (6) are slowly rotated at a certain speed to promote the gas in the glass melt to escape. 3) Stop rotating, lower the high-temperature heating furnace (7), change the device from vertical to horizontal placement through the top controller (1), and move the annealing furnace (9) to the left through the parallel movement connector (10) so that the crucible container (6) is in the annealing furnace (9) and the crucible container (6) is suspended. Then turn on the controller (2) and rotate the clamp (4), hollow connector (5) and crucible container (6) at a certain speed so that the glass liquid in the crucible container (6) forms a hollow tube of uniform thickness under the action of centrifugal force. 4) After the hollow tube is formed and the temperature is stable, the clamp (4), hollow connector (5) and crucible container (6) stop rotating and are annealed in the annealing furnace (9).

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