A PCVD process uniform deposition apparatus and method

Abstract

This invention relates to a PCVD (Polycarbonyl Vapor Deposition) process uniform deposition apparatus and method. The apparatus includes rotary sealing chucks coaxially mounted on both sides of the bed, connected to a synchronous rotary drive device. A microwave resonant cavity is disposed between the two rotary sealing chucks. Each rotary sealing chuck includes an inlet rotary sealing chuck and an exhaust rotary sealing chuck. The inlet rotary sealing chuck is connected to a raw material gas source via an inlet pipe, and the exhaust rotary sealing chuck is connected to a vacuum pump extraction system via an exhaust pipe. The invention is characterized by an auxiliary exhaust pipe connected alongside the exhaust pipe, which is connected to an auxiliary vacuum pump extraction device via a series-connected electrically controlled valve. This invention effectively improves the axial uniformity of PCVD deposition by adding intermittent extraction, thereby increasing the effective length of the deposition mandrel and the quality of the deposition liner.

Description

Technical Field

[0001] This invention relates to a PCVD process uniform deposition apparatus and method, belonging to the technical field of optical fiber processing equipment. Background Technology

[0002] In recent years, with the accelerated construction of 5G in China, the demand for optical fiber and cable in the communication market has been continuously increasing. As an indispensable part of 5G construction, optical fiber and cable are playing an increasingly important role in 5G communication networks. Optical fiber is drawn from preforms, so preform manufacturing technology plays a crucial role in optical fiber production. The PCVD process in optical fiber preform preparation utilizes microwave plasma chemical vapor deposition to perform vapor deposition and high-temperature oxidation reactions within a high-purity quartz glass liner. The reaction gases are SiCl4, O2, and other small amounts of dopants. The heat source used for the reaction is a microwave source. The reaction mechanism involves using a variable-frequency vacuum pump at the pump end to maintain a constant low-pressure state. The microwave activates the gas to generate plasma, ionizing the reaction gas. The ionized reaction gas becomes charged ions, and the heat released by the recombination of these charged ions melts the gaseous reactants, forming a transparent quartz glass deposition layer. Deposition is achieved by using low-pressure plasma to directly deposit gaseous chlorides and oxygen flowing into the high-purity quartz glass tube into the designed optical fiber core-cladding glass layer in a high-temperature reaction chamber. The advantages of PCVD technology are good repeatability of parameters between mandrel roots, high deposition reaction efficiency, precise control of refractive index distribution, and the ability to fabricate optical fibers with complex refractive index profiles. However, its disadvantages are low deposition rate, low glass deposition per unit time, high purity requirements for reactant gas raw materials, and extremely high purity requirements for the substrate quartz liner.

[0003] PCVD (Polycarbonate Vapor Deposition) is a process that involves depositing material onto a quartz liner using a PCVD deposition apparatus. During the actual PCVD deposition process, a bulging phenomenon can easily occur where the core diameter is too large in the axial direction. This excessive core diameter leads to poor axial uniformity of the core, causing it to easily exceed the allowable diameter, resulting in decreased core quality, reduced effective length, and even core scrap. This reduces the utilization rate of the PCVD deposition liner and increases the manufacturing cost of the PCVD deposition core. Summary of the Invention

[0004] The technical problem to be solved by the present invention is to provide a PCVD process uniform deposition apparatus and method that can effectively improve the axial uniformity of PCVD deposition, thereby improving the effective rod length of the deposition core and the quality of the deposition liner.

[0005] The device technical solution adopted by the present invention to solve the above-mentioned problems is as follows:

[0006] The device includes two rotary sealing chucks coaxially mounted on both sides of the bed. The rotary sealing chucks on both sides are connected to a synchronous rotary drive device. A microwave resonant cavity is provided between the two rotary sealing chucks and connected to an axial reciprocating motion device. The microwave resonant cavity is installed in a heat-preserving furnace. The two rotary sealing chucks include an inlet rotary sealing chuck and an exhaust rotary sealing chuck. The inlet rotary sealing chuck is connected to a raw material gas source through an inlet pipe, and the exhaust rotary sealing chuck is connected to a vacuum pump extraction system through an exhaust pipe. The device is characterized in that an auxiliary exhaust pipe is connected alongside the exhaust pipe, and the auxiliary exhaust pipe is connected to an auxiliary vacuum pump extraction device through a series-connected electrically controlled valve.

[0007] According to the above scheme, the electrically controlled valve is an electrically controlled shut-off valve or an electrically controlled throttle valve.

[0008] According to the above scheme, the electrical control terminal of the electrically controlled valve is connected to the PLC control module.

[0009] According to the above scheme, the electrically controlled shut-off valve periodically opens and closes as the resonant cavity moves back and forth along the axial direction, so that the auxiliary exhaust pipe and the auxiliary vacuum pump device are periodically connected or disconnected.

[0010] According to the above scheme, the electronically controlled throttle valve periodically and intermittently increases and throttles the flow as the resonant cavity moves back and forth along the axial direction, causing the connection between the auxiliary exhaust pipe and the auxiliary vacuum pump device to periodically and intermittently amplify or reduce.

[0011] The technical solution adopted by this invention to solve the above-mentioned problems is as follows:

[0012] First, a pure glass liner is used as the base tube, clamped onto the aforementioned PCVD deposition apparatus, and then the circuit is closed. Auxiliary exhaust The tube is subjected to conventional PCVD deposition processing. After processing, the deposited liner is melted and shrunk into a solid mandrel. The core layer of the solid mandrel is inspected to determine the portion of the core diameter deviation along the axial direction in the core layer.

[0013] The relevant data and results of the test are input into the PLC control module for the control of the auxiliary exhaust pipe electronic valve;

[0014] Then, using a pure glass liner as the base tube, it is clamped onto the PCVD deposition apparatus for PCVD deposition. Simultaneously, the auxiliary function of the PLC control module is activated. Whenever the resonant cavity moves to the region with a larger core diameter, the PLC controls the electronic control valve to connect to the auxiliary vacuum pump, allowing the newly added vacuum pump to be connected to the exhaust pipe system, increasing the pumping flow rate to reduce the concentration of reactive gases deposited in the region with a larger core diameter. In other regions with normal core diameter, the electronic control valve is closed, and deposition is performed under normal operating conditions. This cycle is repeated until deposition is complete.

[0015] According to the above scheme, the gas pressure inside the glass liner tube is maintained at 5 to 40 mbar during deposition.

[0016] According to the above scheme, the specifications of the glass liner are: outer diameter 30-80mm, single-sided wall thickness 1.5-25mm, and length 1.0-4.0m.

[0017] According to the above scheme, the power of the resonant cavity during deposition is 1kW to 30kW.

[0018] According to the above scheme, the furnace temperature range during deposition is 600–1800℃.

[0019] According to the above scheme, the fluctuation range of the core diameter deviation is 5-15mm.

[0020] The beneficial effects of this invention are as follows: 1. By connecting an auxiliary exhaust pipe and adding a vacuum pump system, and controlling the on / off state of the electronically controlled valve via PLC, when the resonant cavity travels to the region with a larger core diameter, a brief increase in pumping force can effectively reduce the concentration of reactive gas in the gas-end reaction region, reduce the amount of glass deposited, and decrease the presence of a larger core diameter. This improves the axial uniformity of the core rod, increases the effective length of the deposited core rod and the quality of the deposited liner, reduces core rod scrap, and increases core rod production capacity. 2. This invention not only has a simple and reasonable structural design, but is also easy to control and operate, achieving significant results. Attached Figure Description

[0021] Figure 1 This is a schematic diagram of the structure of one embodiment of the device of the present invention.

[0022] Figure 2 This is a comparison diagram of the core diameter distribution of the mandrel in this invention and a comparative example. Detailed Implementation

[0023] The present invention will be further described below with reference to the accompanying drawings and embodiments.

[0024] The device of the present invention, such as Figure 1As shown, the device includes rotary sealing chucks coaxially mounted on both sides of the bed. The rotary sealing chucks on both sides are connected to a synchronous rotary drive device. A microwave resonant cavity 4 is disposed between the two rotary sealing chucks and is connected to an axial reciprocating motion device. The microwave resonant cavity is installed in a heat preservation furnace 2. A glass liner 3 passes through the microwave resonant cavity and is placed inside the heat preservation furnace 2. Both ends of the glass liner 3 are fixed and sealed by rotary chucks. The two rotary sealing chucks include an air inlet rotary sealing chuck 1 and an exhaust rotary sealing chuck 5. The air inlet rotary sealing chuck is connected to the original [device / system] via an air inlet pipe. The material (reaction) gas source is connected, and the exhaust rotary sealing clamp is connected to the vacuum pump pumping system 7 through the exhaust pipe 6. An auxiliary exhaust pipe 8 is connected to the exhaust pipe. The auxiliary exhaust pipe is connected to the auxiliary vacuum pump pumping device 11 through a series-connected electric control valve 9. The electric control terminal of the electric control valve is connected to the PLC control module 10. The electric control valve is an electric shut-off valve. The electric shut-off valve periodically opens and closes intermittently as the resonant cavity moves along the axial direction, so that the auxiliary exhaust pipe and the auxiliary vacuum pump device are periodically connected or disconnected.

[0025] The deposition process and method of this invention are as follows: First, a pure glass liner is used as the base tube, clamped onto the PCVD deposition apparatus, the auxiliary exhaust pipe is closed, and conventional PCVD deposition is performed. The liner length is 2.5m, the wall thickness is 5mm, the outer diameter of the liner is 55mm, the working pressure is 22mbar, the deposition mandrel power is 12.5Kw, and the actual furnace temperature during deposition is 995℃. After processing, the deposited liner is melted and shrunk into a solid mandrel. The core layer of the solid mandrel is inspected. A portion A, with a significant core diameter deviation along the axial direction, is found in the core layer of the solid mandrel, with a maximum core diameter fluctuation of 5mm. Figure 2 As shown in Scheme 1, based on the detection results, the relevant data and information are input into the PLC control module to control the auxiliary exhaust pipe's electronic valve. Then, using a pure glass liner with the same specifications as the base tube, it is clamped onto the PCVD deposition device and PCVD deposition is performed under the same process conditions. Simultaneously, the auxiliary function of the PLC control module is activated. Whenever the resonant cavity moves to a region with a larger core diameter, the PLC controls the electronic valve to connect to the auxiliary vacuum pump, connecting the newly added vacuum pump to the exhaust pipe's extraction system, increasing the extraction flow rate to reduce the concentration of reactive gases deposited in the region with a larger core diameter. In other regions with normal core diameters, the electronic valve is closed, and deposition is performed under normal operating conditions. This cycle is repeated until deposition is complete. The deposited liner is then melted and processed into a solid mandrel. The core layer of the solid mandrel is tested. The maximum difference in core diameter fluctuation in region A, where the core diameter is larger along the axial direction, is 2mm, which has been significantly reduced and returned to the normal core diameter range. The axial uniformity of the mandrel's core diameter has been significantly improved. Figure 2 As shown in Scheme 2.

Claims

1. A PCVD process uniform deposition apparatus, comprising rotary sealing chucks coaxially mounted on both sides of a bed, the rotary sealing chucks being connected to a synchronous rotary drive device, a microwave resonant cavity disposed between the two rotary sealing chucks, the microwave resonant cavity being connected to an axial reciprocating motion device, the microwave resonant cavity being installed in a holding furnace, the two rotary sealing chucks comprising an inlet rotary sealing chuck and an exhaust rotary sealing chuck, the inlet rotary sealing chuck being connected to a raw material gas source via an inlet pipe, and the exhaust rotary sealing chuck being connected to a vacuum pump extraction system via an exhaust pipe, characterized in that... An auxiliary exhaust pipe is connected to the exhaust pipe, and the auxiliary exhaust pipe is connected to the auxiliary vacuum pump pumping device through a series-connected electronically controlled valve. The on and off of the electronically controlled valve is controlled by PLC. When the resonant cavity travels to the region with a larger core diameter, the increase of the pumping force for a short period of time can effectively reduce the concentration of reactant gas in the gas end reaction region, reduce the amount of glass deposition, and reduce the presence of a larger core diameter.

2. The PCVD process uniform deposition apparatus according to claim 1, characterized in that... The electrically controlled terminal of the electrically controlled valve is connected to the PLC control module.

3. The PCVD process uniform deposition apparatus according to claim 1 or 2, characterized in that... The solenoid valve is either a solenoid shut-off valve or a solenoid throttle valve.

4. The PCVD process uniform deposition apparatus according to claim 3, characterized in that... The electrically controlled shut-off valve periodically opens and closes as the resonant cavity moves back and forth along the axial direction, causing the auxiliary exhaust pipe to be periodically connected or disconnected from the auxiliary vacuum pump device.

5. The PCVD process uniform deposition apparatus according to claim 3, characterized in that... The electronically controlled throttle valve periodically increases and decreases the flow as the resonant cavity moves back and forth along the axial direction, causing the connection between the auxiliary exhaust pipe and the auxiliary vacuum pump device to periodically amplify or reduce.

6. A method for uniform deposition in PCVD process, characterized in that... Using any of the devices described in claims 1-5, First, a pure glass liner is used as the base tube and clamped on the PCVD deposition device. The auxiliary exhaust pipe is closed, and conventional PCVD deposition is performed. After the process is completed, the deposited liner is melted and shrunk into a solid mandrel. The core layer of the solid mandrel is inspected to determine the core diameter deviation part along the axial direction in the core layer. The relevant data and results of the test are input into the PLC control module for the control of the auxiliary exhaust pipe electronic valve; Then, using a pure glass liner as the base tube, it is clamped onto the PCVD deposition apparatus for PCVD deposition. Simultaneously, the auxiliary function of the PLC control module is activated. Whenever the resonant cavity moves to the region with a larger core diameter, the PLC controls the electronic control valve to connect to the auxiliary vacuum pump, allowing the newly added vacuum pump to be connected to the exhaust pipe system, increasing the pumping flow rate to reduce the concentration of reactive gases deposited in the region with a larger core diameter. In other regions with normal core diameter, the electronic control valve is closed, and deposition is performed under normal operating conditions. This cycle is repeated until deposition is complete.

7. The PCVD process uniform deposition method according to claim 6, characterized in that... During deposition, the gas pressure inside the liner is maintained at 5~40 mbar.

8. The PCVD process uniform deposition method according to claim 6 or 7, characterized in that... The specifications of the glass liner are: outer diameter 30~80mm, single-sided wall thickness 1.5~25mm, and length 1.0~4.0m.

9. The PCVD process uniform deposition method according to claim 6 or 7, characterized in that... The resonant cavity power during deposition is 1kW~30kW.

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