CN117185646B - Preparation of F-SiO by plasma deposition 2 Optical fiber preform cladding device and method - Google Patents
Preparation of F-SiO by plasma deposition 2 Optical fiber preform cladding device and method Download PDFInfo
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- 230000008021 deposition Effects 0.000 title claims abstract description 43
- 238000000034 method Methods 0.000 title claims abstract description 39
- 238000005253 cladding Methods 0.000 title claims abstract description 29
- 239000013307 optical fiber Substances 0.000 title claims abstract description 17
- 238000002360 preparation method Methods 0.000 title claims description 8
- 210000002381 plasma Anatomy 0.000 claims abstract description 99
- 230000008878 coupling Effects 0.000 claims abstract description 75
- 238000010168 coupling process Methods 0.000 claims abstract description 75
- 238000005859 coupling reaction Methods 0.000 claims abstract description 75
- 238000000151 deposition Methods 0.000 claims abstract description 50
- 239000002344 surface layer Substances 0.000 claims abstract description 18
- 229910004298 SiO 2 Inorganic materials 0.000 claims abstract description 14
- 230000005284 excitation Effects 0.000 claims abstract description 13
- 230000005540 biological transmission Effects 0.000 claims abstract description 10
- 239000007789 gas Substances 0.000 claims description 45
- XKRFYHLGVUSROY-UHFFFAOYSA-N Argon Chemical compound [Ar] XKRFYHLGVUSROY-UHFFFAOYSA-N 0.000 claims description 40
- 239000010410 layer Substances 0.000 claims description 38
- 239000002994 raw material Substances 0.000 claims description 31
- QVGXLLKOCUKJST-UHFFFAOYSA-N atomic oxygen Chemical compound [O] QVGXLLKOCUKJST-UHFFFAOYSA-N 0.000 claims description 23
- 239000001301 oxygen Substances 0.000 claims description 23
- 229910052760 oxygen Inorganic materials 0.000 claims description 23
- 229910052786 argon Inorganic materials 0.000 claims description 20
- YCKRFDGAMUMZLT-UHFFFAOYSA-N Fluorine atom Chemical compound [F] YCKRFDGAMUMZLT-UHFFFAOYSA-N 0.000 claims description 16
- 229910052731 fluorine Inorganic materials 0.000 claims description 16
- 239000011737 fluorine Substances 0.000 claims description 16
- XUIMIQQOPSSXEZ-UHFFFAOYSA-N Silicon Chemical compound [Si] XUIMIQQOPSSXEZ-UHFFFAOYSA-N 0.000 claims description 14
- 229910052710 silicon Inorganic materials 0.000 claims description 14
- 239000010703 silicon Substances 0.000 claims description 14
- 230000006835 compression Effects 0.000 claims description 8
- 238000007906 compression Methods 0.000 claims description 8
- 238000006243 chemical reaction Methods 0.000 claims description 6
- 238000005507 spraying Methods 0.000 claims description 4
- XLYOFNOQVPJJNP-UHFFFAOYSA-N water Substances O XLYOFNOQVPJJNP-UHFFFAOYSA-N 0.000 claims description 4
- 230000008569 process Effects 0.000 abstract description 13
- 238000002679 ablation Methods 0.000 abstract description 7
- 238000005245 sintering Methods 0.000 abstract description 5
- 230000008018 melting Effects 0.000 abstract description 4
- 238000002844 melting Methods 0.000 abstract description 4
- VYPSYNLAJGMNEJ-UHFFFAOYSA-N silicon dioxide Inorganic materials O=[Si]=O VYPSYNLAJGMNEJ-UHFFFAOYSA-N 0.000 description 12
- 239000010453 quartz Substances 0.000 description 9
- 238000004519 manufacturing process Methods 0.000 description 5
- 238000005498 polishing Methods 0.000 description 5
- 230000009471 action Effects 0.000 description 3
- 238000000137 annealing Methods 0.000 description 3
- 230000005684 electric field Effects 0.000 description 3
- 230000004907 flux Effects 0.000 description 3
- MYMOFIZGZYHOMD-UHFFFAOYSA-N Dioxygen Chemical compound O=O MYMOFIZGZYHOMD-UHFFFAOYSA-N 0.000 description 2
- 238000013461 design Methods 0.000 description 2
- 238000009792 diffusion process Methods 0.000 description 2
- 229910001882 dioxygen Inorganic materials 0.000 description 2
- 239000000428 dust Substances 0.000 description 2
- 238000005530 etching Methods 0.000 description 2
- 238000011068 loading method Methods 0.000 description 2
- 230000002035 prolonged effect Effects 0.000 description 2
- 239000000243 solution Substances 0.000 description 2
- 239000007921 spray Substances 0.000 description 2
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Abstract
The invention discloses a method for preparing F-SiO by plasma deposition 2 Optical fiber preform cladding apparatus and method, the apparatus comprising depositing F-SiO on a preform surface layer 2 A plurality of sets of plasma excited deposition structures; each group of plasma excitation deposition structures comprises a microwave generator, a waveguide transmission structure, a coupling ionization structure and an air inlet structure; the microwave generator is used for emitting a plurality of electromagnetic waves; the waveguide transmission structure comprises a plurality of groups of waveguide structures and is used for transmitting a plurality of electromagnetic waves in a one-to-one correspondence manner; the coupling ionization structure is used for receiving and coupling a plurality of electromagnetic waves; the gas inlet structure is used for conveying target gas into the coupling ionization structure; wherein, a plurality of groups of the coupling ionization structures are used for ionizing target gas and a plurality of groups of electromagnetic waves to generate a plurality of groups of plasmas, and the plasmas are sprayed to the surface layer of the prefabricated rod to deposit F-SiO 2 . The invention can effectively avoid the ablation phenomenon of the discharge tube caused by the transmission of a single high-power microwave source to the coupling ionization structure through the single-path waveguide, and simultaneously effectively avoid the secondary melting and sintering of the traditional process.
Description
Technical Field
The invention relates to the technical field of optical fibers and photoelectrons, in particular to a method for preparing F-SiO by plasma deposition 2 An optical fiber preform cladding apparatus and method.
Background
Aiming at the preparation technology of large-size high-F-doped quartz cladding prefabricated rod, the traditional four-large prefabricated rod process has certain limitation in the preparation of the synthetic quartz glass, the VAD, OVD and MCVD processes are limited by the heat balance condition, the F-doped concentration limit is 1.5-2%, and the numerical aperture of the corresponding optical fiber is lower than 0.17.PCVD utilizes a non-thermal equilibrium plasma process to break through the limitation of the thermal equilibrium condition on the doping F concentration, and can accurately control the doping concentration and the radial refractive index, but the PCVD in-tube method is difficult to manufacture a large-diameter preform. In addition, the four methods all need secondary sintering or fusion shrinkage, and the low-viscosity nonmetallic doping element is extremely easy to diffuse and volatilize for the second time, thus being not suitable for preparing the high-doping F-SiO 2 And (3) cladding the preform.
Meanwhile, the preparation of large-size synthetic quartz glass is mentioned in the related art, a PCVD process is adopted, a core rod for preparing a fluorine-doped layer is firstly deposited on a quartz liner tube, and then a cladding is externally deposited through an OVD or VAD process, so that the large-diameter synthetic quartz glass is obtained, the process is complex, and the production cost is high.
Disclosure of Invention
The invention aims to overcome the defects of the prior art and provides a method for preparing F-SiO by plasma deposition 2 The optical fiber preform cladding device and the method can manufacture a large-diameter preform, effectively avoid the discharge tube ablation phenomenon caused when a single high-power microwave source is transmitted to a coupling ionization structure through a single-path waveguide, and simultaneously effectively avoid secondary melting and sintering in the traditional process.
In a first aspect, a method for preparing F-SiO by plasma deposition is provided 2 An optical fiber preform cladding apparatus comprising a cladding layer disposed around the preform and for depositing F-SiO on the surface layer of the preform 2 Multiple groups of plasma excitation deposition structures, and driving the multiple groups of plasma excitation deposition structures to do horizontal reciprocating motion and driving the prefabricated rod to rotate around the central shaft of the prefabricated rodA lathe driver;
each set of the plasma excited deposition structures comprises:
a microwave generator for emitting a plurality of electromagnetic waves;
the waveguide transmission structure comprises a plurality of groups of waveguide structures connected with the microwave generator, and the plurality of groups of waveguide structures are used for transmitting a plurality of electromagnetic waves in a one-to-one correspondence manner;
the coupling ionization structure is connected with the waveguide structures and used for receiving and coupling a plurality of electromagnetic waves; the method comprises the steps of,
the air inlet structure is connected with the coupling ionization structure and is used for conveying target gas into the coupling ionization structure;
wherein, a plurality of groups of the coupling ionization structures are used for ionizing target gas and a plurality of groups of electromagnetic waves to generate a plurality of groups of plasmas, and the plasmas are sprayed to the surface layer of the prefabricated rod to deposit F-SiO 2 。
In some embodiments, the waveguide structure comprises a rectangular waveguide with one end connected with the microwave generator, a water load, a power detector and an automatic tuner arranged on the rectangular waveguide, and a compression waveguide with one end connected with the other end of the rectangular waveguide, and the other end of the compression waveguide is connected with the coupling ionization structure.
In some embodiments, the height dimension of the waveguide at the junction of the compressed waveguide and the coupled ionization structure is less than the height dimension of the rectangular waveguide.
In some embodiments, the gas inlet structure is configured to receive argon, oxygen, gaseous silicon feedstock, and gaseous fluorine feedstock in a delivery target gas;
the air inlet structure comprises an air inlet pipe arranged at the air inlet end of the coupling ionization structure and a plurality of air inlet interface pieces arranged on the periphery of the air inlet pipe.
In some embodiments, the coupling ionization structure comprises a coupling resonant cavity which is connected with the compression waveguide and is in a hollow structure, a discharge tube which is arranged in the hollow structure of the coupling resonant cavity and is communicated with the air inlet pipe, and an ignition device for igniting argon of target gas in the discharge tube.
In some embodiments, the discharge tube is provided in a three-layer tube structure including an outer layer tube, an intermediate layer tube, and an inner layer tube;
the outer layer tube is filled with oxygen; the middle layer pipe is filled with gaseous silicon raw material, argon and oxygen; the inner layer tube is filled with gaseous fluorine raw material.
In some embodiments, part of the discharge tubes in the coupling ionization structure are used for spraying the oxygen, the ignited argon and the first beam of plasma generated by the ionization reaction of the coupled multiple beams of electromagnetic waves to the surface layer of the preform through the air outlet end so as to heat and polish the preform.
In some embodiments, part of the discharge tubes in the coupling ionization structure are further used for spraying a second beam of plasma generated by ionization reaction of oxygen, gaseous silicon raw material, gaseous fluorine raw material and the coupled multiple beams of electromagnetic waves to the surface layer of the preform through the gas outlet end to deposit F-SiO 2 。
In a second aspect, a method for preparing F-SiO by plasma deposition is provided 2 An optical fiber preform cladding method comprising:
starting a lathe driver to drive the preform rod to rotate around a central shaft of the preform rod;
argon and oxygen are introduced into a discharge tube of a part of plasma excitation deposition structure, a microwave generator is started, an ignition device is started to ignite the argon, so that first plasma is generated by ionization and is sprayed to the surface layer of the preform;
starting a lathe driver to drive a part of plasma excitation deposition structure for generating a first beam of plasma to do horizontal reciprocating motion so as to heat and polish the preform;
closing the argon gas, continuing to introduce oxygen gas, introducing the gaseous silicon raw material and the gaseous fluorine raw material into a discharge tube of a partial plasma excitation deposition structure, and ionizing to generate a second beam of plasma which is sprayed to the surface layer of the preform rod through the gas outlet end to deposit F-SiO 2 ；
When the deposition is detected to reach the preset condition, the oxygen, the gaseous silicon raw material and the fluorine-containing raw material are closed, and the microwave generator and the lathe driver are closed.
Compared with the prior art, the multi-waveguide structure transmits a plurality of electromagnetic waves to the coupling ionization structure in a one-to-one correspondence manner, so that the multi-waveguide coupling mode excites plasmas, and the phenomenon of ablation of a discharge tube caused when a single high-power microwave source is transmitted to the coupling ionization structure through a single waveguide can be effectively avoided, and the service life of equipment is prolonged. Meanwhile, the multi-path waveguide coupling mode excites the plasmas, so that the total energy of the plasma torch is high, and the flux of the gaseous fluorine raw material gas in the target gas is high, thereby being capable of directly depositing the glassy state high-doped F-SiO on the preform rod in a normal pressure state 2 And manufacturing the large-diameter preform by cladding the preform.
Meanwhile, the combined deposition of a plurality of groups of plasma torches excited by the ionization of a plurality of groups of coupling ionization structures can effectively avoid the secondary melting shrinkage and sintering of the traditional process and effectively avoid the high doping F-SiO 2 The prepared preform cladding F has high content by diffusion and volatilization of nonmetallic F element.
Drawings
FIG. 1 is a schematic cross-sectional view of a plasma excited deposition structure of the present invention;
FIG. 2 is a cross-sectional elevation view of two sets of coupled ionization structures, air intake structures, and preforms of the present invention;
FIG. 3 is a F-SiO produced according to the present invention 2 Sample EDX profile;
FIG. 4 is a further F-SiO produced according to the invention 2 Sample EDX profile;
FIG. 5 shows the preparation of F-SiO by plasma deposition according to the present invention 2 A schematic flow chart of the cladding method of the optical fiber preform.
Reference numerals:
1. a microwave generator; 2. a water load; 3. a rectangular waveguide; 4. a power detector; 5. an automatic tuner; 6. a compressed waveguide; 7. coupling the resonant cavity; 8. a discharge tube; 9. an air intake structure; 10. a plasma; 11. a preform.
Detailed Description
For the purpose of making the objects, technical solutions and advantages of the embodiments of the present invention more apparent, the technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings in the embodiments of the present invention, and it is apparent that the described embodiments are some embodiments of the present invention, but not all embodiments of the present invention. All other embodiments, which can be made by those skilled in the art based on the embodiments of the invention without making any inventive effort, are intended to be within the scope of the invention.
Referring to FIGS. 1 and 2, the embodiment of the invention provides a method for preparing F-SiO by plasma deposition 2 Cladding means for an optical fiber preform 11 comprising a cladding means disposed around the preform 11 for depositing F-SiO on the surface layer of the preform 11 2 A plurality of groups of plasma excitation deposition structures, and a lathe driver for driving the plurality of groups of plasma excitation deposition structures to do horizontal reciprocating motion and driving the preform 11 to rotate around the central axis of the lathe driver;
each set of the plasma excited deposition structures comprises:
the microwave generator 1 is used for emitting a plurality of electromagnetic waves, the frequency of the electromagnetic waves output by the microwave generator 1 is 900 MHz-50 GHz, and the power is 1-50 kW;
the waveguide transmission structure comprises a plurality of groups of waveguide structures connected with the microwave generator 1, and the plurality of groups of waveguide structures are used for transmitting a plurality of electromagnetic waves in a one-to-one correspondence manner;
the coupling ionization structure is connected with the waveguide structures and used for receiving and coupling a plurality of electromagnetic waves; the method comprises the steps of,
an air inlet structure 9 connected with the coupling ionization structure and used for conveying target gas into the coupling ionization structure;
wherein the coupling ionization structure is used for ionizing target gas and a plurality of electromagnetic waves to generate a plurality of groups of plasmas 10, and spraying the plasmas onto the surface layer of the preform 11 to deposit F-SiO 2 。
It should be noted that the number of plasmas 10 can be set to be 1-10, and the included angles of multiple groups of plasmas 10 torches can be set to be 0-180 o 。
In particular, in this embodiment, the present invention transmits multiple electromagnetic waves into the coupling ionization structure through multiple waveguide structures in one-to-one correspondence, so that the multiple waveguidesThe coupling mode excites the plasma 10, so that the ablation phenomenon of the discharge tube 8 caused when a single high-power microwave source is transmitted to the coupling ionization structure through a single-path waveguide can be effectively avoided, and the service life of equipment is prolonged. Meanwhile, the multi-path waveguide coupling mode excites the plasma 10, so that the total energy of the plasma 10 torch is high, and the flux of the gaseous fluorine raw material gas in the target gas is large, thereby directly depositing the glassy state high doping F-SiO on the preform 11 in the normal pressure state 2 The preform 11 is clad, thereby manufacturing a large-diameter preform 11.
Meanwhile, a plurality of groups of plasma 10 torches excited by ionization of a plurality of groups of coupling ionization structures are deposited in a combined way, so that the secondary melting shrinkage and sintering of the traditional process can be effectively avoided, and the high doping F-SiO can be effectively avoided 2 The prepared preform 11 has high cladding F content by diffusion and volatilization of nonmetallic F elements.
Optionally, the waveguide structure includes a rectangular waveguide 3 with one end connected to the microwave generator 1, a water load 2, a power detector 4 and an automatic tuner 5 disposed on the rectangular waveguide 3, and a compressed waveguide 6 with one end connected to the other end of the rectangular waveguide 3, where the other end of the compressed waveguide 6 is connected to the coupling ionization structure.
Optionally, the height dimension of the waveguide at the connection of the compression waveguide 6 and the coupling ionization structure is smaller than the height dimension of the rectangular waveguide 3.
Specifically, in this embodiment, the width a of the inner section of the rectangular waveguide 3 is 70-120 mm, the height b is 30-60 mm, and the height of the compressed short side of the compressed waveguide 6 connected to the coupling ionization structure is smaller than the height of the rectangular waveguide 3, which can be set as b/4~b.
Thus, the short side b of the waveguide with the coupling ionization structure portion is compressed to b/4~b to enhance the electric field strength of the coupling into the coupling ionization structure. The high electric field intensity generated by the compressed waveguide 6 can enable gas molecules to be excited and ionized more effectively, and the raw material utilization efficiency is high.
Optionally, the gas inlet structure 9 is configured to receive argon, oxygen, gaseous silicon raw material and gaseous fluorine raw material in the target gas;
the air inlet structure 9 comprises an air inlet pipe arranged at the air inlet end of the coupling ionization structure and a plurality of air inlet connectors arranged on the periphery of the air inlet pipe.
Specifically, in this embodiment, multiple gas injection ports are formed on the side surface of the gas inlet pipe, multiple gas inlet ports are connected to the gas inlet pipe along the tangential direction of the cylinder of the inner wall, and form a certain angle with the horizontal plane, the number of the gas inlet ports is 2-20, and the angle ranges from 0 ° to 90 °. The air inlet interface piece of the innermost layer of the discharge tube 8 which is introduced into the coupling ionization structure is arranged along the central axis direction.
Optionally, the coupling ionization structure includes a coupling resonant cavity 7 connected with the compression waveguide 6 and having a hollow structure, a discharge tube 8 disposed in the hollow structure of the coupling resonant cavity 7 and communicating with the air inlet pipe, and an ignition device for igniting argon of a target gas in the discharge tube 8.
Alternatively, the discharge tube 8 is provided in a three-layer tube structure including an outer layer tube, an intermediate layer tube, and an inner layer tube;
the outer layer tube is filled with oxygen; the middle layer pipe is filled with gaseous silicon raw material, argon and oxygen; and the inner layer pipe is filled with fluorine-containing raw materials.
Specifically, in this embodiment, the coupling resonant cavity 7 is a hexahedral or cylindrical hollow structure, and a coupling hole is formed on a connection surface of the coupling resonant cavity and the compression waveguide 6, the coupling hole is matched with the cross section of the compression waveguide 6, and the edge distance of the coupling hole is 10-100 mm.
The upper end face and the lower end face of the coupling resonant cavity 7 are provided with central round holes, and the quartz discharge tube 8 is inserted into the central round holes, wherein the diameter of the central round holes is 10-80 mm.
The discharge tube 8 is of a three-layer tube structure design, and the outer diameter of the outer quartz tube is matched with the opening of the coupling resonant cavity 7.
In the related art, F-SiO is prepared 2 When the power of the input microwave source is low, the energy and the temperature of the plasma 10 torch are low, and the deposited F-SiO is deposited when the cladding of the preform 11 is low 2 Is opaque and powdery. The energy and the temperature of the plasma 10 torch can be improved by improving the power of the microwave source, but the ablation phenomenon of the discharge tube 8 is easily caused by the local temperature increase of the plasma 10 torch, and the discharge tube 8 is easily etched by high-energy ionized F ions, so that the perforation and collapse of the discharge tube 8 are caused in a very short timeMaking it unusable for highly doped F-SiO 2 And (5) preparing a cladding layer. Therefore, the quartz discharge tube 8 of the invention is designed for a three-layer discharge tube 8, the inner layer tube is filled with fluorine-containing raw material, the middle layer tube is filled with gaseous silicon raw material, argon and oxygen, thereby effectively avoiding the ablation of the discharge tube 8 by the high-temperature plasma 10 and the etching of the discharge tube 8 by the high-energy ionization state F and the SiO on the inner surface of the discharge tube 8 2 Dust is accumulated.
Optionally, a part of the discharge tube 8 in the coupling ionization structure is configured to spray the first beam of plasma 10 generated by ionization reaction of oxygen, ignited argon and coupled multiple beams of electromagnetic waves to the surface layer of the preform 11 through the air outlet end, so as to heat and polish the preform 11.
Optionally, part of the discharge tube 8 in the coupling ionization structure is further configured to spray the second beam plasma 10 generated by ionization reaction of oxygen, gaseous silicon raw material, gaseous fluorine raw material and coupled multiple electromagnetic waves to the surface layer of the preform 11 through the gas outlet end to deposit F-SiO 2
Specifically, in this embodiment, two sets of plasma excited deposition structures are taken as an example.
Simultaneously referring to FIG. 1, two paths of electromagnetic waves are coupled into a coupling resonant cavity through a waveguide, plasma is excited, and F-SiO doped core rod surface with the diameter of 40mm is prepared 2 And (3) cladding the preform. The electromagnetic wave frequency is 2.45GHz, two paths of BJ26 waveguides are adopted for microwave transmission, the short sides of the waveguides connected with the coupling resonant cavity are compressed to b/4, and the transmission power of a single waveguide is 10kW. Two groups of normal pressure plasmas shown in fig. 2 are adopted to work simultaneously, wherein one plasma torch is used for increasing the surface temperature of the preform rod, and one plasma torch is used for depositing F-SiO 2 . Firstly, a preform to be processed is installed, the outer diameter of the preform in the embodiment is 40mm, a lathe is started to enable a target rod to rotate, the rotation speed is set to be 20rpm, and the distance from the surface of the preform to the upper end face of a discharge tube is 40mm. Then two groups of discharge tubes are simultaneously introduced with gas to generate plasma torches, ar is respectively introduced into the middle discharge tubes through two opposite tangential air inlets, the flow rates are respectively 20SLM, a microwave generator is turned on, and ignition is realized through an ignition device to generate plasma. Successful under argonOn the basis of ignition, oxygen is introduced into the middle layer discharge tube through the 2-path tangential air inlet, the total flow is 50SLM, the plasma torch is generated by ionization, and Ar gas is closed. Starting a lathe driver to drive the two symmetrically distributed plasma torches to horizontally reciprocate by a bearing platform at a speed of 20mm/min, wherein the surface temperature of the preform is 1950 o And C, preheating and polishing treatment of the preform are realized. After polishing, feeding one path of plasma torch, and introducing SiCl into the middle layer discharge quartz tube through a 2 path tangential air inlet 4 Steam is introduced into the innermost discharge quartz tube through the bottom axial air inlet 2 F 6 The gas is ionized to generate plasma which is ejected out of the discharge tube by the jet and collected by the rotary preform rod, siCl 4 The gas flow is 4SLM, C 2 F 6 The flow rate was 1SLM. After deposition to an outer diameter of 44mm, siCl was turned off 4 Gas and C 2 F 6 And (3) stopping gas deposition, inputting power of all microwave sources to 2kW, and continuously annealing the plasma torch at a low temperature for 10min to eliminate stress. And (5) turning off a plasma power supply, turning off all gases, and collecting and loading the preform after the preform is naturally cooled. As can be seen from FIG. 3, F-SiO was prepared 2 The F content in the cladding was 4.1%.
Referring to FIG. 1, two paths of electromagnetic waves are coupled into a resonant cavity through a waveguide to excite plasmas, and the F-SiO doped core rod surface with the diameter of 50mm is prepared 2 And (3) cladding the preform. The microwave source frequency is 2.45GHz, two paths of BJ26 waveguides are adopted for microwave transmission, the short sides of the waveguides connected with the coupling resonant cavity are compressed to b/4, and the transmission power of a single waveguide is 10kW. Two groups of normal pressure plasmas shown in fig. 2 are adopted to work simultaneously, wherein one plasma torch is used for increasing the surface temperature of a target rod, and the other plasma torch is used for depositing F-SiO 2 . Firstly, a preform to be processed is installed, the outer diameter of the preform in the embodiment is 40mm, a lathe is started to enable the preform to rotate, the rotating speed is set to be 20rpm, and the distance from the surface of the preform to the upper end face of a discharge tube is 35mm. Then two groups of discharge tubes are simultaneously introduced with gas to generate plasma torches which are respectively put into the middle layer through two opposite tangential air inletsAr is introduced into the electric tube, the flow rates are respectively 20SLM, the microwave generator is turned on, and ignition is realized through the ignition device, so that plasma is generated. Oxygen is introduced into the middle layer discharge tube through the 2-path tangential air inlet on the basis of successful ignition of argon, the total flow is 50SLM, the plasma torch is generated by ionization, and Ar gas is closed. And starting a lathe driver to drive the two symmetrically distributed plasma torches to horizontally reciprocate by the bearing platform at the speed of 10mm/min, so as to realize the preheating and polishing treatment of the preform. After polishing, feeding one path of plasma torch, and introducing SiCl into the middle layer discharge quartz tube through a 2 path tangential air inlet 4 Steam is introduced into the innermost discharge quartz tube through the bottom axial air inlet 2 F 6 The gas is ionized to generate plasma which is ejected out of the discharge tube by the jet and collected by the rotary preform rod, siCl 4 The gas flow is 4SLM, C 2 F 6 The flow rate was 2SLM. After deposition to an outer diameter of 55mm, siCl was turned off 4 Gas and C 2 F 6 And (3) stopping gas deposition, inputting power of all microwave sources to 2.5kW, and continuously annealing the plasma torch at a low temperature for 10min to eliminate stress. And (5) turning off a plasma power supply, turning off all gases, and collecting and loading the preform after the preform is naturally cooled. As can be seen from FIG. 4, F-SiO was prepared 2 The F content of the clad layer was 5.5%.
Referring to FIG. 5, the embodiment of the invention also provides a method for preparing F-SiO by plasma deposition 2 An optical fiber preform cladding method comprising the steps of:
and S100, starting a lathe driver to drive the preform to rotate around the central shaft of the preform, wherein the distance between the end face of the discharge tube and the surface of the preform is 2-100 mm.
S200, introducing argon and oxygen into a discharge tube of a part of plasma excitation deposition structure in a normal pressure or micro negative pressure state, starting a microwave generator, starting an ignition device to ignite the argon, so as to ionize and generate a first beam of plasma to be sprayed onto the surface layer of the preform; the purpose of introducing oxygen is to increase microwave power to working power, realize the cooperative ignition of multiple waveguides, adjust flow to working flow, wherein Ar flow0 to 50SLM, O 2 The flow is 0-100 SLM.
And S300, starting a lathe driver to drive a part of plasma excitation deposition structure for generating a first beam of plasma to horizontally reciprocate on the lathe bed along the support rod under the drive of the traction device so as to heat and polish the preform, wherein the distance between the end face of the discharge tube and the surface of the target rod is 2-100 mm.
S400, after finishing polishing treatment, closing the argon gas, continuing to introduce oxygen gas, introducing the gaseous silicon raw material and the gaseous fluorine raw material into a discharge tube of a partial plasma excitation deposition structure, and simultaneously adjusting the moving speed of the second beam plasma torch and the rotating speed of the target rod to ensure that the surface temperature of the preform rod is 1600-2000 DEG C o C, maintaining stability, starting to perform reciprocating deposition, and ionizing to generate a second beam of plasma which is sprayed to the surface layer of the preform rod through the air outlet end to deposit F-SiO 2 ；
S500, when the deposition is detected to reach the preset thickness, or the preset time, or the preset reciprocating times, closing the feeding of oxygen, gaseous silicon raw materials and fluorine-containing raw materials after the deposition is finished, and removing the plasma torch from the deposition area.
Reducing the power of a microwave source, controlling the plasma torch to reciprocate, and enabling the surface temperature of the preform to be 1100-1200 o And C, carrying out low-temperature annealing on the preform for 5-30 minutes to eliminate stress, closing the microwave generator, closing the lathe driver, and carrying out collection after the preform is naturally cooled.
The distance from the end face of the plasma discharge tube to the surface of the preform is 2-100 mm, the rotating speed of the preform is 1-100 rmp, and the transverse moving speed of the plasma torch is 0.1-30 mm/s.
Therefore, the invention adopts a multi-waveguide coupling resonant cavity structure, a plurality of microwave sources are coupled into the resonant cavity and the discharge tube by the multi-path waveguide, the short sides of the waveguide at the connecting part of the coupling resonant cavity are compressed to different degrees, and the air inlet end of the discharge tube is designed into a three-layer structure. Therefore, the microwave energy and the electric field intensity of the coupling resonant cavity can be obviously enhanced, and the multi-path waveguide coupling structure can effectively avoid the ablation of the discharge tube caused by the local energy and the overhigh temperature of the plasma torch, and the high-concentration high-energy ionization state F is opposite to the discharge tubeEtching phenomenon of (a). The three-layer structure design of the air inlet end of the discharge tube can effectively avoid the etching phenomenon and SiO of the high-energy ionization state F to the outer discharge tube 2 Dust is accumulated. The plasma torch produced by the invention has high energy, the flux of the F-containing raw material gas in the raw material is large, the service life of the discharge tube is long, and the large-diameter high-doping concentration F-SiO can be directly prepared by a one-step method 2 The optical fiber preform cladding has simple and stable preparation process and low cost.
In the description of the present invention, it should be noted that the azimuth or positional relationship indicated by the terms "upper", "lower", etc. are based on the azimuth or positional relationship shown in the drawings, and are merely for convenience of describing the present invention and simplifying the description, and are not indicative or implying that the apparatus or element in question must have a specific azimuth, be constructed and operated in a specific azimuth, and thus should not be construed as limiting the present invention. Unless specifically stated or limited otherwise, the terms "mounted," "connected," and "coupled" are to be construed broadly, and may be, for example, fixedly connected, detachably connected, or integrally connected; can be mechanically or electrically connected; can be directly connected or indirectly connected through an intermediate medium, and can be communication between two elements. The specific meaning of the above terms in the present invention can be understood by those of ordinary skill in the art according to the specific circumstances.
It should be noted that in the present invention, relational terms such as "first" and "second" and the like are used solely to distinguish one entity or action from another entity or action without necessarily requiring or implying any actual such relationship or order between such entities or actions. Moreover, the terms "comprises," "comprising," or any other variation thereof, are intended to cover a non-exclusive inclusion, such that a process, method, article, or apparatus that comprises a list of elements does not include only those elements but may include other elements not expressly listed or inherent to such process, method, article, or apparatus. Without further limitation, an element defined by the phrase "comprising one … …" does not exclude the presence of other like elements in a process, method, article, or apparatus that comprises the element.
The foregoing is only a specific embodiment of the invention to enable those skilled in the art to understand or practice the invention. Various modifications to these embodiments will be readily apparent to those skilled in the art, and the generic principles defined herein may be applied to other embodiments without departing from the spirit or scope of the invention. Thus, the present invention is not intended to be limited to the embodiments shown herein but is to be accorded the widest scope consistent with the principles and novel features disclosed herein.
Claims (4)
1. F-SiO preparation by plasma deposition 2 An optical fiber preform cladding apparatus comprising a cladding layer disposed around a preform and for depositing F-SiO on a surface layer of the preform 2 A plurality of groups of plasma excitation deposition structures, and a lathe driver for driving the plurality of groups of plasma excitation deposition structures to do horizontal reciprocating motion and driving the prefabricated rod to rotate around a central shaft of the lathe driver;
each set of the plasma excited deposition structures comprises:
a microwave generator for emitting a plurality of electromagnetic waves;
the waveguide transmission structure comprises a plurality of groups of waveguide structures connected with the microwave generator, and the plurality of groups of waveguide structures are used for transmitting a plurality of electromagnetic waves in a one-to-one correspondence manner;
the coupling ionization structure is connected with the waveguide structures and used for receiving and coupling a plurality of electromagnetic waves; the method comprises the steps of,
the air inlet structure is connected with the coupling ionization structure and is used for conveying target gas into the coupling ionization structure;
wherein, a plurality of groups of the coupling ionization structures are used for ionizing target gas and a plurality of groups of electromagnetic waves to generate a plurality of groups of plasmas, and the plasmas are sprayed to the surface layer of the prefabricated rod to deposit F-SiO 2 ；
The waveguide structure comprises a rectangular waveguide with one end connected with the microwave generator, a water load, a power detector and an automatic tuner which are arranged on the rectangular waveguide, and a compressed waveguide with one end connected with the other end of the rectangular waveguide, wherein the other end of the compressed waveguide is connected with the coupling ionization structure;
the air inlet structure is used for receiving and conveying argon, oxygen, gaseous silicon raw materials and gaseous fluorine raw materials in the target gas;
the air inlet structure comprises an air inlet pipe arranged at the air inlet end of the coupling ionization structure and a plurality of air inlet interface pieces arranged at the periphery of the air inlet pipe;
the coupling ionization structure comprises a coupling resonant cavity which is connected with the compression waveguide and is in a hollow structure, a discharge tube which is arranged in the hollow structure of the coupling resonant cavity and is communicated with the air inlet pipe, and an ignition device for igniting argon of target gas in the discharge tube;
the discharge tube is provided with a three-layer tube structure comprising an outer layer tube, an intermediate layer tube and an inner layer tube;
the outer layer tube is filled with oxygen; the middle layer pipe is filled with gaseous silicon raw material, argon and oxygen; the inner layer tube is filled with gaseous fluorine raw material.
2. The method for preparing F-SiO by plasma deposition according to claim 1 2 The optical fiber preform cladding device is characterized in that the height dimension of the waveguide at the joint of the compressed waveguide and the coupling ionization structure is smaller than the height dimension of the rectangular waveguide.
3. The method for preparing F-SiO by plasma deposition according to claim 1 2 The optical fiber preform cladding device is characterized in that part of the discharge tube in the coupling ionization structure is used for spraying first beam plasma generated by ionization reaction of oxygen, ignited argon and a plurality of coupled electromagnetic waves to the surface layer of the preform through an air outlet end so as to heat and polish the preform.
4. The method for preparing F-SiO by plasma deposition according to claim 1 2 An optical fiber preform cladding apparatus characterized in that a part of said discharge tube in said coupling ionization structure,the second beam plasma generated by ionization reaction of the oxygen, the gaseous silicon raw material, the gaseous fluorine raw material and the coupled multiple beams of electromagnetic waves is sprayed to the surface layer of the preform rod through the gas outlet end so as to deposit F-SiO 2 。
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