CN115557693B - Deposition device and preparation method of optical fiber preform - Google Patents

Deposition device and preparation method of optical fiber preform Download PDF

Info

Publication number
CN115557693B
CN115557693B CN202211095609.2A CN202211095609A CN115557693B CN 115557693 B CN115557693 B CN 115557693B CN 202211095609 A CN202211095609 A CN 202211095609A CN 115557693 B CN115557693 B CN 115557693B
Authority
CN
China
Prior art keywords
clamping unit
inner cavity
optical fiber
fiber preform
plasma torch
Prior art date
Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
Active
Application number
CN202211095609.2A
Other languages
Chinese (zh)
Other versions
CN115557693A (en
Inventor
吴椿烽
沈一春
陈京京
陈娅丽
周建峰
张烨锋
Current Assignee (The listed assignees may be inaccurate. Google has not performed a legal analysis and makes no representation or warranty as to the accuracy of the list.)
Zhongtian Technology Advanced Materials Co ltd
Jiangsu Zhongtian Technology Co Ltd
Original Assignee
Zhongtian Technology Advanced Materials Co ltd
Jiangsu Zhongtian Technology Co Ltd
Priority date (The priority date is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the date listed.)
Filing date
Publication date
Application filed by Zhongtian Technology Advanced Materials Co ltd, Jiangsu Zhongtian Technology Co Ltd filed Critical Zhongtian Technology Advanced Materials Co ltd
Priority to CN202211095609.2A priority Critical patent/CN115557693B/en
Publication of CN115557693A publication Critical patent/CN115557693A/en
Application granted granted Critical
Publication of CN115557693B publication Critical patent/CN115557693B/en
Active legal-status Critical Current
Anticipated expiration legal-status Critical

Links

Classifications

    • C—CHEMISTRY; METALLURGY
    • C03—GLASS; MINERAL OR SLAG WOOL
    • C03B—MANUFACTURE, SHAPING, OR SUPPLEMENTARY PROCESSES
    • C03B37/00—Manufacture or treatment of flakes, fibres, or filaments from softened glass, minerals, or slags
    • C03B37/01—Manufacture of glass fibres or filaments
    • C03B37/012—Manufacture of preforms for drawing fibres or filaments
    • C03B37/014—Manufacture of preforms for drawing fibres or filaments made entirely or partially by chemical means, e.g. vapour phase deposition of bulk porous glass either by outside vapour deposition [OVD], or by outside vapour phase oxidation [OVPO] or by vapour axial deposition [VAD]
    • C03B37/018—Manufacture of preforms for drawing fibres or filaments made entirely or partially by chemical means, e.g. vapour phase deposition of bulk porous glass either by outside vapour deposition [OVD], or by outside vapour phase oxidation [OVPO] or by vapour axial deposition [VAD] by glass deposition on a glass substrate, e.g. by inside-, modified-, plasma-, or plasma modified- chemical vapour deposition [ICVD, MCVD, PCVD, PMCVD], i.e. by thin layer coating on the inside or outside of a glass tube or on a glass rod
    • C03B37/01807—Reactant delivery systems, e.g. reactant deposition burners
    • C03B37/01815—Reactant deposition burners or deposition heating means

Landscapes

  • Chemical & Material Sciences (AREA)
  • Engineering & Computer Science (AREA)
  • Chemical Kinetics & Catalysis (AREA)
  • General Chemical & Material Sciences (AREA)
  • Life Sciences & Earth Sciences (AREA)
  • General Life Sciences & Earth Sciences (AREA)
  • Geochemistry & Mineralogy (AREA)
  • Manufacturing & Machinery (AREA)
  • Materials Engineering (AREA)
  • Organic Chemistry (AREA)
  • Manufacture, Treatment Of Glass Fibers (AREA)

Abstract

The invention provides a deposition device and a preparation method of an optical fiber preform, wherein the device comprises a shell, a first clamping unit, a second clamping unit, a plasma torch and a heating unit; the shell comprises an inner cavity surrounded by a side wall, a top wall and a bottom wall; the first clamping unit is connected with the top wall, and the second clamping unit is connected with the bottom wall; the first clamping unit and the second clamping unit rotate along the axis of the first clamping unit and move in the depth direction of the inner cavity; the first clamping unit and the second clamping unit are used for mutually matching and clamping a rod to be deposited in the inner cavity; the spraying direction of the plasma torch faces the inner cavity; the heating unit is positioned in the inner cavity; the side wall of the shell is respectively provided with an exhaust hole and an air inlet hole, the trend of the air flow discharged through the exhaust holes is consistent with the spraying direction, the trend of the air flow entering the inner cavity through the air inlet hole and the spraying direction have an included angle theta which is more than or equal to 20 degrees and less than or equal to 60 degrees, and the device can be used for preparing the optical fiber preform with uniform fluorine doping of the outer cladding.

Description

Deposition device and preparation method of optical fiber preform
Technical Field
The invention belongs to the technical field of optical fiber production, and particularly relates to a deposition device and a preparation method of an optical fiber preform.
Background
Optical fibers are widely used as optical information transmission media in fiber lasers. Optical fiber preforms are the starting material for optical fiber manufacture. The optical fiber preform is generally composed of a core layer of quartz glass core rod and a fluorine-doped outer cladding layer of fluorine-doped quartz glass having different refractive indexes. The refractive index of the fluorine-doped outer cladding can be reduced by doping fluorine in the outer cladding, so that the refractive index of the fiber core layer is larger than that of the outer cladding layer, and the total reflection condition of optical fiber transmission is met.
The core/cladding relative refractive index difference Δn (Δn= (n) core -n clad )/n 0 X 100%) numerical aperture NA (therein) For measuring the light receiving capacity of the optical fiber, wherein n core Is the refractive index of the core layer, n clad To refractive index of the cladding, n 0 Is the refractive index of the pure silicon layer. In order to reduce the loss of optical power, the optical fiber preform is required to have uniformity of Δn and NA in the longitudinal direction and the circumferential direction (radial direction), respectively.
The uniformity of fluorine doping of the fluorine-doped overclad in the optical fiber preform directly affects the uniformity of the refractive index of the overclad, thereby affecting the uniformity of deltan and the uniformity of NA of the optical fiber preform in the longitudinal and radial directions. If the fluorine doping of the outer cladding of the optical fiber preform is uneven in the longitudinal direction and the circumferential direction (radial direction), the Δn and NA in the longitudinal direction and the radial direction directly cause larger fluctuation, so how to improve the fluorine doping uniformity of the optical fiber preform is a technical problem to be solved in the art.
Disclosure of Invention
The invention provides a deposition device, by which an optical fiber preform with uniform fluorine doping of an outer cladding layer can be manufactured, so that the consistency of delta n and NA of the optical fiber preform in the longitudinal direction and the radial direction is improved.
The invention also provides a preparation method of the optical fiber preform, which adopts the deposition device to prepare the optical fiber preform with uniform fluorine doping of the outer cladding, thereby obtaining the optical fiber with strong light receiving capability.
In one aspect of the present invention, there is provided a deposition apparatus including a housing, a first clamping unit, a second clamping unit, a plasma torch, and a heating unit; the shell comprises an inner cavity surrounded by a side wall, a top wall and a bottom wall; the first clamping unit is connected with the top wall, and the second clamping unit is connected with the bottom wall; the first clamping unit and the second clamping unit rotate along the axis of the first clamping unit and the second clamping unit and move in the depth direction of the inner cavity; the first clamping unit and the second clamping unit are used for mutually matching and clamping a rod to be deposited in the inner cavity; the spraying direction of the plasma torch faces the inner cavity; the heating unit is positioned in the inner cavity; the side wall of the shell is respectively provided with an exhaust hole and an air inlet hole, the trend of the air flow discharged through the exhaust holes is consistent with the spraying direction, and the trend of the air flow entering the inner cavity through the air inlet holes and the spraying direction form an included angle theta which is more than or equal to 20 degrees and less than or equal to 60 degrees.
According to an embodiment of the invention, the heating unit is arranged around the inside of the side wall.
According to one embodiment of the invention, the heating device further comprises a heat preservation unit and an isolation unit, wherein the isolation unit is arranged around the inside of the heating unit, and the heat preservation unit is arranged between the isolation unit and the heating unit in a surrounding mode.
According to one embodiment of the invention, a raw material inlet is arranged on the side wall, and the nozzle of the plasma torch faces to the raw material inlet.
According to one embodiment of the invention, the flame spraying device further comprises a shielding cover, wherein the shielding cover is clamped at the raw material inlet and is used for shielding the spraying flame from the shell.
According to an embodiment of the invention, the device further comprises a driving pump, wherein the driving pump is positioned outside the shell and connected with the exhaust hole.
According to an embodiment of the invention, the air inlet is provided with an air inlet hole, and the air inlet hole is provided with an air inlet hole.
According to an embodiment of the invention, the air intake valve is connected with the air intake hole and is used for controlling the air flow entering the air intake hole.
In another aspect of the present invention, there is provided a method for preparing an optical fiber preform, characterized in that the preparation is performed using the above-mentioned deposition apparatus, comprising the steps of: preheating the inner cavity by using a heating unit; forming gas circulation in the inner cavity by utilizing the air inlet hole and the air outlet hole, and controlling the pressure of the inner cavity to be-2 Pa to-5 Pa; the first clamping unit and the second clamping unit are respectively matched with each other to fixedly clamp a rod to be deposited, and a nozzle of the plasma torch points to one end of the rod to be deposited; starting the plasma torch, and performing first movement and first rotation on the rod to be deposited under the action of the first clamping unit and the second clamping unit and carrying out deposition treatment to obtain an optical fiber preform precursor; in the deposition treatment, the raw materials of the plasma torch are gaseous silicon-containing compounds, gaseous fluorides and oxygen; the optical fiber preform precursor moves and rotates for the second time under the action of the first clamping unit and the second clamping unit, and polishing is carried out, so that an optical fiber preform is obtained; in the polishing process, the source gas of the plasma torch is oxygen.
According to one embodiment of the invention, the preheating temperature is 800-900 ℃ and the preheating time is 20-40 min; and/or, in the deposition treatment, the power of the plasma torch is 50kW to 80kW; and/or, in the polishing treatment, the power of the plasma torch is 20kW to 30kW; and/or the rotation speed of the first rotation is 30 rpm-40 rpm/min; and/or the rotation speed of the second rotation is 30 rpm-40 rpm/min; and/or the speed of the first movement is 40 mm/min-60 mm/min; and/or the speed of the second movement is 250 mm/min-350 mm/min.
The implementation of the invention has at least the following beneficial effects:
the invention provides a deposition device which comprises a shell, a first clamping unit, a second clamping unit, a plasma torch and a heating unit. According to the invention, the first clamping unit and the second clamping unit are mutually matched to clamp the rod to be deposited in the inner cavity, and the raw materials sprayed by the plasma torch can be uniformly sprayed on the rod to be deposited along with the rotation of the first clamping unit and the second clamping unit along the axis and the movement of the first clamping unit and the second clamping unit in the depth direction of the inner cavity, so that a fluorine-doped outer cladding layer is formed on the surface of the rod to be deposited, and then the optical fiber preform is obtained. The invention maintains the pressure and air flow stability of the inner cavity through the exhaust hole and the air inlet hole on the side wall, and simultaneously can ensure that the undeposited raw materials are discharged out of the inner cavity through the exhaust hole; according to the invention, the heating unit is used for heating the inner cavity of the shell, so that the temperature stability of the end part and the middle part of the rod to be deposited is maintained, the axial temperature gradient of the rod to be deposited is avoided, the axial and radial temperature uniformity of the surface of the rod to be deposited is improved, the fluorine doping uniformity of the outer cladding is improved, the optical fiber preform with uniform fluorine doping of the outer cladding can be prepared, and the uniformity of delta n and the NA of the optical fiber preform in the longitudinal direction and the radial direction are improved.
The preparation method of the optical fiber preform provided by the invention adopts the deposition device to prepare, the difference between the maximum value and the minimum value of the prepared single optical fiber preform in the longitudinal direction is not more than 0.04%, and the difference between the maximum value and the minimum value of NA is not more than 0.005, so that the preparation method has good delta n consistency and NA consistency. In the longitudinal direction, the delta n average value of the optical fiber preform rod can reach more than 0.7 percent, the numerical aperture NA average value can reach more than 0.17, and the optical fiber preform rod has good light receiving capability.
Drawings
FIG. 1 is a schematic view of a deposition apparatus according to an embodiment of the present invention;
FIG. 2 is a schematic cross-sectional view of a deposition apparatus according to an embodiment of the present invention;
figure 3 is a schematic side view of a gas guide according to an embodiment of the invention,
FIG. 4 is a schematic end view of a first inlet of a gas guide according to an embodiment of the invention;
FIG. 5 is a schematic end view of a second inlet of a gas guide according to an embodiment of the invention;
FIG. 6 is a NA chart showing the longitudinal distribution of an optical fiber preform according to embodiment 2 of the present invention;
FIG. 7 is a cross-sectional view showing the radial distribution relative refractive index difference corresponding to the 9 th point of the optical fiber preform of example 3 of the present invention;
FIG. 8 is a NA chart showing the longitudinal distribution of an optical fiber preform according to comparative example 2 of the present invention.
Reference numerals illustrate:
1-a rod to be deposited; 21-a first clamping unit; 22-a second clamping unit; 3-chuck; 4-a metering element; 5-sealing the flange; 6-a pressure gauge; 7-exhaust holes; 8-an air inlet hole; 81-gas guide; 801-a first inlet; 802-a second inlet; 803-intake valve; 804-a guide plate; 9-isolation units; 10-a heat preservation unit; 11-a heating unit; 12-a shell and 13-a shielding cover; 14-plasma torch; 15-an induction coil; 16-a base rail; 17-lumen.
Detailed Description
The following detailed description is merely illustrative of the principles and features of the present invention, and examples are set forth for the purpose of illustration only and are not intended to limit the scope of the invention. All other embodiments, which can be made by those skilled in the art based on the examples of the invention without making any inventive effort, are intended to be within the scope of the invention.
The invention provides a deposition device, which comprises a shell, a first clamping unit, a second clamping unit, a plasma torch and a heating unit, wherein the first clamping unit is arranged on the shell; the shell comprises an inner cavity surrounded by a side wall, a top wall and a bottom wall; the first clamping unit is connected with the top wall, and the second clamping unit is connected with the bottom wall; the first clamping unit and the second clamping unit rotate along the axis of the first clamping unit and move in the depth direction of the inner cavity; the first clamping unit and the second clamping unit are used for mutually matching and clamping a rod to be deposited in the inner cavity; the spraying direction of the plasma torch faces the inner cavity; the heating unit is positioned in the inner cavity; the side wall of the shell is respectively provided with an exhaust hole and an air inlet hole, the trend of the air flow discharged through the exhaust holes is consistent with the spraying direction, and an included angle theta is formed between the trend of the air flow entering the inner cavity through the air inlet hole and the spraying direction, and is more than or equal to 20 degrees and less than or equal to 60 degrees.
The invention does not limit the placement mode of the deposition device, and the deposition device can be placed horizontally or vertically. It should be noted that the top wall and the bottom wall of the present invention are only used to distinguish the respective components, and are not to be construed as indicating directions.
The housing of the present invention has an annular outer shell, a top shell, and a bottom shell. The annular shell is provided with a first opening and a second opening which are opposite, a cavity communicated with the outside through the first opening and the second opening is formed by surrounding the annular shell, the top shell is matched and connected with the first opening in size, and the bottom shell is matched and connected with the second opening in size. Thus, the annular housing forms a side wall, the top and bottom shells form top and bottom walls, respectively, and an interior cavity defined by the side wall, top and bottom walls is formed.
The first clamping unit is connected with the top wall in a telescopic mode, and the second clamping unit is connected with the bottom wall in a telescopic mode. The first clamping unit and the second clamping unit can reciprocate along the direction far away from the inner cavity and the direction close to the inner cavity.
The first clamping unit and the second clamping unit are used for clamping the rod to be deposited. The first clamping unit and the second clamping unit are matched with each other, and the rod to be deposited is clamped between the first clamping unit and the second clamping unit, so that the rod to be deposited is positioned in the inner cavity.
Specifically, the first clamping unit, the second clamping unit and the rod to be deposited are respectively and independently provided with two ends extending along the depth direction of the inner cavity, one end of the first clamping unit, which is close to the inner cavity, is abutted with one end of the rod to be deposited, and one end of the second clamping unit, which is close to the inner cavity, is abutted with the other end of the rod to be deposited, so that the rod to be deposited in the inner cavity is clamped between the first clamping unit and the second clamping unit.
The clamping mode is not limited, and the rod to be deposited, the first clamping unit and the second clamping unit preferably extend coaxially as long as the rod to be deposited is clamped between the first clamping unit and the second clamping unit.
The rod to be deposited can rotate along the self axis in the inner cavity and reciprocate in the depth direction of the inner cavity along with the rotation of the first clamping unit and the second clamping unit along the self axis and the movement of the rod in the depth direction of the inner cavity.
The first clamping unit and the second clamping unit can be all positioned in the inner cavity or partially positioned in the inner cavity, so long as the condition that the rods to be deposited clamped by the first clamping unit and the second clamping unit are positioned in the inner cavity is satisfied.
When the first clamping unit and the second clamping unit are all positioned in the inner cavity, one ends of the first clamping unit and the second clamping unit, which are far away from the inner cavity, are connected with the top wall and the bottom wall.
When the first clamping unit and the second clamping unit are partially positioned in the inner cavity, one ends of the first clamping unit and the second clamping unit, which are far away from the inner cavity, are positioned outside the inner cavity. The middle parts of the first clamping unit and the second clamping unit are respectively connected with the top and the bottom wall.
The present invention is not limited to the structure of the first sandwiching unit and the second sandwiching unit, and may be the same, or may be different, and preferably the same. The specific types of the first sandwiching means and the second sandwiching means are not limited in the present invention, and may be made of quartz glass, for example.
The specific kind of the rod to be deposited is not limited in the present invention, for example, the rod to be deposited is a pure silica core rod (pure silicon core rod) or a germanium-doped core rod.
The plasma torch is used to spray the raw materials to be deposited into the inner cavity. Specifically, in the deposition process, the raw material to be deposited is converted into particles in a plasma flame sprayed by a plasma torch, and in order to ensure that the raw material to be deposited can be sprayed on the surface of the rod to be deposited, the spraying direction of the plasma torch faces the rod to be deposited. Wherein the plasma torch is surrounded by an induction coil.
The position and the installation mode of the plasma torch are not limited, and the position and the installation mode of the plasma torch are only required to meet the condition that the nozzle of the plasma torch faces to a rod to be deposited in the deposition process.
In the invention, the heating unit is positioned in the inner cavity and is used for heating the inner cavity. The heating unit is used for heating the inner cavity, so that the temperature stability of the inner cavity can be ensured, the temperature stability of the rod to be deposited in the longitudinal direction and the radial direction can be maintained in the process of depositing the outer cladding, the temperature uniformity of the surface of the rod to be deposited can be improved, and the fluorine doping uniformity of the outer cladding can be facilitated.
In the invention, the exhaust hole is used for exhausting the air flow of the inner cavity, the air inlet hole is used for enabling the air flow to enter the inner cavity, and the air inlet hole and the exhaust hole are used for exhausting the air, so that stable pressure and stable air circulation are formed in the inner cavity.
By making the trend of the air flow discharged from the exhaust hole consistent with the spraying direction, the particles which are not deposited can be discharged from the inner cavity through the exhaust hole, thereby ensuring the pressure and the air flow in the inner cavity to be stable.
In order to prevent the air inlet of the air inlet from influencing the stability of the air flow in the spraying direction, the direction of the air flow entering the inner cavity from the air inlet is provided with an included angle theta which is more than or equal to 20 degrees and less than or equal to 60 degrees, and the air flow in the inner cavity is not influenced by setting a certain angle, so that the discharge of undeposited particles is facilitated.
The invention does not limit the positions of the exhaust hole and the air inlet hole, and only needs to be positioned on the side wall of the shell, and the trend and the spraying direction of the air flow meet the requirements.
The number of air intake holes may be one or more. When the number of the air inlets is two, in order to ensure the stability of the air flow in the inner cavity, the two air outlets are symmetrically arranged along the axis of the shell.
Therefore, the deposition device provided by the invention adopts the first clamping unit and the second clamping unit to mutually match and clamp the rod to be deposited in the inner cavity, and the raw materials sprayed by the plasma torch can be uniformly sprayed on the rod to be deposited along with the rotation of the first clamping unit and the second clamping unit along the axis of the first clamping unit and the movement of the second clamping unit in the depth direction of the inner cavity, so that a fluorine-doped outer cladding layer is formed on the surface of the rod to be deposited, and further the optical fiber preform is obtained. Meanwhile, the invention maintains the pressure and air flow stability of the inner cavity through the exhaust hole and the air inlet hole on the side wall, and ensures that the undeposited raw materials can be discharged out of the inner cavity through the exhaust hole while the air flow stability in the jet direction is not influenced; the heating unit is used for heating the inner cavity of the shell, so that the temperature stability of the end part and the middle part of the rod to be deposited is maintained, the axial and radial temperature uniformity of the surface of the rod to be deposited is improved, the fluorine doping uniformity of the outer cladding is improved, the optical fiber perform with uniform fluorine doping of the outer cladding can be prepared, and the uniformity of delta n and the NA of the optical fiber perform in the longitudinal direction and the radial direction are improved.
The invention further comprises a first adjusting unit and a second adjusting unit which are respectively used for adjusting the rotation and the movement of the first clamping unit and the second clamping unit. Specifically, the first adjusting unit and the second adjusting unit respectively and independently comprise a chuck and a sealing flange, wherein the chuck is connected with one end of the clamping unit far away from the inner cavity, and the clamping unit can rotate along the axis of the chuck and move along the depth direction of the shell by utilizing a movable piece on the chuck; the sealing flange is positioned at the clamping part of the clamping unit and the top wall and the bottom wall and is used for sealing the gap between the clamping unit and the top wall and the bottom wall.
Further, the chuck is connected with a metering piece, and the mass of the rod to be deposited in the deposition process can be weighed through the metering piece, so that the weight of the prepared optical fiber preform rod is accurately controlled.
Still further, the first and second adjustment units may be supported by the base rail.
The position of the heating unit is not limited, and the heating unit can heat the inner cavity, so that the heating unit is annularly arranged in the side wall for further ensuring the stability and consistency of the temperature of the inner cavity.
In the implementation process of the invention, the heating unit is electrically connected with the outside through an electric wire, and under the action of an electric field, the heating unit is used for generating heat energy for the heat conductor and transmitting the heat energy into the inner cavity, so that the inner cavity is heated. The specific kind of the heating unit is not limited in the present invention, and for example, a graphite heating body made of a graphite material may be used.
Due to the arrangement of the heating unit in the inner cavity, when the temperature in the inner cavity is too high, materials in the heating unit can volatilize when being heated, and in order to avoid the influence of volatilized impurities on a deposition process, the deposition device further comprises an isolation unit, wherein the isolation unit is arranged around the inside of the heating unit.
The inner cavity is heated by the heating unit, and in order to prevent heat from dissipating faster, the invention is also provided with the heat preservation unit which is arranged in the heating unit in a surrounding way.
In order to avoid the influence of volatilized impurities of the heating unit and the heat preservation unit on the deposition process, the isolation unit is arranged inside the heat preservation unit in a surrounding mode, namely the heat preservation unit is arranged between the isolation unit and the heating unit, wherein the isolation unit can be a quartz furnace core tube made of quartz materials.
In the invention, a raw material inlet is arranged on the side wall of the shell, and raw materials to be deposited are conveyed into the inner cavity through the raw material inlet. In order to realize the conveying of raw materials, the nozzle of the plasma torch faces to the raw material inlet.
In the invention, the plasma torch can be positioned in the inner cavity or outside the inner cavity, so long as the condition that the plasma torch can spray raw materials into the inner cavity is satisfied. When the plasma torch is positioned in the inner cavity, the plasma torch is clamped at the raw material inlet, so that the nozzle of the torch can be positioned in the inner cavity. When the plasma torch is positioned outside the inner cavity, in order to avoid the reaction between the plasma flame sprayed by the torch and the shell, the isolation cover is clamped at the raw material inlet for isolating the flame sprayed by the torch and the shell. Wherein, the isolation cover can be a quartz anti-sparking cover made of quartz.
The position of the plasma torch on the side wall is not limited, as long as the direction of the plasma torch is toward the rod to be deposited. In order to realize that the spraying direction of the plasma torch faces the rod to be deposited, the first clamping unit and the second clamping unit move on two sides of the plasma torch in the depth direction of the inner cavity.
The plasma torch of the present invention is not limited and may be a conventional plasma torch in the art. In one embodiment, in a plasma torch, the feedstock inlets are disposed in a central layer of the torch, and the other inlets for oxygen, nitrogen, etc. are disposed around the periphery of the central layer.
The invention promotes the inner cavity to form a stable pressure field and a stable circulating air flow field by means of the driving pump, and particularly, the driving pump is arranged outside the shell and is used for pumping air into the inner cavity or pumping air from the inner cavity to the outside of the shell.
When the driving pump is positioned outside the shell and connected with the exhaust hole, the driving pump is used for exhausting air from the inner cavity to the outside of the shell so as to control the inner cavity to be in a negative pressure state, for example, the pressure of the inner cavity can be controlled to be-2 Pa to-5 Pa. Unreacted particles and unburned gas in the inner cavity are continuously pumped out through the exhaust hole.
When the driving pump is positioned outside the shell and connected with the air inlet hole, the driving pump is used for air inlet from outside to the inner cavity. Due to the arrangement of the air inlet holes and the flow of the air, the air in the external environment is continuously pumped into the inner cavity, and a stable circulating air flow field is formed in the inner cavity under the combined action of the air inlet holes and the air outlet holes.
The number of the driving pumps is determined according to the number of the exhaust holes and the air inlet holes, and when the number of the exhaust holes and the air inlet holes is multiple, each exhaust hole and each air inlet hole are respectively and independently connected with one driving pump.
In order to realize that the trend of the air flow discharged from the air discharge holes is consistent with the spraying direction, the air discharge holes are positioned on the opposite side of the side wall where the plasma torch is positioned. Further, the exhaust hole and the plasma torch may be located in the same radial direction of the sidewall, or may not be located in the same radial direction, and preferably in the same radial direction. When the exhaust hole and the plasma torch are not in the same radial direction, the vertical distance between the exhaust hole and the plasma torch in the depth direction is not more than 30cm.
The position of the air inlet hole is set according to the position of the air outlet hole, and the air outlet hole and the air inlet hole are positioned on the same radial direction of the side wall for better controlling air inlet and air outlet.
In the invention, the trend of the air flow entering the inner cavity through the air inlet hole can be adjusted by adjusting the angle of the air inlet hole, and the trend of the air flow entering the inner cavity through the air inlet hole can also be adjusted by arranging the air guide piece. In one embodiment, a gas guide is connected to the gas inlet aperture, the gas guide being adapted to control the direction of the gas flow into the gas inlet aperture.
The gas guide may be located entirely outside the lumen or may be located partially outside the lumen. When the gas guide piece is all positioned outside the inner cavity, the gas outlet of the gas guide piece faces the gas inlet hole; when the gas guide part is positioned in the inner cavity, the gas guide part is clamped on the air inlet hole.
The invention does not limit the communication mode of the plurality of guide plates, so long as the condition that the air flows through the air guide member and the direction of the air flow entering the inner cavity has an included angle theta with the spraying direction is satisfied.
The flow of gas entering through the air inlet hole directly affects the pressure and gas circulation of the inner cavity. When the air inlet valve is connected with the air inlet hole, the air inlet valve can rotate along the axis of the air inlet valve, and the opening and closing degree is adjusted through rotation, so that the air flow through the air inlet hole is controlled.
Further, the air guide piece is also provided with a first inlet far away from the inner cavity and a second inlet close to the inner cavity, the number of the first inlets is one or more, and the first inlet is provided with an adjustable air inlet valve for controlling the air flow passing through the air guide piece and further controlling the air flow passing through the air inlet hole. The number of second inlets is one or more, for example more than six. The first inlet and the second inlet are communicated through a plurality of guide plates.
The deposition device also comprises a temperature measuring unit and a pressure measuring unit, and is used for monitoring the temperature and the pressure of the inner cavity in real time.
The preparation method of the optical fiber preform provided by the invention is carried out by adopting the deposition device, and comprises the following steps: (1) preheating the inner cavity by using a heating unit; forming gas circulation in the inner cavity by utilizing the air inlet hole and the air outlet hole, and controlling the pressure of the inner cavity to be-2 Pa to-5 Pa; the first clamping unit and the second clamping unit are respectively matched with each other to fixedly clamp a rod to be deposited, and a nozzle of the plasma torch points to one end of the rod to be deposited;
(2) Starting the plasma torch, and performing first movement and first rotation on the rod to be deposited under the action of the first clamping unit and the second clamping unit and carrying out deposition treatment to obtain an optical fiber preform precursor; in the deposition treatment, the raw materials of the plasma torch are gaseous silicon-containing compounds, gaseous fluorides and oxygen;
(3) The optical fiber preform precursor moves and rotates for the second time under the action of the first clamping unit and the second clamping unit, and polishing is carried out, so that an optical fiber preform is obtained; in the polishing process, the source gas of the plasma torch is oxygen.
Before preparing the optical fiber preform, each component of the deposition apparatus is first installed in a corresponding position. In the step (1), each operation has no sequence, specifically, the rod to be deposited is clamped by using the first clamping unit and the second clamping unit to be matched with each other, so that the rod to be deposited is positioned in the inner cavity, and the nozzle of the plasma torch points to one end of the rod to be deposited.
The heating unit is electrified outside, and the heating unit is used for generating heat to preheat the inner cavity, and further, the heat preservation unit is used for preserving heat. Through the design of self-contained heat supply and heat preservation, the surface of the rod to be deposited has enough heat and is uniform in temperature, the temperature gradient of the surface of the rod to be deposited is avoided, and the uniform temperature of the rod to be deposited in the axial direction is realized.
The temperature and time of preheating have a certain influence on the temperature uniformity of the surface of the rod to be deposited, and in one embodiment, the temperature of preheating is 800-900 ℃ and the time is 20-40 min.
As the fluorine doping uniformity depends on the uniformity of the surface temperature of the rod to be deposited, the heating and heat preserving mode is adopted in the invention, which is favorable for improving the uniformity of the surface temperature of the rod to be deposited, thereby improving the fluorine doping uniformity of the outer cladding. As the fluorine doping amount is reduced along with the temperature increase of the plasma flame, the surface temperature of the rod to be deposited is increased in a heating and heat preserving mode, so that the rod to be deposited is heated without additionally increasing the power of a plasma torch, the temperature of the plasma flame is reduced, and the fluorine doping amount in the outer cladding is improved.
Pumping gas towards the air inlet hole by using an external driving pump, pumping air through the air outlet hole by using the external driving pump, forming stable gas circulation in the inner cavity, and controlling the pressure of the inner cavity to be stable at-2 Pa to-5 Pa.
In the step (2), a plasma torch is started, gaseous silicon-containing compounds and gaseous fluorides are introduced through a raw material inlet of the plasma torch, and oxygen is introduced through other material inlets. The method comprises the steps of reacting and burning gaseous silicon-containing compound, gaseous fluoride and oxygen at the nozzle of a blast lamp under the action of plasma flame to generate silicon dioxide particles and fluorine, wherein the first movement and the first rotation of a rod to be deposited are carried out under the action of a first clamping unit and a second clamping unit, and the deposition treatment is carried out, in the process, the silicon dioxide particles and the fluorine are deposited on the columnar peripheral surface of the rod to be deposited in a layered manner, and an outer cladding layer to be polished is formed on the surface of the rod to be deposited, so that the optical fiber preform precursor is obtained.
Wherein, the first movement means that the rod to be deposited moves towards one direction, the displacement distance of the first movement is the longitudinal length of the rod to be deposited, and the first rotation means that the rod to be deposited rotates along the axis of the rod to be deposited.
The displacement speed of the first movement and the rotational speed of the first rotation directly affect the deposition rate, in one embodiment the rotational speed of the first rotation is 30rpm to 40rpm/min and the speed of the first movement is 40mm/min to 60mm/min.
In the step (2), a protective gas for protecting the raw materials, such as argon, can be introduced through a raw material inlet of the plasma torch, and nitrogen can be introduced through other material inlets to avoid the influence of the too high oxygen content on the safety of the reaction. Further, chlorine (Cl) can be introduced into the raw material inlet 2 ) To eliminate the hydroxyl generated in the reaction, thereby reducing the hydroxyl content in the optical fiber preform and improving the optical performance of the optical fiber preform.
The power of the plasma torch during the deposition process directly affects the rate of generation of silica particles and fluorine, which in turn affects the deposition rate, and in one embodiment, the power of the plasma torch is 50kW to 80kW during the deposition process.
Wherein the gaseous fluoride comprises SiF 4 、CF 4 、SF 6 、C 2 F 6 、SOF 2 At least one of (a) and (b).
In the step (3), a raw material inlet of the plasma torch is closed, and the optical fiber preform precursor moves and rotates for the second time under the action of the first clamping unit and the second clamping unit and is subjected to polishing treatment, so that an optical fiber preform is obtained;
wherein the second movement means that the rod to be deposited moves in the opposite direction to the first movement, the displacement distance of the second movement means that the rod to be deposited is the longitudinal length of the rod to be deposited, and the second rotation means that the rod to be deposited rotates along the axis of the rod to be deposited.
The displacement speed of the second movement and the rotational speed of the second rotation directly affect the polishing rate, and in one embodiment, the rotational speed of the second rotation is 30rpm to 40rpm/min and the speed of the second movement is 250mm/min to 350mm/min.
In step (3), the overclad to be polished is vitrified by means of a plasma flame to form a fluorine-doped overclad, whereby the composite of the rod to be deposited and the overclad is formed into an optical fiber preform.
The surface temperature of the rod to be deposited is raised in an active heating and heat preserving mode, so that the optical fiber preform precursor is polished without additionally increasing the power of a plasma torch, and the power of the plasma torch is 20 kW-30 kW in the polishing treatment.
According to the invention, the fluorine-doped outer cladding is formed on the surface of the rod to be deposited in a deposition-before-polishing mode, so that the thermal stress of the fluorine-doped outer cladding can be effectively removed, and the cracking problem caused by the difference of the thermal expansion coefficients of all layers after the process is finished is avoided.
In the invention, the deposition and polishing treatment of the second round are carried out by repeating the steps (2) and (3), the deposition amount can be controlled, and the weight of the optical fiber preform can be monitored by the metering piece, so that the weight of the optical fiber preform which is actually required can be obtained.
The present invention will be further illustrated by the following specific examples and comparative examples.
In the following examples and comparative examples, the measurement methods are as follows:
monitoring the appearance of the optical fiber preform in real time by using a CCD appearance automatic detector;
taking a point every 100mm along the longitudinal direction of the optical fiber preform by using a PK2600 instrument; testing the refractive index n of the core layer in the vertical circumferential direction corresponding to each point core Refractive index n of outer cladding clad According to the relative refractive index difference deltan= (n) of the core package core -n clad )/n 0 X 100%, numerical apertureCalculating the relative refractive index of the core pack in the vertical circumferential direction corresponding to each pointThe difference delta n and the numerical aperture NA, and calculating the average value of delta n and NA and the difference between the maximum value and the minimum value;
the optical transmittance of the optical fiber preform is tested by adopting a Fourier infrared spectrometer FTIR, and the hydroxyl concentration of the optical fiber preform is calculated according to the lambert-beer law and the formula as follows: c (C) OH ＝[M OH /(ε×ρ)]×(1/d)×log 10 (I 0 I), wherein C OH Is the hydroxyl mass concentration, ppm (10 -6 )；M OH Is hydroxyl molar mass, g/mol; epsilon is the absorptivity of quartz glass at 2.73 mu m, L/mol cm; ρ is the density of quartz, g/cm 3 The method comprises the steps of carrying out a first treatment on the surface of the d is the thickness of the sample to be measured, mm; log of 10 (I 0 and/I) is the absorbance of the sample to be tested.
In the following examples, the rods to be deposited were either pure silica rods (pure silicon rods) or germanium-doped rods (the relative refractive index difference of the germanium-doped rods with respect to the pure silicon rods was 0.1% to 0.3%), wherein the refractive index of the pure silicon rods was 1.4571.
In the following examples, the deposition apparatus used, as shown in fig. 1 to 5, includes: a housing 12, a first clamping unit 21, a second clamping unit 22, a plasma torch 14, a heating unit 11, a heat preservation unit 10, and an isolation unit 9;
wherein the housing 12 includes an interior cavity 17 defined by side walls, a top wall and a bottom wall; the first clamping unit 21 is connected with the top wall, and the second clamping unit 22 is connected with the bottom wall; the first clamping unit 21 and the second clamping unit 22 rotate along their own axes and move in the depth direction a of the inner cavity; the first clamping unit 21 and the second clamping unit 22 are used for mutually matching and clamping the rod 1 to be deposited in the inner cavity 17;
the first adjusting unit and the second adjusting unit are respectively used for adjusting the rotation and the movement of the first clamping unit 21 and the second clamping unit 22, the first adjusting unit 31 and the second adjusting unit 32 respectively and independently comprise a chuck 3 and a sealing flange 5, the chuck 3 is connected with one end of the clamping unit far away from the inner cavity, and the clamping unit can be rotated along the axis of the chuck 3 and can be moved along the depth direction a of the shell by utilizing a movable piece on the chuck 3; the sealing flange 5 is positioned at the clamping joint of the clamping unit and the top wall and the bottom wall and is used for sealing the gap between the clamping unit and the top wall and the bottom wall; the chuck 3 is connected with a metering piece 4, and the mass of the rod to be deposited in the deposition process can be weighed through the metering piece 4;
The plasma torch 14 is outside the inner cavity 17, and an induction coil 15 is wound around the outer periphery of the plasma torch 14; a raw material inlet is formed in the side wall of the shell 12, a nozzle of the plasma torch 14 faces the raw material inlet, and a spraying direction of the plasma torch 14 faces the rod 1 to be deposited; the isolation cover 13 is clamped at the raw material inlet and is used for isolating the spraying flame from the shell 12;
the central layer of the plasma torch 14 is a raw material inlet, and other material inlets are arranged around the periphery of the central layer, and sequentially comprise a second layer, a third layer and a fourth layer along the direction away from the central layer;
the heating unit 11 is positioned in the inner cavity 17, the isolation unit 9 is arranged around the inside of the heating unit 11, and the heat preservation unit 10 is arranged between the isolation unit 9 and the heating unit 11 in a surrounding manner;
the side wall of the shell is respectively provided with an exhaust hole 7 and an air inlet hole 8, and the trend b of the air flow discharged through the exhaust hole 7 is consistent with the spraying direction; the driving pump is positioned outside the shell and connected with the exhaust hole 7;
the air guide piece 81 is connected with the air inlet hole 8 and is used for controlling the trend of air flow flowing through the air inlet hole; an included angle theta is formed between the trend c of the air flow entering the inner cavity through the air inlet and the spraying direction, and the theta is more than or equal to 20 degrees and less than or equal to 60 degrees;
the air guide 81 comprises a plurality of guide plates 804, a first inlet 801 far from the inner cavity and a second inlet 802 close to the inner cavity are arranged, and an air inlet valve 803 with adjustable opening and closing degree is arranged at the first inlet 801 and is used for controlling the air flow entering the air inlet hole;
A pressure gauge 6 for monitoring the pressure of the inner chamber 17 in real time;
the base rail 16 supports the first clamping unit 21 and the second clamping unit 22.
Example 1
The rod to be deposited is a germanium-doped core rod (the relative refractive index is 0.2%), the outer diameter of the core rod is 40mm, and the length of the core rod is 800mm;
(1) Starting a heating unit and a heat preservation unit, preheating the inner cavity by using the heating unit, and preserving heat of the inner cavity by using the heat preservation unit; wherein the preheating temperature is 800 ℃, and the constant temperature is kept for 20min; the pressure of the inner cavity is controlled to be minus 2Pa by the driving pump connected with the exhaust hole, and the air circulation is formed in the inner cavity by utilizing the air inlet hole and the exhaust hole; the first clamping unit and the second clamping unit are respectively used for fixedly clamping the rod to be deposited, and the nozzle of the plasma torch points to one end of the rod to be deposited;
(2) Starting a plasma torch, and carrying out first movement and first rotation on a rod to be deposited under the action of a first clamping unit and a second clamping unit and carrying out deposition treatment to obtain an optical fiber preform precursor; during the deposition process, the central layer of the plasma torch is fed with SiCl 4 The flow rate is 25g/min, CF 4 100mL/min, ar flow of 10L/min, and introducing O into the second layer 2 The flow is 30L/min, and the third layer is introduced with O 2 The flow is 40L/min, and the fourth layer is filled with N 2 The flow is 10L/min;
wherein, in the deposition treatment, the power of the plasma torch is 50kW, the first moving speed is 60mm/min, and the first rotating speed is 40rpm/min;
(3) Closing the central layer of the plasma torch, and performing second movement and second rotation on the optical fiber preform precursor under the action of the first clamping unit and the second clamping unit and performing polishing treatment to obtain an optical fiber preform;
wherein, in the polishing treatment, the power of the plasma torch is 20kW, the speed of the second movement is 350mm/min, and the speed of the second rotation is 40rpm/min;
(4) Repeating the steps (2) and (3) until the weight of the optical fiber preform reaches 5kg and the outer diameter is 60.5mm;
adopting the process steps of the embodiment 1, repeating 3 groups, wherein the prepared 3 optical fiber preforms have no cracking phenomenon; after the optical fiber preform was cooled to room temperature, a spot was taken every 100mm in the longitudinal direction of the optical fiber preform using a PK2600 meter, 7 spots were taken in total, refractive indices in the vertical circumferential direction corresponding to the 7 spots were tested, and the average value of Δn and NA and the difference between the maximum value and the minimum value of Δn and NA in the vertical circumferential direction corresponding to the 7 spots were calculated, respectively, as shown in table 1.
Example 2
The difference from example 1 is that:
The rod to be deposited is a pure silicon core rod, the outer diameter of the core rod is 50mm, and the length of the core rod is 1000mm;
preheating at 850 deg.C for 30min; controlling the pressure of the inner cavity to be-3 Pa;
in the deposition process, siCl is introduced into the central layer of the plasma torch 4 The flow rate is 35g/min and SF 6 150mL/min, ar flow of 12.5L/min, cl 2 The flow rate is 300mL/min, and the second layer is introduced with O 2 The flow is 35L/min, and the third layer is introduced with O 2 The flow is 45L/min, the fourth layer N 2 The flow is 15L/min; wherein, in the deposition treatment, the power of the plasma torch is 65kW, the first moving speed is 50mm/min, and the first rotating speed is 35rpm/min;
in the polishing process, the power of the plasma torch was 25kW, the speed of the second movement was 300mm/min, and the speed of the second rotation was 35rpm/min;
repeating the steps (2) and (3) until the weight of the optical fiber preform reaches 6.6kg and the outer diameter is 62.4mm; other conditions were unchanged.
Adopting the process steps of the embodiment 2, repeating 3 groups, wherein the prepared 3 optical fiber preforms have no cracking phenomenon; after the prepared optical fiber preform is cooled to room temperature, taking a point every 100mm along the longitudinal direction of the optical fiber preform by using a PK2600 instrument, taking 9 points altogether, testing the refractive index, and respectively calculating the average value of delta n and NA and the difference between the maximum value and the minimum value of delta n and NA in the circumferential direction corresponding to the 9 points, wherein the average value and the difference are shown in Table 1;
A graph of NA values at 9 points of each of the 3 optical fiber preforms is shown in FIG. 6.
Example 3
The difference from example 1 is that:
the rod to be deposited is a pure silicon core rod, the outer diameter of the core rod is 45mm, and the length of the core rod is 1000mm;
preheating at 900 deg.C for 40min; controlling the pressure of the inner cavity to be-5 Pa;
in the deposition process, siCl is introduced into the central layer of the plasma torch 4 The flow rate is 45g/min and SF 6 200mL/min, ar flow of 15L/min, cl 2 The flow rate is 400mL/min, and the second layer is introduced with O 2 The flow is 40L/min, and the third layer is introduced with O 2 The flow rate is 50L/min, and the outermost layer N 2 The flow is 20L/min; wherein, in the deposition treatment, the power of the plasma torch is 80kW, the speed of the first movement is 40mm/min, and the speed of the first rotation is 30rpm/min;
in the polishing process, the power of the plasma torch was 30kW, the speed of the second movement was 250mm/min, and the speed of the second rotation was 30rpm/min;
repeating the steps (2) and (3) until the weight of the optical fiber preform reaches 7.3kg and the outer diameter is 65.3mm; other conditions were unchanged.
Adopting the process steps of the embodiment 3, repeating 3 groups, wherein the prepared optical fiber preform has no cracking phenomenon; after the optical fiber preform is cooled to room temperature, taking a point every 100mm along the longitudinal direction of the optical fiber preform by using a PK2600 instrument, taking 9 points altogether, testing the refractive index, and respectively calculating the average value of delta n and NA and the difference between the maximum value and the minimum value of delta n and NA in the circumferential direction corresponding to the 9 points, wherein the difference is shown in a table 1;
The graph of the relative refractive index difference of the radial distribution of the 9 th point of the optical fiber preform manufactured in group 3 is shown in fig. 7.
Example 4
The rod to be deposited is a germanium-doped core rod (the relative refractive index is 0.3%), the outer diameter of the core rod is 40mm, and the length of the core rod is 800mm;
(1) Starting a heating unit, and preheating the inner cavity by using the heating unit; wherein the preheating temperature is 800 ℃, and the constant temperature is kept for 20min; the pressure of the inner cavity is controlled to be minus 2Pa by the driving pump connected with the exhaust hole, and the air circulation is formed in the inner cavity by utilizing the air inlet hole and the exhaust hole; the first clamping unit and the second clamping unit are respectively used for fixedly clamping the rod to be deposited, and the nozzle of the plasma torch points to one end of the rod to be deposited;
(2) Starting a plasma torch, and enabling the rod to be deposited to perform first movement and under the action of the first clamping unit and the second clamping unitA first rotation is carried out and a deposition treatment is carried out, so that an optical fiber preform precursor is obtained; during the deposition process, the central layer of the plasma torch is fed with SiCl 4 The flow rate is 25g/min, CF 4 100mL/min, ar flow of 10L/min, and introducing O into the second layer 2 The flow is 30L/min, and the third layer is introduced with O 2 The flow is 40L/min, and the fourth layer is filled with N 2 The flow is 10L/min;
wherein, in the deposition treatment, the power of the plasma torch is 50kW, the first moving speed is 60mm/min, and the first rotating speed is 40rpm/min;
(3) Closing the central layer of the plasma torch, and performing second movement and second rotation on the optical fiber preform precursor under the action of the first clamping unit and the second clamping unit and performing polishing treatment to obtain an optical fiber preform;
wherein, in the polishing treatment, the power of the plasma torch is 20kW, the speed of the second movement is 350mm/min, and the speed of the second rotation is 40rpm/min;
(4) Repeating the steps (2) and (3) until the weight of the optical fiber preform reaches 5kg and the outer diameter is 60.5mm;
adopting the process steps of the embodiment 4, repeating 3 groups, wherein the prepared 3 optical fiber preforms have no cracking phenomenon; after the optical fiber preform was cooled to room temperature, a spot was taken every 100mm in the longitudinal direction of the optical fiber preform using a PK2600 meter, 7 spots were taken in total, refractive indices in the vertical circumferential direction corresponding to the 7 spots were tested, and the average value of Δn and NA and the difference between the maximum value and the minimum value of Δn and NA in the vertical circumferential direction corresponding to the 7 spots were calculated, respectively, as shown in table 1.
Comparative example 1
The rod to be deposited is a pure silicon core rod, the outer diameter of the core rod is 40mm, and the length of the core rod is 1000mm;
(1) The first clamping unit and the second clamping unit are used for fixedly clamping a rod to be deposited, and a nozzle of the plasma torch points to one end of the rod to be deposited;
(2) Starting a plasma torch, and performing first movement and first rotation of the rod to be deposited under the action of the first clamping unit and the second clamping unit and accompanying deposition treatment to obtain the optical fiber preformA body; in the deposition process, siCl is introduced into the central layer of the plasma torch 4 The flow rate is 45g/min, CF 4 200mL/min, argon flow of 15L/min, and O into the second layer 2 The flow is 40L/min, and the third layer is introduced with O 2 The flow rate is 50L/min, and the outermost layer N 2 The flow is 20L/min;
wherein, in the deposition treatment, the power of the plasma torch is 80kW, the speed of the first movement is 40mm/min, and the speed of the first rotation is 30rpm/min;
(3) Closing the central layer of the plasma torch, and performing second movement and second rotation on the optical fiber preform precursor under the action of the first clamping unit and the second clamping unit and performing polishing treatment to obtain an optical fiber preform;
wherein, in the polishing treatment, the power of the plasma torch is 80kW, the speed of the second movement is 40mm/min, and the speed of the second rotation is 30rpm/min;
(4) Repeating the steps (2) and (3),
after the optical fiber preform is cooled to room temperature, taking one point every 100mm along the longitudinal direction of the optical fiber preform by using a PK2600 instrument, taking 7 points in total, testing the refractive index, and calculating the relative refractive index difference delta n and the numerical aperture NA of the core package, as shown in Table 1;
3 sets of 3 preforms were obtained by repeating the process steps of comparative example 1, wherein the ends of 1 preform had cracks and the other 2 preforms had white mist bubbles within a distance of 250mm from the return end. Therefore, no normal product was obtained and no data was detected.
Comparative example 2
The rod to be deposited is a pure silicon core rod, the outer diameter of the core rod is 50mm, and the length of the core rod is 1000mm;
(1) The first clamping unit and the second clamping unit are used for fixedly clamping a rod to be deposited, and a nozzle of the plasma torch points to one end of the rod to be deposited;
(2) Starting a plasma torch, and carrying out first movement and first rotation on a rod to be deposited under the action of a first clamping unit and a second clamping unit and carrying out deposition treatment to obtain an optical fiber preform precursor; in the deposition process, the plasma torchSiCl introduced into heart layer 4 The flow rate is 35g/min and SF 6 150mL/min, argon flow of 12.5L/min, and O is introduced into the second layer 2 The flow is 35L/min, and the third layer is introduced with O 2 The flow rate is 45L/min, and the outermost layer N 2 The flow is 15L/min;
wherein, in the deposition treatment, the power of the plasma torch is 65kW, the first moving speed is 50mm/min, and the first rotating speed is 35rpm/min;
(3) Closing the central layer of the plasma torch, and performing second movement and second rotation on the optical fiber preform precursor under the action of the first clamping unit and the second clamping unit and performing polishing treatment to obtain an optical fiber preform;
Wherein, in the polishing treatment, the power of the plasma torch is 25kW, the speed of the second movement is 300mm/min, and the speed of the second rotation is 35rpm/min;
(4) Repeating the steps (2) and (3) until the weight of the optical fiber preform reaches 6.6kg and the outer diameter is 62.3mm;
3 groups of the process steps of comparative example 2 are repeatedly carried out to obtain 3 prefabricated rods, wherein 1 prefabricated rod is cracked integrally, after the other 2 prefabricated rods are cooled to room temperature, a PK2600 instrument is adopted to obtain 9 points every 100mm along the longitudinal direction of the prefabricated rods, the refractive indexes are tested, and the average value of delta n and NA and the difference between the maximum value and the minimum value of delta n and NA in the circumferential direction corresponding to the 9 points are respectively calculated, as shown in table 1;
the NA graphs in the longitudinal direction on the other 2 optical fiber preforms are shown in FIG. 8.
Comparative example 3
The rod to be deposited is a pure silicon core rod, the outer diameter of the core rod is 45mm, and the length of the core rod is 1000mm;
(1) Starting a heating unit and a heat preservation unit, wherein the preheating temperature is 900 ℃, and the constant temperature is kept for 40min; controlling the pressure of the inner cavity to be-5 Pa;
(2) In the deposition process, siCl is introduced into the central layer of the plasma torch 4 The flow rate is 45g/min and SF 6 200mL/min, ar flow of 15L/min, cl 2 The flow rate is 400mL/min, and the second layer is introduced with O 2 The flow rate is40L/min, the third layer is introduced with O 2 The flow rate is 50L/min, and the outermost layer N 2 The flow is 20L/min; wherein, in the deposition treatment, the power of the plasma torch is 80kW, the speed of the first movement is 15mm/min, and the speed of the first rotation is 20rpm/min;
(3) In the polishing process, the power of the plasma torch was 30kW, the speed of the second movement was 100mm/min, and the speed of the second rotation was 30rpm/min;
repeating the steps (2) and (3) until the weight of the optical fiber preform reaches 7.3kg and the outer diameter is 65.3mm; other conditions are unchanged; the prepared optical fiber preform has a bending phenomenon.
Comparative example 4
The rod to be deposited is a pure silicon core rod, the outer diameter of the core rod is 45mm, and the length of the core rod is 1000mm;
(1) Starting a heating unit and a heat preservation unit, wherein the preheating temperature is 900 ℃, and the constant temperature is kept for 40min; controlling the pressure of the inner cavity to be-5 Pa;
(2) In the deposition process, siCl is introduced into the central layer of the plasma torch 4 The flow rate is 45g/min and SF 6 200mL/min, ar flow of 15L/min, cl 2 The flow rate is 400mL/min, and the second layer is introduced with O 2 The flow is 40L/min, and the third layer is introduced with O 2 The flow rate is 50L/min, and the outermost layer N 2 The flow is 20L/min; wherein, in the deposition treatment, the power of the plasma torch is 80kW, the first moving speed is 80mm/min, and the first rotating speed is 10rpm/min;
(3) In the polishing treatment, the power of the plasma torch was 30kW, the speed of the second movement was 300mm/min, and the speed of the second rotation was 15rpm/min;
repeating the steps (2) and (3) until the weight of the optical fiber preform reaches 7.3kg and the outer diameter is 65.3mm; other conditions are unchanged; the longitudinal diameter of the prepared optical fiber preform rod is corrugated, does not meet the appearance requirement, and the refractive index and the numerical aperture are not tested.
Comparative example 5
The rod to be deposited is a pure silicon core rod, the outer diameter of the core rod is 45mm, and the length of the core rod is 1000mm;
(1) Starting a heating unit and a heat preservation unit, wherein the preheating temperature is 900 ℃, and the constant temperature is kept for 40min; controlling the pressure of the inner cavity to be-5 Pa; the included angle theta between the trend of the air flow entering the inner cavity from the air inlet hole and the spraying direction is set to be 0 degrees.
(2) In the deposition process, siCl is introduced into the central layer of the plasma torch 4 The flow rate is 45g/min and SF 6 200mL/min, ar flow of 15L/min, cl 2 The flow rate is 400mL/min, and the second layer is introduced with O 2 The flow is 40L/min, and the third layer is introduced with O 2 The flow rate is 50L/min, and the outermost layer N 2 The flow is 20L/min; wherein, in the deposition treatment, the power of the plasma torch is 80kW, the speed of the first movement is 40mm/min, and the speed of the first rotation is 30rpm/min;
(3) In the polishing process, the power of the plasma torch was 30kW, the speed of the second movement was 300mm/min, and the speed of the second rotation was 30rpm/min;
repeating the steps (2) and (3) until the weight of the optical fiber preform reaches 7.3kg and the outer diameter is 65.3mm; other conditions are unchanged; with the increase of the times, powder particles generated by flame remain in part of the area, so that the appearance pits of the prepared optical fiber preform do not meet the appearance requirements, and the refractive index and the numerical aperture are not tested.
Comparative example 6
The rod to be deposited is a pure silicon core rod, the outer diameter of the core rod is 45mm, and the length of the core rod is 1000mm;
(1) Starting a heating unit and a heat preservation unit, wherein the preheating temperature is 900 ℃, and the constant temperature is kept for 40min; controlling the pressure of the inner cavity to be-5 Pa; the included angle theta between the trend of the air flow entering the inner cavity from the air inlet hole and the spraying direction is set to be 90 degrees.
(2) In the deposition process, siCl is introduced into the central layer of the plasma torch 4 The flow rate is 45g/min and SF 6 200mL/min, ar flow of 15L/min, cl 2 The flow rate is 400mL/min, and the second layer is introduced with O 2 The flow is 40L/min, and the third layer is introduced with O 2 The flow rate is 50L/min, and the outermost layer N 2 The flow is 20L/min; wherein, in the deposition treatment, the power of the plasma torch is 80kW, the speed of the first movement is 40mm/min, and the speed of the first rotation is 30rpm/min;
(3) In the polishing process, the power of the plasma torch was 30kW, the speed of the second movement was 300mm/min, and the speed of the second rotation was 30rpm/min;
repeating the steps (2) and (3) until the weight of the optical fiber preform reaches 7.3kg and the outer diameter is 65.3mm; other conditions are unchanged; the air flow is unstable due to the collision of the air supply on two sides, and the flame shake causes extinction and cannot be prepared.
TABLE 1
In the table, "" indicates normal appearance, "×" indicates occurrence of cracking, partial cracking, or blank of the preform without vitrification, and "/" indicates no detection data.
As can be seen from Table 1, the deposition apparatus provided by the invention can be used for preparing an optical fiber preform with normal appearance, the circumferential dimension of the optical fiber preform can reach 60-80 mm, the fluorine doping of the outer cladding of the prepared optical fiber preform is uniform, the difference between the maximum value and the minimum value of delta n in the longitudinal direction is not more than 0.085%, the difference between the maximum value and the minimum value of NA is not more than 0.01, the difference between the maximum value and the minimum value of delta n in the circumferential direction is not more than 0.005%, the difference between the maximum value and the minimum value of NA is not more than 0.0005, and the optical fiber preform has good delta n consistency and NA consistency. And the delta n average value of the optical fiber preform in the longitudinal direction can reach more than 0.7 percent, the NA average value of the numerical aperture can reach more than 0.17, and the optical fiber preform has good light receiving capability.
Preferred embodiments of the present invention and experimental verification are described in detail above. It should be understood that numerous modifications and variations can be made in accordance with the concepts of the invention without requiring creative effort by one of ordinary skill in the art. Therefore, all technical solutions which can be obtained by logic analysis, reasoning or limited experiments based on the prior art by the person skilled in the art according to the inventive concept shall be within the scope of protection defined by the claims.

Claims (9)

1. A method for preparing an optical fiber preform is characterized in that the preparation is carried out by adopting a deposition device,
the deposition device comprises a shell, a first clamping unit, a second clamping unit, a plasma torch and a heating unit;
the shell comprises an inner cavity surrounded by a side wall, a top wall and a bottom wall; the first clamping unit is connected with the top wall, and the second clamping unit is connected with the bottom wall; the first clamping unit and the second clamping unit rotate along the axis of the first clamping unit and the second clamping unit and move in the depth direction of the inner cavity; the first clamping unit and the second clamping unit are used for mutually matching and clamping a rod to be deposited in the inner cavity;
the spraying direction of the plasma torch faces the inner cavity;
The heating unit is positioned in the inner cavity;
the side wall of the shell is respectively provided with an exhaust hole and an air inlet, the trend of the air flow discharged through the exhaust hole is consistent with the spraying direction, and the air flow entering the inner cavity through the air inlet has an included angle theta with the spraying direction, wherein theta is more than or equal to 20 degrees and less than or equal to 60 degrees;
the preparation method of the optical fiber preform comprises the following steps:
preheating the inner cavity by using a heating unit;
forming gas circulation in the inner cavity by using the air inlet and the air outlet, and controlling the pressure of the inner cavity to be-2 Pa to-5 Pa;
the first clamping unit and the second clamping unit are respectively matched with each other to fixedly clamp a rod to be deposited, and a nozzle of the plasma torch points to one end of the rod to be deposited;
starting the plasma torch, and performing first movement and first rotation on the rod to be deposited under the action of the first clamping unit and the second clamping unit and carrying out deposition treatment to obtain an optical fiber preform precursor; in the deposition treatment, the raw materials of the plasma torch are gaseous silicon-containing compounds, gaseous fluorides and oxygen;
the optical fiber preform precursor moves and rotates for the second time under the action of the first clamping unit and the second clamping unit, and polishing is carried out, so that an optical fiber preform is obtained; in the polishing treatment, the raw material gas of the plasma torch is oxygen;
The rotation speed of the first rotation is 30 rpm-40 rpm/min; the rotation speed of the second rotation is 30 rpm-40 rpm/min; the speed of the first movement is 40-60 mm/min; the speed of the second movement is 250 mm/min-350 mm/min.
2. The method of manufacturing an optical fiber preform according to claim 1, wherein the heating unit is annularly provided inside the sidewall.
3. The method for manufacturing an optical fiber preform according to claim 1, further comprising a heat preservation unit and an isolation unit, wherein the isolation unit is disposed around the inside of the heating unit, and the heat preservation unit is disposed around between the isolation unit and the heating unit.
4. The method of manufacturing an optical fiber preform according to claim 1, wherein a raw material inlet is provided on the sidewall, and a nozzle of the plasma torch is directed toward the raw material inlet.
5. The method of manufacturing an optical fiber preform according to claim 4, further comprising a shielding case, which is provided to the raw material inlet by being caught, for shielding the jet flame from the housing.
6. The method of fabricating an optical fiber preform according to claim 1, further comprising a driving pump located outside the housing and connected to the exhaust hole.
7. The method of manufacturing an optical fiber preform according to claim 1, further comprising a gas guide connected to the gas inlet hole for controlling a direction of a gas flow entering the gas inlet hole.
8. The method of manufacturing an optical fiber preform according to claim 1, further comprising an intake valve connected to the intake hole for controlling the amount of air flow into the intake hole.
9. The method for manufacturing an optical fiber preform according to any one of claims 1 to 8, wherein the preheating temperature is 800 ℃ to 900 ℃ and the time is 20min to 40min; and/or the number of the groups of groups,
in the deposition treatment, the power of the plasma torch is 50 kW-80 kW; and/or the number of the groups of groups,
in the polishing process, the power of the plasma torch is 20 kW-30 kW.
CN202211095609.2A 2022-09-06 2022-09-06 Deposition device and preparation method of optical fiber preform Active CN115557693B (en)

Priority Applications (1)

Application Number Priority Date Filing Date Title
CN202211095609.2A CN115557693B (en) 2022-09-06 2022-09-06 Deposition device and preparation method of optical fiber preform

Applications Claiming Priority (1)

Application Number Priority Date Filing Date Title
CN202211095609.2A CN115557693B (en) 2022-09-06 2022-09-06 Deposition device and preparation method of optical fiber preform

Publications (2)

Publication Number Publication Date
CN115557693A CN115557693A (en) 2023-01-03
CN115557693B true CN115557693B (en) 2023-12-22

Family

ID=84738719

Family Applications (1)

Application Number Title Priority Date Filing Date
CN202211095609.2A Active CN115557693B (en) 2022-09-06 2022-09-06 Deposition device and preparation method of optical fiber preform

Country Status (1)

Country Link
CN (1) CN115557693B (en)

Citations (5)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
JPH11268926A (en) * 1998-03-23 1999-10-05 Fujikura Ltd Production of optical fiber preform
JP2010285330A (en) * 2009-06-15 2010-12-24 Sumitomo Electric Ind Ltd Method for producing glass porous body and apparatus for producing glass porous body
CN105541102A (en) * 2015-12-03 2016-05-04 富通集团有限公司 Thermal stress relief process of prefabricated rod and thermal stress relief equipment thereof
CN106495461A (en) * 2016-11-02 2017-03-15 中国电子科技集团公司第四十六研究所 A kind of rare-earth-doped fiber precast rod gas phase doping heating and heat-insulating device and doping method
CN208454818U (en) * 2018-05-08 2019-02-01 成都富通光通信技术有限公司 A kind of prefabricated rods cvd reactive chamber

Patent Citations (5)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
JPH11268926A (en) * 1998-03-23 1999-10-05 Fujikura Ltd Production of optical fiber preform
JP2010285330A (en) * 2009-06-15 2010-12-24 Sumitomo Electric Ind Ltd Method for producing glass porous body and apparatus for producing glass porous body
CN105541102A (en) * 2015-12-03 2016-05-04 富通集团有限公司 Thermal stress relief process of prefabricated rod and thermal stress relief equipment thereof
CN106495461A (en) * 2016-11-02 2017-03-15 中国电子科技集团公司第四十六研究所 A kind of rare-earth-doped fiber precast rod gas phase doping heating and heat-insulating device and doping method
CN208454818U (en) * 2018-05-08 2019-02-01 成都富通光通信技术有限公司 A kind of prefabricated rods cvd reactive chamber

Also Published As

Publication number Publication date
CN115557693A (en) 2023-01-03

Similar Documents

Publication Publication Date Title
WO2001016039A1 (en) Method of making a tubular member for optical fiber production using plasma outside vapor deposition
CN108046582B (en) Device and method for continuously preparing optical fiber preform rod and drawing wires
US9656902B2 (en) Method of manufacturing preforms for optical fibres having low water peak
CN113024102B (en) Device and method for preparing optical fiber preform by plasma chemical vapor deposition method
US8820121B2 (en) Method of manufacturing optical fiber base material
CN102092934B (en) Method for fabricating core rod sections useable for production of finished optical fiber
AU750390B2 (en) Method of making an optical fiber preform
GB2059944A (en) Fabrication method of optical fiber preforms
CN106746589A (en) A kind of method that PCVD depositions prepare large-diameter fibre-optical mandrel
CN103663958A (en) Method for preparing low water peak optical fiber preform
CN115159833A (en) Device and method for manufacturing large-size high-deposition-rate optical fiber preform
CN114436521A (en) Device and method for preparing optical fiber preform rod by plasma chemical vapor deposition outside tube
EP2551248A2 (en) Methods for manufacturing low water peak optical waveguide
CN101987778B (en) A method for manufacturing a primary preform for optical fibres
CN115557693B (en) Deposition device and preparation method of optical fiber preform
CN101987779B (en) Method and device for manfacturing a primary preform for optical fibres
GB2062615A (en) Preparing glass preform for optical transmission
CN112062460B (en) Low-loss G.652.D optical fiber and manufacturing method thereof
US7437893B2 (en) Method for producing optical glass
CN210340703U (en) Plasma deposition apparatus
CN112441736A (en) Optical fiber preform, preparation method thereof and plasma deposition equipment
KR100508707B1 (en) a manufacturing method and a manufacturing device by Outside Vapor Deposition
CN114349327A (en) Low-cost processing technology of bending insensitive single-mode optical fiber
CN109133608B (en) Doping equipment for optical fiber preform
US8904827B2 (en) Method of manufacturing an optical fibre, preform and optical fibre

Legal Events

Date Code Title Description
PB01 Publication
PB01 Publication
SE01 Entry into force of request for substantive examination
SE01 Entry into force of request for substantive examination
GR01 Patent grant
GR01 Patent grant