CN115557693A - Deposition apparatus and method for manufacturing optical fiber preform - Google Patents

Deposition apparatus and method for manufacturing optical fiber preform Download PDF

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Publication number
CN115557693A
CN115557693A CN202211095609.2A CN202211095609A CN115557693A CN 115557693 A CN115557693 A CN 115557693A CN 202211095609 A CN202211095609 A CN 202211095609A CN 115557693 A CN115557693 A CN 115557693A
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clamping unit
inner cavity
optical fiber
unit
plasma torch
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CN115557693B (en
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吴椿烽
沈一春
陈京京
陈娅丽
周建峰
张烨锋
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Zhongtian Technology Advanced Materials Co ltd
Jiangsu Zhongtian Technology Co Ltd
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Zhongtian Technology Advanced Materials Co ltd
Jiangsu Zhongtian Technology Co Ltd
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    • 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

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  • 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 perform rod, 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 enclosed 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 axes 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 matched with each other to clamp the rod to be deposited in the inner cavity; the injection 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 air exhaust hole and an air inlet hole, the air flow discharged through the air exhaust hole flows to the direction consistent with the spraying direction, the air flow entering the inner cavity through the air inlet hole has an included angle theta with the spraying direction, the theta is more than or equal to 20 degrees and less than or equal to 60 degrees, and the optical fiber perform rod with the outer cladding layer doped with fluorine uniformly can be prepared by utilizing the device.

Description

Deposition apparatus and method for manufacturing 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 in fiber lasers as media for optical information transmission. Optical fiber preforms are the starting material for optical fiber manufacture. An optical fiber preform is generally composed of a core layer having a different refractive index, which is a core rod of silica glass, and a fluorine-doped outer cladding layer, which is fluorine-doped silica glass. The refractive index of the fluorine-doped outer cladding layer can be reduced by doping fluorine into the outer cladding layer, so that the refractive index of the core layer is larger than that of the outer cladding layer, and the total reflection condition of optical fiber transmission is met.
Core/clad relative refractive index difference Δ n (Δ n = (n) of optical fiber preform core -n clad )/n 0 X 100%), numerical aperture NA (where
Figure BDA0003835309080000011
) For measuring the ability of an optical fiber to receive light, where n core Is the refractive index of the core layer, n clad Is the 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 in Δ n and NA in the longitudinal direction and the circumferential direction (radial direction), respectively.
The uniformity of the refractive index of the outer cladding layer can be directly influenced by the uniformity of the fluorine doping of the fluorine-doped outer cladding layer in the optical fiber preform, and further the uniformity of delta n and the uniformity of NA of the optical fiber preform in the longitudinal direction and the radial direction are influenced. If the outer cladding of the optical fiber preform is not uniformly doped with fluorine in the longitudinal and circumferential directions (radial directions), the longitudinal and radial delta n and NA will directly fluctuate greatly, and therefore, how to improve the fluorine doping uniformity of the optical fiber preform is a technical problem to be solved in the field.
Disclosure of Invention
The invention provides a deposition device, which can be used for preparing an optical fiber perform with an outer cladding layer doped with fluorine uniformly, so that the consistency of delta n in the longitudinal direction and the radial direction of the optical fiber perform and the consistency of NA are 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 the uniform fluorine doping outer cladding layer, thereby obtaining the optical fiber with strong light receiving capability.
In one aspect of the present invention, a deposition apparatus is provided, including a housing, a first clamping unit, a second clamping unit, a plasma torch, and a heating unit; wherein the housing comprises an inner cavity enclosed by side walls, 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 axes 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 being matched with each other to clamp a rod to be deposited in the inner cavity; the injection 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 air flow discharged through the exhaust hole has the same flowing direction as the spraying direction, the air flow entering the inner cavity through the air inlet hole has an included angle theta with the spraying direction, and the theta 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 annularly arranged inside the side wall.
According to an 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 heating unit, and the heat preservation unit is arranged between the isolation unit and the heating unit in an enclosing manner.
According to an embodiment of the present invention, a material inlet is provided on the sidewall, and an outlet of the plasma torch faces the material inlet.
According to an embodiment of the invention, the device further comprises a shielding cover, wherein the shielding cover is clamped at the raw material inlet and used for shielding the jet flame from the shell.
According to an embodiment of the present invention, further comprising a driving pump located outside the housing and connected to the exhaust hole.
According to an embodiment of the present invention, the gas guiding device further comprises a gas guiding member, wherein the gas guiding member is connected to the gas inlet hole and is used for controlling the direction of the gas flow entering the gas inlet hole.
According to an embodiment of the present invention, the air conditioner further comprises an air inlet valve connected to the air inlet hole for controlling the flow of air into the air inlet hole.
In another aspect of the present invention, a method for preparing an optical fiber preform is provided, wherein the method is performed by using the deposition apparatus, and 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; a first clamping unit and a second clamping unit are respectively utilized to mutually match and 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 carrying out 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 plasma torch is prepared from gaseous silicon-containing compounds, gaseous fluorides and oxygen; under the action of the first clamping unit and the second clamping unit, the optical fiber preform precursor is subjected to second movement and second rotation and polishing treatment, so that an optical fiber preform is obtained; in the polishing treatment, the raw material gas of the plasma torch is oxygen.
According to one embodiment of the invention, the preheating temperature is 800-900 ℃, and the time is 20-40 min; and/or, in the deposition treatment, the power of the plasma torch is 50 kW-80 kW; and/or, in the polishing treatment, the power of the plasma blast lamp is 20 kW-30 kW; and/or the rotating 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 first moving speed 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. The invention adopts the first clamping unit and the second clamping unit which are mutually matched to clamp the rod to be deposited in the inner cavity, and can uniformly spray the raw materials sprayed by the plasma torch on the rod to be deposited along with the rotation of the first clamping unit and the second clamping unit along the self axis and the movement of the first clamping unit and the second clamping unit in the depth direction of the inner cavity, so as to form the fluorine-doped outer cladding layer on the surface of the rod to be deposited and further obtain the optical fiber preform. The invention maintains the pressure and the airflow stability of the inner cavity through the exhaust holes and the air inlets on the side wall, and simultaneously can ensure that the undeposited raw materials are exhausted out of the inner cavity through the exhaust holes; the inner cavity of the shell is heated by the heating unit, 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 layer is improved, the optical fiber preform rod with the uniform fluorine doping of the outer cladding layer can be prepared, and the uniformity of delta n and the uniformity of NA of the optical fiber preform rod in the longitudinal direction and the radial direction are improved.
According to the preparation method of the optical fiber preform rod, which is provided by the invention, the difference between the maximum value and the minimum value of the delta n in the longitudinal direction of the single optical fiber preform rod prepared by adopting the deposition device is not more than 0.04%, and the difference between the maximum value and the minimum value of the NA is not more than 0.005, so that the optical fiber preform rod has good delta n consistency and NA consistency. In addition, the average value of delta n of the optical fiber preform in the longitudinal direction can reach more than 0.7%, the average value of numerical aperture NA can reach more than 0.17, and the optical fiber preform has good light receiving capability.
Drawings
FIG. 1 is a schematic structural diagram 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 side view schematic of a gas guide according to an embodiment of the present invention,
FIG. 4 is a schematic end view of a first inlet of a gas guide according to an embodiment of the present invention;
FIG. 5 is a schematic end view of a second inlet of a gas guide according to an embodiment of the present invention;
FIG. 6 is a NA diagram of the optical fiber preform of example 2 of the present invention along the longitudinal direction;
FIG. 7 is a cross-sectional view showing the relative refractive index difference in the radial distribution at the 9 th position of the optical fiber preform of example 3 according to the present invention;
FIG. 8 is a NA pattern of the optical fiber preform of comparative example 2 of the present invention distributed in the longitudinal direction.
Description of reference numerals:
1-a rod to be deposited; 21-a first clamping unit; 22-a second clamping unit; 3-a chuck; 4-a metering member; 5-sealing the flange; 6-a pressure gauge; 7-air vent; 8-air inlet; 81-gas guide; 801-a first inlet; 802-a second inlet; 803-an air inlet valve; 804-a guide plate; 9-an isolation unit; 10-a heat preservation unit; 11-a heating unit; 12-housing, 13-cage; 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 the examples are intended to be illustrative of the invention and not limiting of the scope of the invention. All other embodiments obtained by a person of ordinary skill in the art based on the embodiments of the present invention without any creative effort belong to the protection scope of the present 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 shell is provided with a first clamping groove and a second clamping groove; the shell comprises an inner cavity enclosed 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 axes 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 matched with each other to clamp the rod to be deposited in the inner cavity; the injection direction of the plasma torch faces to the inner cavity; the heating unit is positioned in the inner cavity; the side wall of the shell is respectively provided with an air exhaust hole and an air inlet hole, the air flow discharged through the air exhaust hole has the same flowing direction as the spraying direction, the air flow entering the inner cavity through the air inlet hole has an included angle theta with the spraying direction, and the theta is more than or equal to 20 degrees and less than or equal to 60 degrees.
The invention does not limit the placing mode of the deposition device, and can be horizontally placed or vertically placed. It should be noted that the top and bottom walls of the present invention are only used to distinguish the 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. Wherein cyclic annular shell has relative first opening and second opening, and this cyclic annular shell encloses to establish and has formed the cavity through first opening and second opening and external intercommunication respectively, and the size adaptation of top shell and first opening is connected, and the drain pan is connected with the size adaptation of second opening. The annular housing thus forms side walls, the top and bottom shells form top and bottom walls, respectively, and an internal cavity is formed enclosed by the side walls, top and bottom walls.
The first unit telescopically that presss from both sides establishes connects the roof, and the second presss from both sides establishes the unit telescopically and connects the diapire. The first clamping unit and the second clamping unit can move back and forth 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 a 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 located in the inner cavity.
Specifically, first clamping unit, second clamping unit, treat that the deposit stick is independent separately have along the both ends that the inner chamber depth direction extends, first clamping unit is close to the one end of inner chamber and treats the one end butt of deposit stick, and the one end that the second clamping unit is close to the inner chamber and treats the other end butt of deposit stick to treat the deposit stick clamp and establish between first clamping unit and second clamping unit in making the inner chamber.
The clamping mode is not limited in the invention, as long as the rod to be deposited is clamped between the first clamping unit and the second clamping unit, and the rod to be deposited, the first clamping unit and the second clamping unit preferably extend coaxially.
The rod to be deposited can rotate along the self axis in the inner cavity and can 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 first clamping unit and the second clamping unit in the depth direction of the inner cavity.
The first clamping unit and the second clamping unit can be completely positioned in the inner cavity or partially positioned in the inner cavity, as long as the rods to be deposited clamped by the first clamping unit and the second clamping unit are positioned in the inner cavity.
When the first clamping unit and the second clamping unit are all positioned in the inner cavity, one ends, far away from the inner cavity, of the first clamping unit and the second clamping unit 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 part and the bottom wall.
In the present invention, the first and second sandwiching units are not limited in structure, and may be the same or different, and preferably the same. The present invention is not limited to a specific type of the first and second sandwiching units, and may be made of, for example, quartz glass.
The invention is not limited to the specific type of rod to be deposited, for example, a pure silica rod (pure silicon rod) or a germanium-doped rod.
The plasma torch is used to inject a material to be deposited into the inner chamber. Specifically, during the deposition process, the raw material to be deposited is converted into particles in the plasma flame sprayed by the 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 is towards the rod to be deposited. Wherein the plasma torch is surrounded by an induction coil.
The invention does not limit the position and the installation mode of the plasma torch, as long as the nozzle of the plasma torch faces the rod to be deposited in the deposition process.
In the invention, the heating unit is positioned in the inner cavity and used for heating the inner cavity. The heating unit supplies temperature to 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 is maintained in the process of depositing the outer cladding layer, the temperature uniformity of the surface of the rod to be deposited is improved, and the fluorine doping uniformity of the outer cladding layer is facilitated.
In the invention, the exhaust hole is used for exhausting air flow in the inner cavity, the air inlet hole is used for allowing air flow to enter the inner cavity, and stable pressure and stable air circulation are formed in the inner cavity along with air inlet of the air inlet hole and air exhaust of the exhaust hole.
By making the direction of the air flow discharged from the air outlet consistent with the spraying direction, it can be ensured that the particles which are not deposited are discharged from the inner cavity through the air outlet, thereby ensuring the pressure and the air flow in the inner cavity to be stable.
In order to avoid the influence of air inflow of the air inlet hole on the stability of air flow in the spraying direction, the air flow direction of the air inlet hole entering the inner cavity 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, and through setting a certain angle, the air inlet hole is not only beneficial to the discharge of non-deposited particles, but also cannot influence the stability of the air flow in the inner cavity.
The positions of the air exhaust hole and the air inlet hole are not limited, and the air exhaust hole and the air inlet hole are positioned on the side wall of the shell, and the air flow direction and the spraying direction meet the requirements.
The number of air intake holes may be one or more. When the number of the air inlet holes is two, in order to ensure the stability of the air flow in the inner cavity, the two air outlet holes are symmetrically arranged along the axis of the shell.
Therefore, according to the deposition device provided by the invention, the first clamping unit and the second clamping unit are matched with each other 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 axes of the first clamping unit and the second clamping unit and the movement of the first clamping unit and the second clamping unit in the depth direction of the inner cavity, so that the fluorine-doped outer cladding layer is formed on the surface of the rod to be deposited, and the optical fiber preform is obtained. Meanwhile, the pressure and the airflow of the inner cavity are kept stable through the exhaust holes and the air inlets on the side walls, so that the stability of the airflow in the jetting direction is not influenced, and meanwhile, the undeposited raw materials can be discharged out of the inner cavity through the exhaust holes; through the heating of the heating unit to the inner chamber of casing, maintain the tip of treating the sedimentation stick and the temperature stability of intermediate part, improve and treat the axial and radial temperature homogeneity on sedimentation stick surface, be favorable to promoting the fluorine homogeneity of doping of surrounding layer, can make the surrounding layer and mix the even optical fiber perform of fluorine to promote optical fiber perform vertically and the uniformity of footpath delta n and NA.
The invention also 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. 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, which is far away from the inner cavity, and the clamping unit can rotate along the axis of the clamping unit 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 position of the clamping unit and the top wall and the bottom wall and is used for sealing the hole between the clamping unit and the top wall and the bottom wall.
Furthermore, 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 manufactured optical fiber preform can be accurately controlled.
Further, the first and second adjusting units may be supported by the base rail.
The position of the heating unit is not limited, the heating unit can heat the inner cavity, and the heating unit is annularly arranged inside the side wall in order to further ensure the temperature of the inner cavity to be stable and consistent.
In the specific implementation process of the invention, the heating unit is electrically connected with the outside through the wire, and under the action of an electric field, the heating unit is used as the heat conductor to generate heat energy which is transferred to the inner cavity, thereby realizing the heating of the inner cavity. The present invention is not limited to a specific type of heating unit, and may be, for example, a graphite heating body made of a graphite material.
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 may volatilize when being heated, and in order to avoid the influence of volatilized impurities on the deposition process, the deposition device further comprises an isolation unit which is arranged around the inner part of the heating unit.
The heating unit is used for heating the inner cavity, and in order to prevent the heat from being rapidly dissipated, the heating unit is further provided with the heat preservation unit which is annularly arranged inside the heating unit.
In order to avoid the influence of the heating unit and the heat preservation unit on the deposition process caused by the volatilized impurities, the isolation unit is annularly arranged inside the heat preservation unit, namely the heat preservation unit is enclosed between the isolation unit and the heating unit, wherein the isolation unit can be a quartz furnace core pipe made of quartz materials.
In the invention, a raw material inlet is arranged on the side wall of the shell, and the raw material to be deposited is conveyed into the inner cavity through the raw material inlet. In order to achieve the transport of the raw material, the nozzle of the plasma torch of the present invention faces the raw material inlet.
In the invention, the plasma torch can be positioned in the inner cavity or outside the inner cavity, and the plasma torch can spray the raw materials to the inner cavity. 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 is positioned in the inner cavity. When the plasma blowtorch is located the inner chamber outside, in order to avoid the plasma flame that the blowtorch jetted to contact with the casing and take place the reaction, establish the cage card at the raw materials entry for keep apart the flame that the blowtorch jetted and casing. Wherein the insulating cover may be a quartz ignition-proof cover made of quartz.
The invention does not limit the position of the plasma torch on the side wall, as long as the spraying direction of the plasma torch is towards the rod to be deposited. In order to realize that the spraying direction of the plasma torch faces to 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 according to the present invention is not limited thereto, and may be a plasma torch that is conventional in the art. In one embodiment, the plasma torch has a material inlet in the center layer of the torch and other material inlets such as oxygen and nitrogen are located around the outer periphery of the center layer.
The invention promotes the inner cavity to form a stable pressure field and a stable circulating airflow field by means of the driving pump, and particularly, the driving pump is arranged outside the shell and 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 is connected with the exhaust hole, the driving pump is used for pumping 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, air is supplied to the inner cavity from the outside. Due to the arrangement of the air inlet holes and the flowing of the air, the air in the external environment is continuously pumped into the inner cavity, and a stable circulating airflow 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 achieve that the air flow exiting the air outlet opening is directed in line with the direction of the spray, the air outlet opening is located on the opposite side of the side wall to which the plasma torch is located. 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, preferably in the same radial direction. When the exhaust hole is not in the same radial direction as the plasma torch, 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 in the same radial direction of the side wall in order to better control air inlet and air outlet.
In the invention, the direction of the airflow entering the inner cavity through the air inlet hole can be adjusted by adjusting the angle of the air inlet hole, and the direction of the airflow 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 opening for controlling the direction of the gas flow entering the gas inlet opening.
The gas guides may be located entirely outside the interior chamber or partially outside the interior chamber. When the gas guide piece is completely 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 gas inlet hole.
The gas guide part comprises a plurality of guide plates which are mutually communicated, the communication mode of the plurality of guide plates is not limited, and the condition that the gas flows through the gas guide part and the direction of the gas flow entering the inner cavity forms an included angle theta with the spraying direction is met.
The flow of gas entering through the inlet port directly affects the pressure and gas circulation in the internal chamber, and the present invention controls the flow through the inlet port by providing an inlet valve. 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 degree is adjusted through rotation, so that the air flow passing through the air inlet hole is controlled.
Furthermore, the gas guide piece is further 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 inlets are provided with adjustable gas inlet valves for controlling the gas flow passing through the gas guide piece and further controlling the gas flow passing through the gas inlet holes. The number of the second inlets is one or more, for example, six or more. 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 which are used for monitoring the temperature and the pressure of the inner cavity in real time.
The preparation method of the optical fiber preform rod provided by the invention is implemented by adopting the deposition device, and comprises the following steps: preheating an 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; a first clamping unit and a second clamping unit are respectively utilized to mutually match and 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 carrying out 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 plasma torch is prepared from gaseous silicon-containing compounds, gaseous fluorides and oxygen as raw materials;
(3) Under the action of the first clamping unit and the second clamping unit, the optical fiber preform precursor is subjected to second movement and second rotation and accompanied with polishing treatment to obtain an optical fiber preform; in the polishing treatment, the raw material gas of the plasma torch is oxygen.
Before preparing the optical fiber preform, the components of the deposition apparatus are first installed in corresponding positions. In the step (1), the operations are not in sequence, and specifically, the first clamping unit and the second clamping unit are respectively matched with each other to clamp the rod to be deposited, 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 externally electrified, the inner cavity is preheated by utilizing heat generated by the heating unit, and further, the heat is preserved by adopting the heat preservation unit. Through the design of self-supporting temperature supply and heat preservation, the surface of the rod to be deposited has enough heat and uniform temperature, the temperature gradient on the surface of the rod to be deposited is avoided, and the uniform temperature on the axial direction of the rod to be deposited is realized.
The preheating temperature and time have certain influence on the temperature uniformity of the surface of the rod to be deposited, and in one embodiment, the preheating temperature is 800-900 ℃ and the preheating time is 20-40 min.
Because the fluorine doping uniformity depends on the uniformity of the surface temperature of the rod to be deposited, the heating and heat preservation mode is favorable for improving the uniformity of the surface temperature of the rod to be deposited and further improving the fluorine doping uniformity of the outer cladding layer. Because the doping amount is reduced along with the temperature increase of the plasma flame, the invention improves the surface temperature of the rod to be deposited by a heating and heat-preserving mode, so the power of a plasma torch is not required to be additionally increased to heat the rod to be deposited, thereby reducing the temperature of the plasma flame and being beneficial to improving the doping amount of fluoride in the outer cladding layer.
And pumping gas towards the gas inlet by using an external driving pump, exhausting gas by using the external driving pump through the exhaust hole, forming stable gas circulation in the inner cavity and controlling the pressure of the inner cavity to be stabilized at-2 Pa to-5 Pa.
And (2) starting the plasma torch, introducing a gaseous silicon-containing compound and a gaseous fluoride through a raw material inlet of the plasma torch, and introducing oxygen through other material inlets. The method comprises the steps that gaseous silicon-containing compounds, gaseous fluorides and oxygen react and combust at a nozzle of a blast burner under the action of plasma flame to generate silica particles and fluorine, at the moment, a rod to be deposited is subjected to first movement and first rotation under the action of a first clamping unit and a second clamping unit and is accompanied with deposition treatment, in the process, the silica particles and the fluorine are deposited on the cylindrical peripheral surface of the rod to be deposited in a layered mode, 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 refers to the movement of the rod to be deposited towards one direction, the displacement distance of the first movement is the longitudinal length of the rod to be deposited, and the first rotation refers to the rotation of the rod to be deposited along the axis of the rod to be deposited.
The displacement speed of the first movement and the rotation speed of the first rotation directly affect the deposition rate, and in one embodiment, the rotation 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), protective gas for protecting the raw material, such as argon, can be introduced through the raw material inlet of the plasma torch, and nitrogen can be introduced through other material inlets to avoid the influence of the excessive oxygen content on the safety of the reaction. Furthermore, chlorine (Cl) can be introduced into the raw material inlet 2 ) So as to eliminate hydroxyl generated in the reaction, further reduce the hydroxyl content in the optical fiber preform and improve the optical performance of the optical fiber preform.
The power of the plasma torch directly affects the rate of generation of silica particles and fluorine during the deposition process, and thus 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).
In the step (3), a raw material inlet of the plasma torch is closed, and the optical fiber preform precursor is subjected to second movement and second rotation under the action of the first clamping unit and the second clamping unit and accompanied with polishing treatment to obtain an optical fiber preform;
wherein, the second movement refers to the movement of the rod to be deposited in the direction opposite to the first movement, the displacement distance of the second movement is the longitudinal length of the rod to be deposited, and the second rotation refers to the rotation of the rod to be deposited along the axis of the rod to be deposited.
The displacement speed of the second movement and the rotation speed of the second rotation directly affect the polishing rate, and in one embodiment, the rotation speed of the second rotation is 30rpm to 40rpm/min, and the speed of the second movement is 250mm/min to 350mm/min.
In the step (3), the outer cladding layer to be polished is vitrified by means of plasma flame to form a fluorine-doped outer cladding layer, whereby a composite body composed of the rod to be deposited and the outer cladding layer becomes an optical fiber preform.
According to the invention, the surface temperature of the rod to be deposited is raised in an active heating and heat preservation mode, so that the power of the plasma torch is not required to be additionally increased to polish the precursor of the optical fiber preform, 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 layer is formed on the surface of the rod to be deposited by adopting a mode of depositing firstly and then polishing, so that the thermal stress of the fluorine-doped outer cladding layer can be effectively removed, and the problem of cracking caused by the difference of thermal expansion coefficients of all layers after the completion of the deposition is avoided.
In the invention, the deposition and polishing treatment of the second round is 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 member, so that the actually required weight of the optical fiber preform can be prepared.
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 were as follows:
monitoring the appearance of the optical fiber perform in real time by using a CCD appearance automatic detection machine;
taking a point every 100mm along the longitudinal direction of the optical fiber preform by adopting a PK2600 instrument; testing the refractive index n of the core layer in the vertical circumferential direction corresponding to each point core An outer cladding refractive index n clad According to which the relative refractive index difference of the core wraps Δ n = (n) core -n clad )/n 0 X 100% and numerical aperture
Figure BDA0003835309080000121
Calculating the relative refractive index difference delta n of the core cladding and the numerical aperture NA in the vertical circumferential direction corresponding to each point, and calculating the mean value of the delta n and the NA and the difference between the maximum value and the minimum value;
adopting a Fourier infrared spectrometer FTIR to test the light transmittance of the optical fiber preform, and calculating the hydroxyl concentration of the optical fiber preform according to a formula according to the Lambert-beer law, wherein the formula is as follows: c OH ＝[M OH /(ε×ρ)]×(1/d)×log 10 (I 0 I) formula, C OH In terms of hydroxyl group mass concentration, ppm (10) -6 )；M OH Hydroxyl group molar mass, g/mol; epsilon is the absorptivity of the quartz glass at the position of 2.73 mu m, L/mol cm; rho is the density of quartz, g/cm 3 (ii) a 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 detected.
In the following examples, the rod to be deposited is a pure silica core rod (pure silicon core rod) or a germanium-doped core rod (the relative refractive index difference of the germanium-doped core rod with respect to the pure silicon core rod is 0.1% to 0.3%), wherein the refractive index of the pure silicon core rod is 1.4571.
In the following examples, the deposition apparatus used is as shown in fig. 1 to 5, and includes: the device comprises a shell 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 bounded by side, top and bottom walls; 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 the axes thereof 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 to clamp 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 rotate along the axis of the clamping unit and move 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 part of the clamping unit and the top wall and the bottom wall and is used for sealing the holes 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 the periphery of the plasma torch 14 surrounds the induction coil 15; a raw material inlet is arranged on the side wall of the shell 12, the nozzle of the plasma torch 14 faces the raw material inlet, and the 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 used for isolating the jet flame from the shell 12;
the central layer of the plasma torch 14 is a raw material inlet, is surrounded on the periphery of the central layer and is provided with other material inlets, and the other material inlets sequentially comprise a second layer, a third layer and a fourth layer along the direction far 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 an enclosing manner;
the side wall of the shell is respectively provided with an exhaust hole 7 and an air inlet hole 8, and the air flow discharged through the exhaust hole 7 is consistent with the spraying direction; the driving pump is positioned outside the shell and is connected with the exhaust hole 7;
the gas guide 81 is connected with the gas inlet 8 and is used for controlling the direction of the gas flow flowing through the gas inlet; 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 gas guide 81 comprises a plurality of guide plates 804, a first inlet 801 far away 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 degree is arranged at the first inlet 801 and used for controlling the flow of gas entering the air inlet hole;
the pressure gauge 6 is used for monitoring the pressure of the inner cavity 17 in real time;
and a base rail 16 for supporting the first and second clamping units 21 and 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 the heating unit and the 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; controlling the pressure of the inner cavity to be-2 Pa by pumping through a driving pump connected with the exhaust hole and forming gas circulation in the inner cavity by utilizing the air inlet hole and the exhaust hole; respectively fixedly clamping a rod to be deposited by using a first clamping unit and a second clamping unit, wherein 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 along with deposition treatment to obtain an optical fiber preform precursor; in the deposition process, siCl is introduced into the central layer of the plasma torch 4 Flow rate of 25g/min, CF 4 100mL/min, ar flow rate of 10L/min, and O is introduced into the second layer 2 The flow rate is 30L/min, and O is introduced into the third layer 2 The flow rate is 40L/min, N is introduced into the fourth layer 2 The flow rate 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 accompanying polishing treatment to obtain an optical fiber preform;
wherein, in the polishing process, the power of the plasma torch is 20kW, the second moving speed is 350mm/min, and the second rotating speed 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;
the process steps of the embodiment 1 are adopted, 3 groups are repeatedly made, and the manufactured 3 optical fiber preforms have no cracking phenomenon; after the optical fiber preform is cooled to room temperature, a PK2600 meter is used to take 7 points every 100mm along the longitudinal direction of the optical fiber preform, the refractive indexes in the vertical circumferential direction corresponding to the 7 points are tested, and the average value of Δ n and NA in the vertical circumferential direction corresponding to the 7 points and the difference between the maximum value and the minimum value of Δ n and NA are respectively calculated, as shown in table 1.
Example 2
Compared with the embodiment 1, the difference 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;
SiCl introduced into the center layer of a plasma torch during deposition 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 O is introduced into the second layer 2 The flow rate is 35L/min, and O is introduced into the third layer 2 The flow rate is 45L/min, and the fourth layer N 2 The flow rate 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 not changed.
The process steps of the embodiment 2 are adopted, 3 groups are repeatedly made, and the manufactured 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 adopting a PK2600 instrument, taking 9 points in total, testing the refractive index, and respectively calculating the mean value of delta n and NA in the circumferential direction corresponding to the 9 points and the difference between the maximum value and the minimum value of the delta n and the NA, wherein the mean value is shown in the table 1;
a graph of NA values at 9 points of each of the 3 optical fiber preforms manufactured is shown in fig. 6.
Example 3
Compared with the embodiment 1, the difference 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;
SiCl introduced into the center layer of a plasma torch during deposition 4 The flow rate is 45g/min, SF 6 200mL/min, ar flow 15L/min, cl 2 The flow rate is 400mL/min, and O is introduced into the second layer 2 The flow rate is 40L/min, and O is introduced into the third layer 2 The flow rate is 50L/min, and the outermost layer N 2 The flow rate is 20L/min; wherein, in the deposition treatment, the power of the plasma torch is 80kW, the first moving speed is 40mm/min, and the first rotating speed is 30rpm/min;
in the polishing process, the power of the plasma torch was 30kW, the second moving speed was 250mm/min, and the second rotating speed 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.
The process steps of the embodiment 3 are adopted, 3 groups are repeatedly made, and the manufactured optical fiber preform does not crack; 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 adopting a PK2600 instrument, taking 9 points in total, testing the refractive index, and respectively calculating the mean value of delta n and NA in the circumferential direction corresponding to the 9 points and the difference between the maximum value and the minimum value of the delta n and the NA, as shown in Table 1;
FIG. 7 is a graph showing the relative refractive index difference in the radial distribution at 9 th points of the optical fiber preform manufactured in group 3.
Example 4
The rod to be deposited is a germanium-doped core rod (the relative refractive index is 0.3 percent), the outer diameter of the core rod is 40mm, and the length of the core rod is 800mm;
(1) Starting the 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; controlling the pressure of the inner cavity to be-2 Pa by pumping the driving pump connected with the exhaust hole and forming gas circulation in the inner cavity by utilizing the air inlet and the exhaust hole; respectively fixedly clamping a rod to be deposited by using a first clamping unit and a second clamping unit, wherein a nozzle of a 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, siCl is introduced into the central layer of the plasma torch 4 Flow rate of 25g/min, CF 4 100mL/min, ar flow rate of 10L/min, and O is introduced into the second layer 2 The flow rate is 30L/min, and O is introduced into the third layer 2 The flow rate is 40L/min, N is introduced into the fourth layer 2 The flow rate 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 a 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 accompanying polishing treatment to obtain an optical fiber preform;
wherein, in the polishing process, the power of the plasma torch is 20kW, the second moving speed is 350mm/min, and the second rotating speed 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;
the process steps of the embodiment 4 are adopted, 3 groups are repeatedly made, and the manufactured 3 optical fiber preforms have no cracking phenomenon; after the optical fiber preform is cooled to room temperature, a PK2600 meter is used to take a point every 100mm along the longitudinal direction of the optical fiber preform, and take a total of 7 points, test the refractive index in the vertical circumferential direction corresponding to the 7 points, and calculate the average value of Δ n and NA in the vertical circumferential direction corresponding to the 7 points and the difference between the maximum value and the minimum value of Δ n and NA, 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) Fixedly clamping a rod to be deposited by using a first clamping unit and a second clamping unit, wherein a nozzle of a 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; siCl introduced into the center layer of a plasma torch during deposition 4 The flow rate is 45g/min, CF 4 200mL/min, argon flow rate of 15L/min, and O is introduced into the second layer 2 The flow rate is 40L/min, and O is introduced into the third layer 2 The flow rate is 50L/min, and the outermost layer N 2 The flow rate is 20L/min;
wherein, in the deposition treatment, the power of the plasma torch is 80kW, the first moving speed is 40mm/min, and the first rotating speed 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 accompanying polishing treatment to obtain an optical fiber preform;
wherein, in the polishing process, the power of the plasma torch is 80kW, the second moving speed is 40mm/min, and the second rotating speed is 30rpm/min;
(4) Repeating the steps (2) and (3),
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 adopting a PK2600 instrument, taking 7 points in total, testing the refractive index, and calculating the relative refractive index difference delta n of the core package and the numerical aperture NA, as shown in Table 1;
and repeating the steps of the process of the comparative example 1 to obtain 3 prefabricated rods, wherein the end parts of 1 prefabricated rod are cracked, and the other 2 prefabricated rods are subjected to white fog bubbles within the range of 250mm from the return end. Thus, no normal product was obtained, and no test data was obtained.
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) Fixedly clamping a rod to be deposited by using a first clamping unit and a second clamping unit, wherein a nozzle of a 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; siCl introduced into the center layer of a plasma torch during deposition 4 The flow rate is 35g/min, SF 6 150mL/min, argon flow rate of 12.5L/min, and O is introduced into the second layer 2 The flow rate is 35L/min, and O is introduced into the third layer 2 The flow rate is 45L/min, and the outermost layer N 2 The flow rate 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 a 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 accompanying polishing treatment to obtain an optical fiber preform;
wherein, in the polishing process, the power of the plasma torch is 25kW, the second moving speed is 300mm/min, and the second rotating speed 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;
repeating 3 groups by adopting the process steps of the comparative example 2 to obtain 3 prefabricated rods, wherein 1 prefabricated rod is cracked integrally, after the 2 prefabricated rods are cooled to room temperature, taking a point every 100mm along the longitudinal direction of the prefabricated rods by adopting a PK2600 instrument, taking 9 points in total, testing the refractive index, and respectively calculating the mean value of delta n and NA and the difference between the maximum value and the minimum value of the delta n and the NA in the circumferential direction corresponding to the 9 points, as shown in the table 1;
the NA profile in the longitudinal direction of the other 2 optical fiber preforms is 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, preheating at 900 ℃, and keeping the temperature for 40min; controlling the pressure of the inner cavity to be-5 Pa;
(2) SiCl introduced into the center layer of a plasma torch during deposition 4 The flow rate is 45g/min and SF 6 200mL/min, ar flow 15L/min, cl 2 The flow rate is 400mL/min, and O is introduced into the second layer 2 The flow rate is 40L/min, and O is introduced into the third layer 2 The flow rate is 50L/min, and the outermost layer N 2 The flow rate is 20L/min; wherein, in the deposition treatment, the power of the plasma torch is 80kW, the first moving speed is 15mm/min, and the first rotating speed is 20rpm/min;
(3) In the polishing process, the power of the plasma torch was 30kW, the second moving speed was 100mm/min, and the second rotating speed 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; the manufactured optical fiber preform is bent.
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, preheating at 900 ℃, and keeping the temperature for 40min; controlling the pressure of the inner cavity to be-5 Pa;
(2) SiCl introduced into the center layer of a plasma torch during deposition 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 O is introduced into the second layer 2 The flow rate is 40L/min, and O is introduced into the third layer 2 The flow rate is 50L/min, and the outermost layer N 2 The flow rate 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 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 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 were unchanged; the diameter of the prepared optical fiber preform rod in the longitudinal direction is corrugated, the optical fiber preform rod 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, preheating at 900 ℃, and keeping the temperature for 40min; controlling the pressure of the inner cavity to be-5 Pa; the direction of the air flow entering the inner cavity from the air inlet hole and the spraying direction form an included angle theta which is set to be 0 degree.
(2) SiCl introduced into the center layer of a plasma torch during deposition 4 The flow rate is 45g/min, SF 6 200mL/min, ar flow of 15L/min, cl 2 The flow rate is 400mL/min, and O is introduced into the second layer 2 The flow rate is 40L/min, and O is introduced into the third layer 2 The flow rate is 50L/min, and the outermost layer N 2 The flow rate is 20L/min; wherein, in the deposition treatment, the power of the plasma torch is 80kW, the first moving speed is 40mm/min, and the first rotating speed is 30rpm/min;
(3) In the polishing process, the power of the plasma torch was 30kW, the second moving speed was 300mm/min, and the second rotating speed 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; as the number of times increases, soot particles generated by flames remain in partial areas, 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, preheating at 900 ℃, and keeping the temperature for 40min; controlling the pressure of the inner cavity to be-5 Pa; the direction of the air flow entering the inner cavity from the air inlet hole and the spraying direction form an included angle theta which is set to be 90 degrees.
(2) SiCl introduced into the center layer of a plasma torch during deposition 4 The flow rate is 45g/min, SF 6 200mL/min, ar flow 15L/min, cl 2 The flow rate is 400mL/min, and O is introduced into the second layer 2 The flow rate is 40L/min, and O is introduced into the third layer 2 The flow rate is 50L/min, and the outermost layer N 2 The flow rate is 20L/min; wherein, in the deposition treatment, the power of the plasma torch is 80kW, the first moving speed is 40mm/min, and the first rotating speed is 30rpm/min;
(3) In the polishing process, the power of the plasma torch is 30kW, the speed of the second movement is 300mm/min, and the speed of the second rotation is 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; the air flow is unstable due to the collision of the air supply at the two sides, and the flame is shaken to extinguish the air, so that the preparation cannot be carried out.
TABLE 1
Figure BDA0003835309080000211
In the table, ". Smallcircle" represents normal appearance, ". Xx" represents the occurrence of cracks, partial cracks or non-vitrification and whitening of the rod body in the optical fiber preform, and "/" represents no detection data.
As can be seen from Table 1, the optical fiber preform rod with normal appearance can be manufactured by adopting the deposition device provided by the invention, the circumferential dimension of the optical fiber preform rod can reach 60-80 mm, the prepared optical fiber preform rod has uniform fluorine doping of the outer cladding layer, the difference between the maximum value and the minimum value of the delta n in the longitudinal direction does not exceed 0.085%, the difference between the maximum value and the minimum value of the NA does not exceed 0.01, the difference between the maximum value and the minimum value of the delta n in the circumferential direction does not exceed 0.005%, and the difference between the maximum value and the minimum value of the NA does not exceed 0.0005, so that the optical fiber preform rod has good delta n consistency and NA consistency. And the optical fiber perform rod delta n mean value in the longitudinal direction can reach more than 0.7%, the numerical aperture NA mean value can reach more than 0.17, and the optical fiber perform rod has good light receiving capacity.
The above detailed description of the preferred embodiments of the invention and experimental verification. It should be understood that numerous modifications and variations could be devised by those skilled in the art in light of the present teachings without departing from the inventive concept. Therefore, the technical solutions available to those skilled in the art through logic analysis, reasoning and limited experiments based on the prior art according to the concept of the present invention should be within the scope of protection defined by the claims.

Claims (10)

1. A deposition device is characterized by comprising a shell, a first clamping unit, a second clamping unit, a plasma torch and a heating unit;
the shell comprises an inner cavity enclosed 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 axes 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 being matched with each other to clamp a rod to be deposited in the inner cavity;
the injection 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 air flow discharged through the exhaust hole has the same flowing direction as the spraying direction, the air flow entering the inner cavity through the air inlet hole has an included angle theta with the spraying direction, and the theta is more than or equal to 20 degrees and less than or equal to 60 degrees.
2. The deposition apparatus of claim 1, wherein the heating unit is annularly disposed inside the sidewall.
3. The deposition apparatus according to claim 2, further comprising a thermal insulation unit and an isolation unit, wherein the isolation unit is disposed around an inside of the heating unit, and the thermal insulation unit is enclosed between the isolation unit and the heating unit.
4. A deposition apparatus according to any of claims 1 to 3, wherein the sidewall is provided with a material inlet, and the plasma torch has an orifice facing the material inlet.
5. The deposition apparatus of claim 4, further comprising a shield engaged with the feedstock inlet for shielding the injection flame from the housing.
6. The deposition apparatus of any one of claims 1-5, further comprising a drive pump located outside the housing and connected to the exhaust vent.
7. The deposition apparatus of any one of claims 1-6, further comprising a gas guide coupled to the gas inlet for controlling the direction of gas flow into the gas inlet.
8. The deposition apparatus of claim 7, further comprising an air inlet valve coupled to the air inlet hole for controlling the amount of air flow into the air inlet hole.
9. A method for preparing an optical fiber preform, characterized by being performed using the deposition apparatus of any one of claims 1 to 8, 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 and the air outlet and controlling the pressure of the inner cavity to be-2 Pa to-5 Pa;
a first clamping unit and a second clamping unit are respectively utilized to be 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 carrying out 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 plasma torch is prepared from gaseous silicon-containing compounds, gaseous fluorides and oxygen as raw materials;
under the action of the first clamping unit and the second clamping unit, the optical fiber preform precursor is subjected to second movement and second rotation and polishing treatment, so that an optical fiber preform is obtained; in the polishing treatment, the raw material gas of the plasma torch is oxygen.
10. The method for preparing an optical fiber preform according to claim 9, wherein the preheating temperature is 800 to 900 ℃ for 20 to 40min; and/or the presence of a gas in the gas,
in the deposition treatment, the power of the plasma torch is 50kW to 80kW; and/or the presence of a gas in the gas,
in the polishing treatment, the power of the plasma blowtorch is 20 kW-30 kW; and/or the presence of a gas in the atmosphere,
the rotating speed of the first rotation is 30 rpm-40 rpm/min; and/or the presence of a gas in the gas,
the rotation speed of the second rotation is 30 rpm-40 rpm/min; and/or the presence of a gas in the atmosphere,
the first moving speed is 40 mm/min-60 mm/min; and/or the presence of a gas in the atmosphere,
the second movement speed is 250 mm/min-350 mm/min.
CN202211095609.2A 2022-09-06 2022-09-06 Deposition device and preparation method of optical fiber preform Active CN115557693B (en)

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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

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