CA2135834A1 - Method and device for manufacturing an optical fiber - Google Patents
Method and device for manufacturing an optical fiberInfo
- Publication number
- CA2135834A1 CA2135834A1 CA002135834A CA2135834A CA2135834A1 CA 2135834 A1 CA2135834 A1 CA 2135834A1 CA 002135834 A CA002135834 A CA 002135834A CA 2135834 A CA2135834 A CA 2135834A CA 2135834 A1 CA2135834 A1 CA 2135834A1
- Authority
- CA
- Canada
- Prior art keywords
- gas flow
- preform
- additional flushing
- protective
- protective gas
- 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.)
- Abandoned
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
- C03B37/02—Manufacture of glass fibres or filaments by drawing or extruding, e.g. direct drawing of molten glass from nozzles; Cooling fins therefor
- C03B37/025—Manufacture of glass fibres or filaments by drawing or extruding, e.g. direct drawing of molten glass from nozzles; Cooling fins therefor from reheated softened tubes, rods, fibres or filaments, e.g. drawing fibres from preforms
- C03B37/029—Furnaces therefor
-
- C—CHEMISTRY; METALLURGY
- C03—GLASS; MINERAL OR SLAG WOOL
- C03B—MANUFACTURE, SHAPING, OR SUPPLEMENTARY PROCESSES
- C03B2205/00—Fibre drawing or extruding details
- C03B2205/60—Optical fibre draw furnaces
- C03B2205/62—Heating means for drawing
- C03B2205/64—Induction furnaces, i.e. HF/RF coil, e.g. of the graphite or zirconia susceptor type
-
- C—CHEMISTRY; METALLURGY
- C03—GLASS; MINERAL OR SLAG WOOL
- C03B—MANUFACTURE, SHAPING, OR SUPPLEMENTARY PROCESSES
- C03B2205/00—Fibre drawing or extruding details
- C03B2205/60—Optical fibre draw furnaces
- C03B2205/90—Manipulating the gas flow through the furnace other than by use of upper or lower seals, e.g. by modification of the core tube shape or by using baffles
-
- C—CHEMISTRY; METALLURGY
- C03—GLASS; MINERAL OR SLAG WOOL
- C03B—MANUFACTURE, SHAPING, OR SUPPLEMENTARY PROCESSES
- C03B2205/00—Fibre drawing or extruding details
- C03B2205/60—Optical fibre draw furnaces
- C03B2205/90—Manipulating the gas flow through the furnace other than by use of upper or lower seals, e.g. by modification of the core tube shape or by using baffles
- C03B2205/92—Manipulating the gas flow through the furnace other than by use of upper or lower seals, e.g. by modification of the core tube shape or by using baffles using means for gradually reducing the cross-section towards the outlet or around the preform draw end, e.g. tapered
Abstract
Abstract of the Disclosure A method for manufacturing an optical fiber (11), wherein the fiber (11) is drawn from one end of a preform (9) which is heated to above the glass softening temperature. The preform (9) is surronded by a protective gas (14) whose flow direction corresponds to the fiber drawing direction. The flow of the gas surrounding the preform (9) in the drawing area (10) is stabilized by an additional flushing gas (16).
Description
213~3~
PATENT
925-01~1 ~thod aIId D6~vic~ for M~nuf2~¢turing a~ Optical ~ibsr ~., ~aa~ Lu~d of the I~v~ntion Field of the Invention The present invention concerns optical fibers and, more particularly, a method for manufacturing an optical fiber, whereby the fiber is drawn from one end of a preform heated to the glass softening temperature, ~hile a gas flaws around the preform and its flow direction corresponds to the fiber drawing direction.
Description of the Prior Art ; `
The direct manu~acture of an optical fiber having the required fiber profile from different types of glass -is not possible because of the small outside dimensions of the optiaal fiber. The manufacture of an optical fiber is therefore based on a preform with a diameter in the centimater range, which can be produced in several;;
different ways, e.g., with multimode-gradients or single mode fibers, depending on the type of optical fiber desired. One method of producing a preform is the chamical vapor deposition method ~CVD-method) which involves applying a core glass material to the inner sur~aces of a quartz glass tube by chemical deposition from the vapor phase of the core glass material onto the i inside surfaces of the quartz glass tube~ which is subsequently collapsed into a preform. The Outside Vapor Deposition method (OVD-method) involves the outside `
coating of a glass core vith a glass material by deposition from the vapor phase of the glass material on the outside of the glass core. The Vapor Axial ~ -~
Deposition method ~V~D-method) provides for the axial 2 1 3 ~ ~ 3 ~
PATENT -925-01~1 coating of a glass core with a glass material by deposition from the vapor phase of the glass material axially along the glass core. ;~
Glass is an amorphous material, which can be brought to a low viscosity condition by heating. With the quartz glass normally used today to manufacture fibers, a noticeable softening of the glass occurs at a glass softening temperature of about 1soo to 2200 K. Glass softening at the glass ~oftening temperature is used to draw a preform into a thin glass fiber. To that end, the preform is heated in a drawing oven, which can be a graphite resistance oven, e.g., wherein a heating element ;~
under protective gas i5 brought to the glass softening ~ ;
temperature by pulsating direct or alternating current, or an induction oven, in which a tube, e.g., made of zirconium oxide or graphite, is brought to the glass softening temperature by an electromagnetic field.
The chimney effect in the circular or tube-shaped internal space of such known drawing ovens produces an air or gas flow through the inside of the oven when at ~;
the operating temperatures required for fiber ~ -~
manufacture. After the preform is introduced into the oven, the local conditions inside the oven lead to turbulence in this air or gas flow, which in turn has -~
detrimental effects on the fiber damping and the fiber strength. Such turbulence still exists when a protective gas is blown from the top through the inside of the ` `
drawing oven. The turbulence of the protective gas results from the temperature of the protective gas ~ -increasing from an upper inlet area of the oven to about the middle of a drawing area, i.e., the production area of the oven containing the heated end of the preform where the fiber is pulled or drawn, and decreasing aga~n : ' 21358~ ~
PATENT
in an outlet area. At the same time, an increase in the cross section of the area adjacent to tha heated end of the preform takes place in the drawing direction of the fiber in an annular gap between the preform surface and the internal oven wall. The increased cross-sectional ;~
area of the annular gap results from the reduced cross~
section of the preform as it is drawn down into a fiber.
The increased cross-sectional area of the annular gap causes a change in the thus far mostly laminar flow of the gas being introduced from above, resulting in a ~`
turbulent flow due to the decrease of the flow speed, precisely in this sensitive fiber drawing area. ;;;:
Particles which may be carried in with the mostly laminar flow are deposited on the heated end of the preform or on the fiber being pulled from it. Such particles are the ~i cause of latar fiber breakage or possible defects in the glass surface or the fiber surface.
Summary of the Invention ~-;
An object of the invention i~ the prevention of gas turbulence inside a drawing oven, or to limit the j~"
influence of gas turbulence to an insignificant effect on the quality of an optical fiber which is drawn from a ;~
preform in the drawing oven.
It has been found that the foregoing ob;ects can be ` -readily attained by stabilizing the flow of a protective -~
gas surrounding the preform in the qrawing area o~ the r~
drawing oven with an additional flushing gas. This ~ ~ ;
additional flushing gas, which i5 guided into the drawing : ~;
area, prevents a separation of the basically laminar flow of the protective gas introduced into the oven space from above as it flo~s down in the annular gap between the extexnal preform surface and the internal oven wall, in ' ~ ~
2135~3~
PATENT
~25010 the free cross-section which is steadily increasing from the heated end of the preform down to the fibar cross section.
It has proven effective for carrying out the invention to allow the additional flushing gas to impa~t the protective gas surrounding the preform crosswise to its flow direction. Another advantageous possibility is to let the additional flu hing gas have an axial component when flowing into the drawing area, where the axial component becomes zero in the extreme case. ;;~
, " ': ' '; ~,.. ...
In one embodiment of the invention, the additional flushing gas iB supplied into the oven space~in the opposite direction to the ~low direction of the protective gas surrounding the preform. The additional ~lushing gas is first ~upplied in the opposite direction ;~
of the gas surrounding the preform, i.e., in the area t~,"~, ,'~ ,,.,.,',~: "' where the fiber is being drawn from the heated lower end of the preform, and then the flow direction of the,~
flushing gas is turned around into the direction in which `~
the fiber is drawn.
According to the inventionl the additional flushing ' gas results in a stabilization of the protective gas that is introduced into the oven space in the drawing direction. The ~low speed of the additional flushing gas must therefore be selected so that the stabilization effect is achieved, but no additional disturbing impulse is exerted on the flowing gas. For this reason, the flow speed of the additional flushing gas can at ~ost be equal to the flow speed of the protective gas surrounding ~-the pre~orm in the drawing direction.
- , .
.:: . . .
~ ~ ~ 4 ~
2~3~
". ~
PATENT
925-~10-1 To carry out the method of the invention, a vertical drawing oven is used, having a heated cy:Lindrical wall surrounding the preform. To heat the glass preform used for drawing optical fibers, induction ovens are known, ~ - -which comprise an internal heating tube Tnade of an electrically conductive high-temperature resistant material, e.g., graphite, for containing the glass preform, heat insulation on the outside of the internal heating tube, and an outer glass tube surrounded by an induction coil. A protective gas flow is introduced into the oven space from above. In accordance with the invention, the oven space contains additional gas injection nozzles in the drawing area of the preform, preferably distributed around the circumference, for the introduction of an additional flushing gas flow, to achieve a laminar flow of the protective gases in the oven space that receives the preform and the drawn fibers. ~ `I; s`
In an advantageous variation of the invention, a ( guide tube, which concentrically surrounds the already drawn fiber, protrudes into the described drawing oven from below. The external surface of the guide tube ~orms an annular gap with the surrounding wall of the drawing oven, and the additional flushing gas is provided in the annular gap. The guide tube has the further effect of providing additional tempering of the just drawn fiber before it leaves the inner oven space through the outlet end of the drawing oven.
Since it is important for the invention to stabilize the gas flow o~ protective gases in the drawing area, as explained earlier, the axial length of the guide tube is selected so that it reaches into the drawing area. Since the guide tube is also exposed to the high-temperature 2 1 3 ~ 8 3 ~
PATENT
area, it is an advantage if the chosen guide tube material is the same as that of the surrounding tube wall, for example graphite. -The foregoing and other objects, features and advantages of the present invention will become more ;~ ~-apparent in light of the following detailcd description ~ -of exemplary embodiments thereof, as illustra~ed in the ~ - -accompanying drawings.
'~
~rie~ Descrip~ion of the Drawings ; ~ ;
9 .. , ~ :
Figure 1 is a cross-sectional view of a drawing oven having stabilized flow of protective gases in accordance with the invention; and Figure 2 is a cross-sectional view of an alternative embodiment of the drawing oven in accordance with the invention.
Detailed Description Qf the Invention ~
~ , " ', The drawing oven illustrated in Figure 1 comprises a cylindrical "susceptor" 1, an outwardly adjacent layer of in~ulation 2 which is also cylindrical, and a surrounding quartz tube 3. In the illustrated configuration, the ~ ~
susceptor 1 and the insulation 2 are made of graphite. ~ ~ -The susceptor, which acts as a heating tube, can also be made of zirconium oxide stabilized with yttrium. The heating tube 1 can be viewed as a short-circuited wind ing ~ ;
of an induation coil 4. A concentric external wall 5 closes off the drawing oven on the outside, in conjunction with a flange-like bottom plate 6 and an oven cover 7.
6 --~
;; :,.:~
:
2 1 3 5 8 3 ~
PATENT
A preform 9 is introduced into the oven space 8 through the oven cover 7, from which, as illustrated, the fiber 11 is drawn from the heated lower end of the preform which is referred to as a "root" or "draw down"
portion 10 of the preform. The draw down portion 10 has an inverted dome or onion shape. A seal 12 seals the oven space 8 in the cover area, and the bottom plate 6 terminates in a flange 13. As indicated by arrows 14, a protective gas, for example argon, nitrogen or similar, -- ~
is injected through not illustrated nozzles in the oven ; ~ ;
cover 7. The protective gas has a laminar flow and flows ~;
around the preform 9 in the drawing direction of the fiber 11. In the high-temperature area of the oven, i which is the area where the draw down portion 10 is `
formed by drawing the fiber 11, the temperature of the ~ i~
protective gas increases, at the same time the open cross section of the oven also increases, due to the reduction of the preform cross section in the drawing area, ;-resulting in turbulence of the protective gas. Such ~ ;
turbulence in this area during operation cannot be tolerated since this turbulence is connected to the danger of glass surface contamination. The invention provides for the introduction of an additional flushing ~i gas in this area, to prev0nt the gas flow 14 of the protective gas surrounding the preform from lifting, and ;~
thereby stabilizing it. To achieve this, additional gas guidance channels 15 are provided, which are advantageously distributed around the circumference of the preform 9 and radially introduce the flushing gas into the oven space 8.
., :-To prevent turbulence caused by the flushing gas, the gas flow speed of the flushing gas may be limited to -a speed less than or equal to the gas flow speed of the protective gas.
PATENT
Another advantageous configuration for carrying out the method of the invention is illustrated in Figure 2. ~ -The construction of the oven itself essentially corresponds to the con~iguration depictecl in Pigure 1.
~he susceptor 1, is surrounded by the adjacent, concentric layer of insulation 2 which ic; surrounded by the surrounding quartz glass tube 3. The induction coil --4 for heating the susceptor 1, which functions as the heating tube, is contained within the concentric external wall 5. The bottom plate 6 and the oven cover 7 of the ~ `
drawing oven are further developed in accordance with thi~ embodiment of the invention.
,:' " ;:., ' ',,',:
. , .
In this embodiment as well, a preform 9 is 15 introduced from above into the oven space 8, where the ~iber 11 is drawn from the drawing dome 10 after the glass material of the preform 9 has been brought to the softened flow condition. To prevent the protective gas 14, which is also introduced from above through not 20 illustrated guide nozzles, from changing from the laminar ;
flow into a turbulent flow in the drawing area, an additional ~lushing gas 16 is introduced from below in the opposite direction of the protective gas flow ~4.
The additional flushing gas 16 ~ills the oven space 8 25 created by the reduction of the preform's cross section in the area of the draw down portion 10, thereby ~
stabilizing the protective gas flow in this area. ~ ;
A particularly useful method of introducing the flushing gas 16 is shown in Figure 2, wherein an additional guide tube 17, made of graphite for example, is introduced into the oven space 8 from below. The additional guide tube 17 reaches into the drawing area, i.e. into the high-temperature area of the oven. At the upper end of the additional guide tube 17, the direction 2 ~ 3 5 8 3 ~
PATENT
of the additional flushing gas 16 is reversed ~y the protective gas 14 coming from above, and is guided downwards on the inside of the guide tube 17, where it practically encloses the fiber 11. The combination of the protective gas 14 and the additional ~lushing gas 16 fills the enlarged open cross-section o~ the oven space 8 , ~, in the drawing area, thus preventing the creation of turbulence. ;
The invention is not restricted to the illustrated ~ -configuration examples, insofar as other oven configurations may also be used. It will be under~tood ;~
by those skilled in the art that the invention can be used for the indicated purpose in any drawing oven in which protective or flushing gases are introduced into ~ ~ ~
the inside of the oven space. ~ -. ~
Although the invention has been described and illustrated with respect to exemplary embodiments thereof, it should be understood by those skilled in the art that the foregoing and various other change~
omis~ions and additions may be made therein and thereto, without departing from the spirit and scope of the present invention.
I Cl~im:
PATENT
925-01~1 ~thod aIId D6~vic~ for M~nuf2~¢turing a~ Optical ~ibsr ~., ~aa~ Lu~d of the I~v~ntion Field of the Invention The present invention concerns optical fibers and, more particularly, a method for manufacturing an optical fiber, whereby the fiber is drawn from one end of a preform heated to the glass softening temperature, ~hile a gas flaws around the preform and its flow direction corresponds to the fiber drawing direction.
Description of the Prior Art ; `
The direct manu~acture of an optical fiber having the required fiber profile from different types of glass -is not possible because of the small outside dimensions of the optiaal fiber. The manufacture of an optical fiber is therefore based on a preform with a diameter in the centimater range, which can be produced in several;;
different ways, e.g., with multimode-gradients or single mode fibers, depending on the type of optical fiber desired. One method of producing a preform is the chamical vapor deposition method ~CVD-method) which involves applying a core glass material to the inner sur~aces of a quartz glass tube by chemical deposition from the vapor phase of the core glass material onto the i inside surfaces of the quartz glass tube~ which is subsequently collapsed into a preform. The Outside Vapor Deposition method (OVD-method) involves the outside `
coating of a glass core vith a glass material by deposition from the vapor phase of the glass material on the outside of the glass core. The Vapor Axial ~ -~
Deposition method ~V~D-method) provides for the axial 2 1 3 ~ ~ 3 ~
PATENT -925-01~1 coating of a glass core with a glass material by deposition from the vapor phase of the glass material axially along the glass core. ;~
Glass is an amorphous material, which can be brought to a low viscosity condition by heating. With the quartz glass normally used today to manufacture fibers, a noticeable softening of the glass occurs at a glass softening temperature of about 1soo to 2200 K. Glass softening at the glass ~oftening temperature is used to draw a preform into a thin glass fiber. To that end, the preform is heated in a drawing oven, which can be a graphite resistance oven, e.g., wherein a heating element ;~
under protective gas i5 brought to the glass softening ~ ;
temperature by pulsating direct or alternating current, or an induction oven, in which a tube, e.g., made of zirconium oxide or graphite, is brought to the glass softening temperature by an electromagnetic field.
The chimney effect in the circular or tube-shaped internal space of such known drawing ovens produces an air or gas flow through the inside of the oven when at ~;
the operating temperatures required for fiber ~ -~
manufacture. After the preform is introduced into the oven, the local conditions inside the oven lead to turbulence in this air or gas flow, which in turn has -~
detrimental effects on the fiber damping and the fiber strength. Such turbulence still exists when a protective gas is blown from the top through the inside of the ` `
drawing oven. The turbulence of the protective gas results from the temperature of the protective gas ~ -increasing from an upper inlet area of the oven to about the middle of a drawing area, i.e., the production area of the oven containing the heated end of the preform where the fiber is pulled or drawn, and decreasing aga~n : ' 21358~ ~
PATENT
in an outlet area. At the same time, an increase in the cross section of the area adjacent to tha heated end of the preform takes place in the drawing direction of the fiber in an annular gap between the preform surface and the internal oven wall. The increased cross-sectional ;~
area of the annular gap results from the reduced cross~
section of the preform as it is drawn down into a fiber.
The increased cross-sectional area of the annular gap causes a change in the thus far mostly laminar flow of the gas being introduced from above, resulting in a ~`
turbulent flow due to the decrease of the flow speed, precisely in this sensitive fiber drawing area. ;;;:
Particles which may be carried in with the mostly laminar flow are deposited on the heated end of the preform or on the fiber being pulled from it. Such particles are the ~i cause of latar fiber breakage or possible defects in the glass surface or the fiber surface.
Summary of the Invention ~-;
An object of the invention i~ the prevention of gas turbulence inside a drawing oven, or to limit the j~"
influence of gas turbulence to an insignificant effect on the quality of an optical fiber which is drawn from a ;~
preform in the drawing oven.
It has been found that the foregoing ob;ects can be ` -readily attained by stabilizing the flow of a protective -~
gas surrounding the preform in the qrawing area o~ the r~
drawing oven with an additional flushing gas. This ~ ~ ;
additional flushing gas, which i5 guided into the drawing : ~;
area, prevents a separation of the basically laminar flow of the protective gas introduced into the oven space from above as it flo~s down in the annular gap between the extexnal preform surface and the internal oven wall, in ' ~ ~
2135~3~
PATENT
~25010 the free cross-section which is steadily increasing from the heated end of the preform down to the fibar cross section.
It has proven effective for carrying out the invention to allow the additional flushing gas to impa~t the protective gas surrounding the preform crosswise to its flow direction. Another advantageous possibility is to let the additional flu hing gas have an axial component when flowing into the drawing area, where the axial component becomes zero in the extreme case. ;;~
, " ': ' '; ~,.. ...
In one embodiment of the invention, the additional flushing gas iB supplied into the oven space~in the opposite direction to the ~low direction of the protective gas surrounding the preform. The additional ~lushing gas is first ~upplied in the opposite direction ;~
of the gas surrounding the preform, i.e., in the area t~,"~, ,'~ ,,.,.,',~: "' where the fiber is being drawn from the heated lower end of the preform, and then the flow direction of the,~
flushing gas is turned around into the direction in which `~
the fiber is drawn.
According to the inventionl the additional flushing ' gas results in a stabilization of the protective gas that is introduced into the oven space in the drawing direction. The ~low speed of the additional flushing gas must therefore be selected so that the stabilization effect is achieved, but no additional disturbing impulse is exerted on the flowing gas. For this reason, the flow speed of the additional flushing gas can at ~ost be equal to the flow speed of the protective gas surrounding ~-the pre~orm in the drawing direction.
- , .
.:: . . .
~ ~ ~ 4 ~
2~3~
". ~
PATENT
925-~10-1 To carry out the method of the invention, a vertical drawing oven is used, having a heated cy:Lindrical wall surrounding the preform. To heat the glass preform used for drawing optical fibers, induction ovens are known, ~ - -which comprise an internal heating tube Tnade of an electrically conductive high-temperature resistant material, e.g., graphite, for containing the glass preform, heat insulation on the outside of the internal heating tube, and an outer glass tube surrounded by an induction coil. A protective gas flow is introduced into the oven space from above. In accordance with the invention, the oven space contains additional gas injection nozzles in the drawing area of the preform, preferably distributed around the circumference, for the introduction of an additional flushing gas flow, to achieve a laminar flow of the protective gases in the oven space that receives the preform and the drawn fibers. ~ `I; s`
In an advantageous variation of the invention, a ( guide tube, which concentrically surrounds the already drawn fiber, protrudes into the described drawing oven from below. The external surface of the guide tube ~orms an annular gap with the surrounding wall of the drawing oven, and the additional flushing gas is provided in the annular gap. The guide tube has the further effect of providing additional tempering of the just drawn fiber before it leaves the inner oven space through the outlet end of the drawing oven.
Since it is important for the invention to stabilize the gas flow o~ protective gases in the drawing area, as explained earlier, the axial length of the guide tube is selected so that it reaches into the drawing area. Since the guide tube is also exposed to the high-temperature 2 1 3 ~ 8 3 ~
PATENT
area, it is an advantage if the chosen guide tube material is the same as that of the surrounding tube wall, for example graphite. -The foregoing and other objects, features and advantages of the present invention will become more ;~ ~-apparent in light of the following detailcd description ~ -of exemplary embodiments thereof, as illustra~ed in the ~ - -accompanying drawings.
'~
~rie~ Descrip~ion of the Drawings ; ~ ;
9 .. , ~ :
Figure 1 is a cross-sectional view of a drawing oven having stabilized flow of protective gases in accordance with the invention; and Figure 2 is a cross-sectional view of an alternative embodiment of the drawing oven in accordance with the invention.
Detailed Description Qf the Invention ~
~ , " ', The drawing oven illustrated in Figure 1 comprises a cylindrical "susceptor" 1, an outwardly adjacent layer of in~ulation 2 which is also cylindrical, and a surrounding quartz tube 3. In the illustrated configuration, the ~ ~
susceptor 1 and the insulation 2 are made of graphite. ~ ~ -The susceptor, which acts as a heating tube, can also be made of zirconium oxide stabilized with yttrium. The heating tube 1 can be viewed as a short-circuited wind ing ~ ;
of an induation coil 4. A concentric external wall 5 closes off the drawing oven on the outside, in conjunction with a flange-like bottom plate 6 and an oven cover 7.
6 --~
;; :,.:~
:
2 1 3 5 8 3 ~
PATENT
A preform 9 is introduced into the oven space 8 through the oven cover 7, from which, as illustrated, the fiber 11 is drawn from the heated lower end of the preform which is referred to as a "root" or "draw down"
portion 10 of the preform. The draw down portion 10 has an inverted dome or onion shape. A seal 12 seals the oven space 8 in the cover area, and the bottom plate 6 terminates in a flange 13. As indicated by arrows 14, a protective gas, for example argon, nitrogen or similar, -- ~
is injected through not illustrated nozzles in the oven ; ~ ;
cover 7. The protective gas has a laminar flow and flows ~;
around the preform 9 in the drawing direction of the fiber 11. In the high-temperature area of the oven, i which is the area where the draw down portion 10 is `
formed by drawing the fiber 11, the temperature of the ~ i~
protective gas increases, at the same time the open cross section of the oven also increases, due to the reduction of the preform cross section in the drawing area, ;-resulting in turbulence of the protective gas. Such ~ ;
turbulence in this area during operation cannot be tolerated since this turbulence is connected to the danger of glass surface contamination. The invention provides for the introduction of an additional flushing ~i gas in this area, to prev0nt the gas flow 14 of the protective gas surrounding the preform from lifting, and ;~
thereby stabilizing it. To achieve this, additional gas guidance channels 15 are provided, which are advantageously distributed around the circumference of the preform 9 and radially introduce the flushing gas into the oven space 8.
., :-To prevent turbulence caused by the flushing gas, the gas flow speed of the flushing gas may be limited to -a speed less than or equal to the gas flow speed of the protective gas.
PATENT
Another advantageous configuration for carrying out the method of the invention is illustrated in Figure 2. ~ -The construction of the oven itself essentially corresponds to the con~iguration depictecl in Pigure 1.
~he susceptor 1, is surrounded by the adjacent, concentric layer of insulation 2 which ic; surrounded by the surrounding quartz glass tube 3. The induction coil --4 for heating the susceptor 1, which functions as the heating tube, is contained within the concentric external wall 5. The bottom plate 6 and the oven cover 7 of the ~ `
drawing oven are further developed in accordance with thi~ embodiment of the invention.
,:' " ;:., ' ',,',:
. , .
In this embodiment as well, a preform 9 is 15 introduced from above into the oven space 8, where the ~iber 11 is drawn from the drawing dome 10 after the glass material of the preform 9 has been brought to the softened flow condition. To prevent the protective gas 14, which is also introduced from above through not 20 illustrated guide nozzles, from changing from the laminar ;
flow into a turbulent flow in the drawing area, an additional ~lushing gas 16 is introduced from below in the opposite direction of the protective gas flow ~4.
The additional flushing gas 16 ~ills the oven space 8 25 created by the reduction of the preform's cross section in the area of the draw down portion 10, thereby ~
stabilizing the protective gas flow in this area. ~ ;
A particularly useful method of introducing the flushing gas 16 is shown in Figure 2, wherein an additional guide tube 17, made of graphite for example, is introduced into the oven space 8 from below. The additional guide tube 17 reaches into the drawing area, i.e. into the high-temperature area of the oven. At the upper end of the additional guide tube 17, the direction 2 ~ 3 5 8 3 ~
PATENT
of the additional flushing gas 16 is reversed ~y the protective gas 14 coming from above, and is guided downwards on the inside of the guide tube 17, where it practically encloses the fiber 11. The combination of the protective gas 14 and the additional ~lushing gas 16 fills the enlarged open cross-section o~ the oven space 8 , ~, in the drawing area, thus preventing the creation of turbulence. ;
The invention is not restricted to the illustrated ~ -configuration examples, insofar as other oven configurations may also be used. It will be under~tood ;~
by those skilled in the art that the invention can be used for the indicated purpose in any drawing oven in which protective or flushing gases are introduced into ~ ~ ~
the inside of the oven space. ~ -. ~
Although the invention has been described and illustrated with respect to exemplary embodiments thereof, it should be understood by those skilled in the art that the foregoing and various other change~
omis~ions and additions may be made therein and thereto, without departing from the spirit and scope of the present invention.
I Cl~im:
Claims (22)
1. A method for manufacturing an optical fiber comprising the steps of:
providing a preform;
heating an end of said preform to above a glass softening temperature;
drawing an optical fiber in a fiber drawing direction from said heated end of said preform;
providing a protective gas flow in a drawing area where said optical fiber is being drawn, said protective gas flow having a protective gas flow direction corresponding to said fiber drawing direction; and stabilizing said protective gas flow in said drawing area with an additional flushing gas flow.
providing a preform;
heating an end of said preform to above a glass softening temperature;
drawing an optical fiber in a fiber drawing direction from said heated end of said preform;
providing a protective gas flow in a drawing area where said optical fiber is being drawn, said protective gas flow having a protective gas flow direction corresponding to said fiber drawing direction; and stabilizing said protective gas flow in said drawing area with an additional flushing gas flow.
2. A method as claimed in claim 1, wherein said additional flushing gas flow impacts said protective gas crosswise to said protective gas flow direction.
3. A method as claimed in claim 2, wherein said additional flushing gas flow is chosen from a group consisting of air, nitrogen and an inert gas.
4. A method as claimed in claim 2, wherein a gas flow speed of said additional flushing gas flow is less than or equal to a gas flow speed of said protective gas flow.
5. A method as claimed in claim 1, wherein said additional flushing gas flow has a flushing gas flow direction opposite to said protective gas flow direction.
6. A method as claimed in claim 5, wherein said additional flushing gas flow is chosen from a group consisting of air, nitrogen and an inert gas.
7. A method as claimed in claim 5, wherein a gas flow speed of said additional flushing gas flow is less than or equal to a gas flow speed of said protective gas flow.
8. A method as claimed in claim 1, wherein said additional flushing gas flow is first guided in an additional flushing gas flow direction opposite to said protective gas flow direction, and then said additional flushing gas flow direction is reversed into said fiber drawing direction in said drawing area.
9. A method as claimed in claim 8, wherein said additional flushing gas flow is chosen from a group consisting of air, nitrogen and an inert gas.
10. A method as claimed in claim 8, wherein a gas flow speed of said additional flushing gas flow is less than or equal to a gas flow speed of said protective gas flow.
11. A device for manufacturing an optical fiber from a preform, comprising:
a vertically oriented drawing oven having a cylindrical heating tube for surrounding the preform and heating an end of the preform to above a glass softening temperature for drawing an optical fiber in a fiber drawing direction from the heated end of the preform, said drawing oven having a drawing area where said optical fiber is drawn from the heated end of the preform;
means for providing a protective gas flow in said drawing area surrounding the preform and said optical fiber, said protective gas flow having a protective gas flow direction corresponding to said fiber drawing direction; and means for providing an additional flushing gas flow in said drawing area for stabilizing said protective gas flow in said drawing area.
a vertically oriented drawing oven having a cylindrical heating tube for surrounding the preform and heating an end of the preform to above a glass softening temperature for drawing an optical fiber in a fiber drawing direction from the heated end of the preform, said drawing oven having a drawing area where said optical fiber is drawn from the heated end of the preform;
means for providing a protective gas flow in said drawing area surrounding the preform and said optical fiber, said protective gas flow having a protective gas flow direction corresponding to said fiber drawing direction; and means for providing an additional flushing gas flow in said drawing area for stabilizing said protective gas flow in said drawing area.
12. A device as claimed in claim 11, further comprising a guide tube protruding into said drawing oven from below for concentrically surrounding said optical fiber drawn from the preform, said guide tube being concentrically positioned with respect to said heating tube, and said additional flushing gas flow being provided an annular gap formed in said drawing oven by an external surface of said guide tube and an internal surface of said heating tube.
13. A device as claimed in claim 12, wherein said guide tube extends into said drawing area.
14. A device as claimed in claim 13, wherein said additional flushing gas flow is first guided a flushing gas flow direction opposite to the gas flow direction of said protective gas, and then said flushing gas flow direction is reversed at an end of said guide tube in said drawing area into said fiber drawing direction.
15. A device as claimed in claim 12, wherein said additional flushing gas flow is chosen from a group consisting of air, nitrogen and an inert gas.
16. A device as claimed in claim 12, wherein a gas flow speed of said additional flushing gas flow is less than or equal to a gas flow speed of said protective gas flow.
17. A device as claimed in claim 12, wherein said guide tube is made of a high-temperature resistant material.
18. A device as claimed in claim 17, wherein said heating tube and said guide tube are made of graphite.
19. A device as claimed in claim 11, wherein said means for providing additional flushing gas flow are gas injection nozzles formed in said heating tube, said gas injection nozzles being distributed around the circum-ference of said heating tube for providing said additional flushing gas flow.
20, A device as claimed in claim 19, wherein said gas flow nozzles direct additional flushing gas flow to impact said protective gas flow crosswise to said protective gas flow direction.
21. A device as claimed in claim 19, wherein said additional flushing gas flow is chosen from a group consisting of air, nitrogen and an inert gas.
22. A device as claimed in claim 19, wherein a gas flow speed of said additional flushing gas flow is less than or equal to a gas flow speed of said protective gas flow.
Applications Claiming Priority (2)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| DE4339077A DE4339077C2 (en) | 1993-11-16 | 1993-11-16 | Method of drawing an optical fiber and device for carrying it out |
| DEP4339077.3 | 1993-11-16 |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| CA2135834A1 true CA2135834A1 (en) | 1995-05-17 |
Family
ID=6502704
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CA002135834A Abandoned CA2135834A1 (en) | 1993-11-16 | 1994-11-15 | Method and device for manufacturing an optical fiber |
Country Status (6)
| Country | Link |
|---|---|
| US (1) | US5545246A (en) |
| EP (1) | EP0653383B1 (en) |
| CA (1) | CA2135834A1 (en) |
| DE (2) | DE4339077C2 (en) |
| DK (1) | DK0653383T3 (en) |
| FI (1) | FI945372A (en) |
Families Citing this family (15)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| EP0849232B1 (en) * | 1996-12-17 | 1999-05-26 | Alcatel | Process and apparatus for drawing an optical fibre from a preform |
| EP0867414A1 (en) * | 1997-03-27 | 1998-09-30 | Alcatel | Graphite liner and heating element impregnated with vitreous carbon for a furnace for drawing optical fibers |
| JP3159116B2 (en) * | 1997-04-11 | 2001-04-23 | 住友電気工業株式会社 | Stretching machine and stretching method for glass base material |
| EP1084085A1 (en) * | 1998-06-13 | 2001-03-21 | Alcatel | Method and device for drawing an optical fibre from a preform |
| DE19900375A1 (en) * | 1999-01-08 | 2000-07-13 | Alcatel Sa | Device for pulling a fiber |
| US6354113B2 (en) | 1999-01-20 | 2002-03-12 | Alcatel | Fiber optic draw furnace featuring a fiber optic preform heating and fiber drawing programmable logic controller |
| DK1181255T3 (en) * | 1999-05-10 | 2005-12-12 | Pirelli & C Spa | Method and induction furnace for drawing large diameter preforms for optical fibers |
| CN1282620C (en) * | 1999-05-27 | 2006-11-01 | 住友电气工业株式会社 | Production device and method for optical fiber |
| JP4356155B2 (en) * | 1999-10-12 | 2009-11-04 | 住友電気工業株式会社 | Optical fiber manufacturing method |
| CN1429181A (en) * | 2000-03-10 | 2003-07-09 | 流体聚焦公司 | Methods for producing optical fiber by focusing high viscosity liquid |
| US20020178762A1 (en) * | 2001-06-01 | 2002-12-05 | Foster John D. | Methods and apparatus for forming and controlling the diameter of drawn optical glass fiber |
| KR100545814B1 (en) * | 2002-08-31 | 2006-01-24 | 엘에스전선 주식회사 | Optical Fiber Edge Melting Furnace and Optical Fiber Edge Cutting Method Using The Same |
| WO2005049516A1 (en) * | 2003-11-18 | 2005-06-02 | Fujikura Ltd. | Method of drawing bare optical fiber, process for producing optical fiber strand and optical fiber strand |
| WO2013105302A1 (en) * | 2012-01-10 | 2013-07-18 | 住友電気工業株式会社 | Optical fiber production method and production device, and optical fiber |
| US10308544B2 (en) * | 2015-10-13 | 2019-06-04 | Corning Incorporated | Gas reclamation system for optical fiber production |
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| US4101300A (en) * | 1975-11-27 | 1978-07-18 | Hitachi, Ltd. | Method and apparatus for drawing optical fiber |
| US4030901A (en) * | 1976-07-19 | 1977-06-21 | Bell Telephone Laboratories, Incorporated | Method for drawing fibers |
| US4249925A (en) * | 1978-05-12 | 1981-02-10 | Fujitsu Limited | Method of manufacturing an optical fiber |
| FR2515693B1 (en) * | 1981-11-03 | 1985-10-11 | Thomson Csf | METHOD FOR MANUFACTURING AN OBJECT HAVING A CHIRAL STRUCTURE ARISING FROM A SOURCE OF FORMABLE MATERIAL AND DEVICE USING THE SAME |
| US4437870A (en) * | 1981-11-05 | 1984-03-20 | Corning Glass Works | Optical waveguide fiber cooler |
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| US4440556A (en) * | 1982-06-23 | 1984-04-03 | International Telephone And Telegraph Corporation | Optical fiber drawing using plasma torch |
| NL8203843A (en) * | 1982-10-04 | 1984-05-01 | Philips Nv | METHOD AND APPARATUS FOR PULLING AN OPTICAL FIBER FROM A FIXED FORM CONSISTING IN MAIN CASE OF SIO2 AND Doped SIO2. |
| GB2159812B (en) * | 1984-06-01 | 1988-02-10 | Stc Plc | Manufacturing optical fibre |
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-
1993
- 1993-11-16 DE DE4339077A patent/DE4339077C2/en not_active Expired - Fee Related
-
1994
- 1994-10-13 DE DE59406011T patent/DE59406011D1/en not_active Expired - Lifetime
- 1994-10-13 EP EP94116152A patent/EP0653383B1/en not_active Expired - Lifetime
- 1994-10-13 DK DK94116152T patent/DK0653383T3/en active
- 1994-11-08 US US08/336,190 patent/US5545246A/en not_active Expired - Lifetime
- 1994-11-15 FI FI945372A patent/FI945372A/en unknown
- 1994-11-15 CA CA002135834A patent/CA2135834A1/en not_active Abandoned
Also Published As
| Publication number | Publication date |
|---|---|
| DE4339077A1 (en) | 1995-05-18 |
| DE4339077C2 (en) | 1997-03-06 |
| DK0653383T3 (en) | 1999-03-08 |
| EP0653383B1 (en) | 1998-05-20 |
| EP0653383A1 (en) | 1995-05-17 |
| FI945372A0 (en) | 1994-11-15 |
| FI945372A (en) | 1995-05-17 |
| DE59406011D1 (en) | 1998-06-25 |
| US5545246A (en) | 1996-08-13 |
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Legal Events
| Date | Code | Title | Description |
|---|---|---|---|
| EEER | Examination request | ||
| FZDE | Discontinued |