JP2005089241A - Optical fiber preform, optical fiber, method of manufacturing optical fiber, and method of manufacturing optical fiber preform - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To efficiently manufacture a high quality optical fiber while suppressing the increase of cost. <P>SOLUTION: A dummy rod 13a is connected to the upper end of a glass rod 12 and a dummy rod 13b is connected to the lower end thereof through a connection rod 14. A combustion gas and a glass raw material are blown on the outer periphery of the glass rod 12 from the upper end side by a burner while rotating the vertically supported glass rod 12. As a result, a porous fine particle deposited body 15 produced by depositing the glass fine particles produced by hydrolyzing the glass raw material in oxyhydrogen flame produced by the combustion of the combustion gas on the outer periphery of the glass rod 12 is formed. After that, the glass fine particle deposited body 15 is heated to be made transparent to be used as the optical fiber preform 10 and the optical fiber preform 10 is softened by heating and drawn to manufacture the optical fiber. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

  The present invention relates to an optical fiber preform manufactured by depositing glass particles while spraying glass particles on a glass rod, a manufacturing method thereof, an optical fiber manufactured by drawing an optical fiber preform, and a manufacturing method thereof.

  In general, an optical fiber having a core and a clad formed around the core is manufactured by heating a transparent glass preform for an optical fiber to make the optical fiber preform transparent. Manufactured by drawing materials. Examples of a method for producing the optical fiber preform include a VAD method (Vapor phase Axial Deposition). In this VAD method, a combustion gas and a glass raw material are blown out from a burner, and the glass raw material is hydrolyzed in an oxyhydrogen flame generated by the combustion of the combustion gas. As shown in FIG. A deposit 3 made of glass fine particles is deposited on a glass rod 2 to which 1 is connected, and a composite of the glass fine particle deposit thus obtained is heated to be transparent, thereby making an optical fiber preform. 5 is obtained.

  Here, a technique is known in which a dummy rod 1 having a viscosity at the time of high-temperature heating that is smaller than that of pure quartz and larger than that of the lowest viscosity portion of the glass rod 2 is known. In the optical fiber preform 5 using the glass rod 2 connected to the dummy rod 1, the generation of bubbles in the vicinity of the boundary between the glass rod 2 and the dummy rod 1 during drawing is suppressed, and the optical fiber is broken during drawing. Can be prevented (see Patent Document 1).

JP 2001-335338 A

  By the way, the optical fiber preform 5 has a predetermined outer diameter in the central portion in the longitudinal direction, and is formed into a tapered shape continuously at both ends of the effective portion 3a that is made into an optical fiber by drawing and the effective portion 3a. The non-effective portions 3b and 3b that are not used as optical fibers. In FIG. 7, the outer periphery of the glass rod 2 is an effective portion 3a having a predetermined diameter, and the outer periphery of the dummy rods 1 and 1 is tapered non-effective portions 3b and 3b.

  However, when this optical fiber preform 5 is drawn, the diameter of the drawn portion of the effective portion 3a varies greatly in the vicinity of the connection portion with the dummy rod 1 due to the difference in viscosity between the glass rod 2 and the dummy rod 1 at the time of drawing. As a result, useless parts that do not become products are produced, and the yield of good optical fibers is reduced.

  Here, in the above technique using the dummy rod 1 having a viscosity at the time of high temperature heating smaller than that of pure quartz and larger than the viscosity of the glass rod 2 having the smallest viscosity, the dummy rod 1 is used. At the time of production, a step of mixing an additive such as germanium, chlorine, or fluorine into quartz glass becomes necessary, and the production efficiency is lowered. Further, the cost is increased by the amount of the additive as compared with the case where the pure quartz dummy rod 1 is used, and the manufacturing cost of the optical fiber itself is increased.

  The present invention has been made in view of the above circumstances, and an optical fiber preform capable of efficiently obtaining a good optical fiber, a manufacturing method thereof, and an optical fiber manufactured from the optical fiber preform, while suppressing costs. The purpose is to provide.

  In order to achieve the above object, an optical fiber preform of the present invention includes an inner glass body having a glass rod, a buffer member having one end connected to the glass rod, and a dummy rod connected to the other end of the buffer member. And an outer glass body formed on the outer periphery of the inner glass body, and the outer glass body has an effective portion having a predetermined outer diameter and an ineffective portion having a tapered shape, The buffer member is connected to the glass rod in the vicinity of a connection portion between the effective portion and the ineffective portion.

  Thus, according to the above optical fiber, the buffer member that reduces the outer diameter fluctuation of the optical fiber at the time of drawing as much as possible is provided in the vicinity of the boundary between the effective portion and the ineffective portion, so that a good optical fiber can be efficiently used. An optical fiber preform that can be obtained can be manufactured.

Specifically, the drawing is transferred from the ineffective portion to the effective portion by configuring the buffer member so that the viscosity of the buffer member during drawing is smaller than that of the dummy rod and equal to or higher than that of the glass rod. In doing so, the outer diameter fluctuation of the optical fiber due to the difference in viscosity can be minimized as compared with the case where the dummy rod and the glass rod are directly connected.
Thereby, even if an inexpensive pure quartz dummy rod is used, a good optical fiber can be efficiently obtained from the effective portion of the optical fiber preform.

  In addition, since it is not necessary to add an additive to the dummy rod in order to bring the viscosity of the dummy rod closer to that of the glass rod, the additive is unnecessary, and the step of adding the additive is also unnecessary, which is favorable while suppressing the manufacturing cost. The optical fiber can be drawn.

The buffer member may be a glass rod made of the same material as the glass rod.
Moreover, it is preferable that the volume of the ineffective part in the arrangement | positioning part of a buffer member is 1/2 or less of the volume of the whole ineffective part.

  The optical fiber manufacturing method of the present invention is an optical fiber manufacturing method for drawing an optical fiber from an optical fiber preform in which an outer glass body is integrally formed on a glass rod having a core portion. Is formed in a tapered shape on the end portion of the glass rod, and when the wire is drawn, the tapered portion of the outer glass body is disposed of, and then the optical fiber that is the product is removed. Draw a line.

  Thus, according to the above-described optical fiber manufacturing method, the glass body is formed in a tapered shape on the end portion of the glass rod, and becomes the tapered shape of the outer glass body at the time of drawing. Since the optical fiber that will be the product is drawn after the part that has been discarded, the outer glass fluctuates in the outer diameter of the tapered outer glass body, and this outer diameter fluctuation occurs in the tapered outer glass. By disposing the body part, it becomes possible to draw an optical fiber having a stable outer diameter as this product in the outer glass body part other than the tapered shape.

  The method for producing an optical fiber preform of the present invention includes a step of connecting a dummy rod to one end of a glass rod via a buffer member to form an inner glass body, and depositing glass particles on the inner glass body. Forming an outer glass body having an effective portion having a predetermined outer diameter and an ineffective portion having a tapered shape on the inner glass body by heating, and the buffer member and the glass. The glass particles are deposited so that a boundary between the effective portion and the ineffective portion is formed in the vicinity of the connecting portion with the rod.

  As described above, according to the above optical fiber preform manufacturing method, the buffer member that reduces the outer diameter fluctuation of the optical fiber at the time of drawing as much as possible is provided in the vicinity of the boundary between the effective portion and the ineffective portion. An optical fiber preform capable of efficiently obtaining an optical fiber can be manufactured.

Specifically, the drawing is transferred from the ineffective portion to the effective portion by configuring the buffer member so that the viscosity of the buffer member is smaller than that of the dummy rod and equal to or higher than that of the glass rod. In doing so, the outer diameter fluctuation of the optical fiber due to the difference in viscosity can be minimized as compared with the case where the dummy rod and the glass rod are directly connected.
Thereby, even if an inexpensive pure quartz dummy rod is used, a good optical fiber can be efficiently obtained from the effective portion of the optical fiber preform.

As described above, according to the present invention, from the vicinity of the boundary between the effective portion and the ineffective portion to the ineffective portion side, the viscosity at the time of drawing is smaller than that of the dummy rod and is equal to or greater than that of the glass rod. By providing a member, when the drawing moves from the ineffective portion to the effective portion, the outer diameter fluctuation of the optical fiber due to the difference in viscosity is minimized as compared with the case where the dummy rod and the glass rod are directly connected. be able to.
Thereby, even if an inexpensive pure quartz dummy rod is used, a good optical fiber can be efficiently obtained from the effective portion of the optical fiber preform.

  In addition, since it is not necessary to add an additive to the dummy rod in order to bring the viscosity of the dummy rod closer to that of the glass rod, the additive is unnecessary, and the step of adding the additive is also unnecessary, which is favorable while suppressing the manufacturing cost. The optical fiber can be drawn.

  DESCRIPTION OF THE PREFERRED EMBODIMENTS Embodiments of an optical fiber preform and a manufacturing method thereof and an optical fiber and a manufacturing method thereof according to the present invention will be described below with reference to the drawings.

(First embodiment)
Hereinafter, an optical fiber preform according to a first embodiment of the present invention and an optical fiber manufacturing method using the optical fiber preform will be described.

FIG. 1 is a view showing an optical fiber preform according to a first embodiment of the present invention.
As shown in FIG. 1, the optical fiber preform 10 includes an inner glass body 11 and an outer glass body 15 formed on the outer peripheral surface of the inner glass body 11. The optical fiber preform 10 is a glass body that serves as a glass supply source when manufacturing an optical fiber.

  The inner glass body 11 is a rod-like member configured by connecting a plurality of glass rods in the longitudinal direction of the optical fiber preform. The glass rod 12, a dummy rod 13a connected to the upper end 12a of the glass rod 12, and a glass The rod 12 includes a connecting rod 14 serving as a buffer member connected to the lower end 12 b of the rod 12, and a dummy rod 13 b connected to the connecting rod 14.

  The glass rod 12 is a portion that mainly becomes a core of a good optical fiber after drawing, and is mixed with impurities such as germanium according to the characteristics of the manufactured optical fiber. Since the glass rod 12 contains a large amount of impurities, the viscosity at the time of drawing (when heated to 2000 ° C.) is smaller than that of pure quartz. In addition, as the glass rod 12, the glass used as a clad may be formed in the circumference | surroundings of the glass used as a core.

  On the other hand, the dummy rods 13a and 13b are glass rods that support the glass rod 12, and are made of, for example, inexpensive pure quartz. The dummy rods 13a and 13b have a higher viscosity at the time of drawing than the glass rod 12. The dummy bars 13a and 13b do not constitute an optical fiber after drawing, and are discarded after drawing.

  The connecting rod 14 serving as a buffer member is a portion that is discarded after drawing like the dummy rods 13a and 13b. The viscosity at the time of drawing is smaller than that of the dummy rods 13a and 13b and is equal to or higher than that of the glass rod 12. It is formed with the material which becomes. For example, the connecting rod 14 may be made of the same material as the glass rod 12. For example, a glass rod member remaining in the manufacturing process of the glass rod 12 may be used as the connecting rod 14.

  In summary, the viscosity at the time of drawing is from the largest to the dummy rods 13a and 13b, the connecting rod 14, and the glass rod 12. Therefore, the difference in viscosity when the glass rod 12 and the connecting rod 14 are drawn is smaller than the difference in viscosity when the glass rod 12 and the dummy rods 13a and 13b are drawn.

  The outer glass body 15 is formed by spraying glass particles on the inner glass body 11 to deposit glass particles to form a glass particle deposit, and dehydrating and sintering the glass particle deposit in a sintering furnace. It is manufactured by making it transparent (vitrified). The outer glass body 15 of the present embodiment includes an effective portion 15a having a constant outer diameter in the longitudinal direction of the optical fiber preform, and tapered ineffective portions 15b formed continuously at both ends of the effective portion 15a. 15c is formed.

  As shown in FIG. 1, the effective portion 15 a is formed on the outer periphery of the glass rod 12, and is a portion that is drawn together with the glass rod 12 and becomes a cladding of a good optical fiber.

  On the other hand, the ineffective portions 15b and 15c are formed on the inner glass body 11 other than the outer periphery of the glass rod 12, and are discarded during drawing or are not drawn. As shown in FIGS. 1 and 3, the non-effective portion 15 c provided below the effective portion 15 a is formed by connecting all the side surfaces of the connecting rod 14 and a part of the dummy rod 13 b from the connecting portion of the glass rod 12 and the connecting rod 14. It is formed in a tapered shape so as to cover it. That is, the glass rod 12 and the connecting rod 14 are connected corresponding to the connecting portion between the effective portion 15a and the non-effective portion 15c, and the connecting rod 14 is covered by the non-effective portion 15c, It is formed in the effective part 15c.

  In the present embodiment, as shown in FIG. 3, the volume of the glass portion 16 provided in the ineffective portion 15 c corresponding to the side surface of the connecting rod 14 corresponds to the ineffective portion corresponding to the side surface of the dummy rod 13 b. It is configured to be smaller than the volume of the glass portion 17 provided in 15c and to be ½ or less of the entire volume of the ineffective portion 15c.

  The optical fiber preform 10 can be manufactured by a VAD method (Vapor phase Axial Deposition), an OVD method (Outside Vaper Deposition), or the like. In the following description, the case where the optical fiber preform 10 is manufactured using the VAD method will be described as an example.

  First, the dummy rod 13a is connected to the upper end 12a of the glass rod 12, and the dummy rod 13b is connected to the lower end 12b of the glass rod 12 through the connecting rod 14, thereby producing the inner glass body 11. The inner glass body 11 is vertically supported and rotated. And a combustion gas is blown out from the burner arrange | positioned toward the inner side glass body 11, an oxyhydrogen flame is formed, and a glass raw material is similarly hydrolyzed by blowing out a glass raw material from a burner in this oxyhydrogen flame. Glass fine particles are generated, and the glass fine particles are deposited on the inner glass body 11 from the upper end 12a side.

  And the effective part 15a is formed in the outer periphery of the glass rod 12 by raising this inner side glass body 11 relatively with respect to a burner, and the connection part of the connection rod 14 and the glass rod 12 The glass fine particles are deposited so that the boundary between the effective portion 15a and the ineffective portion 15b is formed in the vicinity, thereby producing a porous glass fine particle deposit. Thereafter, the glass fine particle deposit is heated to be transparent, whereby the optical fiber preform 10 in which the outer glass body 15 is formed on the outer peripheral surface of the inner glass body 11 is manufactured.

Next, a manufacturing method for manufacturing an optical fiber by drawing the optical fiber preform will be described.
FIG. 2 is a diagram for explaining a method of manufacturing an optical fiber. First, an optical fiber manufacturing apparatus for manufacturing an optical fiber will be described with reference to FIG.

  As shown in FIG. 2, the optical fiber manufacturing apparatus 21 has a cylindrical drawing furnace 23 having a heat generating portion 22, and the optical fiber preform 10 is supplied into the drawing furnace 23. The optical fiber preform 10 supplied into the drawing furnace 23 is heated and melted by the heat generating portion 22 at the tip side, and is drawn downward to be reduced in diameter to be a glass fiber 11a.

  Below the drawing furnace 23, an outer diameter measuring device 24 for measuring the outer diameter of the glass fiber 11a is provided. Further, on the downstream side of the outer diameter measuring device 24, a resin coating die 25 for coating the resin on the outer periphery of the glass fiber 11a and a curing furnace 26 for curing the coated resin are provided. The glass fiber 11a is formed into an optical fiber 11b coated with resin by applying resin on the outer periphery with a resin application die 25 and curing the resin in a curing furnace 26.

  On the downstream side of the curing furnace 26, a guide roller 27 and a capstan 28 are sequentially provided.

  The capstan 28 includes a capstan belt 31 wound around a plurality of rollers 29 and a capstan wheel 32 to which the capstan belt 31 is in close contact. The optical fiber 11b is sandwiched and pulled between the capstan belt 31 and the capstan roller 32. As a result, the optical fiber 11 b is sent to the winding device 33 provided on the downstream side of the capstan 28, and is wound around the winding bobbin 34 provided in the winding device 33.

Next, the manufacturing method of the optical fiber by the said manufacturing apparatus 21 is demonstrated.
First, the optical fiber preform 10 is supplied to the drawing furnace 23, heated and melted by the heat generating portion 22, and drawn downward to obtain a glass fiber 11a having a reduced diameter.
Thereafter, the resin is coated on the outer periphery of the glass fiber 11a with a resin coating die 25, and further, the resin is cured by a curing furnace 26 to obtain an optical fiber 11b coated with the resin.
Thereafter, the optical fiber 11 b is sandwiched and pulled by the capstan belt 31 and the capstan wheel 32 of the capstan 28, sent to the winding device 33, and wound on the winding bobbin 34.

  Here, when the optical fiber 11b is manufactured as described above, the glass fiber 11a in which the optical fiber preform 10 is drawn is removed by the difference in viscosity at the time of drawing at the connection portion between the dummy rod 13b and the connecting rod 14. Although the diameter fluctuates, the difference in viscosity between the connecting rod 14 and the glass rod 12 is made smaller than the difference in viscosity between the dummy rod 13b and the glass rod 12, so that the connecting portion between the connecting rod 14 and the glass rod 12 is used. The outer diameter fluctuation of the optical fiber 11b is greatly reduced.

  That is, in the optical fiber preform 10 of this embodiment, the viscosity at the time of drawing is smaller than the dummy rod 13b between the dummy rod 13b and the glass rod 12, and is equal to or higher than that of the glass rod 12. Because the connecting rod 14 is interposed and used as a buffer member, a large outside diameter fluctuation occurs in the drawing portion near the boundary portion between the ineffective portion 15c not used as the optical fiber 11a and the effective portion 15a used as the optical fiber 11a. Although it occurs, fluctuations in the outer diameter of the drawn portion of the effective portion 15a that is a product as the optical fiber 11a can be greatly reduced.

As a result, a good optical fiber 11b can be efficiently obtained from the effective portion of the optical fiber preform 10 even if an inexpensive pure quartz dummy rod 13b is used.
Further, since it is not necessary to add an additive during the manufacture of the dummy rod 13b in order to make the viscosity of the dummy rod 13b close to the glass rod 12, no additive is required, and no step of adding the additive is required, resulting in a manufacturing cost. This makes it possible to draw the optical fiber 11b with good performance.

Further, according to the method for manufacturing the optical fiber preform 10, the connecting rod 14 as a buffer member for reducing the outer diameter fluctuation of the optical fiber 11b during drawing as much as possible is provided near the boundary between the effective portion and the ineffective portion. Thus, it is possible to manufacture the optical fiber preform 10 capable of efficiently obtaining a good optical fiber 11b.
Furthermore, according to the manufacturing method of the optical fiber 11b using the optical fiber preform 10, the outer diameter fluctuation at the start of drawing the effective portion is suppressed as much as possible, and the good optical fiber 11b is efficiently manufactured from the effective portion. Can do.

  In the present embodiment, the connecting portion between the glass rod 12 and the connecting rod 14 is located at the boundary between the ineffective portion 15c and the effective portion 15a. However, the present invention is not limited to this. For example, the glass rod 12 is ineffective. You may comprise so that it may protrude to the part 15c side and the glass rod 12 and the connection rod 14 may be connected in the non-effective part 15c.

  In the present embodiment, the connection rod 14 is connected only to one end side of the glass rod 12, but the present invention is not limited to this. The connection rod 14 is provided at both ends of the glass rod 12, and the two The optical fiber preform may be configured so that the connecting rod is covered with the ineffective portions 15b and 15c, respectively.

(Second Embodiment)
Hereinafter, an optical fiber preform according to a second embodiment of the present invention and an optical fiber manufacturing method using the optical fiber preform will be described.

FIG. 6 is a view showing an optical fiber preform according to the second embodiment of the present invention.
As shown in FIG. 6, the optical fiber preform 40 includes an inner glass body 41 and an outer glass body 45 formed on the outer peripheral surface of the inner glass body 41. The optical fiber preform 40 is a glass body that serves as a glass supply source when an optical fiber is manufactured.

  The inner glass body 41 is a rod-like member configured by connecting a plurality of glass rods in the longitudinal direction of the optical fiber preform. The glass rod 42, a dummy rod 43a connected to the upper end 42a of the glass rod 42, and a glass And a dummy bar 43b connected to the lower end 42b of the rod 42.

  The glass rod 42 is a portion that mainly becomes a core of a good optical fiber after drawing, and is mixed with impurities such as germanium according to the characteristics of the manufactured optical fiber. Since this glass rod 42 contains a lot of impurities, the viscosity at the time of drawing (when heated to 2000 ° C.) is smaller than that of pure quartz. In addition, as the glass rod 42, the glass used as a clad may be formed around the glass used as a core.

  On the other hand, the dummy rods 43a and 43b are glass rods that are connected to the glass rod 42 and support the glass rod 42, and are made of, for example, inexpensive pure quartz. The dummy rods 43a and 43b have a viscosity higher than that of the glass rod 42 at the time of drawing. The dummy bars 43a and 43b do not constitute an optical fiber after drawing, and are discarded at the time of drawing.

  The outer glass body 45 is formed by spraying glass particles onto the inner glass body 41 to form glass particle deposits, and the glass particle deposits are made transparent (vitrified) in a sintering furnace. It is manufactured. The outer glass body 45 of the present embodiment includes an effective portion 45a having a constant outer diameter in the longitudinal direction of the optical fiber preform, and tapered ineffective portions 45b formed continuously at both ends of the effective portion 45a, 45c is formed.

  As shown in FIG. 6, the effective portion 45 a is formed on the outer periphery of the glass rod 42, and is a portion that is drawn together with the glass rod 42 and becomes the cladding of the non-defective optical fiber.

  On the other hand, the ineffective portion 45b is formed on the dummy rod 43a, and the ineffective portion 45c is formed on the one end portion 42a of the glass rod 42 and the dummy rod 43b. These ineffective portions 45b and 45 are portions that are discarded during drawing or are not drawn. As shown in FIG. 6, the non-effective part 45c provided below the effective part 45a is formed in a tapered shape so as to cover the connection part between the one end part 42b of the glass rod 42 and the dummy rod 43b. That is, the glass rod 42 and the dummy rod 43b are connected on the non-effective part 45c side of the connection part between the effective part 45a and the non-effective part 45c.

  The optical fiber preform 40 can be manufactured by a VAD method (Vapor phase Axial Deposition), an OVD method (Outside Vaper Deposition), or the like. The manufacturing method of the optical fiber preform 40 is basically the same as the manufacturing method of the optical fiber preform 10 described in the first embodiment except that the structure of the inner glass body 41 is different. That is, in the optical fiber preform 40, the outer glass body 45 is arranged so that the glass rod 42 and the dummy rod 43b are connected on the non-effective portion 45c side of the connection portion between the effective portion 45a and the non-effective portion 45c. Form.

  Next, an optical fiber manufacturing method using the optical fiber preform 40 will be described. As an optical fiber manufacturing apparatus for drawing the optical fiber preform 40, an optical fiber manufacturing apparatus 21 shown in FIG. 2 can be used.

First, an optical fiber preform 40 (see FIG. 6) is supplied to the drawing furnace 23 instead of the optical fiber preform 10, and the glass fiber 11a is heated and melted by the heat generating portion 22 and drawn downward to reduce the diameter. To do.
Thereafter, the resin is coated on the outer periphery of the glass fiber 11a with a resin coating die 25, and further, the resin is cured by a curing furnace 26 to obtain an optical fiber 11b coated with the resin.
Thereafter, the optical fiber 11 b is sandwiched and pulled by the capstan belt 31 and the capstan wheel 32 of the capstan 28, sent to the winding device 33, and wound on the winding bobbin 34.

  Here, in this embodiment, the optical fiber 11b drawn from the ineffective portion 45c having a tapered shape is disposed of as not satisfying the specification as an optical fiber, and is drawn from the effective portion 45a. Only the optical fiber 11b is used as this product. Here, the discarding process of the ineffective portion 45c may be performed by discarding the glass fiber 11a before being coated with the resin coating die 25.

  Since the dummy rod 43b has a higher viscosity at the time of drawing than the glass rod 42, when the optical fiber 11b is manufactured as described above, the glass fiber 11a drawn from the optical fiber preform 40 is composed of the glass rod 42 and the dummy rod. The outer diameter fluctuates due to the viscosity difference at the time of drawing at the connection point with 43b. However, the fluctuation of the outer diameter occurs when the non-effective portion 45c is drawn, and the fluctuation of the outer diameter is stable when the effective portion 45a is drawn. That is, since the connecting portion between the glass rod 42 and the dummy rod 43b is provided on the non-effective portion 45c side, the outer diameter does not vary at the time of drawing from the non-effective portion 45c to the effective portion 45a. Therefore, the optical fiber 11b (or the glass fiber 11a) drawn from the ineffective portion 45c is discarded, and only the optical fiber 11b (or the glass fiber 11a) drawn from the effective portion 45a is used as the product. All the optical fibers drawn from 45a can be adopted as good products.

As a result, a good optical fiber 11b can be efficiently obtained from the effective portion 45a of the optical fiber preform 40 even if an inexpensive pure quartz dummy rod 43b is used.
Further, since it is not necessary to add an additive when manufacturing the dummy rod 43b in order to bring the viscosity of the dummy rod 43b closer to the glass rod 42, an additive is not necessary, and a process for adding the additive is also unnecessary, resulting in a manufacturing cost. This makes it possible to draw the optical fiber 11b with good performance.

  In addition, the connection location of the glass rod 42 and the dummy rod 43b is on the axially ineffective portion 45c side to such an extent that the fluctuation of the outer diameter of the glass fiber manufactured at the time of drawing the effective portion 45a is sufficiently suppressed. It is preferable to be provided.

  As an example, the following optical fiber preform 10 according to the present invention shown in FIG. 1 was drawn.

(Example)
As the glass rod 12, a core made of pure quartz having an outer diameter of 4.6 mm and having an outer diameter of 23 mm and a length of 500 mm having a part of a clad made of quartz with 1.25% by mass of fluorine added to the outer periphery thereof was used. .

  A quartz dummy rod 13a having an outer diameter of 23 mm is connected to the upper end of the glass rod 12, and an outer diameter of 23 mm having a viscosity equivalent to that of the glass rod 12 at the time of drawing (about 2000 ° C.) is long at the lower end. A connecting rod 14 having a thickness of 30 mm was connected to provide a buffer member, and a quartz dummy rod 13b having an outer diameter of 23 mm was further connected.

  Next, on the outer periphery of the glass rod 12 having the dummy rod 13a connected to the upper end and the dummy rod 13b connected to the lower end via the connecting rod 14 as described above, a uniform glass particle (pure Sio2) having an outer diameter of 150 mm. The deposited body was deposited and heated to 1500 ° C. in a sintering furnace to be transparent, whereby an optical fiber preform 10 having an effective part with an outer diameter of 70 mm and a length of 150 mm was obtained. Note that, on the upper end side, the boundary between the effective portion 15a and the ineffective portion 15c coincides with the connection portion between the glass rod 12 and the dummy rod 13b, and on the lower end side, the glass rod 12 and the connecting rod 14 are aligned. The boundary between the effective portion 15a and the non-effective portion 15b is made to coincide with the connection location. As a result, on the lower end side of the optical fiber preform 10, the volume of the connecting rod corresponding portion 16 corresponding to the ineffective portion 15c in the portion where the connecting rod 14 is disposed is about 20% of the entire ineffective portion. The volume of the connecting rod corresponding portion 16 corresponds to 7 km in terms of the optical fiber length when drawn.

  As a result of drawing the optical fiber preform 10, fluctuations in the outer diameter of the optical fiber 11 b occurred at the connection point between the dummy rod 13 and the connecting rod 14 as shown in FIG. The diameter variation has converged. Thereafter, the outer diameter of the optical fiber 11b slightly changed at the connection point between the connecting rod 14 and the glass rod 12, but converged to the outer diameter of the predetermined optical fiber 11b at about 2 km, and as a result, good The characteristic optical fiber 11b could be obtained over 98 km. Therefore, the length of the optical fiber corresponding to the glass rod 12 lost due to the fluctuation of the outer diameter was 2 km.

(Comparative example)
As a comparative example, the conventional optical fiber preform 5 shown in FIG. 7 was drawn.
As the glass rod 2, a core made of pure quartz having an outer diameter of 4.6 mm and having an outer diameter of 23 mm and a length of 500 mm having a part of a clad made of quartz with 1.25% by mass of fluorine added to the outer periphery thereof was used. .
A quartz dummy rod 1 having an outer diameter of 23 mm was connected to the upper and lower ends of the glass rod 2.

  Next, a deposit 3 of uniform glass fine particles (pure Sio2) having an outer diameter of 150 mm is synthesized on the outer periphery of the glass rod 2 having the dummy rods 1 connected to the upper and lower ends as described above, and 1500 is obtained in a sintering furnace. The optical fiber preform 5 having an effective part with an outer diameter of 70 mm and a length of 150 mm was obtained by heating to ° C. to make it transparent. In each of the upper end side and the lower end side, the boundary between the effective portion and the ineffective portion coincided with the connection portion between the glass rod 2 and the dummy rod 1.

  As a result of drawing the optical fiber preform 5, as shown in FIG. 5, the connection portion between the dummy rod 1 and the glass rod 2 from the time when the drawing of the ineffective portion is completed and the drawing of the effective portion is started. The outer diameter variation of the optical fiber 11b occurred and the outer diameter variation continued for about 5 km.

  As described above, since the outer diameter fluctuates over 5 km in the effective portion, which is a region where the optical fiber 11b having good characteristics can be obtained, the non-defective product cannot be obtained in this portion, and the obtained optical fiber 11b having good characteristics is It was 95 km. That is, the length of the optical fiber corresponding to the glass rod 12 lost due to the fluctuation of the outer diameter is 5 km. Compared with the embodiment, the length of the good optical fiber 11b is reduced by 3 km, and the yield is reduced. .

It is a schematic sectional drawing of the optical fiber preform explaining 1st Embodiment of the optical fiber preform concerning this invention. It is a schematic block diagram of the manufacturing apparatus explaining the manufacturing method which manufactures an optical fiber using an optical fiber preform. It is a schematic diagram which shows an ineffective part. It is a graph explaining the result of an Example. It is a graph explaining the result of the comparative example with respect to an Example. It is a schematic sectional drawing of the optical fiber preform explaining 2nd Embodiment of the optical fiber preform concerning this invention. It is a schematic sectional drawing of the optical fiber preform explaining the structure of an optical fiber preform.

Explanation of symbols

DESCRIPTION OF SYMBOLS 10 Optical fiber base material 11 Inner glass body 11b Optical fiber 12 Glass rod 13a, 13b Dummy rod 14 Connection rod (buffer member)
15 Outer glass body

Claims (10)

An inner glass body having a glass rod, a buffer member having one end connected to the glass rod, and a dummy rod connected to the other end of the buffer member;
An outer glass body formed on the outer periphery of the inner glass body,
In the outer glass body, an effective portion having a predetermined outer diameter and a non-effective portion having a tapered shape are formed,
The optical fiber preform, wherein the buffer member is in the ineffective portion. 2. The optical fiber preform according to claim 1, wherein the viscosity of the buffer member at the time of drawing is smaller than that of the dummy rod and equal to or higher than that of the glass rod. The optical fiber preform according to claim 1, wherein the buffer member is a glass rod made of the same material as the glass rod. The volume of the non-effective part in the arrangement | positioning part of the said buffer member is made into 1/2 or less of the volume of the said whole non-effective part, The any one of Claims 1-3 characterized by the above-mentioned. Optical fiber preform. An optical fiber produced by drawing the optical fiber preform according to any one of claims 1 to 4. An optical fiber manufacturing method for drawing an optical fiber from an optical fiber preform integrally formed with an outer glass body on a glass rod having a core part,
The glass body is formed in a tapered shape on the end of the glass rod,
An optical fiber manufacturing method comprising: drawing an optical fiber to be the product after the taper-shaped portion of the outer glass body is discarded at the time of drawing. Connecting a dummy rod to one end of the glass rod via a buffer member to form an inner glass body;
Forming an outer glass body on the inner glass body with an effective portion having a predetermined outer diameter and an ineffective portion having a tapered shape by depositing and heating glass fine particles on the inner glass body; and Have
The said buffer member deposits the said glass particulate so that it may be formed in the said ineffective part, The manufacturing method of the optical fiber preform | base_material characterized by the above-mentioned. 8. The method of manufacturing an optical fiber preform according to claim 7, wherein the viscosity of the buffer member at the time of drawing is smaller than that of the dummy rod and equal to or higher than that of the glass rod. 9. The method of manufacturing an optical fiber preform according to claim 7, wherein the buffer member is a glass rod made of the same material as the glass rod. 10. The volume according to claim 7, wherein a volume of the ineffective portion in the portion where the buffer member is disposed is equal to or less than a half of a volume of the entire ineffective portion. Manufacturing method of optical fiber preform.

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