JP2023117084A - Method for manufacturing optical fiber preform and method for manufacturing optical fiber - Google Patents

Abstract

To provide a method for manufacturing an optical fiber preform, capable of preventing a support part from being damaged.SOLUTION: A method for manufacturing an optical fiber preform including: a seed rod including a core part and a support part bonded at one or both ends of the core part by heat fusion; and a porous glass part formed in the outer periphery of the core part comprises the steps of: holding the holding part of the support part and depositing porous glass on the seed rod to form a porous glass part; slowly cooling a boundary part between the core part and the support part and the vicinity area of the boundary part at a predetermined cooling rate in a predetermined temperature range; and heating and transparently vitrify the optical fiber preform.SELECTED DRAWING: Figure 5

Description

The present invention relates to a method for manufacturing an optical fiber preform and a method for manufacturing an optical fiber.

In recent years, with the increase in size of OVD (Outside Vapor Deposition) soot, the load on the support rods is increasing. On the other hand, a method for manufacturing an optical fiber preform that prevents cracks in the porous glass preform has been proposed. The method for manufacturing an optical fiber preform described in Patent Document 1 includes a step of gradually decreasing the flow rate of the fuel gas supplied to the burner and slowly cooling the surface temperature of the porous optical fiber preform while heating it with the burner. The deposition apparatus described in Patent Document 2 has a configuration for preventing cracks of glass particles at both ends of an optical fiber preform. Furthermore, in order to reduce the load associated with the increase in size, it is conceivable to use a vertical OVD. glass particles are deposited on the

Japanese Patent No. 5163416 Japanese Patent No. 6960728 JP 2021-175695 A

However, the method for manufacturing an optical fiber preform described in Patent Document 1 only slowly cools the glass particles deposited on the core portion. When the optical fiber preform is cooled, the cooling speed is increased because the support section has no porous layer or is thinner than the optical fiber preform on which the glass particles are deposited. As a result, the support portion may be distorted and damaged. The structure described in Patent Literature 2 prevents the deposition of glass particles on the support portion to prevent cracks in the porous base material, but does not prevent damage to the support portion. Although the deposition apparatus described in Patent Document 3 reduces the load applied to the support portion due to the increase in size of the optical fiber preform, there is no description of distortion, and it is necessary to control the upward air flow due to the chimney effect. Deposition equipment becomes complicated and expensive.

SUMMARY OF THE INVENTION It is an object of the present invention to provide a method of manufacturing an optical fiber preform that can prevent the support portion of the optical fiber preform from being damaged.

According to one aspect of the present invention, it has a seed rod having a core portion and support portions joined to both ends of the core portion by heat-sealing, and a porous glass portion formed on the outer periphery of the core portion. A method for manufacturing an optical fiber preform, comprising: holding a holding portion of the support portion; depositing porous glass on the seed rod to form the porous glass portion; and heating the optical fiber preform. and transparently vitrifying, wherein after forming the porous glass portion on the seed rod, a boundary portion between the core portion and the support portion and a region near the boundary portion are formed using a burner flame. There is provided a method for manufacturing an optical fiber preform, further comprising the step of cooling at a predetermined cooling rate.

According to the present invention, it is possible to provide a method of manufacturing an optical fiber preform that can prevent the support portion from being damaged.

FIG. 1 is a perspective view of a seed rod of an optical fiber preform in a first embodiment of the present invention. FIG. 2 is a perspective view of part II of the seed rod of the optical fiber preform shown in FIG. 1 in the first embodiment of the present invention. FIG. 3 is a side view of the deposition apparatus used for manufacturing the optical fiber preform in the first embodiment of the present invention. FIG. 4 is a cross-sectional view of a sintering apparatus used for manufacturing an optical fiber preform in the first embodiment of the present invention. FIG. 5 is a flow chart of a method for manufacturing a glass base material according to the first embodiment of the present invention. FIG. 6 is a graph showing temperature changes during slow cooling of support portions of Examples and Comparative Examples in the first embodiment of the present invention. FIG. 7 is a table showing the presence or absence of cracks in the support portions of Examples and Comparative Examples in the first embodiment of the present invention.

An embodiment of the present invention will be described below based on the drawings. The same reference numbers throughout the specification denote substantially the same components.

[First embodiment]
FIG. 1 is a perspective view of the seed rod of the optical fiber preform in this embodiment, and FIG. 2 is a perspective view of the II portion of the seed rod of the optical fiber preform shown in FIG.

The seed rod of the optical fiber preform comprises a core portion 11 and support portions 12A and 12B. The core portion 11 is a starting material of an optical fiber preform and is made of silica glass or the like. The core portion 11 can be formed by heating and drawing a rod having a core and a clad layer formed around the core. The core portion 11 has a substantially cylindrical shape and includes a side portion 111 and end portions 112 and 113 . Side 111 has a length and ends 112, 113 have a diameter. For example, it may be 4000 mm long and 70 mm in diameter. Glass particles are deposited on the outer periphery of the side portion 111 in a deposition process described later to form an optical fiber preform. In FIG. 1, the direction in which the virtual core axis 114 of the core portion 11 extends is the X direction, the direction perpendicular to the X direction is the Y direction, and the direction perpendicular to the X and Y directions is the Z direction.

The support portions 12A and 12B are support rods, and the support portions 12A and 12B are provided at both ends of the core portion 11, respectively. The support portions 12A and 12B are used to support the core portion 11 in the step of depositing glass particles and the step of sintering. The support portions 12A and 12B are made of quartz or the like, like the core portion 11. As shown in FIG. The support portions 12A, 12B are generally cylindrical and have side portions 121A, 121B and end portions 122A, 122B, 123A, 123B, respectively. Sides 121A, 121B have a length and ends 122A, 122B, 123A, 123B have a diameter. For example, it can be 1000 mm long and 65 mm in diameter. The lengths of the side portions 121A and 121B and the diameters of the end portions 122A, 122B, 123A and 123B are determined according to the length of the side portion 111 of the core portion 11, the diameter of the end portions 112 and 113, the thickness at which the glass particles are deposited, and the like. It may be changed as appropriate.

The virtual support axes 124A, 124B of the support parts 12A, 12B and the core axis 114 are positioned substantially on the same line, and the support part 12A is arranged such that the end part 122A is in contact with the end part 112 and the end part 122B is in contact with the end part 113. , 12B are joined to the core portion 11 . Edge 122A and edge 112, edge 122B and edge 113 are welded using an oxyhydrogen burner or the like. The method of welding and joining is not limited to this, and welding and joining may be performed using an electric furnace or the like. Here, the joining portion between the end portion 122A and the end portion 112 and its periphery are referred to as a boundary portion 115A (the boundary between the end portion 122A and the end portion 112 and the hatched area in FIG. 2). A side portion 121 having a length of is referred to as a neighboring area 125A (the dotted hatched area in FIG. 2). For example, proximal region 125A may be the region of side 121A up to 800 mm in the direction from end 122A to end 123A. The same applies to the boundary portion 115B and the neighboring area 125B of the support portion 12B. The neighboring regions 125A and 125B may be appropriately changed according to the length of the side portion 111, the diameter of the end portions 112 and 113, the thickness of the deposited glass particles, and the like.

The support portions 12A and 12B can be bonded to one end or both ends of the core portion 11 depending on the deposition device used in the later-described glass particle deposition step. For example, when glass particles are deposited by a horizontal deposition apparatus, support portions 12A and 12B are joined to both ends of the core portion 11, respectively. In this embodiment, a case where glass particles are deposited by a horizontal deposition apparatus will be described.

FIG. 3 is a side view of a deposition apparatus used for manufacturing an optical fiber preform in this embodiment. The porous glass portion 13 is a layer of glass particles deposited on the core portion 11 . The porous glass portion 13 is deposited on the core portion 11 by a depositing device. A method for depositing the porous glass portion 13 may be, for example, a VAD (Vapor phase Axial Deposition) method, an OVD (Outside Vapor Deposition) method, or the like. The VAD method is a method in which the core portion 11 is held vertically and glass particles are vertically deposited from the lower end portion of the core portion 11 toward the upper end portion. The OVD method is a method in which the core portion 11 is held at both ends and the glass particles are deposited horizontally on the side portions of the core portion 11 . In this embodiment, the horizontal deposition apparatus is used as described above, and the porous glass portion 13 is deposited by the OVD method.

The deposition device 3 includes a base 31, support portions 32A and 32B, a grip portion 33, a stress applying portion 34, a burner 38, and burners 39A and 39B. The base 31 is a member that serves as the base of the deposition device 3 and has a substantially rectangular parallelepiped shape. The base 31 is installed substantially horizontally with respect to the ground plane. The base 31 extends in the longitudinal direction of the base 31 and includes rails and the like provided below the core portion 11, along which the support portions 32A and 32B and the burner 38 can move. In plan view, the longitudinal direction of the base 31 is the X direction, the lateral direction of the base 31 is the Y direction, and the vertical direction of the base 31 is the Z direction.

The support portions 32A and 32B are columnar, opposed to each other, and provided above the base 31 . That is, the support portion 32A is provided at one end of the base 31, and the support portion 32B is provided at the other end of the base 31. As shown in FIG. At least one of the support portions 32A and 32B is movable on rails laid on the base 31 . The support portions 32A and 32B include a rotary motor, a transmission, and the like that rotationally drive the core portion 11 via the support portions 12A and 12B.

The gripping portion 33 and the stress applying portion 34 constitute a chuck and are provided on the supporting portions 32A and 32B, respectively. The gripping portion 33 is made of metal such as SUS (Steel Use Stainless) or a heat-resistant fluororesin, and has a plurality of claws that can be brought close to or separated from each other. Gripping holes for gripping the support portions 12A and 12B are formed in the centers of the plurality of claws.

The stress applying portion 34 is provided around the grip portion 33 and can apply stress to the grip portion 33 . When the stress-applying portion 34 applies stress to the gripping portion 33, the plurality of claws are brought closer to each other and the diameter of the gripping hole is reduced. As a result, the support portions 12A and 12B inserted into the gripping holes are gripped by the gripping portion 33. As shown in FIG.

The burner 38 is a burner that blows glass particles onto the core portion 11, and is a burner that uses oxyhydrogen as fuel, for example. A burner 38 is installed on the rail of the base 31 . The burner 38 can move on rails and deposit glass particles on the core portion 11 rotating about the core axis 114 . The burner 38 includes a nozzle for supplying combustible gas, a nozzle for supplying combustion supporting gas, a nozzle for supplying raw material for glass, and the like. For example, the combustible gas can be hydrogen or the like, and the combustible gas can be oxygen or the like. Also, the glass raw material can be, for example, SiCl ₄ or the like. The burner 38 introduces glass raw materials into a flame to generate glass microparticles through a flame hydrolysis reaction. The burner 38 can adjust the nozzle position in the vertical direction of the core axis 114 according to the thickness of the glass particles deposited on the side portion 111 . In this manner, the porous glass portion 13 is deposited on the outer circumference of the core portion 11, and the optical fiber preform 1 is formed.

The burner 39A is an oxyhydrogen burner that densifies the porous glass adhered to the boundary portion 115A and the neighboring region 125A, and the burner 39B is an oxyhydrogen burner that densifies the porous glass adhered to the boundary portion 115B and the neighboring region 125B. be. The burners 39A and 39B are also called auxiliary burners for quenching or side burners, and are provided with nozzles for supplying combustible gas and nozzles for supplying auxiliary combustion gas. Burners 39A and 39B are provided so as not to contact burner 38. FIG. The burners 39A, 39B can heat predetermined regions of the support parts 12A, 12B rotating around the support shafts 124A, 124B. The burners 39A and 39B may heat not only the boundary portions 115A and 115B and the neighboring regions 125A and 125B, but also a predetermined region in the direction from the boundary portions 115A and 115B to the optical fiber preform 1. For example, the periphery of both ends of the optical fiber preform 1 where the amount of deposited glass particles is smaller than that of the central periphery of the optical fiber preform 1 in the X direction may be heated.

The burners 39A and 39B may be installed on the rail on which the burner 38 is installed, or may be installed on another rail by laying a rail different from the rail on which the burner 38 is installed. In this case, the burners 39A, 39B can move on rails and heat the support portions 12A, 12B.

The burners 39A, 39B can slowly cool the support portions 12A, 12B by gradually lowering the flame temperature. When the deposition by the burner 38 reaches the required amount and finishes the deposition, the deposition support portions 12A and 12B have no porous layer or are thinner than the porous glass portion 13, so the cooling rate of the glass surface increases. Further, as the deposition amount of the porous glass portion 13 increases, the load applied to the support portions 12A and 12B increases. As a result, the support portions 12A and 12B are likely to be distorted, and the support portions 12A and 12B are cracked and damaged. By slowly cooling the support portions 12A and 12B within a predetermined temperature range and at a predetermined cooling rate after the step of depositing the glass fine particles, generation of distortion in the support portions 12A and 12B can be suppressed.

FIG. 4 is a cross-sectional view of an apparatus used in the sintering process used to manufacture the optical fiber preform in the embodiment. The sintering apparatus 5 includes a furnace core tube 51 , an intake hole 52 , an exhaust hole 53 , a heater 54 , an upper lid 55 and a support portion 56 .

The furnace core tube 51 is a cylindrical reaction vessel capable of storing the optical fiber preform 1, and can be made of transparent quartz glass or the like. The intake hole 52 is provided at the bottom of the core tube 51 and introduces dehydration gas, inert gas, etc. into the interior 511 of the core tube 51 . For example, the dehydrating gas can be chlorine, thionyl chloride, etc., and the inert gas can be argon, helium, etc. The exhaust hole 53 is provided above the side portion of the furnace core tube 51, and exhausts dehydration gas, inert gas, etc. filled in the furnace core tube 51 as necessary. A heater 54 is provided around the core tube 51 and heats the optical fiber preform 1 . The upper lid 55 is provided on the upper part of the furnace core tube 51 and seals the upper part of the furnace core tube 51 after the optical fiber preform 1 is stored in the furnace core tube 51 . The upper lid 55 is formed with an opening 551 into which the support portion 12A can be inserted.

The support portion 56 is provided on the upper portion of the core tube 51, holds the support portion 12A, and suspends and supports the optical fiber preform 1. As shown in FIG. The support portion 56 is configured to be rotatable by a driving mechanism (not shown). By rotating the support portion 56 , the optical fiber preform 1 rotates in the interior 511 of the furnace core tube 51 and is heated by the heater 54 . As a result, the core portion 11 and the porous glass portion 13 of the optical fiber preform 1 are sintered and vitrified.

FIG. 5 is a flow chart of a method for manufacturing a glass base material according to this embodiment. First, the support portions 12A and 12B are joined to both ends of the core portion 11 (step S101). Support portions 12A and 12B are fusion-bonded to core portion 11 using an oxyhydrogen burner or the like so that core shaft 114, support shaft 124A, and support shaft 124B are positioned substantially on the same line.

Next, the core portion 11 (optical fiber preform) to which the support portions 12A and 12B are joined is installed in the deposition device 3 (step S102). The support portions 12A and 12B are gripped by gripping portions 33 of the deposition device 3, respectively. Here, it is desirable that the gripping portion 33 grips the support portions 12A, 12B so as not to prevent the burners 39A, 39B from heating the neighboring regions 125A, 125B.

The depositing device 3 rotates the support portions 12A and 12B and the core portion 11, and the burner 38 deposits glass particles on the side portion 111 (step S103). The burner 38 reciprocates, for example, the lower portion of the core portion 11 in the X direction, and throws the glass raw material into the flame. The burners 39A, 39B may heat the porous glass portions 13 deposited on both ends of the core portion 11 while the porous glass portions 13 are deposited on the side portions 111 . At both ends of the core portion 11, since a porous glass body with a low density is deposited, cracks and the like are likely to occur. Therefore, by heating the porous glass portions 13 deposited on both ends of the core portion 11 by the burners 39A and 39B, it is possible to prevent cracks or the like from occurring in the portions of the porous glass portions 13 where the deposition amount is small. can.

When the porous glass portion 13 is sufficiently deposited on the core portion 11, the supply of frit, combustible gas, and combustion-supporting gas to the burner 38 is stopped, and the burner 38 is extinguished. After that, the support portions 12A and 12B are slowly cooled to the target temperature by the burners 39A and 39B (step S104). A method of gradually cooling the support portions 12A and 12B will be described in detail. The flames of the burners 39A, 39B are blown to the boundaries 115A, 115B and the neighboring areas 125A, 125B while gradually lowering the temperature of the flames of the burners 39A, 39B. As a result, the temperatures of the boundary portions 115A, 115B and the neighboring regions 125A, 125B are gradually lowered from the predetermined temperature to the target temperature. That is, boundary portions 115A and 115B and neighboring regions 125A and 125B are gradually cooled at a predetermined cooling rate within a temperature range from a predetermined temperature to a target temperature. The predetermined temperature and target temperature can be, for example, 1150° C. and 1050° C., respectively. The temperature range from the predetermined temperature to the target temperature preferably includes temperatures around the strain point of quartz, for example, more preferably 1090°C, and the temperature range may be from 1100°C to 1050°C. . The predetermined cooling rate can be, for example, a cooling rate of 5°C/min, 10°C/min, 20°C/min, 30°C/min, and the like. When the temperatures of the boundary portions 115A, 115B and the neighboring regions 125A, 125B are lowered to the target temperature, the burners 39A, 39B are extinguished, and the boundary portions 115A, 115B and the neighboring regions 125A, 125B are naturally cooled (step S105).

Since the amount of deposited glass particles around the end portions 112 and 113 is small compared to the portion where the amount of deposited glass particles is large, the cooling rate increases. Similarly, the cooling rate also increases in the support portions 12A and 12B where no glass particles are deposited. Moreover, the load applied to the support portions 12A and 12B increases according to the deposition amount of the porous glass portion 13 . As a result, the support portions 12A and 12B are likely to be distorted, and the support portions 12A and 12B may be damaged. After the step of depositing the glass particles, the boundary between the core and the support and its neighboring area are gradually cooled to the target temperature at a predetermined cooling rate, thereby suppressing distortion of the support. Therefore, it is possible to prevent damage to the support portion.

When the temperature of the support portions 12A and 12B is lowered to a predetermined temperature by natural cooling, the support portions 12A and 12B are removed from the holding portion 33 and the optical fiber preform 1 is removed from the deposition device 3 (step S106). Furthermore, the joint between the support portion 12B and the core portion 11 may be melted by a burner or an electric furnace, and the support portion 12B may be separated and removed from the optical fiber preform 1 (step S107).

The support portion 12A is supported by the support portion 56, and the optical fiber preform 1 is installed vertically in the interior 511 of the core tube 51 (step S108). The optical fiber preform 1 is heated and sintered by the sintering device 5 (step S109). First, chlorine (Cl ₂ ) or the like is introduced into the interior 511 through the intake hole 52 . Next, the optical fiber preform 1 is heated by the heater 54 while rotating in the interior 511 . As a result, impurities and the like contained in the optical fiber preform 1 are removed. Further, chlorine is discharged from the exhaust hole 53 to the outside of the furnace core tube 51, and helium (He) is introduced into the interior 511 from the intake hole 52 as atmospheric gas. The optical fiber preform 1 is heated to a predetermined temperature by the heater 54 while rotating in the interior 511 . The predetermined temperature can be, for example, 1500°C. When the sintering of the optical fiber preform 1 is completed, the helium is discharged from the exhaust hole 53 to the outside of the furnace core tube 51 , and the transparent vitrified optical fiber preform 1 is taken out from the furnace core tube 51 . In the subsequent steps, the transparent vitrified optical fiber preform 1 is heated and drawn. Thus, an optical fiber is formed.

As described above, according to the present embodiment, the boundary between the core portion and the support portion and the region in the vicinity thereof are slowly cooled in a predetermined temperature range and at a predetermined cooling rate, thereby preventing damage to the support portion. It becomes possible to

[Example]
FIG. 6 is a graph showing temperature changes during slow cooling of the support portions of Examples and Comparative Examples of the present embodiment, and FIG. 7 shows the presence or absence of cracks in the support portions of Examples and Comparative Examples of the present embodiment. It is a table. As described above, after the step of depositing the porous glass portion 13, the support portions 12A and 12B were slowly cooled at a predetermined cooling rate, and the presence or absence of cracks in the support portions 12A and 12B was examined. The weight of the optical fiber preform 1 after the deposition process used in the example was 180 kg, and the diameter of the support portions 12A and 12B made of quartz was 63 mm. After the burner 38 was extinguished after the deposition process, the flames of the burners 39A, 39B were blown to the boundary portions 115A, 115B and the neighboring regions 125A, 125B to slowly cool the support portions 12A, 12B.

The temperature change of the support portions 12A and 12B when the support portions 12A and 12B are slowly cooled at a cooling rate of 5° C./min from 1150° C. to 1050° C. is shown in FIG. The weight of the optical fiber preform, the diameter of the support portion, and the presence or absence of cracks in the support portion are shown (Example 1). The temperature change of the support parts 12A and 12B when the support parts 12A and 12B are slowly cooled at a cooling rate of 10° C./min from 1150° C. to 1050° C. is shown in FIG. The weight of the optical fiber preform, the diameter of the support portion, and the presence or absence of cracks in the support portion are shown (Example 2). The temperature change of the support portions 12A and 12B when the support portions 12A and 12B are slowly cooled at a cooling rate of 20° C./min from 1150° C. to 1050° C. is shown in FIG. shows the weight of the optical fiber preform, the diameter of the support portion, and the presence or absence of cracks in the support portion (Example 3). When the temperature of the support portions 12A, 12B reached the target temperature, the burners 39A, 39B were extinguished, and the support portions 12A, 12B were naturally cooled. In the case of Example 1-3, no cracks occurred in the support portions 12A and 12B, and the support portions 12A and 12B were not damaged when the optical fiber preform 1 was removed from the deposition device 3.

[Comparative example]
On the other hand, as a comparative example, the weight of the optical fiber preform 1 after the deposition process is 180 kg, the diameter of the support portions 12A and 12B is 63 mm, and the cooling rate from 1150° C. to 1050° C. is 30° C./min. FIG. 6 shows the temperature change of the support portions 12A and 12B when the support portions 12A and 12B are gradually cooled. FIG. (Comparative Example 1). Furthermore, as another comparative example, the weight of the optical fiber preform 1 after the deposition process is 300 kg, the diameter of the support portions 12A and 12B is 63 mm, and the cooling rate from 1150° C. to 1050° C. is 20° C./min. The presence or absence of cracks in the support portions 12A and 12B was examined (Comparative Example 2). In Comparative Examples 1 and 2, cracks were generated in the support portions 12A and 12B, and the support portions 12A and 12B were damaged before the optical fiber preform 1 was removed from the deposition device 3. As described above, it was confirmed that the support portions 12A and 12B are easily damaged when the cooling rate is high within a predetermined temperature range.

Reference Signs List 1: Optical fiber preform 11: Core portion 115: Boundary portion 12: Support portion 125: Neighboring region 13: Porous glass portion 3: Deposition device 38: Burner 39: Burner 5: Sintering device

Claims (13)

a seed rod having a core portion and support portions joined to both ends of the core portion by heat-sealing;
A method for manufacturing an optical fiber preform comprising: a porous glass portion formed on the outer periphery of the core portion;
a step of holding a holding portion of the support portion and depositing porous glass on the seed rod to form the porous glass portion;
a step of heating the optical fiber preform to turn it into transparent glass,
Further comprising a step of cooling, after forming the porous glass portion on the seed rod, a boundary portion between the core portion and the support portion and a region near the boundary portion using a burner flame at a predetermined cooling rate. A method for manufacturing an optical fiber preform, characterized by: 2. The method of manufacturing an optical fiber preform according to claim 1, wherein said cooling step cools said boundary portion and said neighboring region by lowering the flame temperature of said burner. 3. The method of manufacturing an optical fiber preform according to claim 1, wherein the predetermined cooling rate is 5[deg.] C./min or more and 20[deg.] C./min or less. 4. The method of manufacturing an optical fiber preform according to any one of claims 1 to 3, wherein the cooling step is performed in a temperature range including 1090[deg.]C. 5. The method of manufacturing an optical fiber preform according to claim 4, wherein the cooling step is performed in a temperature range of at least 1080[deg.] C. or higher and 1100[deg.] C. or lower. 6. The method of manufacturing an optical fiber preform according to claim 4, wherein the cooling step is performed in a temperature range of at least 1050[deg.] C. or higher and 1150[deg.] C. or lower. The weight of the optical fiber preform is 180 kg or more,
7. The method of manufacturing an optical fiber preform according to any one of claims 1 to 6, wherein the support portion has a substantially cylindrical shape and has a diameter of 63 mm or more. 8. The method of manufacturing an optical fiber preform according to claim 1, wherein said optical fiber preform is of horizontal type. 9. The method of manufacturing an optical fiber preform according to any one of claims 1 to 8, wherein the neighboring region includes part of the support portion. 10. The method of manufacturing an optical fiber preform according to claim 9, wherein said neighboring region further includes an end portion of said porous glass portion. 11. The method of manufacturing an optical fiber preform according to claim 9, wherein the part of the support portion is a region with a length of 800 mm or less from the boundary portion in the longitudinal direction of the support portion. . 12. The method of manufacturing an optical fiber preform according to any one of claims 2 to 11, wherein the burner is an auxiliary burner for quenching. 13. A method for manufacturing an optical fiber, wherein the optical fiber preform manufactured by the method for manufacturing an optical fiber preform according to any one of claims 1 to 12 is drawn at a high temperature to manufacture an optical fiber.

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