JP6081534B2 - Optical fiber manufacturing method and optical fiber manufacturing apparatus - Google Patents

Description

  The present invention relates to an optical fiber manufacturing method and an optical fiber manufacturing apparatus.

  Currently, the production method of optical fiber preforms for long distances is mainly based on the gas phase method, and the process up to the completion of the fiber is roughly divided into the production of porous preforms and sintering of the preforms (transparency) 3) Fiber drawing.

There are the following four typical methods for producing a porous base material by a vapor phase method.
{1} OVD method (Outside Vapor Deposition Method)
{2} MCVD method (Modified Chemical Vapor Deposition Method)
{3} PCVD method (Plasma Chemical Vapor Deposition Method)
{4} VAD method (Vapor-phase Axial Deposition Method)

Here, the manufacturing method of an optical fiber will be described by taking the {4} VAD method, which is the current mainstream, as an example (FIG. 1). In the production of the porous base material, the raw material gas (SiCl ₄ , GeCl ₄ ) supplied from the raw material supply system is guided into the flame of the oxyhydrogen burner, and the SiCl _{4 is} burned in the burner combustion section by the water generated by the combustion. + 2H ₂ O-> SiO ₂ + 4HCl
_{GeCl 4 + 2H 2 O ->} GeO 2 + 4HCl
Subject to flame hydrolysis. Upon undergoing this flame hydrolysis, quartz glass fine particles (soot) are formed. The fine particles are deposited on the tip of the starting material. Since the glass fine particles are deposited in the axial direction, the starting material is pulled upward while rotating in accordance with the growth rate, and a porous base material is formed. Next, when the porous base material is put in a heating furnace and heated to a high temperature, the sintering proceeds, the volume shrinks, and the voids in the base material are connected to reach outside the base material. When the temperature is further increased, a complete transparent glass body (base material) is obtained. Furthermore, this transparent glass body is inserted into an optical fiber drawing device, and drawing is performed (Non-Patent Document 1).

  As shown in Non-Patent Document 2, a general optical fiber manufacturing apparatus includes a heating furnace, a fiber outer diameter measuring device, a die (coating (resin) coating), a coating (resin) curing device (heating furnace, UV irradiator, etc. ), A capstan, a winding device, a base material feeding device that holds the drawing base material and sends the base material to the heating furnace in accordance with the amount of drawing. (FIG. 2). The transparent glass preform is heated in an electric furnace at about 2000 ° C., and the locally softened glass is reduced in diameter to a desired fiber outer diameter (generally 125 μm). The optical fiber drawn from the lower end of the heating furnace passes through the outer diameter measuring device, the resin coats the fiber surface with a resin applicator, and the resin is cured by a resin curing device (UV light source). Further, the optical fiber is drawn out by a capstan and wound around a bobbin by a winding device. Based on the measurement result of the outer diameter measuring device, the capstan speed is adjusted so that the outer diameter of the fiber is constant.

  On the other hand, in the manufacturing method of a multi-core optical fiber (MCF) that has been rapidly researched and developed in recent years, the drawing process of the optical fiber is basically the same as that of the conventional fiber described above. However, since it is necessary to form a plurality of cores, the manufacturing process of the base material requires a more complicated process than the conventional method described above. Examples of methods for producing these base materials include a stack and draw method and a rod-in-tube method. In the stack and draw method, a plurality of core glass rods and clad glass rods produced by a vapor phase method or the like are inserted into a jacket tube and integrated to produce a base material. On the other hand, in the rod-in-tube method, a core glass rod is inserted into a large-diameter clad glass rod that has been drilled with a drill or the like and integrated to produce a base material.

Shojiro Kawakami, Kazuo Shiraishi, Masaharu Ohashi, “Optical Fiber and Fiber-Type Device”, issued July 10, 1996, p. 11-13 Tetsuya Miki, Shoichi Sudo, “Optical Communication Handbook”, Optronics, published on January 30, 2002, p. 244 T. T. Yajima et al. "OH-Free, Low loss single-mode fiber fabricated by slurry casting / Rod-in-tube method", ECOC2014, Th. 2.4.4 2014.

  However, in the vapor phase method, which is a general base material manufacturing method, it is theoretically difficult to manufacture a base material of a complex structure MCF having a large number of cores in a clad in a series of steps. Even when this is realized, the number of processes increases, and it is difficult to manufacture an MCF base material having a complicated cross-sectional structure with high accuracy, and there is also a problem from the viewpoint of economy. As a method for avoiding these difficulties, the above-described stack and draw method or rod-in-tube method is used. However, in the stack and draw method, it is necessary to combine a large number of rods, and there is a problem that the arrangement of the core is almost limited to a structure in which the rods can be filled finely without gaps. In addition, due to the fact that the drilling process is necessary in the rod-in-tube method, the number of processes is increased, the length of the base material that can be drilled is limited, the base material is destroyed during drilling, and the positional accuracy is deteriorated. There is a problem that there is a possibility of doing.

  In addition to these methods, there is a study example (Non-Patent Document 3) that realizes an increase in the size of the base material by using a powder material as a cladding material, but the study is limited to a single core base material, and the MCF. The example applied to is not known. Further, as shown in the literature, even if it is limited to the production of a base material, it requires a complicated process process that is very finely divided into seven stages, and then an optical fiber drawing process is further added.

  The present invention has been made in view of the above circumstances, and an object thereof is to provide an optical fiber manufacturing method and an optical fiber manufacturing apparatus that can easily manufacture an optical fiber having a complicated structure without including a complicated process. To do.

  In order to achieve the above object, an optical fiber manufacturing method according to the present invention includes one or more core rods (glass rods) or capillary tubes placed in a jacket tube having a closed bottom, and the jacket tube is introduced into a heating furnace. The silica powder was gradually discharged into the gap in the jacket tube, and the silica powder in the jacket tube was melted by a heating source in the heating furnace to form a clad, and at the same time, stretched to the desired fiber outer diameter.

Specifically, an optical fiber manufacturing method according to the present invention includes a jacket tube that is the outermost periphery of a clad portion of an optical fiber with one end of the glass tube closed, and a capillary tube or an optical fiber that is a hole of the optical fiber. An optical fiber manufacturing method for manufacturing an optical fiber using a glass rod as a core part,
Inserting the at least one or more capillary tubes or at least one or more glass rods into the jacket tube;
After the insertion step, the optical fiber is introduced into the gap between the capillary tubes or between the glass rods and between the capillary tube or the glass rod and the jacket tube while introducing the jacket tube into the heating furnace. A silica supplying step of supplying silica powder as a raw material of the cladding part of
A fiber drawing step of heating the jacket tube, melting the silica powder supplied in the silica supply step, and extending the jacket tube to a desired outer diameter to reduce the diameter,
I do.

  In the present optical fiber manufacturing method, a capillary tube or a glass rod is arranged at a desired position in the jacket tube, and heating is performed while supplying silica powder, so that the process from forming the base material to drawing can be performed all at once. For this reason, this invention can provide the optical fiber manufacturing method which can manufacture the optical fiber of a complicated structure more easily than before without including a complicated process.

  The optical fiber manufacturing method according to the present invention is characterized in that the inside of the jacket tube is kept in a vacuum in the silica supplying step and the fiber drawing step. If any gas is present in the jacket tube, it may remain as bubbles in the manufactured optical fiber. The present optical fiber manufacturing method solves this problem by making the jacket tube in a vacuum state.

  The optical fiber manufacturing method according to the present invention is characterized in that, in the fiber drawing step, the jacket tube is heated in the longitudinal direction sequentially at a first temperature and a second temperature. The temperature of the upper heating source is made relatively low, the silica powder is melted slightly to form a porous state, and the shape of the cladding is formed, and the porous portion is completely melted by the lower high-temperature heating source to form a complete glass Can be.

  The optical fiber manufacturing method according to the present invention is characterized in that the silica powder is a glass having a lower melting point than the jacket tube and the capillary tube or the glass rod. Only the charged silica powder is melted first, and the melted silica melt can be evenly distributed in the gaps while maintaining the structure of the jacket tube, the glass rod and the capillary tube.

An optical fiber manufacturing apparatus capable of realizing the above-described optical fiber manufacturing method includes a jacket tube that is the outermost periphery of the cladding portion of the optical fiber with one end of the glass tube closed, and a capillary tube or optical fiber that is a hole of the optical fiber. An optical fiber manufacturing apparatus that manufactures an optical fiber using a glass rod as a core part,
Introducing means for introducing the jacket tube into which at least one or more capillary tubes or at least one or more glass rods are inserted into a heating furnace;
From the end opposite to the heating furnace of the jacket tube introduced into the heating furnace, between the capillary tubes or between the glass rods, and between the capillary tube or the glass rod and the jacket tube Silica supply means for supplying silica powder as a raw material for the clad portion of the optical fiber into the gap,
A fiber drawing unit that heats the jacket tube in the heating furnace, melts the silica powder supplied by the silica supply unit, and extends the jacket tube to a desired outer diameter to reduce the diameter.
Is provided.

  Therefore, the present invention can provide an optical fiber manufacturing apparatus that can easily manufacture an optical fiber having a complicated structure without including a complicated process.

  INDUSTRIAL APPLICABILITY The present invention can provide an optical fiber manufacturing method and an optical fiber manufacturing apparatus that can easily manufacture an optical fiber having a complicated structure without complicated processes.

It is explanatory drawing regarding base material preparation. It is a block diagram of a general optical fiber manufacturing apparatus. It is explanatory drawing regarding the drawing apparatus which concerns on embodiment of this invention. It is explanatory drawing regarding the drawing apparatus which concerns on embodiment of this invention. It is explanatory drawing regarding the drawing apparatus which concerns on embodiment of this invention. It is explanatory drawing regarding the drawing apparatus which concerns on embodiment of this invention. It is explanatory drawing regarding the drawing apparatus which concerns on embodiment of this invention.

  Embodiments of the present invention will be described with reference to the accompanying drawings. The embodiments described below are examples of the present invention, and the present invention is not limited to the following embodiments. In the present specification and drawings, the same reference numerals denote the same components.

(Outline of the embodiment)
The optical fiber manufacturing method described in the following embodiment is:
Placing at least one core rod (glass rod) or capillary tube in a jacket tube having a closed bottom;
A step of gradually discharging the silica powder into the gap between the jacket tube and the glass rod or the capillary tube while gradually introducing the jacket tube produced in the above step into the heating furnace of the drawing apparatus;
The process consists of melting the silica powder introduced by the heating source in the heating furnace, forming the cladding of the optical fiber, reducing the outer diameter of the fiber to the desired fiber diameter, and performing the fiber drawing all at once. And

  Since silica powder can be introduced into the jacket tube in accordance with the production rate of the fiber, productivity can be greatly improved as compared with vapor deposition. In addition, since there is no sintering process required for vapor deposition and the process is performed from the clad formation to the drawing process, the number of processes is reduced compared with the vapor deposition method. Further, the method using the powder material proposed in Non-Patent Document 3 has an advantage that the degreasing step and the sintering step are not required.

  Further, in the discharge step and the drawing step of the optical fiber manufacturing method of the present invention, the inside of the jacket tube is maintained in a vacuum. If any gas is present in the jacket tube, it may remain as bubbles in the manufactured optical fiber, but this problem is solved by making the jacket tube in a vacuum state.

  In the heating furnace of the optical fiber manufacturing method of the present invention, two heating sources are provided above and below the heating furnace and heated at different temperatures. The temperature of the upper heating source is set to a relatively low temperature, the silica powder is melted slightly to form a porous state, and the shape of the clad is formed. To do.

  The silica powder of the optical fiber manufacturing method of the present invention is characterized in that glass having a lower melting point than that of the jacket tube, the glass rod, and the capillary tube is used. The reason for using a silica powder with a low melting point is that only the silica powder that has been introduced melts first, and the melted silica melt spreads evenly between the jacket tube, glass rod, and capillary tube while maintaining the structure. It is for doing so. Examples of silica glass having a low melting point include bromine-added glass, chlorine-added glass, and phosphorus-added glass.

(Embodiment 1)
FIG. 2 is also an optical fiber manufacturing apparatus that realizes the optical fiber manufacturing method of the present embodiment. This optical fiber manufacturing apparatus uses a jacket tube that is the outermost periphery of the clad portion of the optical fiber, and a capillary tube that becomes a hole of the optical fiber or a glass rod that becomes the core portion of the optical fiber, with one end of the glass tube closed. An optical fiber manufacturing apparatus for manufacturing an optical fiber,
Introducing means for introducing the jacket tube into which at least one or more capillary tubes or at least one or more glass rods are inserted into a heating furnace;
From the end opposite to the heating furnace of the jacket tube introduced into the heating furnace, between the capillary tubes or between the glass rods, and between the capillary tube or the glass rod and the jacket tube Silica supply means for supplying silica powder as a raw material for the clad portion of the optical fiber into the gap,
A fiber drawing unit that heats the jacket tube in the heating furnace, melts the silica powder supplied by the silica supply unit, and extends the jacket tube to a desired outer diameter to reduce the diameter.
Is provided.

The optical fiber manufacturing method performed by the optical fiber manufacturing apparatus includes a jacket tube that is the outermost periphery of the cladding portion of the optical fiber, and a capillary tube or an optical fiber core portion that is a hole of the optical fiber, with one end of the glass tube closed. An optical fiber manufacturing method for manufacturing an optical fiber using a glass rod,
Inserting the at least one or more capillary tubes or at least one or more glass rods into the jacket tube;
After the insertion step, an optical fiber is introduced into the gap between the capillary tubes or between the glass rods and between the capillary tube or the glass rod and the jacket tube while introducing the jacket tube into the heating furnace. A silica supplying step of supplying silica powder as a raw material of the cladding part of
A fiber drawing step of heating the jacket tube, melting the silica powder supplied in the silica supply step, and extending the jacket tube to a desired outer diameter to reduce the diameter,
I do.

  Although not shown in FIG. 2, the introducing means performs an insertion process. The fiber drawing means performs a fiber drawing process. In FIG. 2, a heating furnace, an outer diameter measuring device, a resin coating device, a resin curing device, a tension measuring device, a capstan, a screening, a bobbin, and a drawing speed detector are fiber drawing means. The silica supply means performs a silica supply process. FIG. 3 is a view for explaining the vicinity of the heating furnace of the optical fiber manufacturing apparatus of FIG. 2, and is a view for explaining the heating furnace of the silica supply means and the fiber drawing means.

  FIG. 3 shows a case where a single-core single-core fiber is manufactured for simplification. The heating furnace has a gas burner. The silica supply means 101 discharges silica powder having a diameter of several to several tens of μm from the discharge pipe to the jacket pipe by gravity. Compared to the case of discharging using a carrier gas, the diffusion of the silica powder is small, and the silica powder can reach the bottom of the jacket tube with high accuracy. If it adheres to the side surface portion of the jacket tube, it may develop uneven outer diameter of the base material, and it is desirable to reach the bottom portion of the jacket tube as much as possible. In the present embodiment, pure quartz glass is used for the jacket tube and the glass rod, and silica powder to which 1.4 wt% bromine is added is used.

  Although the silica powder was intermittently supplied in units of several to several tens of mg, it can be supplied continuously. The amount of input per unit time is adjusted so as to maintain the same or proportional relationship as the amount of glass consumed per unit time by drawing. As a result of drawing, the light propagation loss was 0.20 dB / km (λ = 1550 nm). Further, as a result of confirming the cross section of the produced optical fiber with a microscope, it is considered that there was no generation of voids and striae in particular, and the effect of using bromine-added quartz glass having a low melting point for the silica powder appeared.

(Embodiment 2)
FIG. 4 is a view for explaining the vicinity of the heating furnace of the optical fiber manufacturing apparatus of FIG. 2, and is a view for explaining the heating furnace of the silica supply means and the fiber drawing means. This embodiment is an example of producing a 6-core single-mode multi-core fiber.

The present embodiment is characterized in that the inside of the jacket tube is kept in a vacuum in the silica supply step and the fiber drawing step.
In this embodiment, the heating furnace is an electric furnace and has a carbon heater. The difference between the present optical fiber manufacturing apparatus and the optical fiber manufacturing apparatus of the first embodiment is that, besides the heating furnace being an electric furnace, an airtight cap 102 that covers from the silica supply means to the electric furnace, a jacket pipe, and a discharge pipe are provided. And a vacuum pump 103 for maintaining a vacuum.

  The silica supply means 101 discharges silica powder having a diameter of several to several tens of μm from the discharge pipe to the jacket pipe by gravity. The silica powder was continuously charged at a constant amount of several g / min. In this embodiment, the jacket tube to the silica supply means 101 are hermetically sealed by the hermetic cap 102 and are evacuated by the vacuum pump 103. As a result, the discharged silica powder does not receive air resistance until it reaches the bottom of the jacket tube, so it is difficult to diffuse and can be discharged to the bottom of the jacket tube at a pinpoint. Another advantage of the vacuum state is that the melt does not sufficiently reach the gap when the initial silica powder is melted, and even if voids are generated, the matrix further melts and approaches the fiber diameter. It is possible to eliminate voids. In the present embodiment, pure quartz glass is used for the jacket tube and the glass rod, and pure quartz is used for the silica powder. The optical propagation loss of the manufactured optical fiber was 0.22 dB / km (λ = 1550 nm) as an average value of 6 cores.

(Embodiment 3)
FIG. 5 is a view for explaining the vicinity of the heating furnace of the optical fiber manufacturing apparatus of FIG. 2, and is a view for explaining the heating furnace of the silica supply means and the fiber drawing means. This embodiment is an example of producing a 6-core single-mode multi-core fiber.

In this embodiment, in the fiber drawing step, the jacket tube is heated in the longitudinal direction in order at a first temperature and a second temperature. The silica powder is glass having a lower melting point than the jacket tube and the capillary tube or the glass rod.
The difference between the optical fiber manufacturing apparatus of this embodiment and the optical fiber manufacturing apparatus of Embodiment 2 is that the electric furnace has two stages of carbon heaters. In this carbon heater, the lower heater is heated at a higher temperature.

  The introducing means gradually introduces the jacket tube into the electric furnace, and at the same time, the silica supplying means 101 gradually introduces silica powder. When the lower end of the jacket tube passes through the upper carbon heater (low temperature, 1000 to 1500 ° C.), the silica powder having a melting point lower than that of the jacket tube and the glass rod is slightly melted to form a porous state. Further, when the lower end of the jacket tube reaches the lower carbon heater (high temperature, 1600 to 2100 ° C.), the porous silica powder is completely melted and further drawn to be reduced to a desired fiber outer diameter. . The reason for making it porous once is to support and fix the multi-core base material by forming a porous glass that fills the gap between the glass rod and the jacket tube before the outer diameter of the jacket tube changes due to heating. Yes, the position accuracy of the multi-core base material can be greatly improved.

  In this embodiment, pure quartz glass is used for the jacket tube and the glass rod, and silica powder to which 1.2 wt% bromine is added is used. The produced single-mode 6-core multi-core optical fiber (MCF) has an optical propagation loss of 0.20 dB / km (λ = 1550 nm) as an average of 6 cores. The core was 0.1 μm or less. When the same 6-core single-mode multi-core fiber was manufactured with the optical fiber manufacturing apparatus of the second embodiment, the average value of the deviation of the inter-core distance was 0.25 μm. Therefore, the optical fiber manufacturing apparatus of the present embodiment is Succeeded in greatly improving the position accuracy.

(Embodiment 4)
FIG. 6 is a view for explaining the vicinity of the heating furnace of the optical fiber manufacturing apparatus of FIG. 2, and is a view for explaining the heating furnace of the silica supply means and the fiber drawing means. This embodiment is an example of producing a six-hole photonic crystal fiber.

  The configuration of the optical fiber manufacturing apparatus of the present embodiment is the same as the configuration of the optical fiber manufacturing apparatus of the third embodiment. The difference from Embodiment 3 is that the element inserted into the jacket tube is not a glass rod but a capillary tube. A capillary tube was prepared in which Ar gas at 1.1 atm was sealed and the upper and lower openings were closed. This is because when the inside of the jacket tube is evacuated, the inside of the holes is slightly pressurized. Hole-type fibers are often drawn while maintaining the shape of the holes in the base material and the ratio of the hole area to the fiber cross-sectional area. Even when the volume of the capillary tube is reduced during drawing, the fiber is broken. Never do.

As in the case of the third embodiment, the inside of the jacket tube is decompressed and is in a vacuum state. The silica supply means 101 discharges silica powder having a diameter on the order of several to several tens of μm from the discharge pipe by gravity. The silica powder was continuously charged at a constant amount of several g / min. In this embodiment, pure quartz glass is used for the jacket tube and the capillary tube, and silica powder to which 1.0 wt% bromine is added is used. The optical propagation loss of the manufactured optical fiber was 0.25 dB / km (λ = 1550 nm) in the LP ₀₁ mode.

(Embodiment 5)
FIG. 7 is a view for explaining the vicinity of the heating furnace of the optical fiber manufacturing apparatus of FIG. 2 and for explaining the heating furnace of the silica supply means and the fiber drawing means. The present embodiment is an example of producing a fiber (hole assist fiber, HAF) having 6 holes and a core capable of single mode propagation at the center.

  The configuration of the optical fiber manufacturing apparatus of the present embodiment is the same as the configuration of the optical fiber manufacturing apparatus of the third embodiment. The difference from Embodiment 3 is that the elements inserted into the jacket tube are one glass rod and six capillary tubes around it. A capillary tube with 1.05 atm Ar gas sealed and with the upper and lower openings closed was prepared. This is because when the inside of the jacket tube is evacuated, the inside of the holes is slightly pressurized. Hole-type fibers are often drawn while maintaining the shape of the holes in the base material and the ratio of the hole area to the fiber cross-sectional area. Even when the volume of the capillary tube is reduced during drawing, the fiber is broken. Never do. A glass rod having a relative refractive index difference of 0.35% was used.

As in the case of the third embodiment, the inside of the jacket tube is decompressed and is in a vacuum state. The silica supply means 101 discharges silica powder having a diameter on the order of several to several tens of μm from the discharge pipe by gravity. The silica powder was continuously charged at a constant amount of several g / min. In this embodiment, pure quartz glass is used for the jacket tube, glass rod, and capillary tube, and silica powder to which 1.0 wt% of bromine is added is used. The optical propagation loss of the manufactured optical fiber was 0.21 dB / km (λ = 1550 nm) in the LP ₀₁ mode.

[Appendix]
The following describes the optical fiber manufacturing method and the optical fiber manufacturing apparatus of the present embodiment.

(the purpose)
Easily fill the clad part with silica material (direct melting while filling the silica material simplifies the deposition and sintering process, and the spinning process is performed in one process), and the MCF and other complicated processes In manufacturing optical fibers with a simple structure, the number of manufacturing processes is reduced and the base material is formed with high accuracy (the clad region is formed in a lump by melting while filling the silica material, and the process from filling to sintering is made one step. ) To drawing all at once.

(1):
Placing at least one glass rod or capillary tube in a jacket tube closed at the bottom;
A step of gradually discharging silica powder into the gap between the jacket tube and the glass rod or capillary tube while introducing the jacket tube produced in the above step into the heating furnace of the drawing apparatus;
An optical fiber comprising a process of melting silica powder introduced by a heating source in a heating furnace, forming an optical fiber clad, and simultaneously reducing the diameter to a desired fiber outer diameter and performing fiber drawing all at once. Manufacturing method.

(2):
The method for producing an optical fiber according to (1) above, wherein the inside of the jacket tube is kept in a vacuum in the discharging step and the drawing step.

(3):
The method for producing an optical fiber according to the above (1) or (2), wherein the heating furnace has two heating sources at the upper and lower sides and is heated at different temperatures.

(4):
4. The method for producing an optical fiber according to any one of (1) to (3), wherein glass having a lower melting point than that of the jacket tube, the glass rod, and the capillary tube is used as the silica powder.

(5):
An apparatus for manufacturing an optical fiber, wherein the discharge step and the drawing step according to any one of (1) to (4) are performed.

(effect)
According to the present invention, it is possible to easily fill the clad part with the silica material, reduce the number of manufacturing steps, and perform batch formation from base material formation to drawing with high accuracy. In addition, since the cladding material can be easily filled, it is easy to produce a large base material.

101: Silica supply means 102: Airtight cap 103: Vacuum pump

Claims (5)

Light that manufactures an optical fiber using a jacket tube that is the outermost periphery of the cladding portion of the optical fiber with one end of the glass tube closed, and a capillary tube that becomes a hole of the optical fiber or a glass rod that becomes the core portion of the optical fiber A fiber manufacturing method comprising:
Inserting the at least one or more capillary tubes or at least one or more glass rods into the jacket tube;
After the insertion step, the optical fiber is introduced into the gap between the capillary tubes or between the glass rods and between the capillary tube or the glass rod and the jacket tube while introducing the jacket tube into the heating furnace. A silica supplying step of supplying silica powder as a raw material of the cladding part of
A fiber drawing step of heating the jacket tube, melting the silica powder supplied in the silica supply step, and extending the jacket tube to a desired outer diameter to reduce the diameter,
An optical fiber manufacturing method.   2. The method of manufacturing an optical fiber according to claim 1, wherein the inside of the jacket tube is kept in a vacuum in the silica supplying step and the fiber drawing step.   3. The method of manufacturing an optical fiber according to claim 1, wherein in the fiber drawing step, the jacket tube is sequentially heated in a longitudinal direction at a first temperature and a second temperature. The fiber drawing step, while holding the jacket tube and the capillary tube or structure of the glass rod, one of claims 1 to 3, characterized that you have a process to melt only the first said silica powder A method of manufacturing the optical fiber according to claim 1.
Light that manufactures an optical fiber using a jacket tube that is the outermost periphery of the cladding portion of the optical fiber with one end of the glass tube closed, and a capillary tube that becomes a hole of the optical fiber or a glass rod that becomes the core portion of the optical fiber A fiber manufacturing device,
Introducing means for introducing the jacket tube into which at least one or more capillary tubes or at least one or more glass rods are inserted into a heating furnace;
From the end opposite to the heating furnace of the jacket tube introduced into the heating furnace, between the capillary tubes or between the glass rods, and between the capillary tube or the glass rod and the jacket tube Silica supply means for supplying silica powder as a raw material for the clad portion of the optical fiber into the gap,
A fiber drawing unit that heats the jacket tube in the heating furnace, melts the silica powder supplied by the silica supply unit, and extends the jacket tube to a desired outer diameter to reduce the diameter.
An optical fiber manufacturing apparatus comprising: