WO2012111436A1 - Method for manufacturing optical fibers - Google Patents

Method for manufacturing optical fibers Download PDF

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Publication number
WO2012111436A1
WO2012111436A1 PCT/JP2012/052303 JP2012052303W WO2012111436A1 WO 2012111436 A1 WO2012111436 A1 WO 2012111436A1 JP 2012052303 W JP2012052303 W JP 2012052303W WO 2012111436 A1 WO2012111436 A1 WO 2012111436A1
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WO
WIPO (PCT)
Prior art keywords
optical fiber
base material
glass base
hole
ratio
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PCT/JP2012/052303
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French (fr)
Japanese (ja)
Inventor
下高原　巌
治巳 稲葉
熊野　尚美
杉崎　隆一
Original Assignee
古河電気工業株式会社
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Publication of WO2012111436A1 publication Critical patent/WO2012111436A1/en

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    • C—CHEMISTRY; METALLURGY
    • C03—GLASS; MINERAL OR SLAG WOOL
    • C03B—MANUFACTURE, SHAPING, OR SUPPLEMENTARY PROCESSES
    • C03B37/00—Manufacture or treatment of flakes, fibres, or filaments from softened glass, minerals, or slags
    • C03B37/01—Manufacture of glass fibres or filaments
    • C03B37/02—Manufacture of glass fibres or filaments by drawing or extruding, e.g. direct drawing of molten glass from nozzles; Cooling fins therefor
    • C03B37/025—Manufacture of glass fibres or filaments by drawing or extruding, e.g. direct drawing of molten glass from nozzles; Cooling fins therefor from reheated softened tubes, rods, fibres or filaments, e.g. drawing fibres from preforms
    • C03B37/027—Fibres composed of different sorts of glass, e.g. glass optical fibres
    • C03B37/02781—Hollow fibres, e.g. holey fibres
    • C—CHEMISTRY; METALLURGY
    • C03—GLASS; MINERAL OR SLAG WOOL
    • C03B—MANUFACTURE, SHAPING, OR SUPPLEMENTARY PROCESSES
    • C03B2203/00—Fibre product details, e.g. structure, shape
    • C03B2203/10—Internal structure or shape details
    • C03B2203/14—Non-solid, i.e. hollow products, e.g. hollow clad or with core-clad interface
    • C—CHEMISTRY; METALLURGY
    • C03—GLASS; MINERAL OR SLAG WOOL
    • C03B—MANUFACTURE, SHAPING, OR SUPPLEMENTARY PROCESSES
    • C03B2203/00—Fibre product details, e.g. structure, shape
    • C03B2203/42—Photonic crystal fibres, e.g. fibres using the photonic bandgap PBG effect, microstructured or holey optical fibres
    • G—PHYSICS
    • G02—OPTICS
    • G02B—OPTICAL ELEMENTS, SYSTEMS OR APPARATUS
    • G02B6/00—Light guides; Structural details of arrangements comprising light guides and other optical elements, e.g. couplings
    • G02B6/02—Optical fibres with cladding with or without a coating
    • G02B6/02295—Microstructured optical fibre
    • G02B6/02314—Plurality of longitudinal structures extending along optical fibre axis, e.g. holes
    • G02B6/02342—Plurality of longitudinal structures extending along optical fibre axis, e.g. holes characterised by cladding features, i.e. light confining region
    • G02B6/02357—Property of longitudinal structures or background material varies radially and/or azimuthally in the cladding, e.g. size, spacing, periodicity, shape, refractive index, graded index, quasiperiodic, quasicrystals

Definitions

  • the present invention relates to a method for manufacturing an optical fiber having a plurality of holes extending along a longitudinal axis.
  • a so-called holey fiber (Holey Fiber: HF) or photonic crystal fiber (Photonic Crystal Fiber: PCF), or a photonic band gap is used.
  • fiber Photonic BandGap Fiber: PBGF
  • hole assist fiber Hole Assisted Fiber: HAF
  • HF is an optical fiber of a type in which holes are regularly arranged in the cladding around the core to lower the average refractive index of the cladding and realize light confinement using the principle of total reflection.
  • PBGF forms photonic band gaps by arranging vacancies in the cladding part so as to form a photonic crystal, and introduces a core part as a crystal defect therein to realize light confinement.
  • a core part may be formed of a void
  • HAF is formed from a solid core portion doped with germanium (Ge) or the like and a cladding portion, as in a normal solid optical fiber, and light confinement is realized mainly by the principle of total reflection.
  • This is an optical fiber of a type in which holes are further provided in the cladding part to lower the average refractive index of the cladding part and to improve the light confinement characteristics in the core part.
  • HAF can improve the light confinement characteristics by providing holes near the core, bending loss can be significantly reduced.
  • HAF not only the fundamental mode but also higher-order mode light is easily confined, so that it is easy to make a multimode.
  • HAF in order to realize single mode propagation by confining only fundamental mode light and to reduce bending loss of single mode propagation, optimization of hole diameter, number of holes, core-hole distance, etc. Will be needed. Recently, from these viewpoints, a design in which the hole diameter is reduced and the number of holes is increased to about 10 has been proposed (see Non-Patent Document 1).
  • the present invention has been made in view of the above, and an object thereof is to provide an optical fiber manufacturing method capable of realizing a reduction in manufacturing cost.
  • an optical fiber manufacturing method is a glass base material having a plurality of holes extending along a longitudinal axis.
  • the ratio with the diameter is the second ratio
  • the pressure in the at least one hole of the glass base material is such that the ratio between the second ratio and the first ratio is less than 1.0.
  • the line drawing is performed by adjusting.
  • the optical fiber manufacturing method according to the present invention is characterized in that, in the above invention, the ratio of the second ratio to the first ratio is 0.5 or more.
  • the optical fiber manufacturing method according to the present invention is characterized in that, in the above invention, the plurality of pores of the glass base material are pressurized with different pressures.
  • the optical fiber manufacturing method according to the present invention is characterized in that, in the above invention, the diameter of the plurality of holes in the glass base material is 3 mm or more.
  • FIG. 1 is a schematic cross-sectional view of an optical fiber manufactured by the manufacturing method according to the first embodiment.
  • FIG. 2 is a schematic perspective view of a glass preform for manufacturing the optical fiber shown in FIG.
  • FIG. 3 is a diagram for explaining a drawing process.
  • FIG. 4 is a diagram showing the relationship between the dimensionless in-hole pressurization amount and the ratio (X / Y).
  • FIG. 5 is a diagram showing the relationship between the ratio (X / Y) and the dimensionless pore diameter variation.
  • FIG. 6 is a schematic cross-sectional view of an optical fiber manufactured by the manufacturing method according to the second embodiment.
  • FIG. 7 is a schematic perspective view of a glass preform for manufacturing the optical fiber shown in FIG.
  • FIG. 8 is a schematic diagram of a pressure mechanism used in the manufacturing method according to the second embodiment.
  • FIG. 9 is a schematic cross-sectional view of another optical fiber that can be manufactured by the manufacturing method according to the second embodiment.
  • the cutoff wavelength is ITU-T (International Telecommunication Union) This refers to the fiber cutoff wavelength defined in 650.1.
  • ITU-T G.A. 650.1 and G.I. It shall follow the definition and measurement method in 650.2.
  • FIG. 1 is a schematic cross-sectional view of an optical fiber manufactured by the manufacturing method according to Embodiment 1 of the present invention.
  • the optical fiber 1 is a HAF and includes a core portion 1a and a clad portion 1b formed on the outer periphery of the core portion 1a.
  • the core portion 1a is made of quartz glass to which a dopant for increasing the refractive index such as germanium (Ge) is added.
  • the clad part 1b is made of quartz glass having a lower refractive index than that of the core part 1a, for example, pure silica glass not containing a dopant for adjusting the refractive index.
  • the cross-sectional refractive index distribution shape around the core portion 1a is a rectangle (step index), a pseudo rectangle (pseudo step index) with a skirt at the boundary with the cladding portion 1b, and a Gaussian distribution shape (refractive index distribution coefficient ⁇ is approximately 2. Graded index) may be used.
  • the clad portion 1b has ten holes 1c formed so as to surround the core portion 1a and extending along the longitudinal axis.
  • Two holes 1c are formed when the center point of the core portion 1a is connected to each of the center points of any two adjacent holes 1c in a cross section perpendicular to the longitudinal direction of the optical fiber 1. Are formed at positions where the angles (center angles) formed by the line segments are equal.
  • the holes 1c have the same diameter (hereinafter referred to as the hole diameter).
  • the hole diameter of the hole 1c is d1.
  • the outer diameter of the optical fiber 1 is D1.
  • X1 d1 / D1.
  • FIG. 2 is a schematic perspective view of a glass base material for manufacturing the optical fiber 1.
  • the glass base material 2 is a columnar shape made of quartz glass, and a core portion 2a for forming each of the core portion 1a, the cladding portion 1b, and the hole 1c of the optical fiber 1, It has a clad portion 2b and a hole 2c.
  • the air holes 2 c extend along the longitudinal axis of the glass base material 2.
  • the holes 2c have the same hole diameter.
  • the hole diameter of the hole 2c is d2.
  • the outer diameter of the glass base material 2 is D2.
  • Y1 d2 / D2.
  • the length of the glass base material 2 is L1.
  • the glass base material 2 can be prepared as follows, for example. First, using a known method such as a VAD (Vapor phase Axial Deposition) method, an OVD (Outside Vapor Deposition) method, or an MCVD (Modified Chemical Vapor Deposition) method, a glass base material having a core portion 2a and a cladding portion 2b is formed. Form. Thereafter, holes 2c are formed along the longitudinal axis of the glass base material using a drill. Thereby, the glass base material 2 shown in FIG. 2 can be prepared.
  • VAD Very phase Axial Deposition
  • OVD Outside Vapor Deposition
  • MCVD Modified Chemical Vapor Deposition
  • FIG. 3 is a diagram for explaining a drawing process.
  • a drawing apparatus 100 shown in FIG. 3 includes a drawing heating furnace 101 having a heater 101a, a pressurizing mechanism 102, an outer diameter measuring device 103, a coating resin coating apparatus 104, a resin curing apparatus 105, and a capstan roller. 106, a guide roll 107, and a controller C.
  • the pressurizing mechanism 102 includes a pressurizing connector 102a, a gas supply path 102b connected to the pressurizing connector 102a, and a pressure adjusting unit 102c connected to the gas supply path 102b.
  • the pressure adjusting unit 102c is configured by, for example, a mass flow controller (MFC).
  • MFC mass flow controller
  • the drawing process of the optical fiber 1 will be described together with the operation of each component.
  • the glass base material 2 shown in FIG. 2 is set in the drawing heating furnace 101, and the pressure connector 102 a is connected to the upper end of the glass base material 2.
  • the lower end of the glass base material 2 is heated and melted by the heater 101a, and the lower end is drawn.
  • the optical fiber 1 shown in FIG. 1 is drawn from the glass preform 2.
  • gas G is supplied into the air holes 2c of the glass base material 2 and pressurized.
  • the gas G is supplied from the pressurizing connector 102a into the hole 2c through the gas supply path 102b.
  • the pressure of the gas G in the hole 2c is controlled by the pressure adjusting unit 102c controlled by the controller C so that the hole diameter of the hole 1c of the optical fiber 1 becomes d1.
  • the gas G is, for example, argon gas, but may be other inert gas such as helium gas or nitrogen gas.
  • the drawn optical fiber 1 is coated with a known coating resin coating device 104 and resin curing device 105, sent by a capstan roller 106 and a guide roll 107, and wound on a winder (not shown). .
  • the controller C controls the rotational speed of the capstan roller 106 (that is, the drawing speed of the optical fiber 1) so that the outer diameter of the optical fiber 1 measured by the outer diameter measuring device 103 becomes D1.
  • (X1 / Y1) (d1 / D1) / (d2 / D2) ⁇ 1.0.
  • the ratio X1 is 0.028.
  • the hole diameter d2 of the glass base material 2 is 3 mm and the outer diameter D2 is 70 mm
  • the ratio Y1 is 0.043, so X1 / Y1 is 0.65, and (X1 / Y1) ⁇ 1.0 holds.
  • the hole diameter of the holes formed in the glass base material must be reduced to about 2 mm. I must.
  • (X1 / Y1) ⁇ 1.0 is established.
  • the hole diameter d2 of the glass base material 2 is, for example, 3 mm, which is larger than 2 mm, and the hole diameter d2 can be made relatively large.
  • the length can be increased. Therefore, the length L1 of the glass base material 2 can be increased.
  • a hole 2c having a large hole diameter d2 is previously formed in the glass preform 2 with respect to the ratio X1 between the hole diameter d1 and the outer diameter D1 of the optical fiber 1 to be manufactured. I have to. Then, by adjusting the pressure of the gas G in the hole 2c during the subsequent drawing, the ratio of the hole diameter d1 and the outer diameter D1 is adjusted to a desired ratio X1. As a result, since the length of the drill that can be used for forming the hole 2c can be increased while maintaining the mechanical strength, the length of the glass base material 2 can also be increased. Accordingly, the length of the optical fiber 1 that can be manufactured from one glass base material 2 is increased, and thus the manufacturing cost is reduced.
  • the ratio ⁇ (optical fiber hole diameter) / (optical fiber outer diameter) ⁇ between the hole diameter and the outer diameter of the optical fiber is set to X
  • the ratio ⁇ (glass base material) between the hole diameter and the outer diameter of the glass base material is set to X
  • the ratio ⁇ (glass base material) between the hole diameter and the outer diameter of the glass base material is set to X
  • the relationship between the pressure in the pores of the glass base material and the ratio (X / Y) will be described where Y is (hole diameter) / (glass base material outer diameter) ⁇ .
  • a glass base material having an outer diameter of 60 mm having the same structure as the glass base material 2 shown in FIG. 2 and having 10 holes having a hole diameter of 3.5 mm was prepared.
  • an experiment was carried out in which an optical fiber having an outer diameter (cladding diameter) of 125 ⁇ m was drawn from the prepared glass base material with various pressure settings in the glass base material.
  • the pressure in the hole is defined by the dimensionless pressure in the hole.
  • the dimensionless vacancy pressure is the difference between the pressure in the cavities and the atmospheric pressure (hereinafter, this pressure difference is referred to as the vacancy pressure) and the ratio (X / Y) is 1. It is defined as the value divided by the amount of pressurization in the hole.
  • FIG. 4 is a diagram showing the relationship between the dimensionless in-hole pressurization amount and the ratio (X / Y). As shown in FIG. 4, when the amount of pressurization in dimensionless holes is increased, the ratio (X / Y) is increased accordingly. Therefore, a desired ratio (X / Y) can be realized by controlling the pressure in the holes in accordance with the relationship between the dimensionless pressure in the holes and the ratio (X / Y) as shown in FIG. it can.
  • the fluctuation of the hole diameter is defined by the dimensionless hole diameter fluctuation.
  • the dimensionless hole diameter variation is the fluctuation amount per 1 km of optical fiber (maximum value and minimum value) of the average hole diameter (unit: ⁇ m) of 10 holes when the ratio (X / Y) is a certain value. (Hereinafter referred to as pore diameter fluctuation) is divided by the hole diameter fluctuation where the ratio (X / Y) is 1.
  • FIG. 5 is a diagram showing the relationship between the ratio (X / Y) and the dimensionless pore diameter variation. As shown in FIG. 5, it is preferable that X / Y is 0.5 or more because the dimensionless pore diameter variation is smaller than 1.5, and the variation in the longitudinal direction of the pore diameter is reduced.
  • the ratio (X / Y) is smaller than 1.0, the length of the glass base material can be increased. However, if the ratio (X / Y) is 0.7 or less, the effect is remarkable. This is more preferable.
  • Example 1 Comparative Example 1
  • a glass base material having a core portion containing Ge in the center portion and a cladding portion around the core portion was obtained. Furthermore, this glass base material was extended
  • stretched with the oxyhydrogen flame burner the method by the heating with an electric furnace may be used.
  • the cross-sectional refractive index distribution shape of this glass base material was a substantially rectangular shape (step index) with a relative refractive index difference of 0.35%.
  • a drilling process was performed on one of the prepared glass base materials to form ten holes having a diameter of 1.9 mm along the longitudinal axis.
  • the length of the glass base material was set to 350 mm because of the mechanical strength of the drill used at this time.
  • the glass base material of the comparative example 1 was prepared.
  • the glass base material of Example 1 was prepared. The distance between the center of the core portion and the center of the hole in the glass base material of Example 1 and the distance in the glass base material of Comparative Example 1 were the same.
  • the optical fiber is drawn while pressurizing the pores of the glass base material of Example 1 and Comparative Example 1, and Examples 1 and 1 of Comparative Example 1 are drawn.
  • An optical fiber was manufactured.
  • Argon gas was used as the pressurized gas.
  • the amount of pressurization in the holes was adjusted so that the average hole diameter of the ten holes was 3.5 ⁇ m.
  • the average hole diameter of the manufactured optical fiber was 3.55 ⁇ m in Example 1, and 3.51 ⁇ m in Comparative Example 1.
  • the outer diameter of each of the optical fibers of Example 1 and Comparative Example 1 was set to 125 ⁇ m. Therefore, in the case of Example 1, the ratio (X / Y) was 0.57, and in the case of Comparative Example 1, the ratio (X / Y) was 1.
  • the transmission loss of the optical fiber of Example 1 was 0.197 dB / km
  • the transmission loss of the optical fiber of Comparative Example 1 was 0.198 dB / km, which was substantially the same.
  • the difference in the values of the optical fibers of Example 1 and Comparative Example 1 was within 10%. Therefore, the optical fibers of Example 1 and Comparative Example 1 had substantially the same characteristics.
  • the glass base material of Example 1 is twice or more longer than the glass base material of Comparative Example 1, the optical fiber of Example 1 is longer than the optical fiber of Comparative Example 1 from each glass base material. Even a long optical fiber was obtained. Therefore, the manufacturing cost of the optical fiber of Example 1 was lower.
  • Example 2 A glass base material having an outer diameter of 70 mm having the same structure as in Example 1 and Comparative Example 1 is prepared, and drilling is performed using a drill to form a hole having a diameter of 3.0 mm along the longitudinal axis. Ten were formed. The drill used at this time had a diameter larger than that of Comparative Example 1 and the drill had higher rigidity, so that the length of the glass base material could be 850 mm. Thereby, the glass base material of Example 2 was prepared.
  • Example 2 the optical fiber was drawn while pressurizing the inside of the glass base material of Example 2 to produce the optical fiber of Example 2.
  • the pressurization amount in the holes was adjusted so that the average hole diameter of the ten holes of the optical fiber was 3.5 ⁇ m.
  • the average hole diameter of the manufactured optical fiber was 3.53 ⁇ m.
  • the outer diameter of the optical fiber was set to 125 ⁇ m. Therefore, in the case of Example 2, the ratio (X / Y) was 0.65.
  • the transmission loss of the optical fiber of Example 2 was 0.196 dB / km, which was substantially the same as Example 1 and Comparative Example 1.
  • the difference in values between the optical fiber of Example 2 and the optical fibers of Example 1 and Comparative Example 1 was within 10%. Therefore, the optical fiber of Example 2 had substantially the same characteristics as those of Example 1 and Comparative Example 1.
  • the glass base material of Example 2 is also twice or more longer than the glass base material of Comparative Example 1, a longer optical fiber was obtained from one glass base material. Therefore, the manufacturing cost of the optical fiber of Example 2 was lower. Further, in the case of the optical fiber of Example 2, the ratio (X / Y) is made larger than that of the optical fiber of Example 1, so that the hole diameter variation in the longitudinal direction of the optical fiber is suppressed to be smaller than that of Example 1. It was done.
  • Example 3 One glass base material having an outer diameter of 70 mm having the same structure as in Example 1 and Comparative Example 1 is prepared, drilling is performed using a drill, and a hole having a diameter of 5.0 mm is formed along the longitudinal axis. Ten were formed. The drill used at this time had a larger diameter than in the case of Examples 1 and 2, and the rigidity of the drill was further increased, so that the length of the glass base material could be 920 mm. Thereby, the glass base material of Example 3 was prepared.
  • Example 3 the optical fiber was drawn while pressurizing the pores of the glass base material of Example 3 to produce the optical fiber of Example 3.
  • the pressurization amount in the holes was adjusted so that the average hole diameter of the ten holes of the optical fiber was 3.5 ⁇ m.
  • the average hole diameter of the manufactured optical fiber was 3.54 ⁇ m.
  • the outer diameter of the optical fiber was set to 125 ⁇ m. Therefore, in the case of Example 3, the ratio (X / Y) was 0.39.
  • the optical fiber of Example 3 had substantially the same characteristics as the optical fibers of Examples 1 and 2 and Comparative Example 1.
  • Example 3 Since the glass base material of Example 3 is longer than the glass base materials of Examples 1 and 2, an optical fiber longer than that of Examples 1 and 2 was obtained from one glass base material. Therefore, the manufacturing cost of the optical fiber of Example 3 was further reduced.
  • the ratio (X / Y) is made smaller than those of Examples 1 and 2, and the hole diameter variation in the longitudinal direction of the optical fiber is the same as that of Comparative Example 1. Although it was about twice as much as the case, it was a value with no problem in use.
  • the hole diameter formed in the glass base material is 3 mm or more because the length of the glass base material can be sufficiently increased and the manufacturing cost can be sufficiently reduced.
  • Example 4 A glass base material having an outer diameter of 70 mm having the same structure as that of Example 1 and Comparative Example 1 was produced, and a drilling process was performed using a drill to form a hole having a diameter of 2.5 mm along the longitudinal axis. Ten were formed. Since the diameter of the drill used at this time was larger than that of Comparative Example 1 and the rigidity of the drill was high, the length of the glass base material was made 480 mm. Thereby, the glass base material of Example 4 was prepared.
  • Example 4 the optical fiber was drawn while pressurizing the pores of the glass base material of Example 4 to produce the optical fiber of Example 4.
  • the pressurization amount in the holes was adjusted so that the average hole diameter of the ten holes of the optical fiber was 3.5 ⁇ m.
  • the average hole diameter of the manufactured optical fiber was 3.54 ⁇ m.
  • the outer diameter of the optical fiber was set to 125 ⁇ m. Therefore, in the case of Example 4, the ratio (X / Y) was 0.79.
  • the transmission loss of the optical fiber of Example 4 was 0.195 dB / km, which was substantially the same as Example 1 and Comparative Example 1. Further, regarding other characteristics such as cutoff wavelength and wavelength dispersion, the difference in values between the optical fiber of Example 4 and the optical fibers of Example 1 and Comparative Example 1 was within 10%. Therefore, the optical fiber of Example 4 had substantially the same characteristics as those of Example 1 and Comparative Example 1.
  • Example 4 Since the glass base material of Example 4 is also longer than the glass base material of Comparative Example 1, a longer optical fiber was obtained from one glass base material. Therefore, the manufacturing cost of the optical fiber of Example 4 was lower. Further, in the case of the optical fiber of Example 4, the ratio (X / Y) was made larger than that of the optical fiber of Example 2, so that the hole diameter variation in the longitudinal direction of the optical fiber was even smaller than that of Example 2. It was suppressed.
  • FIG. 6 is a schematic cross-sectional view of an optical fiber manufactured by the manufacturing method according to the second embodiment. As shown in FIG. 6, the optical fiber 3 has holes 3a and 3b extending along the longitudinal axis.
  • the optical fiber 3 is made of a material such as pure quartz glass.
  • the holes 3 a and 3 b are regularly arranged in a triangular lattice pattern in a cross section perpendicular to the longitudinal axis of the optical fiber 3. However, there is a region where there is no hole in the region where the holes 3a and 3b are arranged.
  • hole functions as the core part 3c, and the circumference
  • the two holes 3b are located on both sides of the core portion 3c.
  • the 16 holes 3a have the same hole diameter.
  • the hole diameter of the hole 3a is d31.
  • the two holes 3b have the same hole diameter.
  • the hole diameter of the hole 3b is d32.
  • the hole diameter d32 is set larger than the hole diameter d31.
  • the outer diameter of the optical fiber 3 is D3.
  • the optical fiber 3 can be used as a polarization-maintaining optical fiber because anisotropy occurs in the refractive index distribution of the core 3c due to the holes 3b.
  • FIG. 7 is a schematic perspective view of a glass base material for manufacturing the optical fiber 3.
  • the glass base material 4 has a cylindrical shape made of quartz glass and has holes 4 a for forming the holes 3 a and 3 b of the optical fiber 3.
  • the air holes 4 a extend along the longitudinal axis of the glass base material 4.
  • the hole diameter of the hole 4a is d4.
  • the outer diameter of the glass base material 4 is D4.
  • the length of the glass base material 4 is L2.
  • the holes 4a having the same hole diameter are formed. is doing. As a result, only one type of drill is required for forming the holes 4a in the drilling process, and the work of replacing the drills with different thicknesses is not necessary. Therefore, since the drilling process is simplified, the manufacturing cost can be reduced.
  • the length of the drill for forming the hole having the smallest hole diameter is the shortest.
  • the length of the glass base material is also limited by the length of the shortest drill.
  • the length L2 of the glass base material 4 can be increased without being restricted as described above.
  • a glass base material is formed using a known method such as the VAD method, and then a glass base material is used using a drill. Holes 4a are formed along the longitudinal axis. Thereby, the glass base material 4 shown in FIG. 7 can be prepared.
  • the optical fiber 3 is drawn from the glass base material 4 using a drawing apparatus 100 as shown in FIG.
  • a drawing apparatus 100 it is necessary to form holes 3 a and 3 b having different hole diameters of the optical fiber 3 from the holes 4 a having the same hole diameter of the glass base material 4. Therefore, it is preferable to control the internal pressure separately for the hole 4a for forming the hole 3a and the hole 4a for forming the hole 3b.
  • FIG. 8 is a schematic diagram of a pressurizing mechanism used in the manufacturing method according to the second embodiment.
  • a pressurizing mechanism 110 shown in FIG. 8 is used instead of the pressurizing mechanism 102 shown in FIG.
  • the pressurization mechanism 110 includes a pressurization connector 111, gas supply paths 112 and 113 connected to the pressurization connector 111, and pressure adjustment units 114 connected to the gas supply paths 112 and 113, respectively. 115.
  • the pressure adjusting units 114 and 115 are connected to the controller C.
  • a gas G is supplied to the pressure adjusting units 114 and 115.
  • the pressure connector 111 includes a first pressure part 111a and a second pressure part 111b.
  • the first pressurizing unit 111 a is configured to supply the gas G only to the hole 4 a for forming the hole 3 a of the optical fiber 3 among the holes 4 a of the glass base material 4.
  • the second pressurizing part 111b is configured to supply the gas G only to the hole 4a for forming the hole 3b.
  • the gas G supplied to the hole 4a for forming the hole 3a is supplied to the first pressurizing unit 111a through the gas supply path 112 and is pressured by the pressure adjusting unit 114 controlled by the controller C. Is adjusted.
  • the gas G supplied to the hole 4a for forming the hole 3b is supplied to the second pressurizing unit 111b through the gas supply path 113 and is pressured by the pressure adjusting unit 115 controlled by the controller C. Is adjusted. Therefore, by using the pressurizing mechanism 110, the pressure in each hole 4a can be controlled separately. Specifically, the pressure in each hole 4a is set so that the pressure in the hole 4a for forming the hole 3b is higher than the pressure in the hole 4a for forming the hole 3a. Be controlled.
  • the ratio (X2 / Y2) is set to be smaller than 1.0, and the ratio (X3 / Y2) is set to 1.0.
  • both the ratio (X2 / Y2) and the ratio (X3 / Y2) may be made smaller than 1.0. By making both smaller than 1.0, the glass base material can be made longer.
  • FIG. 9 is a schematic cross-sectional view of another optical fiber that can be manufactured by the manufacturing method according to the second embodiment. As shown in FIG. 9, the optical fiber 5 has holes 5a and 5b extending along the longitudinal axis.
  • the optical fiber 5 is made of a material such as pure quartz glass.
  • the holes 5a and 5b are regularly arranged in a triangular lattice pattern in a cross section perpendicular to the longitudinal axis of the optical fiber 5.
  • region where the hole 5a, 5b is arranged functions as the core part 5c, and the circumference
  • the six holes 5b are positioned so as to surround the core portion 5c.
  • the 12 holes 5a have the same hole diameter.
  • the hole diameter of the hole 5a is d51.
  • the six holes 5b have the same hole diameter.
  • the hole diameter of the hole 5b is d52.
  • the hole diameter d52 is set larger than the hole diameter d51.
  • this optical fiber 5 a region having a low refractive index is formed around the core portion 5c by the hole 5b having a large hole diameter, and a so-called W-shaped cross-sectional refractive index profile is formed.
  • the optical fiber 5 is also controlled to have a different internal pressure depending on each hole 4a from the glass base material 4 having the holes 4a having the same hole diameter shown in FIG. 7 using the manufacturing method according to the second embodiment. However, it can be manufactured by drawing while drawing. Specifically, the pressure in the hole 4a of the glass base material 4 for forming the hole 5b of the optical fiber 5 is higher than the pressure in the hole 4a for forming the hole 5a. The pressure in each hole 4a may be controlled.
  • the glass base material has holes formed by a drill.
  • the present invention can also be applied to a case where a base material is prepared using a glass tube that becomes a hole.
  • the glass tube can be lengthened. Therefore, a longer and larger glass base material can be prepared using a longer glass tube.
  • pressure control is performed so that the ratio (X / Y) ⁇ 1.0 is satisfied for some or all of the plurality of holes in the glass base material.
  • pressure control may be performed so that the ratio (X / Y) ⁇ 1.0 is satisfied with respect to at least one hole.
  • the outer diameter of the glass base material may be adjusted by applying a known jacket method to the glass base material of the above embodiment.
  • the jacket method is a method of forming a glass base material having a larger outer diameter by inserting the glass base material into a quartz glass tube having an inner diameter that is substantially the same as the outer diameter of the glass base material.
  • the present invention can be applied to the manufacture of various optical fibers having a plurality of holes extending along the longitudinal axis such as PBGF.
  • the optical fiber manufacturing method according to the present invention is suitable for use in manufacturing an optical fiber having a plurality of holes.

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Abstract

This method for manufacturing optical fibers comprises: a preparation step for preparing a glass preform, which has multiple holes extending along the longitudinal axis, and for which the ratio between the diameter of the holes and the outer diameter of the glass preform is defined as a first ratio; and a drawing step for heating and melting one end of the glass preform while applying pressure inside the multiple holes of the glass preform, and drawing an optical fiber having multiple holes extending along the longitudinal axis. If the ratio between the diameter of at least one the holes in the optical fiber and the outer diameter of the optical fiber is defined as a second ratio, the optical fiber is drawn after adjusting the pressure inside at least one hole in the glass preform in such a manner that the ratio between the second ratio and the first ratio decreases to less than 1.0. Manufacturing costs can thus be reduced.

Description

光ファイバの製造方法Optical fiber manufacturing method
　本発明は、長手方向の軸に沿って延びる複数の空孔を有する光ファイバの製造方法に関するものである。 The present invention relates to a method for manufacturing an optical fiber having a plurality of holes extending along a longitudinal axis.
　長手方向の軸に沿って延びる複数の空孔を有する空孔構造光ファイバとして、ホーリーファイバ（Holey　Fiber：ＨＦ）あるいはフォトニッククリスタルファイバ(Photonic　Crystal　Fiber：ＰＣＦ)と呼ばれるものや、フォトニックバンドギャップファイバ（Photonic　BandGap　Fiber：ＰＢＧＦ）や、ホールアシストファイバ（Hole　Assisted　Fiber：ＨＡＦ）等がある。 As a hole-structured optical fiber having a plurality of holes extending along the longitudinal axis, a so-called holey fiber (Holey Fiber: HF) or photonic crystal fiber (Photonic Crystal Fiber: PCF), or a photonic band gap is used. There are fiber (Photonic BandGap Fiber: PBGF), hole assist fiber (Hole Assisted Fiber: HAF), and the like.
　ＨＦとは、コア部の周囲のクラッド部に空孔を規則的に配列してクラッド部の平均屈折率を下げ、全反射の原理を用いて光の閉じ込めを実現するタイプの光ファイバである。また、ＰＢＧＦは、クラッド部に空孔をフォトニック結晶を形成するように配列してフォトニックバンドギャップを形成し、そこに結晶欠陥としてのコア部を導入して、光の閉じ込めを実現するというタイプの光ファイバである。なお、ＰＢＧＦは、コア部も空孔により形成される場合がある。また、ＨＡＦは、通常のソリッド型光ファイバと同じく、ゲルマニウム（Ｇｅ）などがドープされた中実のコア部とクラッド部とから形成され、光の閉じ込めは主に全反射の原理で実現するが、クラッド部にさらに空孔を設けてクラッド部の平均屈折率を下げ、コア部への光の閉じ込め特性を向上させたタイプの光ファイバである。 HF is an optical fiber of a type in which holes are regularly arranged in the cladding around the core to lower the average refractive index of the cladding and realize light confinement using the principle of total reflection. In addition, PBGF forms photonic band gaps by arranging vacancies in the cladding part so as to form a photonic crystal, and introduces a core part as a crystal defect therein to realize light confinement. Type of optical fiber. In addition, as for PBGF, a core part may be formed of a void | hole. HAF is formed from a solid core portion doped with germanium (Ge) or the like and a cladding portion, as in a normal solid optical fiber, and light confinement is realized mainly by the principle of total reflection. This is an optical fiber of a type in which holes are further provided in the cladding part to lower the average refractive index of the cladding part and to improve the light confinement characteristics in the core part.
　ＨＡＦは、空孔をコア近傍に設けることで、光の閉じ込め特性を向上できるため、曲げ損失を著しく低減できる。しかし、ＨＡＦでは、基底モードだけでなく、高次モードの光も閉じ込めやすくなるため、マルチモード化しやすい。ＨＡＦにおいて、基底モードの光のみを閉じ込めてシングルモード伝搬を実現し、かつシングルモード伝搬の曲げ損失を低減するためには、空孔径や、空孔数、コア－空孔間距離などの最適化が必要となってくる。最近では、これらの観点から、空孔直径を小さくし、空孔を１０個程度に増やした設計も提案されている（非特許文献１参照）。 Since HAF can improve the light confinement characteristics by providing holes near the core, bending loss can be significantly reduced. However, in HAF, not only the fundamental mode but also higher-order mode light is easily confined, so that it is easy to make a multimode. In HAF, in order to realize single mode propagation by confining only fundamental mode light and to reduce bending loss of single mode propagation, optimization of hole diameter, number of holes, core-hole distance, etc. Will be needed. Recently, from these viewpoints, a design in which the hole diameter is reduced and the number of holes is increased to about 10 has been proposed (see Non-Patent Document 1).
　これらの空孔構造光ファイバを製造する方法として以下のようなものがある。まず、ガラス母材にドリル装置などで空孔を形成する（特許文献１参照）か、空孔となる石英ガラス管の周囲をガラス材料で充填して（特許文献２参照）、空孔を有するガラス母材を準備する。そして、この空孔を有するガラス母材の空孔もしくは空孔となる石英ガラス管の内圧を制御しつつ線引きを行い、空孔構造光ファイバを製造する（特許文献３参照）。 There are the following methods for manufacturing these hole-structured optical fibers. First, holes are formed in a glass base material with a drill device or the like (see Patent Document 1), or the periphery of a quartz glass tube serving as a hole is filled with a glass material (see Patent Document 2) to have holes. Prepare a glass base material. Then, drawing is performed while controlling the internal pressure of the glass glass material having the holes or the quartz glass tube serving as the holes, and a hole-structured optical fiber is manufactured (see Patent Document 3).
特開２００２－１４５６３４号公報JP 2002-145634 A 特開２００３－３４２０３２号公報JP 2003-342032 A 特開２００４－３０７２５０号公報JP 2004-307250 A
　しかしながら、特許文献１のようにドリルでガラス母材に空孔を開ける場合、直径に比して長いドリルを使用すると、空孔の穿孔中にドリルの曲がりなどが発生するおそれがある。したがって、ガラス母材に形成すべき空孔の直径が設定されると、使用できるドリルの長さが制限され、これによって空孔を有するガラス母材の長さも制限される場合がある。したがって、１つのガラス母材から製造できる空孔構造光ファイバの長さも制限される場合がある。その結果、空孔構造光ファイバの製造コストの低減が困難な場合があるという問題があった。 However, when a hole is made in a glass base material with a drill as in Patent Document 1, if a drill having a length longer than the diameter is used, the drill may be bent while the hole is drilled. Therefore, when the diameter of the hole to be formed in the glass base material is set, the length of the drill that can be used is limited, and thus the length of the glass base material having the hole may be limited. Therefore, the length of the hole-structured optical fiber that can be manufactured from one glass preform may be limited. As a result, there has been a problem that it may be difficult to reduce the manufacturing cost of the hole-structured optical fiber.
　本発明は、上記に鑑みてなされたものであって、製造コストの低減を実現できる光ファイバの製造方法を提供することを目的とする。 The present invention has been made in view of the above, and an object thereof is to provide an optical fiber manufacturing method capable of realizing a reduction in manufacturing cost.
　上述した課題を解決し、目的を達成するために、本発明に係る光ファイバの製造方法は、長手方向の軸に沿って延びる複数の空孔を有するガラス母材であって、前記空孔の直径と当該ガラス母材の外径との比が第１の比であるガラス母材を準備する準備工程と、前記ガラス母材の前記複数の空孔内を加圧しつつ当該ガラス母材の一端を加熱溶融して、長手方向の軸に沿って延びる複数の空孔を有する光ファイバを線引きする線引き工程と、を含み、前記光ファイバの前記空孔の少なくとも一つの直径と当該光ファイバの外径との比を第２の比とすると、前記第２の比と前記第１の比との比が１．０よりも小さくなるように前記ガラス母材の前記少なくとも一つの空孔内の圧力を調整して前記線引きを行うことを特徴とする。 In order to solve the above-described problems and achieve the object, an optical fiber manufacturing method according to the present invention is a glass base material having a plurality of holes extending along a longitudinal axis. A preparation step of preparing a glass base material in which the ratio of the diameter to the outer diameter of the glass base material is a first ratio; and one end of the glass base material while pressurizing the inside of the plurality of pores of the glass base material And drawing an optical fiber having a plurality of holes extending along a longitudinal axis, and drawing at least one diameter of the holes of the optical fiber and an outside of the optical fiber. When the ratio with the diameter is the second ratio, the pressure in the at least one hole of the glass base material is such that the ratio between the second ratio and the first ratio is less than 1.0. The line drawing is performed by adjusting.
　また、本発明に係る光ファイバの製造方法は、上記の発明において、前記第２の比と前記第１の比との比が０．５以上であることを特徴とする。 The optical fiber manufacturing method according to the present invention is characterized in that, in the above invention, the ratio of the second ratio to the first ratio is 0.5 or more.
　また、本発明に係る光ファイバの製造方法は、上記の発明において、前記ガラス母材の前記複数の空孔を互いに異なる圧力で加圧することを特徴とする。 The optical fiber manufacturing method according to the present invention is characterized in that, in the above invention, the plurality of pores of the glass base material are pressurized with different pressures.
　また、本発明に係る光ファイバの製造方法は、上記の発明において、前記ガラス母材の前記複数の空孔の直径を３ｍｍ以上にすることを特徴とする。 The optical fiber manufacturing method according to the present invention is characterized in that, in the above invention, the diameter of the plurality of holes in the glass base material is 3 mm or more.
　本発明によれば、光ファイバの製造コストを低減できるという効果を奏する。 According to the present invention, it is possible to reduce the manufacturing cost of the optical fiber.
図１は、実施の形態１に係る製造方法によって製造する光ファイバの模式的な断面図である。FIG. 1 is a schematic cross-sectional view of an optical fiber manufactured by the manufacturing method according to the first embodiment. 図２は、図１に示す光ファイバを製造するためのガラス母材の模式的な斜視図である。FIG. 2 is a schematic perspective view of a glass preform for manufacturing the optical fiber shown in FIG. 図３は、線引き工程を説明する図である。FIG. 3 is a diagram for explaining a drawing process. 図４は、無次元空孔内加圧量と比（Ｘ／Ｙ）との関係を示す図である。FIG. 4 is a diagram showing the relationship between the dimensionless in-hole pressurization amount and the ratio (X / Y). 図５は、比（Ｘ／Ｙ）と無次元空孔径変動との関係を示す図である。FIG. 5 is a diagram showing the relationship between the ratio (X / Y) and the dimensionless pore diameter variation. 図６は、実施の形態２に係る製造方法によって製造する光ファイバの模式的な断面図である。FIG. 6 is a schematic cross-sectional view of an optical fiber manufactured by the manufacturing method according to the second embodiment. 図７は、図６に示す光ファイバを製造するためのガラス母材の模式的な斜視図である。FIG. 7 is a schematic perspective view of a glass preform for manufacturing the optical fiber shown in FIG. 図８は、実施の形態２に係る製造方法において用いる加圧機構の模式図である。FIG. 8 is a schematic diagram of a pressure mechanism used in the manufacturing method according to the second embodiment. 図９は、実施の形態２に係る製造方法によって製造できる他の光ファイバの模式的な断面図である。FIG. 9 is a schematic cross-sectional view of another optical fiber that can be manufactured by the manufacturing method according to the second embodiment.
　以下に、図面を参照して本発明に係る光ファイバの製造方法の実施の形態を詳細に説明する。なお、この実施の形態によりこの発明が限定されるものではない。また、本明細書においては、カットオフ波長とは、ＩＴＵ－Ｔ（国際電気通信連合）Ｇ．６５０．１で定義するファイバカットオフ波長をいう。その他、本明細書で特に定義しない用語についてはＩＴＵ－Ｔ　Ｇ．６５０．１およびＧ．６５０．２における定義、測定方法に従うものとする。 Embodiments of an optical fiber manufacturing method according to the present invention will be described below in detail with reference to the drawings. Note that the present invention is not limited to the embodiments. In this specification, the cutoff wavelength is ITU-T (International Telecommunication Union) This refers to the fiber cutoff wavelength defined in 650.1. For other terms not specifically defined in this specification, ITU-T G.A. 650.1 and G.I. It shall follow the definition and measurement method in 650.2.
（実施の形態１）
　図１は、本発明の実施の形態１に係る製造方法によって製造する光ファイバの模式的な断面図である。図１に示すように、光ファイバ１は、ＨＡＦであって、コア部１ａと、コア部１ａの外周に形成されたクラッド部１ｂとを備える。 (Embodiment 1)
FIG. 1 is a schematic cross-sectional view of an optical fiber manufactured by the manufacturing method according to Embodiment 1 of the present invention. As shown in FIG. 1, the optical fiber 1 is a HAF and includes a core portion 1a and a clad portion 1b formed on the outer periphery of the core portion 1a.
　コア部１ａは、ゲルマニウム（Ｇｅ）などの屈折率を高めるためのドーパントが添加された石英系ガラスからなる。クラッド部１ｂは、コア部１ａよりも屈折率が低い石英系ガラス、たとえば屈折率調整用のドーパントを含まない純石英ガラスからなる。コア部１ａ周辺の断面屈折率分布形状は、矩形（ステップインデックス）、クラッド部１ｂとの境界にすそが有る疑似矩形（疑似ステップインデックス）、ガウス分布形状（屈折率分布係数αが略２であるグレーデッドインデックス）などでも良い。 The core portion 1a is made of quartz glass to which a dopant for increasing the refractive index such as germanium (Ge) is added. The clad part 1b is made of quartz glass having a lower refractive index than that of the core part 1a, for example, pure silica glass not containing a dopant for adjusting the refractive index. The cross-sectional refractive index distribution shape around the core portion 1a is a rectangle (step index), a pseudo rectangle (pseudo step index) with a skirt at the boundary with the cladding portion 1b, and a Gaussian distribution shape (refractive index distribution coefficient α is approximately 2. Graded index) may be used.
　また、クラッド部１ｂは、コア部１ａを囲むように形成された、長手方向の軸に沿って延びている１０個の空孔１ｃを有している。空孔１ｃは、光ファイバ１の長手方向に垂直な断面において、コア部１ａの中心点と、隣接する任意の２つの空孔１ｃの中心点のそれぞれとを結んだときに形成される２本の線分の成す角度（中心角）が、いずれも等しくなるような位置に形成されている。 Further, the clad portion 1b has ten holes 1c formed so as to surround the core portion 1a and extending along the longitudinal axis. Two holes 1c are formed when the center point of the core portion 1a is connected to each of the center points of any two adjacent holes 1c in a cross section perpendicular to the longitudinal direction of the optical fiber 1. Are formed at positions where the angles (center angles) formed by the line segments are equal.
　空孔１ｃは同一の直径（以下、空孔径と呼ぶ）を有している。空孔１ｃの空孔径はｄ１である。また、光ファイバ１の外径はＤ１である。空孔１ｃの直径ｄ１と光ファイバ１の外径Ｄ１との比を第２の比Ｘ１とすると、Ｘ１＝ｄ１／Ｄ１である。 The holes 1c have the same diameter (hereinafter referred to as the hole diameter). The hole diameter of the hole 1c is d1. The outer diameter of the optical fiber 1 is D1. When the ratio of the diameter d1 of the hole 1c and the outer diameter D1 of the optical fiber 1 is the second ratio X1, X1 = d1 / D1.
　つぎに、本実施の形態１に係る製造方法について具体的に説明する。はじめに、光ファイバ１を製造するためのガラス母材を準備する。図２は、光ファイバ１を製造するためのガラス母材の模式的な斜視図である。図２に示すように、ガラス母材２は、石英系ガラスからなる円柱状であり、光ファイバ１のコア部１ａ、クラッド部１ｂ、および空孔１ｃのそれぞれを形成するためのコア部２ａ、クラッド部２ｂ、および空孔２ｃを有している。空孔２ｃはガラス母材２の長手方向の軸に沿って延びている。 Next, the manufacturing method according to the first embodiment will be specifically described. First, a glass base material for manufacturing the optical fiber 1 is prepared. FIG. 2 is a schematic perspective view of a glass base material for manufacturing the optical fiber 1. As shown in FIG. 2, the glass base material 2 is a columnar shape made of quartz glass, and a core portion 2a for forming each of the core portion 1a, the cladding portion 1b, and the hole 1c of the optical fiber 1, It has a clad portion 2b and a hole 2c. The air holes 2 c extend along the longitudinal axis of the glass base material 2.
　空孔２ｃは同一の空孔径を有している。空孔２ｃの空孔径はｄ２である。また、ガラス母材２の外径はＤ２である。空孔２ｃの直径ｄ２とガラス母材２の外径Ｄ２との比を第１の比Ｙ１とすると、Ｙ１＝ｄ２／Ｄ２である。本実施の形態１では、所望のＸ１に対して、Ｘ１がＹ１より小さくなるようにｄ２、Ｄ２を設定する。すなわち、（Ｘ１／Ｙ１）＝（ｄ１／Ｄ１）／（ｄ２／Ｄ２）＜１．０である。なお、ガラス母材２の長さはＬ１である。 The holes 2c have the same hole diameter. The hole diameter of the hole 2c is d2. Moreover, the outer diameter of the glass base material 2 is D2. When the ratio of the diameter d2 of the air hole 2c and the outer diameter D2 of the glass base material 2 is the first ratio Y1, Y1 = d2 / D2. In the first embodiment, d2 and D2 are set so that X1 is smaller than Y1 with respect to desired X1. That is, (X1 / Y1) = (d1 / D1) / (d2 / D2) <1.0. The length of the glass base material 2 is L1.
　ガラス母材２は、たとえば以下のようにして準備できる。まず、ＶＡＤ（Vapor　phase　Axial　Deposition）法、ＯＶＤ（Outside　Vapor　Deposition）法、ＭＣＶＤ（Modified　Chemical　Vapor　Deposition）法などの周知の方法を用いて、コア部２ａとクラッド部２ｂとを備えるガラス母材を形成する。その後、ドリルを用いてガラス母材の長手方向の軸に沿って空孔２ｃを形成する。これによって、図２に示すガラス母材２を準備できる。 The glass base material 2 can be prepared as follows, for example. First, using a known method such as a VAD (Vapor phase Axial Deposition) method, an OVD (Outside Vapor Deposition) method, or an MCVD (Modified Chemical Vapor Deposition) method, a glass base material having a core portion 2a and a cladding portion 2b is formed. Form. Thereafter, holes 2c are formed along the longitudinal axis of the glass base material using a drill. Thereby, the glass base material 2 shown in FIG. 2 can be prepared.
　つぎに、このガラス母材２から光ファイバ１を線引きする。図３は、線引き工程を説明する図である。図３に示す線引装置１００は、ヒータ１０１ａを有する線引加熱炉１０１と、加圧機構１０２と、外径測定器１０３と、被覆樹脂塗布装置１０４と、樹脂硬化装置１０５と、キャプスタンローラ１０６と、ガイドロール１０７と、制御器Ｃを備える。加圧機構１０２は、加圧用コネクタ１０２ａと、加圧用コネクタ１０２ａに接続したガス供給路１０２ｂと、ガス供給路１０２ｂに接続した圧力調整部１０２ｃとを備える。圧力調整部１０２ｃはたとえばマスフローコントローラ（ＭＦＣ）で構成される。 Next, the optical fiber 1 is drawn from the glass base material 2. FIG. 3 is a diagram for explaining a drawing process. A drawing apparatus 100 shown in FIG. 3 includes a drawing heating furnace 101 having a heater 101a, a pressurizing mechanism 102, an outer diameter measuring device 103, a coating resin coating apparatus 104, a resin curing apparatus 105, and a capstan roller. 106, a guide roll 107, and a controller C. The pressurizing mechanism 102 includes a pressurizing connector 102a, a gas supply path 102b connected to the pressurizing connector 102a, and a pressure adjusting unit 102c connected to the gas supply path 102b. The pressure adjusting unit 102c is configured by, for example, a mass flow controller (MFC).
　つぎに、各構成の作用とともに光ファイバ１の線引き工程を説明する。
　はじめに、図２に示すガラス母材２を線引加熱炉１０１にセットし、ガラス母材２の上端に加圧用コネクタ１０２ａを接続する。つぎに、ガラス母材２の下端をヒータ１０１ａにて加熱溶融して、下端を線引きする。これによって、ガラス母材２から図１に示す光ファイバ１が線引きされる。 Next, the drawing process of the optical fiber 1 will be described together with the operation of each component.
First, the glass base material 2 shown in FIG. 2 is set in the drawing heating furnace 101, and the pressure connector 102 a is connected to the upper end of the glass base material 2. Next, the lower end of the glass base material 2 is heated and melted by the heater 101a, and the lower end is drawn. As a result, the optical fiber 1 shown in FIG. 1 is drawn from the glass preform 2.
　線引きの際には、ガラス母材２の空孔２ｃ内にはガスＧが供給されて加圧される。ガスＧは、加圧用コネクタ１０２ａから、ガス供給路１０２ｂを介して空孔２ｃ内に供給される。ガスＧの空孔２ｃ内での圧力は、制御器Ｃによって制御された圧力調整部１０２ｃによって、光ファイバ１の空孔１ｃの空孔径がｄ１になるように制御される。ガスＧは、たとえばアルゴンガスであるが、ヘリウムガスや窒素ガスなどの他の不活性ガスでもよい。 During drawing, gas G is supplied into the air holes 2c of the glass base material 2 and pressurized. The gas G is supplied from the pressurizing connector 102a into the hole 2c through the gas supply path 102b. The pressure of the gas G in the hole 2c is controlled by the pressure adjusting unit 102c controlled by the controller C so that the hole diameter of the hole 1c of the optical fiber 1 becomes d1. The gas G is, for example, argon gas, but may be other inert gas such as helium gas or nitrogen gas.
　線引きされた光ファイバ１は、公知の被覆樹脂塗布装置１０４と樹脂硬化装置１０５とによって被覆を形成され、キャプスタンローラ１０６とガイドロール１０７とによって送られ、不図示の巻取り器に巻取られる。制御器Ｃは、外径測定器１０３によって測定される光ファイバ１の外径がＤ１になるようにキャプスタンローラ１０６の回転速度（すなわち光ファイバ１の線引き速度）を制御する。 The drawn optical fiber 1 is coated with a known coating resin coating device 104 and resin curing device 105, sent by a capstan roller 106 and a guide roll 107, and wound on a winder (not shown). . The controller C controls the rotational speed of the capstan roller 106 (that is, the drawing speed of the optical fiber 1) so that the outer diameter of the optical fiber 1 measured by the outer diameter measuring device 103 becomes D1.
　本実施の形態１では、（Ｘ１／Ｙ１）＝（ｄ１／Ｄ１）／（ｄ２／Ｄ２）＜１．０になるようにしている。たとえば光ファイバ１について、所望の空孔径ｄ１が３．５μｍ、外径Ｄ１が１２５μｍであるとすると、その比Ｘ１は０．０２８である。これに対して、ガラス母材２の空孔径ｄ２を３ｍｍ、外径Ｄ２を７０ｍｍとすれば、その比Ｙ１は０．０４３となるので、Ｘ１／Ｙ１は０．６５となり、（Ｘ１／Ｙ１）＜１．０が成立する。 In the first embodiment, (X1 / Y1) = (d1 / D1) / (d2 / D2) <1.0. For example, regarding the optical fiber 1, if the desired hole diameter d1 is 3.5 μm and the outer diameter D1 is 125 μm, the ratio X1 is 0.028. On the other hand, if the hole diameter d2 of the glass base material 2 is 3 mm and the outer diameter D2 is 70 mm, the ratio Y1 is 0.043, so X1 / Y1 is 0.65, and (X1 / Y1) <1.0 holds.
　ここで、ガラス母材の空孔径と外径との比と、製造する光ファイバの空孔径と外径との比とが同じになるように光ファイバを製造する場合を考える。この場合、当該比が０．０２８の光ファイバを製造する場合に、外径が７０ｍｍのガラス母材を使用する場合は、ガラス母材に形成する空孔の空孔径を約２ｍｍと小さくしなければならない。これに対して、本実施の形態１では、上述したように、（Ｘ１／Ｙ１）＜１．０が成り立つようにしている。これによって、ガラス母材２の空孔径ｄ２は２ｍｍより大きいたとえば３ｍｍであり、空孔径ｄ２を比較的大きくすることができる。この場合、ガラス母材２に空孔２ｃを形成するためのドリルとして太いものを使用できるので、長さを長くできる。したがって、ガラス母材２の長さＬ１も長くできる。 Here, consider a case where an optical fiber is manufactured such that the ratio between the hole diameter and the outer diameter of the glass base material is the same as the ratio between the hole diameter and the outer diameter of the optical fiber to be manufactured. In this case, when manufacturing an optical fiber having a ratio of 0.028, when using a glass base material having an outer diameter of 70 mm, the hole diameter of the holes formed in the glass base material must be reduced to about 2 mm. I must. On the other hand, in the first embodiment, as described above, (X1 / Y1) <1.0 is established. Thereby, the hole diameter d2 of the glass base material 2 is, for example, 3 mm, which is larger than 2 mm, and the hole diameter d2 can be made relatively large. In this case, since a thick drill can be used as the drill for forming the holes 2c in the glass base material 2, the length can be increased. Therefore, the length L1 of the glass base material 2 can be increased.
　すなわち、本実施の形態１では、製造すべき光ファイバ１の空孔径ｄ１と外径Ｄ１との比Ｘ１に対して、ガラス母材２に、あらかじめ空孔径ｄ２の大きな空孔２ｃを形成するようにしている。そして、その後の線引きの際の空孔２ｃ内のガスＧの圧力の調整によって、空孔径ｄ１と外径Ｄ１との比が所望の比Ｘ１になるように調整している。その結果、空孔２ｃの形成に使用することができるドリルの長さを、機械的強度を維持しつつ長くすることができるため、ガラス母材２の長さも長くすることができる。これによって、１つのガラス母材２から製造できる光ファイバ１の長さが長くなるので、製造コストが低減される。 That is, in the first embodiment, a hole 2c having a large hole diameter d2 is previously formed in the glass preform 2 with respect to the ratio X1 between the hole diameter d1 and the outer diameter D1 of the optical fiber 1 to be manufactured. I have to. Then, by adjusting the pressure of the gas G in the hole 2c during the subsequent drawing, the ratio of the hole diameter d1 and the outer diameter D1 is adjusted to a desired ratio X1. As a result, since the length of the drill that can be used for forming the hole 2c can be increased while maintaining the mechanical strength, the length of the glass base material 2 can also be increased. Accordingly, the length of the optical fiber 1 that can be manufactured from one glass base material 2 is increased, and thus the manufacturing cost is reduced.
　つぎに、光ファイバの空孔径と外径との比{（光ファイバ空孔径）／（光ファイバ外径）}をＸとし、ガラス母材の空孔径と外径との比{（ガラス母材空孔径）／（ガラス母材外径）}をＹとし、ガラス母材の空孔内の圧力と、比（Ｘ／Ｙ）との関係について説明する。以下では、図２に示すガラス母材２と同様の構造を有し、空孔径が３．５ｍｍの空孔を１０個形成した外径６０ｍｍのガラス母材を準備した。そして、ガラス母材の空孔内の圧力の設定を様々な値にして、準備したガラス母材から外径（クラッド径）１２５μｍの光ファイバを線引きする実験を行った。 Next, the ratio {(optical fiber hole diameter) / (optical fiber outer diameter)} between the hole diameter and the outer diameter of the optical fiber is set to X, and the ratio {(glass base material) between the hole diameter and the outer diameter of the glass base material. The relationship between the pressure in the pores of the glass base material and the ratio (X / Y) will be described where Y is (hole diameter) / (glass base material outer diameter)}. In the following, a glass base material having an outer diameter of 60 mm having the same structure as the glass base material 2 shown in FIG. 2 and having 10 holes having a hole diameter of 3.5 mm was prepared. Then, an experiment was carried out in which an optical fiber having an outer diameter (cladding diameter) of 125 μm was drawn from the prepared glass base material with various pressure settings in the glass base material.
　また、以下では、無次元空孔内加圧量によって空孔内の圧力を規定する。無次元空孔内加圧量は、空孔内の圧力と大気圧との圧力差（以下、この圧力差を空孔内加圧量という）を、比（Ｘ／Ｙ）が１となる空孔内加圧量で除した値として定義する。 Also, in the following, the pressure in the hole is defined by the dimensionless pressure in the hole. The dimensionless vacancy pressure is the difference between the pressure in the cavities and the atmospheric pressure (hereinafter, this pressure difference is referred to as the vacancy pressure) and the ratio (X / Y) is 1. It is defined as the value divided by the amount of pressurization in the hole.
　図４は、無次元空孔内加圧量と比（Ｘ／Ｙ）との関係を示す図である。図４に示すように、無次元空孔内加圧量を大きくするとそれに従って比（Ｘ／Ｙ）も大きくなる。したがって、図４に示すような無次元空孔内加圧量と比（Ｘ／Ｙ）との関係に従って空孔内の圧力を制御すれば、所望の比（Ｘ／Ｙ）を実現することができる。 FIG. 4 is a diagram showing the relationship between the dimensionless in-hole pressurization amount and the ratio (X / Y). As shown in FIG. 4, when the amount of pressurization in dimensionless holes is increased, the ratio (X / Y) is increased accordingly. Therefore, a desired ratio (X / Y) can be realized by controlling the pressure in the holes in accordance with the relationship between the dimensionless pressure in the holes and the ratio (X / Y) as shown in FIG. it can.
　つぎに、比（Ｘ／Ｙ）と、製造した光ファイバの空孔径の変動との関係について説明する。以下では、無次元空孔径変動によって空孔径の変動を規定する。無次元空孔径変動は、比（Ｘ／Ｙ）が或る値のときの１０個の空孔の平均空孔径（単位はμｍ）の、光ファイバ１ｋｍ当たりの変動量（最大値と最小値との差。以下、空孔径変動という）を、比（Ｘ／Ｙ）が１となる空孔径変動で除した値である。 Next, the relationship between the ratio (X / Y) and fluctuations in the hole diameter of the manufactured optical fiber will be described. In the following, the fluctuation of the hole diameter is defined by the dimensionless hole diameter fluctuation. The dimensionless hole diameter variation is the fluctuation amount per 1 km of optical fiber (maximum value and minimum value) of the average hole diameter (unit: μm) of 10 holes when the ratio (X / Y) is a certain value. (Hereinafter referred to as pore diameter fluctuation) is divided by the hole diameter fluctuation where the ratio (X / Y) is 1.
　図５は、比（Ｘ／Ｙ）と無次元空孔径変動との関係を示す図である。図５に示すように、Ｘ／Ｙが０．５以上であれば、無次元空孔径変動が１．５よりも小さくなり、空孔径の長手方向での変動が少なくなるので好ましい。 FIG. 5 is a diagram showing the relationship between the ratio (X / Y) and the dimensionless pore diameter variation. As shown in FIG. 5, it is preferable that X / Y is 0.5 or more because the dimensionless pore diameter variation is smaller than 1.5, and the variation in the longitudinal direction of the pore diameter is reduced.
　なお、比（Ｘ／Ｙ）が１．０よりも小さければ、ガラス母材の長さを長くできる効果があるが、比（Ｘ／Ｙ）を０．７以下にすればその効果が顕著になるのでより好ましい。 If the ratio (X / Y) is smaller than 1.0, the length of the glass base material can be increased. However, if the ratio (X / Y) is 0.7 or less, the effect is remarkable. This is more preferable.
（実施例１、比較例１）
　本発明の実施例１、比較例１として、図１に示す構造の光ファイバを以下の工程にて製造した。
　周知のＶＡＤ法およびＯＶＤ法によって、Ｇｅを含むコア部を中心部に有し、コア部の周囲にクラッド部を有するガラス母材を得た。さらにこのガラス母材を酸水素バーナにて延伸して、外径７０ｍｍのガラス母材を２本作製した。なお、当該ガラス母材の延伸は酸水素火炎バーナで実施したが、電気炉での加熱による方法でも良い。このガラス母材の断面屈折率分布形状は、比屈折率差０．３５％の略矩形（ステップインデックス）とした。 (Example 1, Comparative Example 1)
As Example 1 and Comparative Example 1 of the present invention, an optical fiber having the structure shown in FIG.
By a known VAD method and OVD method, a glass base material having a core portion containing Ge in the center portion and a cladding portion around the core portion was obtained. Furthermore, this glass base material was extended | stretched with the oxyhydrogen burner, and two glass base materials with an outer diameter of 70 mm were produced. In addition, although the said glass base material was extended | stretched with the oxyhydrogen flame burner, the method by the heating with an electric furnace may be used. The cross-sectional refractive index distribution shape of this glass base material was a substantially rectangular shape (step index) with a relative refractive index difference of 0.35%.
　作製したガラス母材のうちの１本に、ドリルを用いた穿孔加工を行い、長手方向の軸に沿って直径１．９ｍｍの空孔を１０個形成した。このとき用いたドリルの機械的強度の制約上、ガラス母材の長さを３５０ｍｍとした。このようにして、比較例１のガラス母材を準備した。 A drilling process was performed on one of the prepared glass base materials to form ten holes having a diameter of 1.9 mm along the longitudinal axis. The length of the glass base material was set to 350 mm because of the mechanical strength of the drill used at this time. Thus, the glass base material of the comparative example 1 was prepared.
　一方、作製したガラス母材の別の１本に、ドリルを用いた穿孔加工を行い、長手方向の軸に沿って直径３．５ｍｍの空孔を１０個形成した。このとき用いたドリルは、上記の比較例１の場合よりも直径が太く、ドリルの剛性が高いため、ガラス母材の長さを９００ｍｍにできた。このようにして、実施例１のガラス母材を準備した。なお、実施例１のガラス母材におけるコア部の中心と空孔の中心との距離と、比較例１のガラス母材における当該距離とは同一とした。 On the other hand, another one of the produced glass base materials was drilled using a drill to form 10 holes having a diameter of 3.5 mm along the longitudinal axis. Since the diameter of the drill used at this time was larger than that in the case of Comparative Example 1 and the rigidity of the drill was high, the length of the glass base material was 900 mm. Thus, the glass base material of Example 1 was prepared. The distance between the center of the core portion and the center of the hole in the glass base material of Example 1 and the distance in the glass base material of Comparative Example 1 were the same.
　つぎに、図３に示す構成の線引装置を用いて、上記実施例１、比較例１のガラス母材の空孔内を加圧しながら光ファイバを線引きし、実施例１、比較例１の光ファイバを製造した。なお、加圧するガスとしてアルゴンガスを使用した。この際、実施例１、比較例１のどちらの光ファイバについても、１０個の空孔の平均空孔径が３．５μｍになるよう空孔内加圧量の調整をおこなった。製造した光ファイバの平均空孔径は、実施例１では３．５５μｍであり、比較例１では３．５１μｍであった。また、実施例１、比較例１のどちらの光ファイバについても、外径が１２５μｍになるようにした。
　したがって、実施例１の場合は比（Ｘ／Ｙ）が０．５７、比較例１の場合は比（Ｘ／Ｙ）が１であった。 Next, using the drawing apparatus having the configuration shown in FIG. 3, the optical fiber is drawn while pressurizing the pores of the glass base material of Example 1 and Comparative Example 1, and Examples 1 and 1 of Comparative Example 1 are drawn. An optical fiber was manufactured. Argon gas was used as the pressurized gas. At this time, in each of the optical fibers of Example 1 and Comparative Example 1, the amount of pressurization in the holes was adjusted so that the average hole diameter of the ten holes was 3.5 μm. The average hole diameter of the manufactured optical fiber was 3.55 μm in Example 1, and 3.51 μm in Comparative Example 1. In addition, the outer diameter of each of the optical fibers of Example 1 and Comparative Example 1 was set to 125 μm.
Therefore, in the case of Example 1, the ratio (X / Y) was 0.57, and in the case of Comparative Example 1, the ratio (X / Y) was 1.
　つぎに、製造した実施例１、比較例１の光ファイバの特性を測定した。波長１５５０ｎｍにおいて、実施例１の光ファイバの伝送損失は０．１９７ｄＢ／ｋｍであり、比較例１の光ファイバの伝送損失は０．１９８ｄＢ／ｋｍであり、略同一であった。また、その他のカットオフ波長や、波長分散等の特性についても、実施例１、比較例１の光ファイバの値の差は１０％以内であった。したがって、実施例１、比較例１の光ファイバは、略同等の特性を有するものであった。 Next, the characteristics of the manufactured optical fibers of Example 1 and Comparative Example 1 were measured. At a wavelength of 1550 nm, the transmission loss of the optical fiber of Example 1 was 0.197 dB / km, and the transmission loss of the optical fiber of Comparative Example 1 was 0.198 dB / km, which was substantially the same. Further, regarding other characteristics such as cutoff wavelength and wavelength dispersion, the difference in the values of the optical fibers of Example 1 and Comparative Example 1 was within 10%. Therefore, the optical fibers of Example 1 and Comparative Example 1 had substantially the same characteristics.
　ただし、実施例１のガラス母材の方が比較例１のガラス母材よりも２倍以上長いので、各ガラス母材からは、実施例１の光ファイバの方が比較例１の光ファイバよりも長い光ファイバを得られた。したがって、実施例１の光ファイバはより製造コストが低いものとなった。 However, since the glass base material of Example 1 is twice or more longer than the glass base material of Comparative Example 1, the optical fiber of Example 1 is longer than the optical fiber of Comparative Example 1 from each glass base material. Even a long optical fiber was obtained. Therefore, the manufacturing cost of the optical fiber of Example 1 was lower.
（実施例２）
　実施例１、比較例１と同様の構造を有する外径７０ｍｍのガラス母材を１本作製し、ドリルを用いた穿孔加工を行い、長手方向の軸に沿って直径３．０ｍｍの空孔を１０個形成した。このとき用いたドリルは、比較例１の場合よりも直径が太く、ドリルの剛性が高いため、ガラス母材の長さを８５０ｍｍにできた。これによって、実施例２のガラス母材を準備した。 (Example 2)
A glass base material having an outer diameter of 70 mm having the same structure as in Example 1 and Comparative Example 1 is prepared, and drilling is performed using a drill to form a hole having a diameter of 3.0 mm along the longitudinal axis. Ten were formed. The drill used at this time had a diameter larger than that of Comparative Example 1 and the drill had higher rigidity, so that the length of the glass base material could be 850 mm. Thereby, the glass base material of Example 2 was prepared.
　つぎに、実施例１、比較例１と同様に、上記実施例２のガラス母材の空孔内を加圧しながら光ファイバを線引きし、実施例２の光ファイバを製造した。この際、光ファイバの１０個の空孔の平均空孔径が３．５μｍになるよう空孔内加圧量の調整をおこなった。製造した光ファイバの平均空孔径は３．５３μｍであった。また、光ファイバの外径が１２５μｍになるようにした。したがって、実施例２の場合は比（Ｘ／Ｙ）が０．６５であった。 Next, as in Example 1 and Comparative Example 1, the optical fiber was drawn while pressurizing the inside of the glass base material of Example 2 to produce the optical fiber of Example 2. At this time, the pressurization amount in the holes was adjusted so that the average hole diameter of the ten holes of the optical fiber was 3.5 μm. The average hole diameter of the manufactured optical fiber was 3.53 μm. The outer diameter of the optical fiber was set to 125 μm. Therefore, in the case of Example 2, the ratio (X / Y) was 0.65.
　つぎに、製造した実施例２の光ファイバの特性を測定した。波長１５５０ｎｍにおいて、実施例２の光ファイバの伝送損失は０．１９６ｄＢ／ｋｍであり、実施例１、比較例１と略同一であった。また、その他のカットオフ波長や、波長分散等の特性についても、実施例２の光ファイバと、実施例１、比較例１の光ファイバとでの値の差は１０％以内であった。したがって、実施例２の光ファイバは、実施例１、比較例１の光ファイバと略同等の特性を有するものであった。 Next, the characteristics of the manufactured optical fiber of Example 2 were measured. At a wavelength of 1550 nm, the transmission loss of the optical fiber of Example 2 was 0.196 dB / km, which was substantially the same as Example 1 and Comparative Example 1. In addition, regarding other characteristics such as cutoff wavelength and wavelength dispersion, the difference in values between the optical fiber of Example 2 and the optical fibers of Example 1 and Comparative Example 1 was within 10%. Therefore, the optical fiber of Example 2 had substantially the same characteristics as those of Example 1 and Comparative Example 1.
　実施例２のガラス母材も、比較例１のガラス母材よりも２倍以上長いので、１本のガラス母材から、より長い光ファイバを得られた。したがって、実施例２の光ファイバはより製造コストが低いものとなった。また、実施例２の光ファイバの場合は、比（Ｘ／Ｙ）を実施例１の光ファイバよりも大きくしたため、光ファイバの長手方向での空孔径変動が実施例１の場合よりも小さく抑えられていた。 Since the glass base material of Example 2 is also twice or more longer than the glass base material of Comparative Example 1, a longer optical fiber was obtained from one glass base material. Therefore, the manufacturing cost of the optical fiber of Example 2 was lower. Further, in the case of the optical fiber of Example 2, the ratio (X / Y) is made larger than that of the optical fiber of Example 1, so that the hole diameter variation in the longitudinal direction of the optical fiber is suppressed to be smaller than that of Example 1. It was done.
（実施例３）
　実施例１、比較例１と同様の構造を有する外径７０ｍｍのガラス母材を１本作製し、ドリルを用いた穿孔加工を行い、長手方向の軸に沿って直径５．０ｍｍの空孔を１０個形成した。このとき用いたドリルは、実施例１、２の場合よりもさらに直径が太く、ドリルの剛性がさらに高くなったため、ガラス母材の長さを９２０ｍｍにできた。これによって、実施例３のガラス母材を準備した。 (Example 3)
One glass base material having an outer diameter of 70 mm having the same structure as in Example 1 and Comparative Example 1 is prepared, drilling is performed using a drill, and a hole having a diameter of 5.0 mm is formed along the longitudinal axis. Ten were formed. The drill used at this time had a larger diameter than in the case of Examples 1 and 2, and the rigidity of the drill was further increased, so that the length of the glass base material could be 920 mm. Thereby, the glass base material of Example 3 was prepared.
　つぎに、実施例１、比較例１と同様に、上記実施例３のガラス母材の空孔内を加圧しながら光ファイバを線引きし、実施例３の光ファイバを製造した。この際、光ファイバの１０個の空孔の平均空孔径が３．５μｍになるよう空孔内加圧量の調整をおこなった。製造した光ファイバの平均空孔径は３．５４μｍであった。また、光ファイバの外径が１２５μｍになるようにした。したがって、実施例３の場合は比（Ｘ／Ｙ）が０．３９であった。 Next, in the same manner as in Example 1 and Comparative Example 1, the optical fiber was drawn while pressurizing the pores of the glass base material of Example 3 to produce the optical fiber of Example 3. At this time, the pressurization amount in the holes was adjusted so that the average hole diameter of the ten holes of the optical fiber was 3.5 μm. The average hole diameter of the manufactured optical fiber was 3.54 μm. The outer diameter of the optical fiber was set to 125 μm. Therefore, in the case of Example 3, the ratio (X / Y) was 0.39.
　つぎに、製造した実施例３の光ファイバの特性を測定した。波長１５５０ｎｍにおいて、実施例３の光ファイバの伝送損失は０．２０５ｄＢ／ｋｍであり、実施例１、比較例１と同等の問題ない値であった。また、その他のカットオフ波長や、波長分散等の特性についても、実施例３の光ファイバと、実施例１、比較例１の光ファイバとでの値の差は１０％以内であった。したがって、実施例３の光ファイバは、実施例１、２、比較例１の光ファイバと略同等の特性を有するものであった。 Next, the characteristics of the manufactured optical fiber of Example 3 were measured. At a wavelength of 1550 nm, the transmission loss of the optical fiber of Example 3 was 0.205 dB / km, which was a value that was not problematic as in Example 1 and Comparative Example 1. In addition, regarding other characteristics such as cutoff wavelength and wavelength dispersion, the difference in values between the optical fiber of Example 3 and the optical fibers of Example 1 and Comparative Example 1 was within 10%. Therefore, the optical fiber of Example 3 had substantially the same characteristics as the optical fibers of Examples 1 and 2 and Comparative Example 1.
　実施例３のガラス母材は、実施例１、２のガラス母材よりもさらに長いので、１本のガラス母材から、実施例１、２よりもより長い光ファイバを得られた。したがって、実施例３の光ファイバはさらに製造コストが低いものとなった。なお、実施例３の光ファイバの場合は、比（Ｘ／Ｙ）を実施例１、２の光ファイバよりも小さくしており、光ファイバの長手方向での空孔径変動は、比較例１の場合の２倍程度であったが、使用上は問題ない値であった。 Since the glass base material of Example 3 is longer than the glass base materials of Examples 1 and 2, an optical fiber longer than that of Examples 1 and 2 was obtained from one glass base material. Therefore, the manufacturing cost of the optical fiber of Example 3 was further reduced. In the case of the optical fiber of Example 3, the ratio (X / Y) is made smaller than those of Examples 1 and 2, and the hole diameter variation in the longitudinal direction of the optical fiber is the same as that of Comparative Example 1. Although it was about twice as much as the case, it was a value with no problem in use.
　なお、上記実施例１～３のように、ガラス母材に形成する空孔径を３ｍｍ以上とすると、ガラス母材の長さを十分に長くでき、製造コストを十分に低減できるので好ましい。 It is to be noted that, as in Examples 1 to 3, it is preferable that the hole diameter formed in the glass base material is 3 mm or more because the length of the glass base material can be sufficiently increased and the manufacturing cost can be sufficiently reduced.
（実施例４）
　実施例１、比較例１と同様の構造を有する外径７０ｍｍのガラス母材を１本作製し、ドリルを用いた穿孔加工を行い、長手方向の軸に沿って直径２．５ｍｍの空孔を１０個形成した。このとき用いたドリルは、比較例１の場合よりも直径が太く、ドリルの剛性が高いため、ガラス母材の長さを４８０ｍｍにできた。これによって、実施例４のガラス母材を準備した。 Example 4
A glass base material having an outer diameter of 70 mm having the same structure as that of Example 1 and Comparative Example 1 was produced, and a drilling process was performed using a drill to form a hole having a diameter of 2.5 mm along the longitudinal axis. Ten were formed. Since the diameter of the drill used at this time was larger than that of Comparative Example 1 and the rigidity of the drill was high, the length of the glass base material was made 480 mm. Thereby, the glass base material of Example 4 was prepared.
　つぎに、実施例１、比較例１と同様に、上記実施例４のガラス母材の空孔内を加圧しながら光ファイバを線引きし、実施例４の光ファイバを製造した。この際、光ファイバの１０個の空孔の平均空孔径が３．５μｍになるよう空孔内加圧量の調整をおこなった。製造した光ファイバの平均空孔径は３．５４μｍであった。また、光ファイバの外径が１２５μｍになるようにした。したがって、実施例４の場合は比（Ｘ／Ｙ）が０．７９であった。 Next, in the same manner as in Example 1 and Comparative Example 1, the optical fiber was drawn while pressurizing the pores of the glass base material of Example 4 to produce the optical fiber of Example 4. At this time, the pressurization amount in the holes was adjusted so that the average hole diameter of the ten holes of the optical fiber was 3.5 μm. The average hole diameter of the manufactured optical fiber was 3.54 μm. The outer diameter of the optical fiber was set to 125 μm. Therefore, in the case of Example 4, the ratio (X / Y) was 0.79.
　つぎに、製造した実施例４の光ファイバの特性を測定した。波長１５５０ｎｍにおいて、実施例４の光ファイバの伝送損失は０．１９５ｄＢ／ｋｍであり、実施例１、比較例１と略同一であった。また、その他のカットオフ波長や、波長分散等の特性についても、実施例４の光ファイバと、実施例１、比較例１の光ファイバとでの値の差は１０％以内であった。したがって、実施例４の光ファイバは、実施例１、比較例１の光ファイバと略同等の特性を有するものであった。 Next, the characteristics of the manufactured optical fiber of Example 4 were measured. At a wavelength of 1550 nm, the transmission loss of the optical fiber of Example 4 was 0.195 dB / km, which was substantially the same as Example 1 and Comparative Example 1. Further, regarding other characteristics such as cutoff wavelength and wavelength dispersion, the difference in values between the optical fiber of Example 4 and the optical fibers of Example 1 and Comparative Example 1 was within 10%. Therefore, the optical fiber of Example 4 had substantially the same characteristics as those of Example 1 and Comparative Example 1.
　実施例４のガラス母材も、比較例１のガラス母材よりも長いので、１本のガラス母材から、より長い光ファイバを得られた。したがって、実施例４の光ファイバはより製造コストが低いものとなった。また、実施例４の光ファイバの場合は、比（Ｘ／Ｙ）を実施例２の光ファイバよりも大きくしたため、光ファイバの長手方向での空孔径変動が実施例２の場合よりもさらに小さく抑えられていた。 Since the glass base material of Example 4 is also longer than the glass base material of Comparative Example 1, a longer optical fiber was obtained from one glass base material. Therefore, the manufacturing cost of the optical fiber of Example 4 was lower. Further, in the case of the optical fiber of Example 4, the ratio (X / Y) was made larger than that of the optical fiber of Example 2, so that the hole diameter variation in the longitudinal direction of the optical fiber was even smaller than that of Example 2. It was suppressed.
（実施の形態２）
　つぎに、本発明の実施の形態２について説明する。本実施の形態２に係る製造方法は、光ファイバを線引きする際に、ガラス母材の空孔内の圧力を空孔によって異なる値とし、互いに異なる空孔径を有する空孔を備えた光ファイバを製造するものである。 (Embodiment 2)
Next, a second embodiment of the present invention will be described. In the manufacturing method according to the second embodiment, when drawing an optical fiber, an optical fiber including holes having different hole diameters and different pressures in the holes of the glass base material is used depending on the holes. To manufacture.
　図６は、本実施の形態２に係る製造方法によって製造する光ファイバの模式的な断面図である。図６に示すように、光ファイバ３は、長手方向の軸に沿って延びる空孔３ａ、３ｂを有している。 FIG. 6 is a schematic cross-sectional view of an optical fiber manufactured by the manufacturing method according to the second embodiment. As shown in FIG. 6, the optical fiber 3 has holes 3a and 3b extending along the longitudinal axis.
　光ファイバ３はたとえば純石英ガラスなどの材料からなる。空孔３ａ、３ｂは光ファイバ３の長手方向の軸に垂直な断面において三角格子状に規則正しく配列している。ただし、空孔３ａ、３ｂが配列された領域内に空孔が無い領域がある。この空孔が無い領域がコア部３ｃとして機能し、コア部３ｃの周囲がクラッド部として機能する。すなわち、この光ファイバ３はＨＦである。なお、２個の空孔３ｂはコア部３ｃを挟んだ両側に位置している。 The optical fiber 3 is made of a material such as pure quartz glass. The holes 3 a and 3 b are regularly arranged in a triangular lattice pattern in a cross section perpendicular to the longitudinal axis of the optical fiber 3. However, there is a region where there is no hole in the region where the holes 3a and 3b are arranged. The area | region without this void | hole functions as the core part 3c, and the circumference | surroundings of the core part 3c function as a clad part. That is, the optical fiber 3 is HF. The two holes 3b are located on both sides of the core portion 3c.
　１６個の空孔３ａは同一の空孔径を有している。空孔３ａの空孔径はｄ３１である。２個の空孔３ｂは同一の空孔径を有している。空孔３ｂの空孔径はｄ３２である。空孔径ｄ３２は空孔径ｄ３１よりも大きく設定されている。また、光ファイバ３の外径はＤ３である。空孔３ａの直径ｄ３１と光ファイバ３の外径Ｄ３との比を第２の比Ｘ２とすると、Ｘ２＝ｄ３１／Ｄ３である。また、空孔３ｂの直径ｄ３２と光ファイバ３の外径Ｄ３との比を第２の比Ｘ３とすると、Ｘ３＝ｄ３２／Ｄ３である。 The 16 holes 3a have the same hole diameter. The hole diameter of the hole 3a is d31. The two holes 3b have the same hole diameter. The hole diameter of the hole 3b is d32. The hole diameter d32 is set larger than the hole diameter d31. The outer diameter of the optical fiber 3 is D3. When the ratio of the diameter d31 of the hole 3a and the outer diameter D3 of the optical fiber 3 is the second ratio X2, X2 = d31 / D3. Further, assuming that the ratio of the diameter d32 of the hole 3b and the outer diameter D3 of the optical fiber 3 is the second ratio X3, X3 = d32 / D3.
　この光ファイバ３は、空孔３ｂによってコア部３ｃの屈折率分布に異方性が発生するために、偏波保持光ファイバとして使用できる。 The optical fiber 3 can be used as a polarization-maintaining optical fiber because anisotropy occurs in the refractive index distribution of the core 3c due to the holes 3b.
　つぎに、本実施の形態２に係る製造方法について具体的に説明する。はじめに、光ファイバ３を製造するためのガラス母材を準備する。図７は、光ファイバ３を製造するためのガラス母材の模式的な斜視図である。図７に示すように、ガラス母材４は、石英系ガラスからなる円柱状であり、光ファイバ３の空孔３ａ、３ｂを形成するための空孔４ａを有している。空孔４ａはガラス母材４の長手方向の軸に沿って延びている。 Next, the manufacturing method according to the second embodiment will be specifically described. First, a glass base material for manufacturing the optical fiber 3 is prepared. FIG. 7 is a schematic perspective view of a glass base material for manufacturing the optical fiber 3. As shown in FIG. 7, the glass base material 4 has a cylindrical shape made of quartz glass and has holes 4 a for forming the holes 3 a and 3 b of the optical fiber 3. The air holes 4 a extend along the longitudinal axis of the glass base material 4.
　ここで、空孔４ａはいずれも同一の空孔径を有している。空孔４ａの空孔径はｄ４である。また、ガラス母材４の外径はＤ４である。空孔４ａの直径ｄ４とガラス母材４の外径Ｄ４との比を第１の比Ｙ２とすると、Ｙ２＝ｄ４／Ｄ４である。本実施の形態２では、Ｘ２がＹ２より小さくなり、かつＸ３がＹ２と等しくなるようにｄ４、Ｄ４を設定する。すなわち、（Ｘ２／Ｙ２）＝（ｄ３１／Ｄ３）／（ｄ４／Ｄ４）＜１．０、かつ（Ｘ３／Ｙ２）＝（ｄ３２／Ｄ３）／（ｄ４／Ｄ４）＝１．０である。なお、ガラス母材４の長さはＬ２である。 Here, all the holes 4a have the same hole diameter. The hole diameter of the hole 4a is d4. Moreover, the outer diameter of the glass base material 4 is D4. When the ratio of the diameter d4 of the air hole 4a and the outer diameter D4 of the glass base material 4 is the first ratio Y2, Y2 = d4 / D4. In the second embodiment, d4 and D4 are set so that X2 is smaller than Y2 and X3 is equal to Y2. That is, (X2 / Y2) = (d31 / D3) / (d4 / D4) <1.0 and (X3 / Y2) = (d32 / D3) / (d4 / D4) = 1.0. The length of the glass base material 4 is L2.
　本実施の形態２に係る製造方法では、ガラス母材４において、空孔径が互いに異なる光ファイバ３の空孔３ａと空孔３ｂとを形成するために、同一の空孔径の空孔４ａを形成している。その結果、穿孔加工において空孔４ａの形成に必要なドリルが一種類でよく、またドリル装置に太さの異なるドリルを付け替える作業も不要である。したがって、穿孔加工の作業が簡略化されるので、製造コストを低減できる。 In the manufacturing method according to the second embodiment, in order to form the hole 3a and the hole 3b of the optical fiber 3 having different hole diameters in the glass base material 4, the holes 4a having the same hole diameter are formed. is doing. As a result, only one type of drill is required for forming the holes 4a in the drilling process, and the work of replacing the drills with different thicknesses is not necessary. Therefore, since the drilling process is simplified, the manufacturing cost can be reduced.
　また、ガラス母材に形成する空孔の空孔径が異なる場合は、空孔径が最も小さい空孔を形成するためのドリルの長さが最も短くなる。この場合、ガラス母材の長さも最も短いドリルの長さによって制限される。これに対して、本実施の形態２では、形成する空孔４ａの空孔径は同一であるので、上記のような制限を受けることなくガラス母材４の長さＬ２を長くできる。 Also, when the hole diameters of the holes formed in the glass base material are different, the length of the drill for forming the hole having the smallest hole diameter is the shortest. In this case, the length of the glass base material is also limited by the length of the shortest drill. On the other hand, in Embodiment 2, since the hole diameters of the holes 4a to be formed are the same, the length L2 of the glass base material 4 can be increased without being restricted as described above.
　本実施の形態２に係る製造方法では、はじめに実施の形態１のガラス母材２と同様に、ＶＡＤ法などの周知の方法を用いてガラス母材を形成し、その後ドリルを用いてガラス母材の長手方向の軸に沿って空孔４ａを形成する。これによって、図７に示すガラス母材４を準備できる。 In the manufacturing method according to the second embodiment, first, similarly to the glass base material 2 of the first embodiment, a glass base material is formed using a known method such as the VAD method, and then a glass base material is used using a drill. Holes 4a are formed along the longitudinal axis. Thereby, the glass base material 4 shown in FIG. 7 can be prepared.
　つぎに、このガラス母材４から、図３に示すような線引装置１００を用いて光ファイバ３を線引きする。ここで、本実施の形態２では、ガラス母材４の同一の空孔径を有する空孔４ａから、光ファイバ３の異なる空孔径を有する空孔３ａ、３ｂを形成する必要がある。そのため、空孔３ａを形成するための空孔４ａと、空孔３ｂを形成するための空孔４ａとで、内部の圧力を別々に制御することが好ましい。 Next, the optical fiber 3 is drawn from the glass base material 4 using a drawing apparatus 100 as shown in FIG. Here, in the second embodiment, it is necessary to form holes 3 a and 3 b having different hole diameters of the optical fiber 3 from the holes 4 a having the same hole diameter of the glass base material 4. Therefore, it is preferable to control the internal pressure separately for the hole 4a for forming the hole 3a and the hole 4a for forming the hole 3b.
　図８は、本実施の形態２に係る製造方法において用いる加圧機構の模式図である。本実施の形態２では、図３に示した加圧機構１０２に代えて図８に示す加圧機構１１０を用いる。図８に示すように、加圧機構１１０は、加圧用コネクタ１１１と、加圧用コネクタ１１１に接続したガス供給路１１２、１１３と、ガス供給路１１２、１１３のそれぞれに接続した圧力調整部１１４、１１５とを備える。圧力調整部１１４、１１５は制御器Ｃに接続している。圧力調整部１１４、１１５にはガスＧが供給される。 FIG. 8 is a schematic diagram of a pressurizing mechanism used in the manufacturing method according to the second embodiment. In the second embodiment, a pressurizing mechanism 110 shown in FIG. 8 is used instead of the pressurizing mechanism 102 shown in FIG. As shown in FIG. 8, the pressurization mechanism 110 includes a pressurization connector 111, gas supply paths 112 and 113 connected to the pressurization connector 111, and pressure adjustment units 114 connected to the gas supply paths 112 and 113, respectively. 115. The pressure adjusting units 114 and 115 are connected to the controller C. A gas G is supplied to the pressure adjusting units 114 and 115.
　加圧用コネクタ１１１は、第１加圧部１１１ａと第２加圧部１１１ｂとを有している。第１加圧部１１１ａは、ガラス母材４の空孔４ａのうち、光ファイバ３の空孔３ａを形成するための空孔４ａにのみガスＧを供給するように構成されている。第２加圧部１１１ｂは、空孔３ｂを形成するための空孔４ａにのみガスＧを供給するように構成されている。空孔３ａを形成するための空孔４ａに供給されるガスＧは、ガス供給路１１２を介して第１加圧部１１１ａに供給され、かつ制御器Ｃによって制御された圧力調整部１１４によって圧力が調整される。空孔３ｂを形成するための空孔４ａに供給されるガスＧは、ガス供給路１１３を介して第２加圧部１１１ｂに供給され、かつ制御器Ｃによって制御された圧力調整部１１５によって圧力が調整される。したがって、この加圧機構１１０を使用することによって、各空孔４ａ内の圧力を別々に制御することができる。具体的には、空孔３ｂを形成するための空孔４ａ内の圧力が、空孔３ａを形成するための空孔４ａ内の圧力よりも高くなるように、各空孔４ａ内の圧力が制御される。 The pressure connector 111 includes a first pressure part 111a and a second pressure part 111b. The first pressurizing unit 111 a is configured to supply the gas G only to the hole 4 a for forming the hole 3 a of the optical fiber 3 among the holes 4 a of the glass base material 4. The second pressurizing part 111b is configured to supply the gas G only to the hole 4a for forming the hole 3b. The gas G supplied to the hole 4a for forming the hole 3a is supplied to the first pressurizing unit 111a through the gas supply path 112 and is pressured by the pressure adjusting unit 114 controlled by the controller C. Is adjusted. The gas G supplied to the hole 4a for forming the hole 3b is supplied to the second pressurizing unit 111b through the gas supply path 113 and is pressured by the pressure adjusting unit 115 controlled by the controller C. Is adjusted. Therefore, by using the pressurizing mechanism 110, the pressure in each hole 4a can be controlled separately. Specifically, the pressure in each hole 4a is set so that the pressure in the hole 4a for forming the hole 3b is higher than the pressure in the hole 4a for forming the hole 3a. Be controlled.
　なお、本実施の形態２では、比（Ｘ２／Ｙ２）を１．０より小さくし、比（Ｘ３／Ｙ２）は１．０となるようにしている。しかしながら、比（Ｘ２／Ｙ２）および比（Ｘ３／Ｙ２）の両方を１．０より小さくなるようにしてもよい。両方を１．０よりも小さくすることによって、ガラス母材をより長くすることができる。 In the second embodiment, the ratio (X2 / Y2) is set to be smaller than 1.0, and the ratio (X3 / Y2) is set to 1.0. However, both the ratio (X2 / Y2) and the ratio (X3 / Y2) may be made smaller than 1.0. By making both smaller than 1.0, the glass base material can be made longer.
　図９は、本実施の形態２に係る製造方法によって製造できる他の光ファイバの模式的な断面図である。図９に示すように、光ファイバ５は、長手方向の軸に沿って延びる空孔５ａ、５ｂを有している。 FIG. 9 is a schematic cross-sectional view of another optical fiber that can be manufactured by the manufacturing method according to the second embodiment. As shown in FIG. 9, the optical fiber 5 has holes 5a and 5b extending along the longitudinal axis.
　光ファイバ５はたとえば純石英ガラスなどの材料からなる。空孔５ａ、５ｂは光ファイバ５の長手方向の軸に垂直な断面において三角格子状に規則正しく配列している。空孔５ａ、５ｂが配列された領域内の空孔が無い領域がコア部５ｃとして機能し、コア部５ｃの周囲がクラッド部として機能する。すなわち、この光ファイバ５はＨＦである。なお、６個の空孔５ｂはコア部５ｃを囲むように位置している。 The optical fiber 5 is made of a material such as pure quartz glass. The holes 5a and 5b are regularly arranged in a triangular lattice pattern in a cross section perpendicular to the longitudinal axis of the optical fiber 5. The area | region without the void | hole in the area | region where the hole 5a, 5b is arranged functions as the core part 5c, and the circumference | surroundings of the core part 5c function as a clad part. That is, the optical fiber 5 is HF. The six holes 5b are positioned so as to surround the core portion 5c.
　１２個の空孔５ａは同一の空孔径を有している。空孔５ａの空孔径はｄ５１である。６個の空孔５ｂは同一の空孔径を有している。空孔５ｂの空孔径はｄ５２である。なお、空孔径ｄ５２は空孔径ｄ５１よりも大きく設定されている。また、光ファイバ５の外径はＤ５である。空孔５ａの直径ｄ５１と光ファイバ５の外径Ｄ５との比を第２の比Ｘ４とすると、Ｘ４＝ｄ５１／Ｄ５である。また、空孔５ｂの直径ｄ５２と光ファイバ５の外径Ｄ５との比を第２の比Ｘ５とすると、Ｘ５＝ｄ５２／Ｄ５である。 The 12 holes 5a have the same hole diameter. The hole diameter of the hole 5a is d51. The six holes 5b have the same hole diameter. The hole diameter of the hole 5b is d52. The hole diameter d52 is set larger than the hole diameter d51. The outer diameter of the optical fiber 5 is D5. Assuming that the ratio of the diameter d51 of the hole 5a and the outer diameter D5 of the optical fiber 5 is the second ratio X4, X4 = d51 / D5. Further, assuming that the ratio of the diameter d52 of the hole 5b and the outer diameter D5 of the optical fiber 5 is the second ratio X5, X5 = d52 / D5.
　この光ファイバ５は、空孔径が大きい空孔５ｂによってコア部５ｃの周囲に屈折率が低い領域が形成され、いわゆるＷ型の断面屈折率分布形状となるため、有効コア断面積が大きい光ファイバとして使用できる。 In this optical fiber 5, a region having a low refractive index is formed around the core portion 5c by the hole 5b having a large hole diameter, and a so-called W-shaped cross-sectional refractive index profile is formed. Can be used as
　この光ファイバ５も、本実施の形態２に係る製造方法を用いて、図７に示した同一の空孔径の空孔４ａを有するガラス母材４から、各空孔４ａによって異なる内部圧力に制御しながら線引きを行うことによって製造できる。具体的には、光ファイバ５の空孔５ｂを形成するためのガラス母材４の空孔４ａ内の圧力が、空孔５ａを形成するための空孔４ａ内の圧力よりも高くなるように、各空孔４ａ内の圧力を制御すればよい。 The optical fiber 5 is also controlled to have a different internal pressure depending on each hole 4a from the glass base material 4 having the holes 4a having the same hole diameter shown in FIG. 7 using the manufacturing method according to the second embodiment. However, it can be manufactured by drawing while drawing. Specifically, the pressure in the hole 4a of the glass base material 4 for forming the hole 5b of the optical fiber 5 is higher than the pressure in the hole 4a for forming the hole 5a. The pressure in each hole 4a may be controlled.
　なお、上記実施の形態では、ガラス母材はドリルにより空孔を形成したものである。しかしながら、本発明は、空孔となるガラス管を用いて母材を準備する場合にも適用できる。本発明によれば、より外径および内径が大きいガラス管を使用できるので、ガラス管を長くすることができる。したがって、より長いガラス管を用いて、より長い大型のガラス母材を準備することができる。また、空孔径が互いに異なる空孔を有する光ファイバを製造する場合でも、内径が異なるガラス管を準備する必要が無いので、部品コストを低減することができる。 In the above embodiment, the glass base material has holes formed by a drill. However, the present invention can also be applied to a case where a base material is prepared using a glass tube that becomes a hole. According to the present invention, since a glass tube having a larger outer diameter and larger inner diameter can be used, the glass tube can be lengthened. Therefore, a longer and larger glass base material can be prepared using a longer glass tube. Moreover, even when manufacturing optical fibers having holes having different hole diameters, it is not necessary to prepare glass tubes having different inner diameters, and thus the component cost can be reduced.
　また、上記実施の形態では、ガラス母材の複数の空孔の一部または全部に対して、比（Ｘ／Ｙ）＜１．０が成り立つような圧力制御を行っている。しかしながら、本発明では、少なくとも１つの空孔に対して比（Ｘ／Ｙ）＜１．０が成り立つような圧力制御を行えばよい。 In the above-described embodiment, pressure control is performed so that the ratio (X / Y) <1.0 is satisfied for some or all of the plurality of holes in the glass base material. However, in the present invention, pressure control may be performed so that the ratio (X / Y) <1.0 is satisfied with respect to at least one hole.
　また、上記実施の形態のガラス母材に公知のジャケット法を適用してガラス母材の外径を調整してもよい。ジャケット法とは、ガラス母材を、内径がガラス母材の外径と略同一である石英ガラス管に挿入し、より外径が大きいガラス母材を形成する方法である。 Further, the outer diameter of the glass base material may be adjusted by applying a known jacket method to the glass base material of the above embodiment. The jacket method is a method of forming a glass base material having a larger outer diameter by inserting the glass base material into a quartz glass tube having an inner diameter that is substantially the same as the outer diameter of the glass base material.
　また、本発明は、ＰＢＧＦ等の長手方向の軸に沿って延びる複数の空孔を有する種々の光ファイバの製造に適用できる。 Also, the present invention can be applied to the manufacture of various optical fibers having a plurality of holes extending along the longitudinal axis such as PBGF.
　また、上記実施の形態により本発明が限定されるものではない。上述した各構成要素を適宜組み合わせて構成したものも本発明に含まれる。また、さらなる効果や変形例は、当業者によって容易に導き出すことができる。よって、本発明のより広範な態様は、上記の実施の形態に限定されるものではなく、様々な変更が可能である。 Further, the present invention is not limited by the above embodiment. What was comprised combining each component mentioned above suitably is also contained in this invention. Further effects and modifications can be easily derived by those skilled in the art. Therefore, the broader aspect of the present invention is not limited to the above-described embodiment, and various modifications can be made.
　以上のように、本発明に係る光ファイバの製造方法は、複数の空孔を有する光ファイバの製造に利用して好適なものである。 As described above, the optical fiber manufacturing method according to the present invention is suitable for use in manufacturing an optical fiber having a plurality of holes.
　１、３、５　光ファイバ
　１ａ、２ａ、３ｃ、５ｃ　コア部
　１ｂ、２ｂ　クラッド部
　１ｃ、２ｃ、３ａ、３ｂ、４ａ、５ａ、５ｂ　空孔
　２、４　ガラス母材
　１００　線引装置
　１０１　線引加熱炉
　１０１ａ　ヒータ
　１０２、１１０　加圧機構
　１０２ａ、１１１　加圧用コネクタ
　１０２ｂ、１１２、１１３　ガス供給路
　１０２ｃ、１１４、１１５　圧力調整部
　１０３　外径測定器
　１０４　被覆樹脂塗布装置
　１０５　樹脂硬化装置
　１０６　キャプスタンローラ
　１０７　ガイドロール
　１１１ａ　第１加圧部
　１１１ｂ　第２加圧部
　Ｇ　ガス DESCRIPTION OF SYMBOLS 1, 3, 5 Optical fiber 1a, 2a, 3c, 5c Core part 1b, 2b Cladding part 1c, 2c, 3a, 3b, 4a, 5a, 5b Hole 2, 4 Glass base material 100 Drawing apparatus 101 Drawing heating Furnace 101a Heater 102, 110 Pressurization mechanism 102a, 111 Pressurization connector 102b, 112, 113 Gas supply path 102c, 114, 115 Pressure adjustment unit 103 Outer diameter measuring device 104 Coating resin coating device 105 Resin curing device 106 Capstan roller 107 Guide roll 111a 1st pressurizing part 111b 2nd pressurizing part G Gas

Claims (4)

  1. 　長手方向の軸に沿って延びる複数の空孔を有するガラス母材であって、前記空孔の直径と当該ガラス母材の外径との比が第１の比であるガラス母材を準備する準備工程と、
    　前記ガラス母材の前記複数の空孔内を加圧しつつ当該ガラス母材の一端を加熱溶融して、長手方向の軸に沿って延びる複数の空孔を有する光ファイバを線引きする線引き工程と、
    　を含み、前記光ファイバの前記空孔の少なくとも一つの直径と当該光ファイバの外径との比を第２の比とすると、前記第２の比と前記第１の比との比が１．０よりも小さくなるように前記ガラス母材の前記少なくとも一つの空孔内の圧力を調整して前記線引きを行うことを特徴とする光ファイバの製造方法。     A glass base material having a plurality of holes extending along an axis in the longitudinal direction, wherein a ratio of a diameter of the holes to an outer diameter of the glass base material is a first ratio is prepared. A preparation process;
    A drawing step of drawing an optical fiber having a plurality of holes extending along a longitudinal axis by heating and melting one end of the glass base material while pressurizing the inside of the plurality of holes of the glass base material;
    When the ratio of at least one of the holes of the optical fiber to the outer diameter of the optical fiber is a second ratio, the ratio of the second ratio to the first ratio is 1. The method of manufacturing an optical fiber, wherein the drawing is performed by adjusting a pressure in the at least one hole of the glass base material so as to be smaller than zero.
  2. 　前記第２の比と前記第１の比との比が０．５以上であることを特徴とする請求項１に記載の光ファイバの製造方法。 The method of manufacturing an optical fiber according to claim 1, wherein a ratio of the second ratio to the first ratio is 0.5 or more.
  3. 　前記ガラス母材の前記複数の空孔を互いに異なる圧力で加圧することを特徴とする請求項１または２に記載の光ファイバの製造方法。 3. The method of manufacturing an optical fiber according to claim 1, wherein the plurality of holes in the glass base material are pressurized with mutually different pressures.
  4. 　前記ガラス母材の前記複数の空孔の直径を３ｍｍ以上にすることを特徴とする請求項１～３のいずれか一つに記載の光ファイバの製造方法。 The method of manufacturing an optical fiber according to any one of claims 1 to 3, wherein a diameter of the plurality of holes in the glass base material is set to 3 mm or more.
PCT/JP2012/052303 2011-02-14 2012-02-01 Method for manufacturing optical fibers WO2012111436A1 (en)

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JP2004191947A (en) * 2002-11-25 2004-07-08 Shin Etsu Chem Co Ltd Holey fiber drawing method
JP2006083037A (en) * 2004-09-17 2006-03-30 Fujikura Ltd Method of manufacturing optical fiber
WO2011052497A1 (en) * 2009-10-26 2011-05-05 株式会社フジクラ Welding method, welding device, and method for manufacturing optical fiber

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* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
JP2004191947A (en) * 2002-11-25 2004-07-08 Shin Etsu Chem Co Ltd Holey fiber drawing method
JP2006083037A (en) * 2004-09-17 2006-03-30 Fujikura Ltd Method of manufacturing optical fiber
WO2011052497A1 (en) * 2009-10-26 2011-05-05 株式会社フジクラ Welding method, welding device, and method for manufacturing optical fiber

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