JP5835823B1 - Multi-core optical fiber preform manufacturing method - Google Patents

Abstract

A method of manufacturing a multi-core optical fiber preform that can easily provide an optical fiber preform capable of manufacturing a multi-core optical fiber having a plurality of cores in a cross section of the optical fiber with a low loss and a long length. A raw material gas is introduced into the outside of the quartz tube of the second quartz tube and inside the first quartz tube 21, and the first quartz tube 21 and the second quartz tube are heated with a heating device. Thus, the first glass fine particles diffused inside the first quartz tube 21 are deposited to form a clad portion deposition step for forming the clad portion 26 of the optical fiber preform, and heating disposed inside the second quartz tube. A removal step of removing the instrument, a core portion deposition step of forming the core portion of the optical fiber preform by flowing the raw material gas into the preheated second quartz tube and depositing the second glass fine particles 27a; A method for manufacturing a multi-core optical fiber preform, which is sequentially performed. [Selection] Figure 6

Description

  The present invention relates to a method for manufacturing a multi-core optical fiber preform.

  Transmission capacity in a communication network increases year by year, and it becomes indispensable to enable large-capacity transmission of 10 Tbit / s or more in an optical fiber core several years later. For this reason, research is being carried out to expand the transmission capacity of a normal single mode optical fiber by wavelength division multiplexing, time division multiplexing, polarization division multiplexing, code division multiplexing, and the like. On the other hand, there is a multi-core optical fiber having a plurality of cores in the cross section of the optical fiber as a spatial multiplexing technique that is one of the techniques for expanding the transmission capacity.

  As a method of manufacturing a multi-core optical fiber preform, a method of manufacturing an optical fiber preform by bundling a plurality of core preforms and inserting them into a quartz tube serving as a cladding part (see, for example, Patent Document 1) is known. Yes. As another method, a method of manufacturing an optical fiber preform by opening a plurality of holes in a quartz pillar serving as a cladding portion, inserting a core preform formed in advance into the voids, and heating and combining them. (See, for example, Patent Document 2). Furthermore, a method of simultaneously manufacturing a plurality of core portions using a plurality of mandrels and quartz tubes (for example, see Patent Document 3) has been proposed.

JP-A-8-119656 JP-A-9-090143 JP 2013-177269 A

  However, in the method of manufacturing the multi-core optical fiber preform described in Patent Document 1, since OH groups and impurities adhere to the surface of the core portion, there is a problem that it is difficult to reduce the loss due to absorption loss due to these impurities. . There is also a problem that it is difficult to precisely control the distance between a plurality of core portions formed in a cross section orthogonal to the axis of the optical fiber.

  In particular, when the core portions are laminated in a cross-sectional direction perpendicular to the axis of the optical fiber, there is a problem that the accuracy of the arrangement of the core portions deteriorates as the number of lamination increases. In addition, since quartz columns that serve as cladding portions are stacked in the gaps between the core portions, there is a problem that it is difficult to reduce costs.

  On the other hand, in the manufacturing method of the multi-core optical fiber preform described in Patent Document 2, since quartz glass is very hard, a special method such as ultrasonic vibration grinding is used when opening a hole in a quartz column serving as a cladding part. There is a need. However, if the length of the grinding tool is increased in order to deeply grind the hole, an axial deviation due to high-speed rotation occurs and grinding becomes impossible. Therefore, there is a problem that it is difficult to increase the size of the base material, that is, to lengthen the optical fiber.

  In the method for producing a multi-core optical fiber preform described in Patent Document 3, glass fine particles that form a cladding portion inside a quartz tube that is the outer diameter of the optical fiber and outside the quartz tube that is the core portion of the optical fiber When depositing glass, the temperature in the vicinity of the quartz tube serving as the core portion of the optical fiber is not heated uniformly, so that there is a problem that the glass fine particles forming the cladding portion are not uniformly deposited.

  In order to solve the above-mentioned problems, the present invention has been proposed in view of the above circumstances, and is an optical fiber mother capable of manufacturing a multi-core optical fiber having a plurality of cores in an optical fiber cross section with a low loss and a long length. It is an object of the present invention to provide a method for producing a multi-core optical fiber preform from which a material can be easily obtained.

  In order to achieve the above object, in the present invention, a quartz tube forming a core portion of an optical fiber preform is disposed in the quartz tube forming the outer shape of the optical fiber preform so as to correspond to each core portion. The glass particles are deposited on the quartz tube while heating.

  More specifically, based on a modified chemical vapor deposition (MCVD) method and a plasma chemical vapor deposition (PCVD) method, glass fibers are deposited while heating a quartz tube to generate an optical fiber preform.

Specifically, the manufacturing method of the multi-core optical fiber preform according to the present invention,
A plurality of second quartz tubes having a diameter smaller than the inner peripheral diameter of the first quartz tube are arranged inside the first quartz tube serving as the outer shape of the optical fiber preform, and the axial direction of the first quartz tube Quartz tube placement process to be placed along,
A heater arrangement step of arranging heaters on the outside of the first quartz tube and the inside of the second quartz tube,
A source gas is introduced into the outside of the second quartz tube and the inside of the first quartz tube, and the first quartz tube and the second quartz tube are heated with a heating instrument, thereby the first quartz tube. A cladding portion deposition step of depositing the first glass fine particles diffused inside the quartz tube and forming a cladding portion of the optical fiber preform;
A removal step of removing the heating device disposed inside the second quartz tube;
A core part deposition step of forming a core part of the optical fiber preform by flowing a source gas into the second quartz tube heated in advance and depositing second glass fine particles is sequentially performed.

In the manufacturing method of the above-mentioned multi-core optical fiber preform according to the present invention,
The cladding part deposition step and the core part deposition step are:
Maintaining the positional relationship of the relative positions of the first quartz tube, the second quartz tube, and the heating device, and using the central axis of the first quartz tube as a rotation axis; The second quartz tube and the heating device may be rotated synchronously.

In the manufacturing method of the above-mentioned multi-core optical fiber preform according to the present invention,
The quartz tube placement step includes:
The refractive index of the second quartz tube may be lower than the refractive index of the cladding part.

In the manufacturing method of the multi-core optical fiber preform according to the present invention,
The heating appliance arrangement step includes
As the heating device, an oxyhydrogen burner, a heating wire, or a cavity that generates microwaves may be used.

Specifically, the manufacturing method of the multi-core optical fiber preform according to the present invention,
A columnar base material in which one core part of an optical fiber base material is formed or a columnar base material in which one core part and a part of a cladding part around the core part are formed in advance for the number of cores. A core manufacturing process for manufacturing;
A plurality of the second quartz tubes having a diameter smaller than the inner peripheral diameter of the first quartz tube are arranged inside the first quartz tube serving as the outer shape of the optical fiber preform. Quartz tube placement step for placing along the axial direction;
A heater arrangement step of arranging heaters on the outside of the first quartz tube and the inside of the second quartz tube,
A source gas is introduced into the outside of the second quartz tube and the inside of the first quartz tube, and the first quartz tube and the second quartz tube are heated with a heating instrument, thereby the first quartz tube. A cladding part deposition step of depositing glass fine particles diffused inside the quartz tube and forming a cladding part of the optical fiber preform;
A removal step of removing the heating device disposed inside the second quartz tube;
A core portion insertion step is sequentially performed in which a columnar base material with the core portion formed in advance is inserted into a second quartz tube in which the glass fine particles are deposited on the outer surface.

In the manufacturing method of the above-mentioned multi-core optical fiber preform according to the present invention,
The cladding part deposition step includes
Maintaining the positional relationship of the relative positions of the first quartz tube, the second quartz tube, and the heating device, and using the central axis of the first quartz tube as a rotation axis; The second quartz tube and the heating device may be rotated synchronously.

In the manufacturing method of the above-mentioned multi-core optical fiber preform according to the present invention,
The quartz tube placement step includes:
The refractive index of the second quartz tube into which the columnar base material on which the core portion is formed is inserted may be lower than the refractive index of the cladding portion.

In the manufacturing method of the above-mentioned multi-core optical fiber preform according to the present invention,
The heating appliance arrangement step includes
As the heating device, an oxyhydrogen burner, a heating wire, or a cavity that generates microwaves may be used.

  The above inventions can be combined as much as possible.

  According to the method for producing a multi-core optical fiber preform according to the present invention, an optical fiber preform capable of producing a multi-core optical fiber having a plurality of cores in a cross section of the optical fiber with a low loss and a long length can be easily obtained.

The figure which shows an example of the cross section of an optical fiber preform Schematic explaining an example of the manufacturing process of the optical fiber preform according to the first embodiment Schematic explaining an example of the manufacturing process of the optical fiber preform according to the first embodiment Schematic explaining an example of the manufacturing process of the optical fiber preform according to the first embodiment Schematic explaining an example of the manufacturing process of the optical fiber preform according to the first embodiment Schematic explaining an example of the manufacturing process of the optical fiber preform according to the first embodiment Schematic explaining an example of the manufacturing process of the optical fiber preform according to the second embodiment Schematic explaining an example of the manufacturing process of the optical fiber preform according to the second embodiment Schematic explaining an example of the manufacturing process of the optical fiber preform according to the second embodiment Schematic explaining an example of the manufacturing process of the optical fiber preform according to the second embodiment Schematic explaining an example of the manufacturing process of the optical fiber preform according to the second embodiment Schematic explaining an example of the manufacturing process of the optical fiber preform which concerns on 3rd Embodiment Schematic explaining an example of the manufacturing process of the optical fiber preform which concerns on 3rd Embodiment Schematic explaining an example of the manufacturing process of the optical fiber preform which concerns on 3rd Embodiment Schematic explaining an example of the manufacturing process of the optical fiber preform which concerns on 3rd Embodiment Schematic explaining an example of the manufacturing process of the optical fiber preform which concerns on 3rd Embodiment Schematic explaining an example of the manufacturing process of the optical fiber preform which concerns on 4th Embodiment Schematic explaining an example of the manufacturing process of the optical fiber preform which concerns on 4th Embodiment Schematic explaining an example of the manufacturing process of the optical fiber preform which concerns on 4th Embodiment Schematic explaining an example of the manufacturing process of the optical fiber preform which concerns on 4th Embodiment Schematic explaining an example of the manufacturing process of the optical fiber preform which concerns on 4th Embodiment

  Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings. In addition, this invention is not limited to embodiment shown below. These embodiments are merely examples, and the present invention can be implemented in various modifications and improvements based on the knowledge of those skilled in the art. In the present specification and drawings, the same reference numerals denote the same components.

  The manufacturing method of the multi-core optical fiber preform according to the present embodiment sequentially performs a quartz tube placement step, a heating device placement step, a cladding portion deposition step, a removal step, and a core portion deposition step. In addition, even if the manufacturing method of the multi-core optical fiber preform is performed in the order of the core part manufacturing process, the quartz tube arranging process, the heating tool arranging process, the cladding part depositing process, the removing process, and the core part inserting process. Good.

  A method for producing a multi-core optical fiber preform according to the present invention will be described with reference to the drawings. First, an optical fiber preform for a multi-core optical fiber to be manufactured in the present invention will be described with reference to FIG. FIG. 1 is a view showing an example of a cross section of an optical fiber preform.

  As shown in FIG. 1, the optical fiber preform 10 has a circular cross section as a whole and extends in a direction penetrating the paper surface. The outer shape of the optical fiber preform is a shape that forms a desired optical fiber outer shape, and may not be circular as long as it forms a desired optical fiber outer shape.

  The optical fiber preform 10 includes a core portion 11 having a plurality (seven in FIG. 1) of arbitrary refractive index distribution (circular in FIG. 1) and a cladding portion 12 having a refractive index smaller than that of the core portion 11. The clad part 12 forms a part other than the core part 11, so that the outer shape of the optical fiber preform 10 forms the outer shape of the clad part 12.

  One of the plurality of core portions 11 is arranged at the center (axial center) of the optical fiber preform 10 by the quartz tube arranging step. The other core part 11 is arranged around the core part 11 of the axial center. In FIG. 1, a plurality of surrounding core portions 11 are arranged so as to take a predetermined distance from the axis, respectively, and adjacent core portions 11 are arranged so as to be equally spaced from each other. In other words, the seven core portions 11 are provided at each vertex of the regular hexagon and the center thereof, and the optical fiber preform 10 has a symmetrical structure. In addition, it is not necessary to arrange | position one of the some core parts 11 in the center (axial center).

  Further, in the quartz tube arranging step, the plurality of surrounding core portions 11 may be simply arranged at positions surrounding the axis, and the optical fiber preform 10 may have an asymmetric structure. Further, although the optical fiber preform 10 having the seven core portions 11 is used, the optical fiber preform 10 is not limited to seven, and may be any optical fiber preform 10 having two or more core portions 11.

  In an optical fiber using quartz as a main component, an optical waveguide structure can be formed by adding a dopant to either the core portion 11 or the cladding portion 12. Further, a dopant may be added to both the core part 11 and the clad part 12. Note that typical dopants include germanium oxide (GeO2) and fluorine (F), but chemical substances other than these can be used as the dopant. The present invention relates to a method for manufacturing such an optical fiber preform 10. The embodiment will be described in detail below.

(First embodiment)
A method for manufacturing the multi-core optical fiber preform 10 according to the first embodiment of the present invention will be described with reference to FIGS. 2-6 is the schematic explaining an example of the manufacturing process of the optical fiber preform 10 which concerns on 1st Embodiment.

  The manufacturing method of the optical fiber according to the present embodiment is a manufacturing method of the optical fiber preform 10 based on the MCVD (Modified Chemical Vapor Deposition) method. First, one first quartz tube 21 having the same size (outer diameter, length) as that of the optical fiber preform 10 is prepared, and the same size (length) as that of the optical fiber preform 10 is prepared. Yes, seven second quartz tubes 22 forming the core of the optical fiber preform 10 are prepared.

  In the quartz tube placement step, the second quartz tube 22 has a diameter smaller than the diameter of the first quartz tube 21. As shown in FIG. 2, the first quartz tube 21 and the seven second quartz tubes 22 are arranged such that the longitudinal direction thereof is horizontal with the axis C2. Specifically, one second quartz tube 22 has an axis C2 so that the second quartz tube 22 corresponds to the formation position of each core portion 11 of the optical fiber preform 10 shown in FIG. The other six second quartz tubes 22 are arranged so as to surround the axis C2 of the first quartz tube 21, and the second quartz tube is placed inside the first quartz tube 21. It arrange | positions in the location which makes each vertex of the regular hexagon centering on 22. FIG. The plurality of second quartz tubes 22 are not limited to be symmetrically disposed so as to surround the axis C2, but may be asymmetrically disposed.

  Further, in the quartz tube arranging step, the second quartz tube 22 is not limited to the one arranged at the position of the axis C2, and the second quartz tube 22 may be arranged around the axis C2. . The number of the second quartz tubes 22 is the same number as the core portion 11 of the optical fiber preform 10, and is not limited to seven and may be two or more.

  For example, when the refractive index distribution of the multi-core optical fiber finally obtained by drawing the optical fiber preform 10 is a step type, the plurality of second quartz tubes 22 are set so that the distance between the cores of the multi-core optical fiber is 45 μm or more. By arranging in such a manner, the crosstalk between the cores after transmission of the multi-core optical fiber by 100 km can be reduced to -30 dB or less.

  Further, when the refractive index distribution of the core portion 11 of the multicore optical fiber finally obtained by drawing the optical fiber preform 10 is a trench type, a plurality of second quartz tubes 22 are connected between the cores of the multicore optical fiber. By arranging the distance to be 38 μm or more, the crosstalk between the cores after transmission of the multi-core optical fiber by 100 km can be set to −30 dB or less.

  In addition, the diameters of the plurality of second quartz tubes 22 are not limited to the same, and the diameters of the different diameters are set so as to match each core diameter of the multi-core optical fiber finally obtained by drawing the optical fiber preform 10. Two quartz tubes 22 may be used. Further, the plurality of second quartz tubes 22 may be formed of a raw material having a refractive index lower than the refractive index of the cladding portion 12 of the optical fiber preform 10.

  For example, the plurality of second quartz tubes 22 are finally drawn by drawing the optical fiber preform 10 by using a quartz tube having a refractive index lower than that of pure quartz by adding fluorine to pure quartz. It becomes possible to reduce the bending loss of the obtained multi-core optical fiber.

  Further, in the quartz tube arranging step, the end portion of the first quartz tube 21 and the end portion of the second quartz tube 22 are arranged on substantially the same plane. The first quartz tube 21 and the second quartz tube 22 are arranged around the axis C2 while maintaining the relative positions of the first quartz tube 21 and the second quartz tube 22 around the axis C2. Are supported by a predetermined support (not shown) so that they can be rotated synchronously in the cladding portion deposition step or the core portion deposition step.

  Next, as shown in FIG. 3, in the heating instrument arrangement step, the first quartz tube 21 and the second quartz tube 22 are heated as the instruments for heating the first quartz tube 21 and the second quartz tube 22, respectively. A first oxyhydrogen burner 23 and a heating wire 24 are disposed inside each quartz tube 22. Here, the instrument for heating the first quartz tube 21 and the second quartz tube 22 may not be an oxyhydrogen burner and a heating wire.

  At this time, a flame polishing process may be performed on the first quartz tube 21 by the first oxyhydrogen burner 23. Here, the first oxyhydrogen burner 23 may be moved in the direction of the arrow L2. Further, quartz tubes that have been subjected to a flame polishing process in advance may be used as the first quartz tube 21 and the second quartz tube 22.

  Subsequently, as shown in FIG. 4, in the cladding portion deposition step, a second oxyhydrogen burner (cladding portion material supply means) 25 is disposed in the vicinity of the axial end portion side of the first quartz tube 21. Subsequently, the first quartz tube 21 and the seven second quartz tubes 22 and the heating wire 24 are synchronously rotated around the axis C2 around the axis C2 of the first quartz tube 21, while the second The first glass fine particles 25 a that are the clad portions 26 of the optical fiber preform 10 are deposited inside the first quartz tube 21 and outside the seven second quartz tubes 22 by the oxyhydrogen burner 25.

  As described above, since the first quartz tube 21 and the second quartz tube 22 are heated by the first oxyhydrogen burner 23 and the heating wire 24, the glass of the cladding portion 26 of the optical fiber preform 10 is thermally oxidized. A layer is formed. Here, the first quartz tube 21 is heated by the first oxyhydrogen burner 23, and the second quartz tube 22 is heated by the heating wire 24, whereby the first glass fine particles 25a are removed from the first glass particles 25a. It is possible to deposit uniformly and at high speed on the inner surface of the quartz tube 21 and the outer surface of the second quartz tube 22.

  In addition, in the heating device arranging step, the second oxyhydrogen burner 25 is used to prevent the first glass fine particles 25 a that become the clad portion 26 of the optical fiber preform 10 from being deposited inside the second quartz tube 22. It is also possible to seal the end of the second quartz tube 22 to be disposed when the heating wire 24 is inserted.

  Then, in the removing step, when a predetermined amount of the first glass particles 25a is deposited in the first quartz tube 21, the heating wire 24 disposed inside the second quartz tube 22 is removed as shown in FIG. At this time, the first oxyhydrogen burner 23 disposed outside the first quartz tube 21 is disposed as it is.

  Next, as shown in FIG. 6, a third oxyhydrogen burner (core part raw material supply means) 27 is arranged in place of the second oxyhydrogen burner 25. Subsequently, in the core portion deposition step, the first quartz tube 21 and the seven second quartz tubes 22 are synchronously rotated around the axis C2 around the axis C2 of the first quartz tube 21, while the first The second glass fine particles 27 a are deposited on the inner side 22 a of the clad portion 26 inside the first quartz tube 21 (that is, inside the second quartz tube 22) by the third oxyhydrogen burner 27. As described above, since the first quartz tube 21 is heated by the oxyhydrogen burner 23, the glass layer of the core portion 28 of the optical fiber preform 10 is formed by thermal oxidation.

  In addition, by adjusting the source gas and flow rate of the third oxyhydrogen burner 27, the core portion 28 having an arbitrary refractive index distribution (for example, step type, step type, trench type, etc.) can be produced. . Then, by depositing a predetermined amount of the second glass fine particles 27a on the inner side 22a of the clad portion 26 inside the first quartz tube 21 (that is, the inner side of the second quartz tube 22), the clad portion 26 and the core portion 28 are deposited. Thus, an optical fiber preform 10 (see, for example, FIG. 1) for manufacturing an optical fiber including a plurality of core portions 28 formed with is obtained. By drawing the optical fiber preform 10, an optical fiber including a plurality of core portions 28 in the cross section can be obtained.

  As described above, according to the method of manufacturing the multi-core optical fiber preform according to the present embodiment, the diameter of the first quartz tube 21 that is the outer shape of the optical fiber preform 10 is smaller than the diameter of the first quartz tube 21. The plurality of second quartz tubes 22 are arranged in the quartz tube arranging step so as to correspond to the respective core portions 28 of the optical fiber preform 10, and the outside of the first quartz tube 21 and the inside of the second quartz tube 22 are arranged. In addition, appliances for heating the first quartz tube 21 and the second quartz tube 22 are arranged in a heating appliance arrangement step, respectively, and the outside of the first quartz tube 21 and the inside of the second quartz tube 22 are arranged. The clad portion of the optical fiber preform 10 on the inner surface of the first quartz tube 21 and the outer surface of the second quartz tube 22 while heating the inner surface of the first quartz tube 21 and the outer surface of the second quartz tube 22. 26, the first glass fine particles 25a to be 26 After removing the device for heating the second quartz tube 22 deposited in the second portion deposition step and heating the second quartz tube 22 in the removal step, the core portion 28 of the optical fiber preform 10 and Since the second glass fine particles 27a to be formed are deposited in the core portion deposition step, the core in the method of manufacturing the optical fiber preform 10 by bundling a plurality of core preforms and inserting them into a quartz tube serving as the cladding portion 26. When the portion 28 is laminated in a cross-sectional direction orthogonal to the axis of the optical fiber, there is an effect that it is possible to reduce processing accuracy deterioration and difficulty in reducing loss due to lamination. In addition, since the diameter of the second quartz tube 22 forming the core portion 28 can be arbitrarily set, it is possible to easily manufacture a base material for a multi-core optical fiber having a different core diameter. Play.

  In addition, since no drilling operation is required, an optical fiber preform 10 for producing an optical fiber including a plurality of core portions 28 with a low loss and a long length is manufactured without being limited by the base material size. Thus, the optical fiber including the plurality of core portions 28 can be mass-produced.

  In the above embodiment, the glass fine particles are deposited while the first quartz tube 21 and the second quartz tube 22 and the heating wire 24 are rotated synchronously in the cladding portion deposition step. The number and arrangement of each burner, the rotation form, etc. are not particularly limited within the range in which the accumulated state can be obtained. For example, in the above embodiment, the first quartz tube 21 and the second quartz tube 22 and the heating wire 24 are rotated synchronously, but the first oxyhydrogen burner 23, the second oxyhydrogen burner 25, and The third oxyhydrogen burner 27 may be rotated about the axis C2.

  Furthermore, in the above embodiment, only one first oxyhydrogen burner 23, second oxyhydrogen burner 25, and third oxyhydrogen burner 27 are used, but a plurality of first oxyhydrogen burners 23 and second oxyhydrogen burners 23 and Two oxyhydrogen burners 25 and a third oxyhydrogen burner 27 may be provided. In particular, if a large number of the first oxyhydrogen burner 23, the second oxyhydrogen burner 25, and the third oxyhydrogen burner 27 are arranged around the axis C2, each quartz tube, each burner, and heating wire are not rotated. It can also be.

  Further, when the heating wire 24 is arranged in the second quartz tube 22, the inside of the second quartz tube 22 is covered with a lid or the like so that the first glass fine particles 25a are not deposited inside the second quartz tube 22. It is also possible to seal. In this case, it is possible to deposit the second glass fine particles 27a on the inner surface of the second quartz tube 22 in a later step by removing the sealing lid in the step of removing the heating wire 24.

(Second Embodiment)
A method for manufacturing the multi-core optical fiber preform 10 according to the second embodiment of the present invention will be described with reference to FIGS. 7 to 11 are schematic diagrams for explaining an example of the manufacturing process of the optical fiber preform 10 according to the second embodiment. The manufacturing method of the optical fiber according to the present embodiment is a manufacturing method of the optical fiber preform 10 based on the MCVD (Modified Chemical Vapor Deposition) method.

  First, a columnar base material in which one core portion 11 of the optical fiber preform 10 shown in FIG. 1 is formed, or one core portion 11 and a part of a cladding portion 12 around the core portion are formed. Seven columnar base materials are prepared. In the core part manufacturing process, for example, a VAD (Vapor Phase Axial Deposition) method, OVD (Outside) is used in accordance with the desired refractive index distribution of the core of the multi-core optical fiber finally obtained by drawing the optical fiber preform 10. Vapor Deposition (MCVD), Modified Chemical Vapor Deposition (MCVD), Plasma Chemical Vapor Deposition (PCVD), etc., and an arbitrary refractive index distribution (eg, step type, step type, trench type, etc.) Can be produced.

  Moreover, the columnar base material in which the core part 11 or the core part 11 and the clad part 12 are formed is mainly a porous base material manufactured by a VAD method, an OVD method, an MCVD method, and a PCVD method. In addition, a glass base material obtained after dehydration and clarification of the porous base material can be mentioned, but other base materials can also be used.

  Next, one first quartz tube 31 having approximately the same size (outer diameter, length) as the optical fiber preform 10 is prepared, and is approximately the same size (length) as the optical fiber preform 10. Seven second quartz tubes 32 for forming the core portion 11 of the optical fiber preform 10 are prepared. The second quartz tube 32 has a diameter smaller than the diameter of the first quartz tube 31. As shown in FIG. 7, in the quartz tube arranging step, the first quartz tube 31 and the seven second quartz tubes 32 are arranged so that the longitudinal direction thereof is horizontal with the axis C3.

  Specifically, in the quartz tube placement step, the second quartz tube 32 is one second quartz tube so as to correspond to the formation position of each core portion 11 of the optical fiber preform 10 shown in FIG. 32 is arranged at the position of the axis C3, and the other six second quartz tubes 32 are arranged so as to surround the axis C3 of the first quartz tube 31, and the inside of the first quartz tube 31 The second quartz tube 32 is arranged at a position where each apex of a regular hexagon is formed.

  The plurality of second quartz tubes 32 are not limited to be symmetrically disposed so as to surround the axis C3, but may be asymmetrically disposed. Further, the second quartz tube 32 is not limited to the one arranged at the position of the axis C3, and the second quartz tube 32 may be arranged around the axis C3. The number of the second quartz tubes 32 is the same number as the core portion 11 of the optical fiber preform 10, and is not limited to seven, and may be two or more.

  For example, when the refractive index distribution of the multi-core optical fiber finally obtained by drawing the optical fiber preform 10 is a step type, the plurality of second quartz tubes 32 are arranged so that the distance between the cores of the multi-core optical fiber is 45 μm or more. By arranging in such a manner, the crosstalk between the cores after transmission of the multi-core optical fiber by 100 km can be reduced to -30 dB or less.

  Further, when the refractive index distribution of the core of the multi-core optical fiber finally obtained by drawing the optical fiber preform 10 is a trench type, the plurality of second quartz tubes 32 are connected to each other with a distance between the cores of the multi-core optical fiber. By arranging it to be 38 μm or more, the crosstalk between the cores after transmission of the multi-core optical fiber by 100 km can be reduced to −30 dB or less.

  Further, the diameters of the plurality of second quartz tubes 32 are not limited to the same one, and the diameters of the different diameters are set so as to match the core diameters of the multi-core optical fiber finally obtained by drawing the optical fiber preform 10. Two quartz tubes 32 may be used. Further, the plurality of second quartz tubes 32 into which the columnar base material formed with the core part is inserted is formed of a raw material having a refractive index lower than the refractive index of the cladding part 12 of the optical fiber base material 10. May be.

  For example, the plurality of second quartz tubes 32 are finally drawn by drawing the optical fiber preform 10 by using a quartz tube having a refractive index lower than that of pure quartz by adding fluorine to pure quartz. It becomes possible to reduce the bending loss of the obtained multi-core optical fiber.

  Further, in the quartz tube arranging step, the end portion of the first quartz tube 31 and the end portion of the second quartz tube 32 are arranged on substantially the same plane. The first quartz tube 31 and the second quartz tube 32 are arranged around the axis C3 while maintaining the relative positions of the first quartz tube 31 and the second quartz tube 32 around the axis C3. Is supported by a predetermined support (not shown) so that it can be rotated synchronously in the cladding deposition process.

  Next, as shown in FIG. 8, in the heating instrument arrangement step, the first quartz tube 31 and the second quartz tube 32 are heated as the instruments for heating the first quartz tube 31 and the second quartz tube 32, respectively. Inside the quartz tube 32, a first oxyhydrogen burner 33 and a heating wire 34 are arranged, respectively.

  Here, the instrument for heating the first quartz tube 31 and the second quartz tube 32 may not be an oxyhydrogen burner and a heating wire. At this time, a flame polishing process may be performed on the first quartz tube 31 by the first oxyhydrogen burner 33. Here, the first oxyhydrogen burner 33 may be moved in the direction of the arrow L3. Further, quartz tubes that have been subjected to a flame polishing process in advance may be used as the first quartz tube 31 and the second quartz tube 32.

  Subsequently, as shown in FIG. 9, in the cladding portion deposition step, a second oxyhydrogen burner (cladding portion raw material supply means) 35 is disposed in the vicinity of the axial end portion side of the first quartz tube 31. Subsequently, the first quartz tube 31 and the seven second quartz tubes 32 are synchronously rotated around the axis C3 about the axis C3 of the first quartz tube 31, while the second oxyhydrogen burner 35 is rotated. Thus, the first glass fine particles 35 a to be the clad portion 36 of the optical fiber preform 10 are deposited inside the first quartz tube 31 and outside the seven second quartz tubes 32.

  As described above, since the first quartz tube 31 and the second quartz tube 32 are heated by the first oxyhydrogen burner 33 and the heating wire 34, the glass of the cladding portion 36 of the optical fiber preform 10 is thermally oxidized. A layer is formed. Here, the first quartz tube 31 is heated by the first oxyhydrogen burner 33 and the second quartz tube 32 is heated by the heating wire 34, whereby the first glass particles 35a are moved to the first glass particles 35a. It is possible to deposit uniformly and at high speed on the inner surface of the quartz tube 31 and the outer surface of the second quartz tube 32.

  In addition, a second oxyhydrogen burner 35 is disposed in order to prevent the first glass fine particles 35 a serving as the cladding portion 36 of the optical fiber preform 10 from being deposited inside the second quartz tube 32. It is also possible to seal the end of the quartz tube 32 when the heating wire 34 is inserted.

  Then, in the removal step, when a predetermined amount of the first glass particles 35a is deposited in the first quartz tube 31, the outside of the first quartz tube 31 and the inside of the second quartz tube 32 as shown in FIG. In addition, the first oxyhydrogen burner 33 and the heating wire 34 arranged respectively are removed.

  Next, as shown in FIG. 11, a columnar base material or one core portion 37 on which one core portion 37 of the optical fiber preform 10 manufactured in advance in the core portion manufacturing step is formed, and the core portion 37. Seven columnar base materials in which a part of the surrounding clad portion 36 is formed are arranged on the inner side 32 a of the clad portion 36 inside the first quartz tube 31 (that is, inside the second quartz tube 32). By inserting each, the optical fiber preform 10 (for example, see FIG. 1) for producing an optical fiber including a plurality of core portions 37 formed with the clad portion 36 and the core portion 37 is obtained.

  Here, an oxyhydrogen burner for depositing glass fine particles to be the clad part 36 or the core part 37 is arranged, and the glass fine particles to be the clad part 36 or the core part 37 are disposed in the gap between the clad part 36 and the core part 37. It is also possible to prevent the core position shift when the optical fiber preform 10 is drawn.

  Further, when the core portion 37 is formed of a porous preform or glass fine particles, an optical fiber preform for manufacturing an optical fiber including a plurality of core portions 37 by performing dehydration and transparency treatment. The material 10 can be obtained. By drawing the optical fiber preform 10, an optical fiber including a plurality of core portions 37 in the cross section can be obtained.

  As described above, according to the manufacturing method of the multi-core optical fiber preform according to the present embodiment, the light including the plurality of core portions 37 is provided as in the manufacturing method of the multi-core optical fiber preform according to the first embodiment. It is possible to easily obtain the optical fiber preform 10 with which the fiber can be manufactured with a low loss and a long length.

  In the above embodiment, the glass fine particles are deposited while the first quartz tube 31 and the second quartz tube 32 and the heating wire 34 are synchronously rotated in the cladding portion deposition step. The number and arrangement of each burner, the rotation form, etc. are not particularly limited within the range in which the accumulated state can be obtained. For example, in the above-described embodiment, the first quartz tube 31 and the second quartz tube 32 and the heating wire 34 are rotated synchronously. However, the first oxyhydrogen burner 33 and the second oxyhydrogen burner 35 are replaced with each other. You may make it rotate centering on the axial center C3.

  Furthermore, in the above embodiment, only one first oxyhydrogen burner 33 and one second oxyhydrogen burner 35 are used, but a plurality of first oxyhydrogen burners 33 and second oxyhydrogen burners 35 are provided. May be. In particular, if a large number of first oxyhydrogen burners 33 and second oxyhydrogen burners 35 are arranged around the axis C3, each quartz tube, each burner, and heating wire can be made non-rotating.

  Further, when the heating wire 34 is disposed in the second quartz tube 32, the inside of the second quartz tube 32 is sealed with a lid or the like so that the glass fine particles 35a are not deposited inside the second quartz tube 32. Is also possible. In this case, by removing the sealing lid in the removing step of removing the heater, the columnar base material in which the core portion 37 is formed inside the second quartz tube 32 can be inserted in the subsequent step. Is possible.

(Third embodiment)
A method for manufacturing a multi-core optical fiber preform according to the third embodiment of the present invention will be described with reference to FIGS. 12 to 16 are schematic diagrams for explaining an example of the manufacturing process of the optical fiber preform according to the third embodiment.

  The manufacturing method of the optical fiber according to the present embodiment is a manufacturing method of the optical fiber preform 10 based on the PCVD (Plasma Chemical Vapor Deposition) method. First, as in the first embodiment, one first quartz tube 41 having the same size (outer diameter and length) as that of the optical fiber preform 10 is prepared. Seven second quartz tubes 42 having the same size (length) and forming the core portion 11 of the optical fiber preform 10 are prepared.

  In the quartz tube placement step, the second quartz tube 42 has a diameter smaller than the diameter of the first quartz tube 41. As shown in FIG. 12, the first quartz tube 41 and the seven second quartz tubes 42 are arranged so that the longitudinal direction thereof is horizontal with the axis C4. Specifically, in the quartz tube placement step, the second quartz tube 42 is one second quartz tube so as to correspond to the formation position of each core portion 11 of the optical fiber preform 10 shown in FIG. 42 is arranged at the position of the axis C4, and other six second quartz tubes 42 are arranged so as to surround the axis C4 of the first quartz tube 41, and the inside of the first quartz tube 41 The second hexagonal tube 42 is arranged at each vertex of the regular hexagon.

  The plurality of second quartz tubes 42 are not limited to be arranged symmetrically so as to surround the axis C4, but may be arranged asymmetrically. Further, the second quartz tube 42 is not limited to the one arranged at the position of the axis C4, and the second quartz tube 42 may be arranged around the axis C4. The number of the second quartz tubes 42 is the same number as the core portion 11 of the optical fiber preform 10, and is not limited to seven, and may be two or more.

  For example, when the refractive index distribution of the multi-core optical fiber finally obtained by drawing the optical fiber preform 10 is a step type, the plurality of second quartz tubes 42 are arranged so that the inter-core distance of the multi-core optical fiber is 45 μm or more. By arranging in such a manner, the crosstalk between the cores after transmission of the multi-core optical fiber by 100 km can be reduced to -30 dB or less.

  Furthermore, when the refractive index distribution of the core of the multicore optical fiber finally obtained by drawing the optical fiber preform 10 is a trench type, the plurality of second quartz tubes 42 are connected to each other with a distance between the cores of the multicore optical fiber. By arranging it to be 38 μm or more, the crosstalk between the cores after transmission of the multi-core optical fiber by 100 km can be reduced to −30 dB or less.

  Further, the diameters of the plurality of second quartz tubes 42 are not limited to the same one, and the diameters of the different diameters are set so as to match each core diameter of the multi-core optical fiber finally obtained by drawing the optical fiber preform 10. Two quartz tubes 42 may be used. Further, the plurality of second quartz tubes 42 may be formed of a raw material having a refractive index lower than the refractive index of the cladding portion 12 of the optical fiber preform 10.

  For example, the plurality of second quartz tubes 42 are finally drawn by drawing the optical fiber preform 10 by using a quartz tube having a refractive index lower than that of pure quartz by adding fluorine to pure quartz. It becomes possible to reduce the bending loss of the obtained multi-core optical fiber.

  Further, in the quartz tube arranging step, the end portion of the first quartz tube 41 and the end portion of the second quartz tube 42 are arranged on substantially the same plane. The first quartz tube 41 and the second quartz tube 42 are arranged around the axis C4 while maintaining the relative positions of the first quartz tube 41 and the second quartz tube 42 around the axis C4. Are supported by a predetermined support (not shown) so that they can be rotated synchronously in the cladding portion deposition step or the core portion deposition step.

  Next, as shown in FIG. 13, in the heating instrument arrangement step, the first quartz tube 41 and the second quartz tube 42 are heated as the instruments for heating the first quartz tube 41 and the second quartz tube 42, respectively. Inside the quartz tube 42, a first cavity 43a and a second cavity 43b for generating microwave plasma are respectively arranged.

  Here, a microwave plasma generator 43 is constituted by the first cavity 43a, the second cavity 43b, and the microwave plasma generation source 43c. At this time, the first quartz tube 41 and the second quartz tube 42 may be polished by a plasma flame using microwave plasma. Here, the first cavity 43a disposed outside the first quartz tube 41 may be moved in the direction of the arrow L4. Further, quartz tubes that have been subjected to flame polishing treatment in advance may be used as the first quartz tube 41 and the second quartz tube 42.

  Subsequently, as shown in FIG. 14, in the cladding portion deposition step, a first oxyhydrogen burner (cladding portion material supply means) 44 is disposed in the vicinity of the axial end portion of the first quartz tube 41. Subsequently, the first quartz tube 41, the seven second quartz tubes 42, the first cavity 43a and the second cavity 43b are arranged around the axis C4 around the axis C4 of the first quartz tube 41. The first oxyhydrogen burner 44 is used as a clad portion of the optical fiber preform 10 inside the first quartz tube 41 and outside the seven second quartz tubes 42. Glass fine particles 44a are deposited.

  As described above, since the first quartz tube 41 and the second quartz tube 42 are heated by the first cavity 43a and the second cavity 43b, the glass of the cladding portion 45 of the optical fiber preform 10 is thermally oxidized. A layer is formed. Here, not only the first cavity 43a but also the second cavity 43b is used to heat the first quartz tube 41 and the second quartz tube 42, whereby the first glass fine particles 44a are moved to the first cavity 43a. It is possible to deposit uniformly and at high speed on the inner surface of the quartz tube 41 and the outer surface of the second quartz tube 42.

  In addition, in the heating device arranging step, the second cavity 43b is arranged in order to prevent the first glass fine particles 44a serving as the clad portion 46 of the optical fiber preform 10 from being deposited inside the second quartz tube 42. It is also possible to seal the end of the second quartz tube 42 when the second cavity 43b is inserted.

  In the removing step, when a predetermined amount of the first glass particles 44a is deposited in the first quartz tube 41, the second cavity 43b disposed inside the second quartz tube 42 is removed as shown in FIG. . At this time, the first cavity 43a arranged outside the first quartz tube 41 is arranged as it is.

  Next, as shown in FIG. 16, a second oxyhydrogen burner (core part material supply means) 46 is arranged in place of the first oxyhydrogen burner 44. Subsequently, in the core portion deposition step, the first quartz tube 41, the seven second quartz tubes 42, and the first cavity 43a are arranged around the axis C4 around the axis C4 of the first quartz tube 41. The second glass particulates 46 a are deposited on the inner side 42 a of the clad portion 45 inside the first quartz tube 41 (that is, inside the second quartz tube 42) by the second oxyhydrogen burner 46. Let As described above, since the first quartz tube 41 is heated by the first cavity 43a, the glass layer of the core portion 47 of the optical fiber preform 10 is formed by thermal oxidation.

  In addition, by adjusting the source gas and flow rate of the second oxyhydrogen burner 46, the core portion 47 having an arbitrary refractive index distribution (for example, a step type, a staircase type, a trench type, etc.) can be produced. . Then, by depositing a predetermined amount of the second glass fine particles 46a on the inner side 42a of the clad portion 45 inside the first quartz tube 41 (that is, the inner side of the second quartz tube 42), the clad portion 45 and the core portion 47 are deposited. As a result, an optical fiber preform 10 (see, for example, FIG. 1) for manufacturing an optical fiber including a plurality of core portions 47 formed with the structure is obtained. By drawing the optical fiber preform 10, an optical fiber including a plurality of core portions 47 in the cross section can be obtained.

  Thus, according to the manufacturing method of the multi-core optical fiber preform according to the present embodiment, a plurality of core portions 47 are formed as in the manufacturing method of the multi-core optical fiber preform according to the first to second embodiments. It is possible to easily obtain the optical fiber preform 10 that can manufacture the optical fiber to be included with a low loss and a long length.

  In the above embodiment, in the cladding portion deposition step, glass particles are deposited while the first quartz tube 41 and the second quartz tube 42, and the first cavity 43a and the second cavity 43b are rotated synchronously. However, the number and arrangement of the burners, the rotation form, etc. are not limited as long as the desired glass particulate deposition state is obtained.

  For example, in the above embodiment, each of the first quartz tube 41 and the second quartz tube 42, and each of the first cavity 43a and the second cavity 43b are synchronously rotated, but the first oxyhydrogen burner 44 is used. The second oxyhydrogen burner 46 may be rotated about the axis C4.

  Further, in the above embodiment, only one first oxyhydrogen burner 44 and one second oxyhydrogen burner 46 are used, but a plurality of first oxyhydrogen burners 44 and second oxyhydrogen burners 46 are provided. May be. In particular, if a large number of first oxyhydrogen burners 44 and second oxyhydrogen burners 46 are arranged around the axis C4, each quartz tube and each cavity can be made non-rotating.

  In addition, when the second cavity 43b is arranged in the second quartz tube 42, the inside of the second quartz tube 42 is covered so that the first glass fine particles 44a are not deposited inside the second quartz tube 42. It is also possible to hermetically seal. In this case, by removing the sealing lid in the step of removing the second cavity 43b, it is possible to deposit the second glass particles 46a on the inner surface of the second quartz tube 42 in the subsequent step.

(Fourth embodiment)
A method for manufacturing a multi-core optical fiber preform according to the fourth embodiment of the present invention will be described with reference to FIGS. 17 to 21 are schematic views for explaining an example of the manufacturing process of the optical fiber preform 10 according to the fourth embodiment.

  The manufacturing method of the optical fiber according to the present embodiment is a manufacturing method of the optical fiber preform 10 based on the PCVD (Plasma Chemical Vapor Deposition) method. First, a columnar base material in which one core portion 11 of the optical fiber preform 10 shown in FIG. 1 is formed, or one core portion 11 and a part of a cladding portion 12 around the core portion 11 are formed. 7 columnar base materials are prepared.

  In the core part manufacturing process, for example, a VAD (Vapor Phase Axial Deposition) method, OVD (Outside) is used in accordance with the desired refractive index distribution of the core of the multi-core optical fiber finally obtained by drawing the optical fiber preform 10. Vapor Deposition (MCVD), Modified Chemical Vapor Deposition (MCVD), Plasma Chemical Vapor Deposition (PCVD), etc., and an arbitrary refractive index distribution (eg, step type, step type, trench type, etc.) Can be produced.

  Moreover, the columnar base material in which the core part 11 or the core part 11 and the clad part 12 are formed is mainly a porous base material manufactured by a VAD method, an OVD method, an MCVD method, and a PCVD method. In addition, a glass base material obtained after dehydration and clarification of the porous base material can be mentioned, but other base materials can also be used.

  Next, one first quartz tube 51 having the same size (outer diameter, length) as the optical fiber preform 10 is prepared, and is approximately the same size (length) as the optical fiber preform 10. Seven second quartz tubes 52 for forming the core portion 11 of the optical fiber preform 10 are prepared. The second quartz tube 52 has a diameter smaller than that of the first quartz tube 51. As shown in FIG. 17, in the quartz tube arranging step, the first quartz tube 51 and the seven second quartz tubes 52 are arranged so that the longitudinal direction thereof is horizontal with the axis C5.

  Specifically, in the quartz tube placement step, the second quartz tube 52 is one second quartz tube so as to correspond to the formation position of each core portion 11 of the optical fiber preform 10 shown in FIG. 52 is arranged at the position of the axis C5, and other six second quartz tubes 52 are arranged so as to surround the axis C5 of the first quartz tube 51, and the inside of the first quartz tube 51 The second hexagonal tube 52 is centered on the second hexagonal tube 52 at the apexes.

  The plurality of second quartz tubes 52 are not limited to be symmetrically disposed so as to surround the axis C5, but may be asymmetrically disposed. Further, the second quartz tube 52 is not limited to the one arranged at the position of the axis C5, and the second quartz tube 52 may be arranged around the axis C5. The number of the second quartz tubes 52 is the same number as the core portion 11 of the optical fiber preform 10, and is not limited to seven, and may be two or more.

  For example, when the refractive index distribution of the multi-core optical fiber finally obtained by drawing the optical fiber preform 10 is a step type, the plurality of second quartz tubes 52 are set so that the distance between the cores of the multi-core optical fiber is 45 μm or more. By arranging in such a manner, the crosstalk between the cores after transmission of the multi-core optical fiber by 100 km can be reduced to -30 dB or less.

  Furthermore, when the refractive index distribution of the core of the multicore optical fiber finally obtained by drawing the optical fiber preform 10 is a trench type, the plurality of second quartz tubes 52 are connected to each other with a distance between the cores of the multicore optical fiber. By arranging it to be 38 μm or more, the crosstalk between the cores after transmission of the multi-core optical fiber by 100 km can be reduced to −30 dB or less.

  In addition, the diameters of the plurality of second quartz tubes 52 are not limited to the same one, and the diameters of the different diameters are set so as to match each core diameter of the multi-core optical fiber finally obtained by drawing the optical fiber preform 10. Two quartz tubes 52 may be used. Further, the plurality of second quartz tubes 52 into which the columnar base material formed with the core part is inserted is formed of a raw material having a refractive index lower than the refractive index of the cladding part 12 of the optical fiber base material 10. May be.

  For example, the plurality of second quartz tubes 52 are finally drawn by drawing the optical fiber preform 10 by using a quartz tube having a refractive index lower than that of pure quartz by adding fluorine to pure quartz. It becomes possible to reduce the bending loss of the obtained multi-core optical fiber.

  Further, in the quartz tube arranging step, the end of the first quartz tube 51 and the end of the second quartz tube 52 are arranged on substantially the same plane. The first quartz tube 51 and the second quartz tube 52 are arranged around the axis C5 while maintaining the relative positions of the first quartz tube 51 and the second quartz tube 52 around the axis C5. Are supported by a predetermined support (not shown) so that they can be rotated synchronously in the cladding portion deposition step.

  Next, as shown in FIG. 18, in the heating appliance arrangement step, as the appliance for heating the first quartz tube 51 and the second quartz tube 52, respectively, the outside of the first quartz tube 51 and the second quartz tube 51. Inside the quartz tube 52, a first cavity 53a and a second cavity 53b for generating microwave plasma are arranged. Here, the first and second cavities 53a and 53b and the microwave plasma generation source 53c constitute a microwave plasma generator 53.

  At this time, the first quartz tube 51 and the second quartz tube 52 may be polished with a plasma flame by microwave plasma. Here, the first cavity 53a arranged outside the first quartz tube 51 may be moved in the direction of the arrow L5. Further, quartz tubes that have been subjected to flame polishing treatment in advance may be used as the first quartz tube 51 and the second quartz tube 52.

  Subsequently, as shown in FIG. 19, in the cladding portion deposition step, an oxyhydrogen burner (cladding portion raw material supply means) 54 is disposed in the vicinity of the axial end portion of the first quartz tube 51. Subsequently, the first quartz tube 51 and the seven second quartz tubes 52, and the first cavity 53a and the second cavity 53b around the axis C5 about the axis C5 of the first quartz tube 51. The glass fine particles 54a to be the cladding portions 55 of the optical fiber preform 10 are deposited inside the first quartz tube 51 and outside the seven second quartz tubes 52 by the oxyhydrogen burner 54. Let As described above, since the first quartz tube 51 and the second quartz tube 52 are heated by the first cavity 53a and the second cavity 53b, the glass of the cladding portion 55 of the optical fiber preform 10 is thermally oxidized. A layer is formed.

  Here, not only the first cavity 53a but also the second cavity 53b is used to heat the first quartz tube 51 and the second quartz tube 52, so that the glass particles 54a are brought into the inner surface of the first quartz tube. And it becomes possible to deposit uniformly and at high speed on the outer surface of the second quartz tube. In addition, in order to prevent the glass fine particles 54a serving as the clad portion 55 of the optical fiber preform 10 from being deposited inside the second quartz tube 52, the end of the second quartz tube 52 where the second cavity 53b is disposed. It is also possible to seal the portion when the second cavity 53b is inserted.

  In the detaching step, when a predetermined amount of glass particles 54a is deposited in the first quartz tube 51, as shown in FIG. 20, outside the first quartz tube 51 and inside the second quartz tube 52, respectively. The arranged first cavity 53a and second cavity 53b are removed.

  Next, as shown in FIG. 21, a columnar base material in which one core part 56 of the optical fiber preform 10 produced in advance in the core part production step or one core part 56 and the periphery of the core part are formed. The seven columnar base materials in which a part of the clad portion 55 is formed are respectively arranged on the inner side 52a of the clad portion 55 inside the first quartz tube 51 (that is, inside the second quartz tube 52). By inserting, an optical fiber preform 10 (see, for example, FIG. 1) for manufacturing an optical fiber including a plurality of core portions in which the cladding portion 55 and the core portion 56 are formed is obtained.

  Here, an oxyhydrogen burner for depositing glass fine particles to be the clad portion 55 or the core portion 56 is disposed, and the glass fine particles to be the clad portion 55 or the core portion 56 in the gap between the clad portion 55 and the core portion 56. It is also possible to prevent the core position shift when the optical fiber preform 10 is drawn.

  Further, when the core portion 56 is formed of a porous base material or glass fine particles, an optical fiber preform for manufacturing an optical fiber including a plurality of core portions 56 by performing dehydration and transparency treatment. The material 10 can be obtained. By drawing the optical fiber preform 10, an optical fiber including a plurality of core portions 56 in the cross section can be obtained.

  As described above, according to the method for manufacturing a multi-core optical fiber preform according to the present embodiment, a plurality of core parts are included as in the method for manufacturing a multi-core optical fiber preform according to the first to third embodiments. It is possible to easily obtain the optical fiber preform 10 capable of manufacturing a long optical fiber with a low loss.

  In the above embodiment, in the cladding portion deposition step, glass particles are deposited while the first quartz tube 51 and the second quartz tube 52, and the first cavity 53a and the second cavity 53b are rotated synchronously. However, the number and arrangement of the burners, the rotation form, etc. are not limited as long as the desired glass particulate deposition state is obtained. For example, in the above embodiment, each of the first quartz tube 51 and the second quartz tube 52, and each of the first cavity 53a and the second cavity 53b are rotated synchronously, but the oxyhydrogen burner 54 is axially centered. You may make it rotate centering on C5.

  Furthermore, although only one oxyhydrogen burner 54 is used in the above embodiment, a plurality of oxyhydrogen burners 54 may be provided. In particular, if a large number of oxyhydrogen burners 54 are arranged around the axis C5, each quartz tube and each cavity can be made non-rotating.

  In addition, when the second cavity 53b is arranged in the second quartz tube 52, the inside of the second quartz tube 52 is sealed with a lid or the like so that the glass fine particles 54a are not deposited inside the second quartz tube 52. It is also possible to do. In this case, by removing the sealing lid in the removal step of removing the heating device, it is possible to insert the columnar base material in which the core portion 56 is formed inside the second quartz tube 52 in the subsequent step. Is possible

  The method for manufacturing a multi-core optical fiber preform according to the present invention can provide an optical fiber preform 10 capable of accurately producing a long optical fiber including a plurality of core portions. As a result, it can be used beneficially in the information communication industry.

10: Optical fiber preforms 11, 28, 37, 47, 56: Core parts 12, 26, 36, 45, 55: Clad parts 21, 31, 41, 51: First quartz tubes 22, 32, 42, 52 : Second quartz tube 23, 33, 44: first oxyhydrogen burner 24: heating wire 25, 35, 46: second oxyhydrogen burner 25a, 35a, 44a: first glass fine particle 27: third Oxyhydrogen burners 27a, 46a: second glass fine particles 29: first glass fine particles 30: second glass fine particles 37: base material 38: third glass fine particles 43a, 53a: first cavity 43b: second Cavity 43c, 53c: Plasma generator 54: Oxyhydrogen burner 54a: Glass fine particles

Claims (8)

A plurality of second quartz tubes having a diameter smaller than the inner peripheral diameter of the first quartz tube are arranged inside the first quartz tube serving as the outer shape of the optical fiber preform, and the axial direction of the first quartz tube Quartz tube placement process to be placed along,
A heater arrangement step of arranging heaters on the outside of the first quartz tube and the inside of the second quartz tube,
A source gas is introduced into the outside of the second quartz tube and the inside of the first quartz tube, and the first quartz tube and the second quartz tube are heated with a heating instrument, thereby the first quartz tube. A cladding portion deposition step of depositing the first glass fine particles diffused inside the quartz tube and forming a cladding portion of the optical fiber preform;
A removal step of removing the heating device disposed inside the second quartz tube;
A core portion deposition step of forming a core portion of the optical fiber preform by flowing a raw material gas into the preheated second quartz tube and depositing second glass particles;
The manufacturing method of the multi-core optical fiber preform characterized by performing these in order. The cladding part deposition step and the core part deposition step are:
Maintaining the positional relationship of the relative positions of the first quartz tube, the second quartz tube, and the heating device, and using the central axis of the first quartz tube as a rotation axis; The method for manufacturing a multi-core optical fiber preform according to claim 1, wherein the second quartz tube and the heating device are rotated synchronously. The quartz tube placement step includes:
3. The method of manufacturing a multi-core optical fiber preform according to claim 1, wherein a refractive index of the second quartz tube is lower than a refractive index of the cladding portion. The heating appliance arrangement step includes
The method for manufacturing a multi-core optical fiber preform according to any one of claims 1 to 3, wherein an oxyhydrogen burner, a heating wire, or a cavity that generates microwaves is used as the heating device. A columnar base material in which one core part of an optical fiber base material is formed or a columnar base material in which one core part and a part of a cladding part around the core part are formed in advance for the number of cores. A core manufacturing process for manufacturing;
A plurality of second quartz tubes having a diameter smaller than the inner peripheral diameter of the first quartz tube are disposed inside the first quartz tube serving as the outer shape of the optical fiber preform. Quartz tube placement process for placing along the direction;
A heater arrangement step of arranging heaters on the outside of the first quartz tube and the inside of the second quartz tube,
A source gas is introduced into the outside of the second quartz tube and the inside of the first quartz tube, and the first quartz tube and the second quartz tube are heated with a heating instrument, thereby the first quartz tube. A cladding part deposition step of depositing glass fine particles diffused inside the quartz tube and forming a cladding part of the optical fiber preform;
A removal step of removing the heating device disposed inside the second quartz tube;
A multi-core light characterized by sequentially performing a core portion insertion step of inserting a columnar base material, on which the core portion is formed in advance, into a second quartz tube in which the glass fine particles are deposited on the outer surface. Manufacturing method of fiber preform. The cladding part deposition step includes
Maintaining the positional relationship of the relative positions of the first quartz tube, the second quartz tube, and the heating device, and using the central axis of the first quartz tube as a rotation axis; 6. The method of manufacturing a multi-core optical fiber preform according to claim 5, wherein the second quartz tube and the heating device are rotated synchronously. The quartz tube placement step includes:
7. The multi-core light according to claim 5, wherein a refractive index of the second quartz tube into which the columnar base material on which the core portion is formed is inserted is lower than a refractive index of the cladding portion. Manufacturing method of fiber preform. The heating appliance arrangement step includes
The method for producing a multi-core optical fiber preform according to any one of claims 5 to 7, wherein an oxyhydrogen burner, a heating wire, or a cavity that generates microwaves is used as the heating device.

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