JPH04285019A - Produciton of preform rod - Google Patents

Abstract

PURPOSE:To obtain a preform rod without making the core rod eccentric by guiding a detachbly fixed eccentricity-preventive moving body along the axis of rotation of the core rod by a guide cylinder when the core rod is moved. CONSTITUTION:A rotary holder 11 is rotated to turn a core rod 10 with the center axis as the axis of rotation. Meanwhile, soot is blown against the rod 10 from burners 14 and 15 and deposited to form a clad layer 20 on the rod 10, and a lift 12 is moved upward in synchronization with the growth rate of the clad layer 20. The lower end of the rod 10 is held through an eccentricity- preventive moving body 17 and a guide cylinder 16 so that the center axis of the rod 10 is positioned on the axis of rotation of the holder 11. Accordingly, the rod 10 is not bent even if soot is blown against it, and the moving body 17 is moved concentrically upward in the guide cylinder 16 along with the rod 10 while the rod 10 is lifted up by the lift 12.

Description

[Detailed description of the invention]

0001

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for manufacturing a preform rod, and more particularly to a method for manufacturing a preform rod by preventing eccentricity of a core rod.

0002

[Prior art] As a method of manufacturing a preform rod,
A so-called external attachment method is known in which a soot containing a low refractive index dopant is sprayed and deposited on the circumferential surface of a core rod to form a cladding layer. That is, in this external attachment method, the upper end of the core rod is fixed to a rotating holder, and the core rod is rotated by rotating the rotating holder with the central axis of the core rod as the rotation axis. At the same time, the rotating holder is pulled up along the rotating shaft by the pulling means, thereby rotating the core rod and moving it upward. On the other hand, soot, which is obtained by hydrolyzing frit gas in the flame of a burner, is sprayed and deposited on the rotating and moving core rod. Therefore, according to this external attachment method, a preform rod having a cladding layer on the circumferential surface of the core rod can be obtained.

0003

However, in the past, only the upper end of the core rod was fixed, so that if the core rod was heated by the flame of the burner during soot spraying, the core rod would be bent. For this reason, the core rod rotates with the center axis of the core rod being misaligned with respect to the rotation axis, so that the cladding layer 1
A preform rod is manufactured in which the core rod 2 is eccentric with respect to the preform rod. Therefore, when such a preform rod is spun, a defective optical fiber with a significantly eccentric core will be obtained. The present invention has been made to solve these problems, and an object of the present invention is to provide a method that can manufacture a preform rod without decentering the core rod.

0004

[Means for Solving the Problems] The present invention is made by hydrolyzing frit gas in a flame on a core rod which is held at one end and rotates about a central axis and gradually moves along the rotation axis. In a method for manufacturing a preform rod in which soot is sprayed and deposited, an eccentricity preventing moving body is removably attached to the other end of the core rod, and the eccentricity preventing moving body is guided along a rotation axis by a guide means when the core rod is moved. It is characterized by

[0005]

[Operation] When the core rod is moved, the eccentricity preventing moving body is guided by the guide means along the rotation axis of the core rod. Therefore, the core rod can be moved along its central axis and eccentricity of the core rod can be prevented.

[0006]

Embodiments Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings. FIG. 1 is a sectional view for explaining the method for manufacturing a preform rod according to the present invention. In this FIG. 1, 10 indicates a core rod. This core rod 10 is made of a quartz rod and has a cylindrical shape. The upper end of the core rod 10 is fixed to a rotating holder (chuck) 11. The rotating holder 11 is rotated about the central axis of the core rod 10 and is attached to a pulling device 12. The pulling device 12 is moved up and down by a pulling motor (not shown). The upper part of the core rod 10 is disposed within a reaction vessel 13, and burners 14 and 15 are provided within the reaction vessel 13. SiCl4 (silicon tetrachloride) gas, which is a frit gas, is fed to the center of these burners 14 and 15, and H2 gas, Ar gas, and O2 gas are fed to the concentric blow-off ports. . Therefore, from these burners 14 and 15, Si synthesized by a hydrolysis reaction is
O2 soot (including low index dopants) is blown out.

A guide tube 16 is attached to the lower surface of the reaction vessel 13. This guide tube 16 is arranged coaxially with the central axis of the core rod 10 and attached to the reaction vessel 13, and the lower part of the core rod 10 extends coaxially. Guide tube 16
An eccentricity prevention moving body 17 is housed inside. This eccentricity prevention moving body 17 is formed in a cylindrical shape, has a structure that moves up and down concentrically within the guide tube 16, and is removably attached to the lower end of the core rod 10. That is, the eccentricity prevention moving body 17 has a conical recess 17a into which the conical part of the lower end of the core rod 10 is inserted, and the tip surface of the plurality of threaded members 18 screwed in the radial direction is connected to the lower end periphery of the core rod 10. It is removably attached to the lower end of the core rod 10 by pressing it against a surface.

Next, the manufacturing method according to the present invention will be explained. The rotation holder 11 is rotated, and the core rod 10 is rotated about the central axis as the rotation axis at a speed of several tens of revolutions per minute. on the other hand,
This rotating core rod 10 from burners 14 and 15
Soot is sprayed and deposited on the core rod 10, thereby forming a cladding layer 20 on the circumferential surface of the core rod 10. Then, the pulling device 12 is moved upward in synchronization with the growth rate of the cladding layer 20.

By the way, the lower end of the core rod 10 is held via an eccentricity prevention moving body 17 and a guide tube 16 such that the center axis of the rod 10 is positioned on the rotation axis of the rotation holder 11. Therefore, even if soot is sprayed, the core rod 10 will not be bent. When the core rod 10 is being pulled up by the pulling device 12, the eccentricity prevention moving body 17 moves upward in the guide tube 16 concentrically with the core rod 10. Therefore, the core rod 10
does not bend even when soot is sprayed onto it, and moves upward while rotating with its central axis aligned with the rotation axis. As a result, as shown in FIG. 2, a preform rod without eccentricity is obtained in which the core rod 10 is located concentrically with respect to the cladding layer 20.

When the core rod 10 is pulled up, the eccentricity preventing moving body 17 moves upward in the guide tube 16, and the upper surface of the moving body 17 hits the stopper 13a formed at the edge of the rod insertion hole on the lower surface of the reaction vessel 13. When they come into contact with each other, the eccentricity preventing moving body 17 comes off the lower end of the core rod 10 and falls below the guide tube 16. Therefore, soot is sprayed only onto the core rod 10, and soot can be prevented from being sprayed onto the eccentricity prevention moving body 17. Incidentally, the eccentricity prevention moving body 17 may be removably attached to the lower end of the core rod 10 via an elastic member, and in short, it may be attached removably.

[0011]

[Effects of the Invention] As explained above, according to the present invention,
The eccentricity preventing moving body is removably attached to the other end of the core rod while holding one end, and when the core rod is moved, the eccentricity preventing moving body is guided by the guide means along the axis of rotation of the core rod, so that the core rod can be held at its center. Soot can be sprayed and deposited while rotating with the shaft always aligned with the rotation axis. Therefore, a preform rod can be manufactured without making the core rod eccentric.

[Brief explanation of the drawing]

FIG. 1 is a cross-sectional view for explaining the manufacturing method according to the present invention.

FIG. 2 is a sectional view of a preform rod manufactured by the manufacturing method according to the present invention.

FIG. 3 is a sectional view of a preform rod manufactured by a conventional manufacturing method.

[Explanation of symbols]

10 Core rod 11 Rotating holder 12 Lifting device 14 Burner 15 Burner 16 Guide tube 17 Eccentricity prevention moving body

Claims (1)

[Claims] 1. A process in which soot, which is obtained by hydrolyzing frit gas in a flame, is sprayed onto a core rod that is held at one end and gradually moves along the rotation axis while rotating about a central axis to deposit the soot. In the method for manufacturing a remodeling rod, an eccentricity preventing moving body is removably attached to the other end of the core rod, and when the core rod is moved, the eccentricity preventing moving body is guided along the rotation axis by a guide means. Method of manufacturing preform rods.