JPS62158130A - Method and device for producing single-mode optical fiber base material - Google Patents

Abstract

PURPOSE:To stably form cladding soot having optional thickness on the outer periphery of a glass core rod by preheating the core glass rod with a flame burner before the clad material is supplied to the core glass rod from a soot forming burner. CONSTITUTION:The core glass rod 1 and the boundary part 6 between the core glass rod 1 and the soot 5 are preheated by the flame burner 4. Then the cladded core glass rod 1 is rotated and elevated by a rod moving means 2, a cladding material and oxyhydrogen are supplied to the periphery of the rod 1 from the soot forming burner 3, the soot 5 for forming a clad is formed, and the single-mode optical fiber base material is formed.

Description

Detailed Description of the Invention [Field of Industrial Application] The present invention relates to a method and apparatus for manufacturing a single-mode optical fiber preform, and particularly relates to a single-mode optical fiber manufacturing method and an apparatus for manufacturing a single-mode optical fiber preform, and particularly relates to a method for manufacturing a single-mode optical fiber preform and an apparatus therefor. The present invention relates to a method for manufacturing a fiber base material and an apparatus therefor.

[Prior art] Single mode optical filter 1 using VAD method (vapor phase attachment method)
The method for manufacturing the fiber base material involves supplying a cladding raw material along with an oxyhydrogen flame from a cladding-forming burner to the outer periphery of a pre-formed core glass rod to form soot to become the cladding.
The porous base material is sintered and vitrified in an electric furnace to form fiber f.
It is made of fl material.

The reason for forming a clad around the outer periphery of the core glass rod is that the light propagating through the core of the single mode optical fiber seeps out to the clad and propagates, so the clad has a radius of about 6 times or more than the core radius. Requires thickness.

Conventionally, in order to obtain this cladding thickness, a large number of cladding burners are arranged around the outer periphery of the core glass rod.

[Problems to be Solved by the Invention] However, it takes 2 to 3 hours for the outer diameter of the formed soot base material to become a stable and uniform area, and some of the dents are large and there is a problem in sweeping.

In addition, because the diameter of the soot base material is large, it is difficult to make the temperature distribution uniform in the circumferential direction of the outermost clad soot, which results in uneven processing density, which tends to cause cracks and bubbles during sintering. There is.

[Object of the Invention] The object of the present invention is to provide a method for manufacturing a single-mode optical fiber preform, which eliminates the drawbacks of the prior art described above and allows a cladding soot of any thickness to be stably formed on the outer periphery of a core glass rod. and to provide its equipment.

Summary of the Invention] The present invention provides a method for manufacturing a single mode optical fiber preform in which a soot serving as a cladding is formed by supplying a cladding raw material and oxyhydrogen from a soot-forming burner to the periphery of a core glass rod. The method includes preheating the core glass rod with a flame burner before supplying the cladding raw material to the glass rod from the soot-forming burner, and also includes a rod moving means that rotates and raises the core glass rod, and a rod moving means that rotates and raises the core glass rod. A soot-forming burner that sprays oxyhydrogen and cladding material onto a core glass rod, and a flame burner that is provided below the soot-forming burner and preheats the boundary between the core glass rod and the soot generated on the rod. When forming cladding soot on a core glass rod, it is possible to form a cladding of any thickness by preheating the boundary between the core glass rod and cladding soot with a flame burner, and it is also capable of sintering. This prevents cracks and bubbles from forming.

[Example] Hereinafter, a preferred example of the method and apparatus for manufacturing a single mode optical fiber preform according to the present invention will be described with reference to the accompanying drawings.

In FIG. 1, reference numeral 1 denotes a core glass rod with a cladding, which is rotated and raised by rod moving means 2. As shown in FIG. The core glass rod 1 is equipped with a cladding and has, for example, a cladding thickness/core radius ratio δ=2.5 and an outer diameter of 15 mm.

A soot-forming burner 3 for supplying cladding raw material and oxyhydrogen to the rotating and rising core glass rod 1 is arranged on the outer periphery of the rod 1 so as to face obliquely upward. This soot-forming burner 2 consists of a quadruple-tube quartz burner, in which StCβ4 (cladding raw material) is fed at a rate of 2 g/min from the first layer in the center, its carrier glass Ar is fed at a rate of 0.25 f/min, and H2 is fed from the second layer. 42/min, Ar from the third layer is 0.
1! /min, and 5β/min of 02 is ejected diagonally upward toward the core rod 1 from the fourth layer.

A flame burner 4 consisting of a double tube burner is provided below the soot-forming burner 3, and 02 is set at 2ffi/2 from the center.
H2 is ejected diagonally upward from the 1in1 outer periphery toward the core glass rod 1 at 4.5 R/min.

In the above, the core glass rod 1 is formed by a flame hydrolysis reaction between the cladding raw material and oxyhydrogen supplied from the soot forming burner 3 from the outer periphery of the upper end thereof.
A porous soot 5 is formed around the outer periphery of the soot. In this case, the flame burner 4 can preheat the core glass rod 1 and the boundary part 6 between the core glass rod 1 and the soot 5 to prevent a temperature drop in that part, and uniformize the bulk density of the soot 5 in the radial direction. It is possible to have a distribution that gradually decreases toward the outer periphery.

The soot 5 thus formed had an outer diameter of 60 mm, and was sintered in an electric furnace in a mixed gas atmosphere of He and Cj22 to obtain a glass rod with a diameter of 35 nm+m.

FIG. 2 shows a cross section of this glass rod. In the figure, 1 is a core glass rod consisting of a core portion 1a and a cladding portion 1b, and 7 is a core glass rod obtained by sintering the soot 5 shown in FIG. It was rad and δ87 was obtained.

This glass rod base material was stretched, placed in a quartz tube, and heated and stretched to obtain a single mode optical fiber. The fiber transmission loss obtained is 0.42 dB/k at 1.3 μm
It was m.

[Effects of the Invention] As is clear from the above detailed description, the present invention provides the following excellent effects.

(1) When forming soot to serve as cladding around the outer periphery of the core glass rod, by preheating the boundary between the core glass rod and soot, a cladding of any thickness can be formed around the outer periphery of the core glass rod. Low loss single mode optical fiber can be manufactured.

(2) Complete synthesis of core glass rod and formed rad can produce optical fiber art materials, with no bubbles and low loss.
Furthermore, high-strength optical fibers can be manufactured.

(3) Cocoa rods for Gr fibers can also be used as core glass rods, resulting in good boundary surface uniformity and low loss.

[Brief explanation of drawings]

FIG. 1 is a diagram showing an embodiment of the method and apparatus for manufacturing a single mode optical fiber preform of the present invention, and FIG. 2 is a cross-sectional view of the optical fiber material obtained by the present invention. In the figure, 1 is a core glass rod, 2 is a rod moving means, and 3 is a core glass rod.
4 is a flame burner, 5 is a soot, and 6 is a boundary portion.

Claims (2)

[Claims] (1) In a method for manufacturing a single-mode optical fiber preform in which a soot serving as a cladding is formed by supplying a cladding raw material and oxyhydrogen from a soot-forming burner to the periphery of a core glass rod, the soot is formed on the core glass rod. A method for producing a single mode optical fiber preform, characterized in that the core glass rod is preheated with a flame burner before the cladding material is supplied from a burner. (2) a rod moving means that rotates and raises the core glass rod; a soot-forming burner that sprays oxyhydrogen and cladding raw material onto the rotating and rising core glass rod; and a soot-forming burner provided below the soot-forming burner; 1. An apparatus for manufacturing a single-mode optical fiber preform, comprising a flame burner that preheats a boundary between a core glass rod and soot generated on the rod.