JPS623032A - Production of optical fiber preform - Google Patents

Abstract

PURPOSE:To produce an optical fiber having high purity, quality and dimensional accuracy, by depositing glass soot to form a high-purity and uniform porous glass rod or pipe, incompletely sintering the rod to get specific mechanical strength and grinding the sintered rod. CONSTITUTION:A gaseous glass raw material, a fuel gas, a combustion stabilizing gas, a seal gas, etc., are supplied to a burner 11 having multi-tube structure, and the burner 11 is kept to the burning state. The produced glass soot is blasted toward and deposited on the lower end of the target 12 which is pulled up under rotation. The produced porous glass rod is sintered incompletely, and the outer and inner surfaces of the incompletely sintered glass rod are ground to desired dimensions. The finished glass rod is vitrified to obtain a transparent glass rod.

Description

[Detailed description of the invention] r Industrial application field” The present invention relates to a method of manufacturing an optical fiber preform.

rPrior art 1 One of the methods for manufacturing optical fiber preforms is to put glass powder raw materials into predetermined molds and press mold them, thereby forming a porous glass rod for the core and a porous glass pipe for the cladding. After manufacturing, there is a method of inserting the porous glass rod into a porous glass pipe and sintering them.

``Problem to be Solved by the Invention J When press-molding powdered raw materials in the above method, the surrounding fields are easily compressed during the forming process.

The central region is difficult to compress, so it is difficult to obtain a porous molded product in which each part is compressed uniformly. sintering begins, and the sintered area becomes non-permeable.

Air bubbles remain inside the molded product, making it impossible to achieve complete transparency.

In addition, during the process of handling the raw material powder, there is a risk that surrounding impurities may be mixed into the raw material powder, making it difficult to obtain a high-purity, high-quality optical fiber preform.

In view of the above-mentioned problems, the present invention aims to provide a method for obtaining an optical fiber preform with high purity, high quality, high characteristics, and high dimensional accuracy.

Means for Solving Problems j The present invention provides a method for manufacturing an optical fiber preform by integrating a glass rod for a core and a glass pipe for a cladding, in which fine glass particles are deposited in a predetermined shape. A process of making a porous glass rod for the core and a porous glass pipe for the cladding, a process of semi-sintering these porous glass rods and porous glass pipes, and a process of semi-sintering the resulting semi-sintered glass rod and semi-sintering. A process of grinding the outer and inner circumferential surfaces of the glass pipe to the desired dimensions,
The method is characterized by a step of converting the semi-sintered glass rod and semi-sintered glass pipe into transparent glass after grinding.

1 Effect, I In the case of the method of the present invention 2 A porous glass rod for the core is produced by, for example, the VAD method, and 1 a porous glass pipe for the cladding is produced by, for example, the OVD method.

Porous glass rods and porous glass pipes produced through these methods have high purity because they are homogeneously deposited soot-like glass particles produced by flame hydrolysis, etc. The conventional method (press molding method)
There is no such non-uniformity.

Next, the porous glass rod and porous glass pipe are semi-sintered, but in this semi-sintering process, these rods and pipes are finished to a hardness that will not be damaged during the subsequent grinding process.

Thereafter, the outer and inner peripheral surfaces of the semi-sintered glass rod and semi-sintered glass pipe obtained above are ground by mechanical grinding means.

In this grinding process, the semi-sintered glass rod and semi-sintered glass pipe can be finished to the desired dimensions without being damaged, and therefore the semi-sintered glass rod and semi-sintered glass pipe can be obtained with high dimensional accuracy in terms of inner and outer diameters. Even if impurities are attached to the surfaces of these glass rods and glass pipes, the impurities are removed by the grinding.

After the above-mentioned grinding, the semi-sintered glass rod and semi-sintered glass pipe are completely sintered to become transparent glass and integrated to obtain an optical fiber base material.

At this time, the semi-sintered glass rod for the core and the semi-sintered glass pipe for the cladding are made into transparent glass separately, or the semi-sintered glass rod for the core is inserted into the semi-sintered glass pipe for the cladding. vitrified into transparent glass.

In the former case, the glass rod for the core after being made into transparent vitrification is placed inside the glass pipe for the cladding and integrated by heat fusion, but in the case of the latter, the glass rod and glass pipe are removed at the same time as the glass rod is made into transparent vitrification. to integrate.

As a means other than the above, a semi-sintered glass rod for the core is made into transparent glass, and the transparent glass rod is inserted into a semi-sintered glass pipe for the cladding, and the semi-sintered glass pipe is made into transparent glass.

In this way, an optical fiber preform with high purity, high quality, high dimensional accuracy, and high characteristics can be obtained.

rExample 1 Examples of the method of the present invention will be described below with reference to the drawings.

First, a porous glass rod la and a porous glass pipe 2a for cladding are manufactured by the VAD method and the OVD method shown in FIGS. 1(a) and 1(b), respectively.

When carrying out the VAD method shown in FIG. 1(A), as is known, the burner 11 with a multi-tube structure is filled with a gaseous glass raw material (which may also contain a gaseous dope material), a combustion gas, an auxiliary combustion gas,
The burner 11 is supplied with seal gas (inert gas), etc.
A porous glass rod 1a is produced by injecting and depositing soot-like glass particles generated by holding the target in a combustion state on the lower end of the target 12 which moves up in a rotating state.

When carrying out the OVD method shown in FIG. 1(b), as is known, a burner 13 with a multi-tube structure is filled with a vapor phase glass raw material (sometimes containing a vapor phase dope material), a combustion gas, an auxiliary combustion gas, and a seal. Soot-like glass particles are generated by supplying gas (inert gas), etc., and maintaining the burner 13 in a combustion state. In this case, the burner 13 and the mandrel 14 are The porous glass pipe 2a is produced by relatively moving the mandrel in the axial direction and injecting and depositing soot-like glass particles on the outer periphery of the rotating mandrel.

The thus obtained porous glass rod 1a and porous glass pipe 2a are semi-sintered by heat treatment in a heating furnace (electric furnace) 15 as shown in FIGS. 2(a) and 2(b), and each has a predetermined hardness. The semi-sintered material becomes the lath rod 1b and the semi-sintered glass pipe 2b.

Note that the semi-sintered glass rod 1h and the semi-sintered glass pipe 2b have a hardness that allows machining.

Next, as shown in FIGS. 3(a) and 3(b), the outer circumferential surface of the semi-sintered glass rod 1b and the inner and outer circumferential surfaces of the semi-sintered glass pipe 2b are ground with a distorted rotary grindstone 16 to obtain the desired outer diameter and inner diameter. Finish to the dimensions.

When grinding the inner circumferential surface of the semi-sintered glass pipe 2b, the mantle 1/14 is removed from its axis, and the inner circumferential surface of the pipe is ground with, for example, a rod-shaped rotating grindstone.

Thereafter, the semi-sintered glass rod 1b and the semi-sintered glass pipe 2b are inserted into the heating furnace 15 and completely sintered as shown in FIGS. Let it be a glass pipe 2c.

In the following, the transparent glass rod 1c is inserted into the transparent glass pipe 2c, and the two are fused and integrated, thereby obtaining the optical fiber preform 3 shown in FIG. 5, and the preform 3 is spun by heating and drawing. Obtain spinning optical fiber.

In addition, when obtaining the optical fiber preform 3, the semi-sintered glass rod 1b may be made into transparent glass, and the transparent glass rod 1c obtained thereby may be placed in the semi-sintered glass pipe 2b to make the pipe 2b into transparent glass. Alternatively, as shown in FIG. 6, a semi-sintered glass rod 1b may be placed inside a semi-sintered glass pipe 2b and both may be made into transparent glass at the same time, and when such a method is used, the process of making the glass transparent and integrating the rod and pipe is possible. This can be done at the same time, and deformation of the pipe during transparent vitrification can be prevented by the internal shield.

Effects of the Invention 1 As explained above, when using the method of the present invention, highly pure and uniform porous glass rods and porous glass pipes are made by depositing glass particles, and these porous glass rods and porous glass vibrators are After semi-sintering to give a predetermined mechanical strength, the outer peripheral surface, inner peripheral surface, etc. of the semi-sintered glass rod and semi-sintered glass pipe are ground, resulting in semi-sintered glass with high dimensional accuracy and no impurity adhesion. A rod and a semi-sintered glass pipe are obtained. Therefore, by completely sintering the above-mentioned grinding semi-sintered glass rod and semi-sintered glass pipe to make transparent glass and integrate them, purity 1 quality, dimensional accuracy, characteristics, etc. A satisfactory optical fiber rectangle can be obtained, which is cost-effective especially for manufacturing single-mode optical fiber preforms that require a high degree of dimensional accuracy.

[Brief explanation of the drawing]

Figures 1 (a) and (b) to 4 (a) and (b) are schematic explanatory diagrams showing the main steps in an embodiment of the method of the present invention, and Figure 5 is a schematic explanatory diagram showing the steps of the main parts in an embodiment of the method of the present invention. FIG. 6 is a cross-sectional view of the optical fiber preform, and is a schematic explanatory view showing another embodiment of the transparent IJ1 vitrification step in the method of the present invention. 1a...Porous glass particles 1b・#-e Semi-sintered glass rod Ice reference jar ◆Transparent [Aiming glass rod 2δ... Porous glass vibe 2b◆・Fistφ semi-sintered glass pipe 2C811#11 Transparent glass Pipe 3 --- Optical fiber base material +1 -- Participating burner 12 -- φ Target 13 -- @ Participating burner +4 -- Mandrel 15 -- Heating furnace 16 -- Participating rotary grinding wheel agent Patent Attorney Yoshio Saito Figure 1 Figure 3

Claims (3)

[Claims] (1) In a method of manufacturing an optical fiber base material by integrating a glass rod for the core and a glass pipe for the cladding, glass fine particles are deposited in a predetermined shape to form a porous glass rod for the core and a porous glass rod for the cladding. A process of making a porous glass pipe, a process of semi-sintering these porous glass rods and porous glass pipes, and grinding the outer and inner circumferential surfaces of the resulting semi-sintered glass rods and semi-sintered glass pipes. 1. A method for producing an optical fiber preform, comprising the steps of: finishing the preform into desired dimensions; and converting the semi-sintered glass rod and semi-sintered glass pipe into transparent glass after grinding. (2) The method for manufacturing an optical fiber preform according to claim 1, wherein the semi-sintered glass rod for the core and the semi-sintered glass pipe for the cladding are separately made into transparent glass. (3) The method for manufacturing an optical fiber preform according to claim 1, wherein a semi-sintered glass rod for the core is inserted into a semi-sintered glass pipe for the cladding to make them transparent glass.