JPH03141133A - Production of porous glass matrix for optical fiber - Google Patents

Abstract

PURPOSE:To obtain the title glass matrix through so called exterior process by moving a burner in a specific way as the outer diameter of the deposition layer increases to prevent glass fine particles from scattering on the surface of the layer and to carry out highly efficient deposition. CONSTITUTION:Both the ends of a target member 1 are held with e. g. a lathe and revolved, and a burner 3 is moved in the axial direction of the member 1 while spraying glass fine particles produced in a flame 4, and each glass fine particle layer 2 is formed around the member 1 per movement operation of the burner 3. In this case, the burner 3 is put to parallel displacement in the direction rectangular to both its axis and that of the member 1 so that the angle theta made by the burner axis with the tangential line on the surface of the deposition layer 2 at the intersection formed by the surface and the burner axis becomes constant within the range between 40 and 80 degrees. With this method, the outer diameter of the deposition layer 2 increases, and the scattering of the glass fine particles on the deposition surface can be reduced even if the flow of combustion gas and/or combustion-aiding gas increases.

Description

[Detailed description of the invention] [Industrial application field]

The present invention relates to a method for manufacturing a porous glass preform for optical fibers, which is generally referred to as an external method.

[Conventional technology]

In the manufacturing method of a porous glass base material for optical fibers, which is generally referred to as the external method, as shown in Fig. 4, both ends of the target member 1 are held and rotated with a glass lathe, etc. The burner 3 is traversed in the axial direction of the target member 1, and the glass particles generated in the flame 4 are deposited around the target member 1 to form a porous glass particles deposited layer 2. This target member 1 may be removed later, or may be a quartz-based glass rod that will become the core of an optical fiber later. Burner 3 uses frit gas (SiC
04, etc.) is fed together with combustion gas (H2) and combustion assisting gas (O2), and glass fine particles such as 5i02 are generated by a hydrolysis reaction or the like occurring in the flame 4. The burner 3 is traversed multiple times in the axial direction of the target member 1, and a glass fine particle deposit layer 2 is formed one layer at a time for each traverse. When the glass fine particle deposited layer 2 reaches a predetermined thickness, the next step 1 to rubber is not performed and the deposition is completed. Since this glass fine particle deposition layer 2 is a porous body as described above, it is later sintered by heat treatment in a high-temperature furnace to become transparent vitrified, and the optical fiber preform obtained in this way is subjected to a drawing device to be made into a thin wire. An optical fiber is produced by this. Conventionally, the burner 3 is
The extension line of the central axis is directed in a direction that intersects with the central axis of the target member 1, and traverse is performed from the start to the end of deposition while maintaining this direction. By the way, if multiple layers of glass fine particle deposited layer 2 are deposited by performing rubberizing several times, the deposition progresses and the deposited layer 2
As the outer diameter of the deposited layer 2 increases, the surface temperature of the deposited layer 2 decreases. The surface temperature of this deposited layer 2 is related to the bulk density of the glass fine particle deposited layer 2, and therefore, in order to obtain the glass fine particle deposited layer 2 with a uniform bulk density, the deposited layer 2 must be
The deposited layer 2 tends to decrease as it becomes thicker.
It is necessary to take measures to raise the surface temperature of the material and maintain it at a constant temperature. Therefore, conventionally, as the outer diameter of the deposited layer 2 increases, the amount of combustion gas and auxiliary combustion gas is increased to keep the surface temperature of the deposited layer 2 constant.

[Problem to be solved by the invention]

However, when depositing glass particles using the same burner for glass particle synthesis, increasing the flow rates of combustion gas and auxiliary combustion gas causes the deposition efficiency of glass particles to gradually deteriorate and the amount of deposition to be saturated. There's a problem. That is, when the flow rates of the combustion gas and the auxiliary combustion gas are increased, the flow rate of the gas flowing out from the burner increases, and the speed of the glass particles increases. However, as mentioned above, in the conventional method, the direction of the burner is set so that the glass particles collide with the surface of the deposited layer at right angles, so if the speed of the glass particles increases, they will be scattered when they collide with the surface of the deposited layer. . Therefore, when we examine the relationship between the number of traverses and the amount of glass particles deposited, we find that
As shown by the dotted line in FIG. 3, it can be seen that as the number of traverses increases, the amount of deposition becomes saturated. This invention is an improved optical fiber that prevents glass particles flowing out of a burner from scattering on the surface of a glass particle accumulation layer and allows efficient deposition even when the outer diameter of the glass particle accumulation layer increases. An object of the present invention is to provide a method for manufacturing a porous glass base material for use in industrial applications.

[Means for Solving the Problems 1] In order to achieve the above object, according to the present invention, a glass raw material is supplied into the flame of a burner for glass fine particle synthesis to generate glass fine particles, and the glass fine particles are transferred to a target member. In a method for preparing a porous glass base material for an optical fiber, the method includes forming a porous glass particle deposit layer around the periphery by one inch,
The deposition is performed so that the angle between the tangent to the surface of the deposited layer and the burner axis at the point where the burner axis intersects with the surface of the glass fine particle deposit layer is substantially constant within the range of 40° to 80°. It is characterized in that as the outer diameter of the layer increases, the burner is moved parallel to the direction perpendicular to both the burner axis and the target member axis. [Function] Each time the burner traverses, a glass fine particle deposit layer is formed around the target member, and the outer diameter of the deposit Pa increases. and the position perpendicular to both the axis of the target member) are changed so that the angle between the burner axis and the tangent to the surface of the glass particle accumulation layer at the point where the burner axis intersects with the surface of the glass particle accumulation layer is 40 It is made to be substantially constant within the range of 80° to 80°. In other words, by changing the position of the burner, the direction of the flow of glass particles generated in the flame of the burner and the surface where this flow contacts the glass particle deposit layer are always 40 degrees to
It is made to remain substantially constant within a range of 80°. Therefore, even when the outer diameter of the glass particle deposit increases, the flow rate of combustion gas and combustion auxiliary gas increases, and the flow speed of glass particles increases, the scattering of glass particles on the surface of the deposit can be reduced. Glass particles can be deposited efficiently.

【Example】

Next, an embodiment of the present invention will be described with reference to the drawings. In FIG. 1, a target member 1 is made of a quartz-based glass rod that will later become a core part when it is made into an optical fiber, and both ends of the target member 1 are gripped and rotated by chucks of a glass lathe. The burner 3 for glass particle synthesis moves (traverses) in the axial direction (lengthwise direction) of this target member 1. This burner 3 is filled with frit gas (5iCI24 in this example).
, combustion gas (H2), combustion assisting gas (02), and inert gas (Ar) are supplied, and a flame hydrolysis reaction occurs in the flame 4 to produce glass particles (5i02). This burner 3 is caused to traverse the rotating target member 1 while spraying glass particles generated in the flame 4, and thereby a layer of glass particle deposits N2 is formed around the target member 1 with each traverse. To go. The surface temperature of the glass particulate deposit layer 2 that is scorched by the flame 4 is measured by the temperature measuring device 5, and the combustion gas and auxiliary combustion gas are Flow rate is controlled. In this way, the traverse is repeated several times in the axial direction of the target member 1 to form a plurality of glass fine particle deposited layers 2, and when the desired thickness of the glass fine particle deposited layer 2 is obtained as a whole, the deposition step is started. be terminated. In this example, the burner 3 is arranged in a plane transverse to the target member 1 (a plane perpendicular to the axis of the target member 1).
When viewed in cross section, as shown in FIG. 2, it faces toward the center of the target member 1 and faces away from the center. That is, the burner 3 is held movable in the vertical direction (that is, in a direction perpendicular to both the central axis of the tartuff 1 to the member 1 and the axis of the burner 3), and the axis of the burner 3 is aligned with the glass fine particle deposit layer 2. Its vertical position is controlled so that the angle θ between the tangent to the surface of the deposited layer 2 and the burner axis at the point where it intersects with the surface of . That is, as the glass fine particle deposition layer 2 is formed layer by layer and its outer diameter increases layer by layer, the burner 3 is moved in parallel to move upward in FIG. 2. The outer diameter of this glass particle accumulation layer 2 is measured at any time by an outer diameter measuring device 6, and the outer diameter is measured every time one glass particle accumulation layer 2 is formed. The vertical position of the burner 3 is adjusted for each traverse according to the measured value. Here, when the deposition was performed while changing the angle θ variously, good deposition efficiency was shown in the range of 40° to 80°. In particular, the highest deposition efficiency was obtained near 65°, and when the amount of deposition per traverse at this time was investigated, good results were obtained as shown by the solid line in FIG. The dotted line represents the results of deposition using the same gas flow rate using the conventional method for comparison. A comparison between the solid line and the dotted line shows that when the number of traverses is small, there is no big difference between the two, but as the number of traverses increases (as the outer diameter of the glass particle deposit body 2 becomes larger), the conventional It can be seen that this method can greatly improve the increase in the amount of deposits, which is saturated when the increase is saturated. Note that in the above embodiment, the target member 1 only rotates and is fixed in the axial direction, and the burner 3 moves. However, conversely, the burner 3 is fixed and the target member 1 side is moved. Of course, it may be moved in the axial direction.

【Effect of the invention】

According to the method of manufacturing a porous glass material for optical fibers of the present invention, the outer diameter of the glass particle deposit increases and the flow rate of combustion gas and combustion auxiliary gas is increased in order to maintain its surface temperature. When the speed of the flow of glass particles increases, the scattering of glass particles on the surface of the deposit is reduced, the deposition efficiency of glass particles is increased, and the amount of deposition becomes saturated as the number of traverses increases. You can improve things.

[Brief explanation of the drawing]

FIG. 1 is a plan view conceptually showing an embodiment of the present invention, FIG. 2 is a cross-sectional view of the same embodiment taken along a plane that crosses the target member, and FIG. The graph showing the f-system, FIG. 4, is a plan view conceptually showing a conventional example. ■...Target member, 2...Glass particulate deposit body, 3...Burner, 4...Flame, 5...Temperature measuring device,
6...Outer diameter measuring device.

Claims (1)

[Claims] (1) A porous optical fiber in which a glass raw material is supplied into the flame of a burner for glass particle synthesis to generate glass particles, and the glass particles are attached around the target member to form a porous glass particle accumulation layer. In the method for producing a quality glass base material, the angle between the tangent to the surface of the deposited layer and the burner axis at the point where the axis of the burner intersects with the surface of the glass fine particle deposited layer is substantially within the range of 40° to 80°. The porous material for optical fibers is characterized in that as the outer diameter of the deposited layer increases, the burner is moved in parallel in a direction perpendicular to both the burner axis and the target member axis. Method for manufacturing glass base material.