JPS5852260Y2 - Torch for making step-type optical fiber base material - Google Patents

Description

[Detailed Description of the Invention] The present invention relates to a glass fine particle synthesis torch used in producing a base material for optical fiber.

This type of synthesis torch is used when manufacturing an optical fiber base material using an optical fiber base material manufacturing apparatus as shown in FIG.

In FIG. 1, 1 is a fine particle synthesis torch, and 2 is a rod-shaped glass sintered body to which glass particles synthesized by the glass particle synthesis torch 1 are attached and sintered.

3 is a substrate of the starting material, 4 is a rotation and pulling device,
5 is a protective container, and 6 is an exhaust volume regulator.

When the rod-shaped sintered body 2 is heated to 1600 to 1700°C, it becomes transparent vitrified and becomes an optical fiber base material.

Conventionally, a glass fine particle synthesis torch used in this method has a structure shown in FIG. 2, and is provided with several types of blow-off ports for glass raw materials, through which glass raw materials having different composition ratios are flowed.

At this time, the shape of the outlet was circular or semicircular.

In addition, the blow-off ports for combustible gas and auxiliary gas were similarly circular.

In such a torch, multiple types of glass raw materials flowing out from the raw material outlet diffuse into each other to some extent before being sintered to produce a glass sintered body with a gentle refractive index distribution in the radial direction. do.

For example, it has a refractive index distribution as shown in part b in Figure 3,
In order to form the part a (referred to as the cladding layer), an auxiliary glass particle synthesis torch (7 shown in Figure 1) is installed in the direction perpendicular to the glass sintered body 2, and the glass raw material is flowed to form the cladding layer. I needed to put it on.

However, according to this method, the ratio of the cladding outer diameter to the core diameter was only about 1.5.

The reason why this ratio cannot be kept large is that if a thick cladding layer is applied using the auxiliary torch 7, the glass sintered body will easily break, and when it is made into transparent glass, the diameter of the glass sintered body will become too large, making it difficult to handle. There are drawbacks such as:

This invention uses a synthesis torch that has a gas outlet between a plurality of raw material outlets lined up in a straight line, suppresses the diffusion of glass raw materials as much as possible, and creates a step-shaped refractive index distribution.
Furthermore, the ratio of the cladding outer diameter to the core diameter is made as large as possible.

FIG. 4 is a diagram showing an embodiment of the present invention, with 11,12°1
2' is a rectangular frit outlet arranged in a straight line,
Further, between the frit outlet ports 11 and 12 and between the frit outlet ports 11 and 12', there are provided blower ports 16 and 1 for a diffusion adjusting gas that changes the diffusion state of these frit outlets.
6', surrounded by an inert gas outlet 13, and further surrounded by a combustible gas outlet 14.
, there is a blowout port 15 for auxiliary gas.

60 cc of 5iC14 from core raw material outlet 11, G
50 cc of eCl4, 45 cc of POCl3, and 20 cc of 5iC14 from the cladding raw material outlet 12.12'
Blow out 0cc and 200cc of BBr3, respectively, and blow out 0.51 of the adjustment gas from the blowout port 16 and 16', and blow out the adjustment gas from the blowout port 13.
0.51 liters of inert gas, 21 liters of combustible gas from the outlet 14, and 51 liters of combustible gas from the outlet 15 were blown out, respectively, and the glass raw material was pulverized into glass particles to create a rod-shaped glass sintered body with a diameter of 8 cm.

This sintered body was heated at 1600° C. and vitrified to obtain an optical fiber base material with a diameter of 3 cm.

The refractive index distribution of this base material is as shown in Figure 5, and as can be seen from this distribution, it has an almost perfect step-type distribution, and the ratio of the cladding outer diameter to the core diameter is 4, which is a large It shows the value.

FIG. 6 shows another embodiment of the present invention, and unlike FIG. 4, the frit outlet is asymmetrical.

In order to operate this, it is only necessary to install it so that the gas flow from the core raw material outlet hits the center of the tip of the glass sintered body.

Since the glass sintered body is rotating, a refractive index distribution similar to that shown in FIG. 5 can be obtained.

As described above, in the torch of the present invention, a step-type refractive index distribution can be obtained and the ratio of the cladding outer diameter to the core diameter can be made large. For example, in FIG. Raw material outlet 12.12
This is because the diffusion mixing of the source gas blown out from the outlet 16, 16' in the X direction shown in FIG. In Figure 4, the size ratio c/d of C and d is 4
It is desirable that there be at least one.

In the torch of the present invention, the rectangular raw material outlet is very effective in increasing the ratio of the cladding outer diameter to the core diameter.
Since a product with a large ratio of the cladding outer diameter to the core diameter can be produced in this way, it is effective to use it for producing a glass preform for a single mode optical fiber in which the cladding thickness is a factor of loss.

Compared to conventional torches that use an auxiliary burner to form a cladding layer, this torch has the advantage that the glass sintered body is less likely to crack and can be easily made into transparent glass.

In addition, this synthetic torch has the advantage that the ratio of the cladding outer diameter to the core diameter can be freely changed by adjusting the dimensional ratio of the raw material outlet. You can choose the ratio of outer diameter to core diameter.

Further, the inert gas blown out from the blow-off ports 16 and 16' can change the diffusion and mixing of raw material gases having different compositions, and it is possible to easily create a step-type refractive index distribution.

[Brief explanation of the drawing]

Figure 1 is a schematic diagram of an optical fiber base material manufacturing device, Figure 2 is a schematic diagram showing the structure of a conventional glass particle synthesis torch, and Figure 3 shows the refractive index distribution shape formed by the torch in Figure 2. 4 is a diagram showing an example of the glass particle synthesis torch according to the present invention, FIG. 5 is a diagram of the refractive index distribution shape formed by the torch shown in FIG. 4, and FIG. 6 is a diagram showing another embodiment according to the present invention. This is an example diagram. 1...Glass particle synthesis torch, 2...
・Rod-shaped glass sintered body, 3...Starting material substrate, 4.
... Rotation and lifting device, 5 ... Protective container, 6 ... Displacement regulator, 7 ...
Auxiliary torch, 11... Glass raw material (core) outlet, 12.12'... Glass raw material (cladding)
Air outlet, 13...Inert gas outlet, 14
...Blowout port for combustible gas, 15...Blowout port for auxiliary gas, 16.16'...Blowout port for diffusion adjustment gas.

Claims (1)

[Scope of utility model registration request] In the flame of burning flammable gas, 5iC14゜GeC
l4. BBr3. Inject glass raw materials such as POCl3,
A torch for producing an optical fiber base material that synthesizes glass fine particles by a hydrolysis reaction or an oxidation reaction has two or more rectangular blow-off ports arranged in a straight line that blow out glass raw materials with different composition ratios. A step-type optical fiber preform production torch characterized by having a gas outlet for adjusting the diffusion and mixing of different glass raw materials.