JPH08119656A - Method for manufacturing multi-core fiber preform - Google Patents

Abstract

(57) [Summary] (Modified) [Objective] The present invention aims to provide a multicore fiber preform manufacturing method for manufacturing a multicore fiber preform having a small propagation loss of light. A method of manufacturing a multi-core fiber preform according to the present invention comprises bundling a plurality of core members in a quartz tube and filling the quartz tube with the core material and the SiO 2 between the core material and the gap between the core material and the quartz tube. It is characterized in that a substance containing ₂ as a main raw material or a substance having a refractive index similar to that of quartz is filled to eliminate a gap, and then the quartz tube is collapsed at a high temperature.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for producing a multi-core fiber preform, and more particularly, since the shape is not distorted even if a plurality of core materials are bundled in a quartz tube and collapsed, the propagation loss of light can be reduced. The present invention relates to a method for manufacturing a multicore fiber preform.

[0002]

2. Description of the Related Art Manufacturing of a multi-core fiber preform is shown in FIG.
As shown in FIG. 1, conventionally, it is performed by bundling and filling a core material in a quartz tube and collapsing it.

[0003]

However, the manufacturing of the multi-core fiber preform by this conventional method is described with reference to FIG.
As shown in (a), first, a plurality of core materials 12 are bundled and filled in a quartz tube 11, and as shown in the drawing, between the core materials, or between the core materials and the quartz. Since a gap 13 is formed between the tube and the tube, the multi-core fiber preform 14 produced by collapsing this has a distorted core as shown in FIG. 5 (b), and thus has a large light propagation loss. There is a disadvantage that.

[0004]

SUMMARY OF THE INVENTION The present invention relates to a method for producing a multi-core fiber preform which solves the above disadvantages and problems, and in the method for producing a multicore fiber preform having a plurality of cores, quartz is used. After bundling and filling a plurality of core materials in a tube, SiO ₂ as a main raw material or a material having a refractive index similar to that of quartz in the gap between the core material and the core material and the quartz tube. It is characterized in that the quartz tube is collapsed at a high temperature after filling a certain substance to eliminate the gap.

That is, the present inventors have conducted various studies to develop a method for producing a multi-core fiber preform having a small light propagation loss. As a result, according to the conventional method, a plurality of core materials are bundled in a quartz tube. while filling, between the core material and the core material in the filling, also with the gap generated between the core member and the quartz tube, ones SiO ₂ as a main raw material in this gap, or refraction comparable to quartz It was found that if the quartz tube is collapsed at a high temperature after filling with a material having a certain ratio to eliminate the gap, the resulting multicore fiber preform has a shape close to a perfect circle, and the propagation loss of light is small. The present invention has been completed by conducting research on the type of substance to be filled in the gap, the filling method, and the like.
This will be described in more detail below.

[0006]

[Operation] In order to see how such a core shape affects the propagation loss of light, a model was set up and a simulation was performed. Simulations were performed for a model A having a perfect circle as shown in FIG. 3A and a model B having a donut shape as shown in FIG. 3B. FIG. 4 shows the result, and the model A,
The two-dimensional interface distribution of the surface cut along the E axis is obtained for B. From this result, the model A having a perfect core shape as shown in FIG. 4 (a) is shown in FIG. 4 (b). It can be seen that the light propagation characteristics of each core as a multi-core fiber are superior to those of the model B having a donut shape, and the propagation loss is small.

As described above, according to the method for producing a multi-core fiber preform according to the present invention, when a plurality of core materials are bundled and filled in a quartz tube, the space between the core materials and the space between the core material and the quartz tube is filled. Because there is a gap in this gap,
The material is made of SiO ₂ as a main raw material or a material having a refractive index similar to that of quartz is filled to fill the gap, and then collapse is performed. According to this, the gap has the same quality as SiO ₂ or the quartz tube. It was found that the core was obtained by collapsing it into a perfect circle because it was filled with the material, and the advantage was obtained that the propagation loss of light became small as confirmed by the simulation.

In the production of the multi-core fiber preform in the present invention, first, a plurality of core materials 2 are bundled and filled in a quartz tube 1 according to a known method. The quartz tube and the core material are known materials. And it is sufficient. For example, as shown in FIG. 5 (a) described above, when a plurality of core materials 12 are bundled and packed in a quartz tube 11, the space between the core materials and between the core material and the quartz tube is increased. Since the gap 13 is formed, the multi-core fiber obtained by collapsing this is distorted as shown in FIG. 5 (b), and the optical propagation loss is large.

Therefore, in the present invention, a material containing SiO ₂ as a main raw material or a material having a refractive index similar to that of the quartz tube is provided between the core material and the gap between the core material and the quartz tube. However, the material is not particularly limited, and non-doped silica fiber, silica powder or the like may be exemplified as long as it is made of such a material. Further, if necessary, fluorine or boron can be doped as a sub-component in order to lower the refractive index. As shown in FIG. 1 (a), this filling is made by using SiO ₂ as a main raw material 4 in the gap 3 between the quartz tube 1 and the core material 2, the gap 3 between the core material 4 and / or the refractive index. It is sufficient to fill the filler 4 which is about the same as the quartz tube, but this filling can be done by filling these gaps 3 with these fibers and powders from the top, and after filling with a rod or the like from the top if necessary. It should be embedded by poking.

The tube material made of the quartz tube and the core material, which are filled with the filler 4 in the gap 3 thus formed, is then collapsed to form a multi-core fiber preform, which is collapsed. For example, as shown in FIG. 2, one end of the quartz tube is heated and sealed by a burner 5 and, if necessary, decompressed, and then the burner 5 is gradually shifted to the other end and collapsed. According to this, since the gap 3 is filled with the filler 4, the obtained multi-core fiber preform has a perfect circular shape as shown in FIG. 1 (b), and the propagation loss of light is small. Gender is given.

[0011]

EXAMPLES Next, examples and comparative examples of the present invention will be described. Examples and Comparative Examples Core material 7 with an inner diameter of 2 mmφ in an anhydrous synthetic quartz tube with an inner diameter of 6 mmφ
When the books were bundled and filled, a gap was created between the quartz tube and the core material, and between the core materials. Therefore, a silica fiber (non-doped) with an outer diameter of 125 μm was filled in the gap to fill the gap. After erasing, one end of this quartz tube was heated and sealed with a burner, then, while depressurizing from the other end, the burner was gradually shifted from the sealing side to the other end, and a collapse was performed. The multicore fiber preform was a perfect circle as shown in FIG. 1 (b).

Then, in order to examine the light propagation characteristics of the multi-core fiber base material, a wire was drawn from the base material to obtain an outer diameter 1
An optical fiber of 25 μm was manufactured, and as a comparative example, collapsed without filling silica fiber in the gap (FIG. 5B).
As shown in Fig. 5, a distorted multi-core fiber preform was drawn in the same way to make an optical fiber with an outer diameter of 125 μm, and the propagation loss of these was determined. It was confirmed that the propagation loss was smaller than that of the distorted one, and it was an excellent multicore fiber preform.

[0013]

According to the present invention, since the core shape is a perfect circle, there is an advantage that a multi-core fiber preform having a small propagation loss of light can be obtained.

[Brief description of drawings]

FIG. 1 (a) is a cross-sectional view of a quartz tube before collapse made of a quartz tube filled with a filler in a gap and a core material according to the present invention, and FIG. 1 (b) is a multi-core fiber preform obtained by collapsing the same. It is a cross-sectional view.

FIG. 2 is a vertical cross-sectional view of a collapse method for a quartz tube including a quartz tube and a core material.

FIG. 3A is a diagram showing a core shape of a model A in simulation, and FIG. 3B is a diagram showing a core shape of a model B in simulation.

4A is a two-dimensional interface diagram of light by simulation of a multicore fiber preform of model A, and FIG. 4B is a two-dimensional interface diagram of light by simulation of a multicore fiber preform of model B. It is a figure.

FIG. 5 (a) is a cross-sectional view of a conventional quartz tube comprising a core material and a quartz tube in which a filler is not filled in a gap in the conventional method, and FIG. It is a front view.

[Explanation of symbols]

 1, 11 ... Quartz tube 2, 12 ... Core material 3, 13 ... Gap 4 ... Filler 5, 14 ... Multi-core fiber 6 ... Burner 7 ... Sealing part 8 ... Decompression direction

Claims (2)

[Claims] 1. A method of manufacturing a multi-core fiber preform composed of a plurality of cores, wherein a plurality of core members are bundled and filled in a quartz tube, and then the core material and the core material and the core material and the quartz tube are packed. A multi-core, characterized in that a substance having SiO ₂ as a main raw material or a substance having a refractive index similar to that of quartz is used as a filler in the gap to fill the gap to eliminate the gap, and then the quartz tube is collapsed at a high temperature. Manufacturing method of fiber preform. 2. The method for producing a multi-core fiber preform according to claim 1, wherein the filler is the same material as quartz or a substance similar thereto.