JP2001343549A - Tip end shape of micro-torch - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide such a tip end shape of a micro-torch that dispenses with the need of moving the micro-torch left and right, that eliminates uneven heating of an optical fiber, and that uniformalizes the expansion of the mode field diameter of the optical fiber. SOLUTION: The tip end 1 of the micro-torch is formed with a gas discharging hole (h) having a hole width of hw and a wavy rectangular shape, and is shaped in such a manner that the flame of the micro-torch reaches over the entire length of the expanding part of the mode field diameter; as a result, the mode field diameter in the essential part of the optical fiber is expanded over the longitudinal direction.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a tip shape of a micro torch used for expanding a mode field diameter (core diameter) of an optical fiber in a longitudinal direction by heating.

[0002]

2. Description of the Related Art When two optical fibers having different core diameters or an optical fiber having a different mode field are interconnected with an optical semiconductor device, the spot size of light at the connection surface becomes discontinuous. A large connection loss occurs. In order to reduce the connection loss, it is desirable that the mode fields at the connection surfaces between the optical fibers or between the optical fibers and the optical semiconductor element be made to have the same size.
As a measure for this, there is a technique of reducing the connection loss by enlarging the core diameter of the connection end of the optical fiber having the smaller core diameter in accordance with the mode field of the optical fiber or the optical semiconductor element to be connected. It has been put to practical use.

[0003] The core diameter of the optical fiber is increased by adding a dopant for increasing the refractive index of the core into the core or using an optical fiber doped with a dopant for lowering the refractive index of the clad in the clad. Is heated by a single pipe-shaped micro torch (micro burner) 1 'or the like as shown in FIG. 6 to thermally diffuse the dopant in the core or clad. Then, in the heated portion (core diameter enlarged portion) s heated by the micro torch 1 'for a required time, the core diameter of the heated portion s is increased from t to u as shown in FIG. Thereafter, for example, the optical fiber is cut at a portion where the core diameter is enlarged, and a connection end face is formed. Since the enlarged portion of the core diameter needs a predetermined length, the width of heating the fiber is increased by moving the micro torch to the left and right in the length direction of the optical fiber.

[0004]

When the conventional single-pipe microtorch is used, it is necessary to move the microtorch right and left in the longitudinal direction of the optical fiber in order to increase the mode field diameter of the optical fiber. There is a problem that it takes time to enlarge the mode field diameter. In addition, moving the microtorch to the left and right caused the flame to fluctuate, resulting in uneven heating temperature distribution, causing variations in dopant diffusion, and was a major factor in making the core diameter of the optical fiber nonuniform. .
Further, there is a problem that the optical fiber is locally softened and bent due to uneven heating. Further, the optical fiber has a very small diameter (for example, a single mode optical fiber has a diameter of φ
0.125 mm), there has been a problem that the expansion width of the mode field diameter becomes non-uniform and the outer diameter of the optical fiber fluctuates. If the micro torch is fixed and heated, the heating width of the optical fiber becomes narrow, and there is a problem that the desired mode field diameter cannot be increased.

SUMMARY OF THE INVENTION The present invention has been made to solve the above-mentioned various problems of the prior art. It is not necessary to move the micro torch to the left and right, the optical fiber is not heated unevenly, and the mode of the optical fiber is not changed. It is an object of the present invention to provide a tip shape of a micro torch in which a field diameter is uniformly increased.

[0006]

According to a first aspect of the present invention, there is provided a tip shape of a micro torch used when a mode field diameter of a main part of an optical fiber is enlarged in a longitudinal direction by heating. The tip of the micro torch is shaped so that the flame of the micro torch hits the entire length of the portion where the mode field diameter is enlarged. In the tip shape of the micro torch according to the first aspect,
Since the tip shape was such that the flame of the micro torch hit the entire length of the part where the mode field diameter was enlarged,
With the micro torch fixed, the heating width of the fiber can be increased in a short time. Therefore, since the micro torch is not moved left and right, the flame does not fluctuate, the heating temperature distribution does not fluctuate, the diffusion of the dopant does not vary, and the expansion of the core diameter of the optical fiber can be made uniform. It becomes possible. Further, there is no problem that the optical fiber is locally softened and bent due to uneven heating, and even with a very small diameter optical fiber, the expansion width of the mode field diameter becomes uneven or the outer diameter of the optical fiber becomes smaller. There is no problem that the value fluctuates.

According to a second aspect of the present invention, the tip shape of the micro torch is a tip shape of a micro torch in which a wavy rectangular gas outlet hole is present.
In the tip shape of the micro torch of the second aspect, since the gas outlet hole has a wavy rectangular shape, the flame of the micro torch hits the entire length of the portion where the mode field diameter is enlarged, and It can be preferably used as the tip shape of the micro torch of the first aspect, and the above-described effects can be obtained. In addition, it is not impossible to use a gas outlet hole having a general rectangular shape, an elliptical shape, or an elliptical shape, but it has been confirmed that a more uniform flame can be obtained by using a wavy rectangular shape. In addition, the external shape for providing the wavy rectangular gas outlet hole is not particularly limited, and may be, for example, a rectangular shape, an oval shape, an elliptical shape, or the like.

According to a third aspect of the present invention, the tip shape of the micro torch is a tip shape of a micro torch having a shape in which a plurality of ultrafine pipes are branched.
In the tip shape of the micro torch according to the third aspect, since a plurality of ultra-fine pipes are branched, the flame of the micro torch hits the entire length of the portion where the mode field diameter is enlarged. It is preferable as the tip shape of the micro torch according to the first aspect, and the above operation and effect can be obtained.

According to a fourth aspect of the present invention, the tip of the micro torch has a plurality of ultrafine pipes arranged in a line in contact with each other, the height thereof is adjusted, and a required mode field is provided. It is in the shape of the tip of a micro torch that can be heated according to its diameter. In the tip shape of the micro torch according to the fourth aspect, a plurality of ultrafine pipes are arranged in a row in contact with each other, the height thereof is adjusted, and heating according to the required mode field diameter can be performed. Therefore, the flame of the micro torch hits over the entire length of the portion where the mode field diameter is enlarged, so that the function and effect of the tip shape of the micro torch of the first aspect can be obtained, and the mode field diameter can be adjusted to the required mode field diameter. Heating can be performed, so that the mode field diameter can be expanded with high accuracy.

[0010]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The contents of the present invention will be described below in more detail with reference to an embodiment shown in the drawings. Note that the present invention is not limited by this. FIG. 1 is a schematic view showing an example in which the tip of the micro torch of the present invention has a wavy rectangular shape. FIG. 2 is a schematic diagram showing an example in which the tip shape of the micro torch of the present invention is such that a plurality of ultrafine pipes are branched. In addition, FIG. 1A shows a case where the tip is branched into two, FIG. 2B shows a case where the tip 1b is branched into three, and FIG. 1C shows a case where the tip 1c is branched into four. Things. FIG. 3 shows the tip shape of the micro torch of the present invention.
It is a schematic diagram showing an example in which a plurality of ultrafine pipe-like bodies are arranged in a row in contact with each other, the height thereof is adjusted, and heating can be performed according to a required mode field diameter. FIG. 4 is a schematic view showing a state in which an optical fiber is held by an optical fiber holder and a mode field diameter is enlarged by a flame of gas generated from a tip shape of the micro torch of the present invention. FIG. 5 is a longitudinal sectional view showing an optical fiber in which the mode field diameter is enlarged using the tip-shaped micro torch of the present invention. In these figures,
1a, 1b, 1c, 1d are the tip of the micro torch, 10
Is an optical fiber, 11 is a core, 12 is a clad, 20 is an optical fiber holder, 30 is an optical fiber holder, f is a gas flame, h is a gas outlet hole (burning hole), hw is a hole width (hole interval). ), M is an ultrafine pipe-like body, s is a mode field diameter enlarged portion (expanded width) (heating portion), t is an original mode field (core) diameter, and u is an enlarged mode field (core) diameter (maximum diameter). is there.

Embodiment 1 A first embodiment of a tip shape of a micro torch of the present invention will be described with reference to FIG. As the tip shape of the micro torch, the shape of the gas outlet hole h at the tip portion 1 is formed in a wavy rectangular shape with a hole width hw. The hole width hw is, for example, 3 mm. The external shape was rectangular. The material of the micro torch is a heat-resistant alloy material.

Embodiments 2 to 4 Second to fourth embodiments of the tip shape of the micro torch of the present invention will be described with reference to FIG. These micro torches have a structure in which a plurality of ultrafine pipes m are branched, and each of the ultrafine pipes m has a gas outlet hole h. FIG. 2 (a) shows a case in which two tip portions 1a are used (Embodiment 2), FIG. 2 (b) shows a case in which three tip portions 1b are used (Embodiment 3),
FIG. 9C shows a case where the number of the tip portions 1c is four (Embodiment 4). The heights of the plurality of ultrafine pipes m may be arbitrarily set in accordance with the state of heating the optical fiber, and may be the same or different. FIG. 2 (a)
In (Embodiment 2), two of them are at the same height. In FIG. (B) (Embodiment 3), the middle one of the three is higher than the other two, and FIG. In form 4), one out of four
The book (second from left) is lower than the other three. The inner diameter of the ultrafine pipe m is, for example, 0.5 mm. The hole width h
w is, for example, 3 mm.

Embodiment 5 A fifth embodiment of the tip shape of the micro torch of the present invention will be described with reference to FIG. As the shape of the micro torch, the tip 1d is arranged such that, for example, seven ultra-fine pipe-like bodies m having gas outlet holes h are arranged in a row in contact with each other, and their tips are aligned in a mountain-like manner. The structure is such that the temperature becomes higher toward the center so that heating can be performed in accordance with the required mode field diameter. The inner diameter of the ultrafine pipe m is, for example, 0.5 mm. The hole width hw is, for example, 3 mm.

An example in which the mode field diameter of the optical fiber is actually enlarged by using the tip shape of the micro torch of the fifth embodiment will be described with reference to FIGS. The optical fiber holding part 30 of the optical fiber holder 20 has the optical fiber 10
Is held horizontally, and the tip 1d of the fixed micro torch
The mode f diameter of the heating unit s was enlarged by vertically applying a gas flame f generated from the gas. The optical fiber 10
A single mode optical fiber having a diameter of 0.125 mm was used. The gas supplied to the tip 1d was a mixed gas of propane and oxygen, and the heating was performed at 1150 ° C. Was about half the time as before. The heating temperature and the heating time vary depending on the type of the optical fiber, the enlarged size of the mode field diameter, and the like. As shown in FIG. 5, in the optical fiber 10 having the enlarged mode field diameter, the enlarged mode field (core) diameter u of the heating unit s is larger than the original core diameter t. For example, if the original core diameter t is 10 μm,
Enlarged mode The field diameter (maximum diameter) is 30 μm, and the width of the heating section s is about 3 mm, which is 2 mm compared to the conventional 1.5 mm.
Doubled. In addition, the mode field diameter of a plurality of optical fibers was increased, but the mode field diameter could be increased to 30 μm with good reproducibility. The optical fiber 10 having the enlarged core diameter is cut, for example, at the center of the heating unit s, and an optical fiber having an enlarged core end surface is obtained.

[0015]

According to the tip shape of the micro torch of the present invention, the shape of the micro torch is such that the width of the flame is enlarged and the flame of the micro torch hits the entire length of the portion where the mode field diameter is enlarged. With this fixed, it became possible to broaden the heating width of the fiber in a short time.
Further, the heating according to the required mode field diameter can be preferably performed. Therefore, there is no need to move the micro torch to the left or right, and there is no unevenness in the heating temperature distribution due to the fluctuation of the flame, there is no dispersion in the diffusion of the dopant, and the expansion of the core diameter of the optical fiber can be made uniform. Was. Further, the time required for increasing the mode field diameter of the optical fiber could be reduced to about half, and the mode field diameter could be expanded with good reproducibility. Therefore, the present invention has an extremely large effect of contributing to industry.

[Brief description of the drawings]

FIG. 1 is a schematic view showing an example in which a tip shape of a micro torch of the present invention is a wavy rectangular shape.

FIG. 2 is a schematic view showing an example in which the tip shape of the micro torch of the present invention is such that a plurality of ultrafine pipe-like bodies are branched. FIG. 3A shows a state in which the tip is branched into two parts.
FIG. 3B shows the tip 1b branched into three parts, and FIG. 3C shows the tip part 1c branched into four parts.

FIG. 3 shows the tip shape of a micro torch according to the present invention, in which a plurality of ultra-fine pipes are arranged in a row in contact with each other, the height thereof is adjusted, and heating according to a required mode field diameter can be performed. It is a schematic diagram showing an example of a structure.

FIG. 4 is a schematic diagram showing a state in which an optical fiber is held by an optical fiber holder and a mode field diameter is enlarged by a flame of gas generated from a tip shape of the micro torch of the present invention.

FIG. 5 is a longitudinal sectional view showing an optical fiber in which a mode field diameter is enlarged by using a tip-shaped micro torch of the present invention. (Also used for explanation of conventional examples)

FIG. 6 is a schematic view showing a tip shape of a conventional micro torch.

[Explanation of symbols]

 1, 1a, 1b, 1c, 1d Micro torch tip 10 Optical fiber 11 Core 12 Cladding 20 Optical fiber holder 30 Optical fiber holder f Gas flame h Gas outlet hole hw Hole width (hole interval) m Extra-fine pipe shape Body s Mode field diameter expansion part (expansion width) (heating part) t Original mode field (core) diameter u Expansion mode field (core) diameter (maximum diameter)

Claims (4)

[Claims] 1. A tip shape of a micro torch used when a mode field diameter of a main portion of an optical fiber is expanded in a longitudinal direction by heating, and extends over the entire length of a portion where the mode field diameter is expanded. The tip shape of the micro torch characterized in that the tip shape is such that the flame of the micro torch hits. 2. The tip shape of the micro torch according to claim 1, wherein the tip shape of the micro torch is a shape having an exit hole of a wavy rectangular gas therein. 3. The tip shape of the micro torch according to claim 1, wherein the tip shape of the micro torch is a shape in which a plurality of ultrafine pipes are branched. 4. The tip shape of the micro torch is such that a plurality of ultrafine pipes are arranged in a row in contact with each other, the height thereof is adjusted, and heating according to a required mode field diameter can be performed. The tip shape of the micro torch according to claim 1, wherein the tip shape is a shape.