JP3428168B2 - Manufacturing method of optical fiber coupler - Google Patents

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for manufacturing an optical fiber coupler, and more particularly to a method for manufacturing an optical fiber coupler for simultaneously manufacturing a plurality of optical fiber couplers having the same characteristics.

[0002]

2. Description of the Related Art An optical fiber coupler is manufactured by removing coatings of a plurality of optical fibers, heating them in a state of closely adhering to each other to fuse and integrate them, and further heating and drawing. The optical fiber has an outer diameter of 125 μm
Since it is an extremely fine glass body, precise precision is required for manufacturing an optical fiber coupler. Therefore, the productivity of the optical fiber coupler is low, and the price is likely to be high.

As a method for improving productivity, JP-A-63 / 1988
As described in JP-A-205615 and JP-A-1-120510, a method of manufacturing a plurality of optical fiber couplers at a time has been proposed.

However, when manufacturing a plurality of optical fiber couplers in a lump, it is necessary to make the characteristics of the individual optical fiber couplers manufactured uniform, but in the conventional manufacturing method, a plurality of optical fiber couplers are used. Since the optical fiber coupler is manufactured by being fused at the same time and drawn at the same time, it is difficult to manufacture the optical fiber coupler with uniform characteristics and good reproducibility.

As a method for solving this, Japanese Patent Laid-Open No. 6-1
As described in Japanese Patent No. 48462, a method has been proposed in which the distance between the optical fiber strands is widened to make the gas flow the same. However, the method of widening the interval requires a gas burner having a large area as a heating source. Further, as shown in FIG. 4, there is a problem of temperature distribution of the gas burner.

FIG. 4 shows the tendency of temperature distribution, with the horizontal axis representing distance and the vertical axis representing thermal power. It was found that the central part had a weaker heating power than the outside, that is, the heating temperature was low. This is because the inside of the flame of the burner has insufficient oxygen due to lack of oxygen.

The influence of the fusion amount depending on the heating temperature was investigated. As shown in FIG. 5, it became clear that the fusion amount fluctuated greatly. In FIG. 5, the optical fiber strands of a four-core tape-shaped optical fiber are plotted on the horizontal axis from the outer side, and the fusion amount of each optical fiber strand is plotted on the vertical axis. The fusion amount was represented by the width W of the fusion-bonded portion of the two strands as shown in FIG. As for the fluctuation of the fusion amount, as shown in FIG. 5, the fusion amount of the outer wire is larger than that of the inner wire. Since the fusion amount largely depends on the temperature of the optical fiber strand during heating, from this result, it is considered that the optical fiber strand is not uniformly heated.

Further, as a result of detailed investigation on this point, as described above, the temperature distribution of the flame of the gas burner,
It was discovered that there was a problem with the gas flow when heating the optical fiber strand. That is, if the interval between the optical fiber wires from which the protective coating has been removed is narrow, it is considered that the gas flow at the time of heating does not flow sufficiently between the optical fiber wires, and all the optical fiber wires cannot be heated uniformly. When a multi-core tape-shaped optical fiber is used as the optical fiber for fusion-stretching, since the distance between the strands is very narrow, about 125 μm, the problems of flame temperature distribution and gas flow are particularly large. It is considered to be a thing. In order to solve this problem, the above-mentioned Japanese Patent Laid-Open No. 6-148.
As described in Japanese Patent No. 462, it is possible to widen the distance between the inner wire and the outer wire. However, a burner flame with a large heating range is required, which causes a problem of being easily affected by the temperature distribution of the flame.

[0009]

SUMMARY OF THE INVENTION The present invention has been made in view of the above circumstances, and an object thereof is to provide a method of manufacturing an optical fiber coupler capable of simultaneously manufacturing a plurality of optical fiber couplers having uniform characteristics. It is what

[0010]

SUMMARY OF THE INVENTION The present invention has two rows, one above and one below.
In a state where the optical fiber of the plurality of rows to the left and right are arranged, the heat source
As a method for manufacturing an optical fiber coupler in which the upper and lower optical fibers are fused and stretched using a gas burner as a plurality of optical fiber couplers at the same time, as the optical fibers, at least upper and lower lights in a fused portion The difference in the clad diameter of the fiber is uniform in the optical fiber cover.
Large at the end of the array so that you can get the pla ,
It is characterized by using an optical fiber arranged so as to be small in the central portion.

It is also characterized in that a multi-core tape-shaped optical fiber is used as the optical fibers arranged vertically.

[0012]

FIG. 7 is a diagram showing an experimental result of measuring the degree of saturation coupling of fiber couplers manufactured by changing the fusion amount.
The fusion amount W is as described in FIG. 6, and in this experiment, one optical fiber had a core diameter of 10 μm and a cladding diameter of 1 μm.
25 μm, and the other optical fiber has the same core diameter of 10 μm and clad diameters of 120 μm and 115 μm.
m was used. In both cases, the degree of saturation bond increases as the fusion amount increases. Further, with the same fusion amount, the cladding diameter of the other optical fiber is 115 μm,
That is, it can be seen that the larger the difference in outer diameter between the two optical fibers, the smaller the degree of saturation coupling. Therefore, in order to obtain the same degree of saturation bond, it can be said that the larger the difference in outer diameter, the larger the fusion amount W needs to be.

FIG. 8 is an experimental result showing an example of the relationship between the difference in the cladding diameters of two optical fibers and the degree of saturation coupling when the fusion amount is constant. In this experiment, one of the optical fibers had a core diameter of 10 μm and a clad diameter of 125 μm,
The other optical fiber has the same core diameter of 10 μm
Then, the cladding diameter is 125 μm, 120 μm, 115 μm
And 105 μm. It can be seen that the saturation coupling degree decreases as the difference in cladding diameter increases.

According to the present invention, as is clear from the above-mentioned experimental results, the difference in the cladding diameters of the upper and lower optical fibers is reduced in the central portion where the fusion amount is reduced due to the above-mentioned heating condition, By increasing the difference between the cladding diameters of the upper and lower optical fibers at the end where the amount of coating increases, an optical fiber coupler with uniform characteristics can be obtained.

By using a multi-core tape-shaped optical fiber as the optical fibers arrayed vertically, manufacturing becomes easy.

[0016]

1 is a cross-sectional view of a fused portion of an optical fiber from which a coating is removed in an embodiment for explaining a method of manufacturing an optical fiber coupler of the present invention. 11, 12,
13, 14 are lower optical fibers 21, 22, 23, 2
Reference numeral 4 is an upper optical fiber. Optical fibers 11, 12,
The diameter of 13, 14 and the optical fiber 2 in the upper center part
The diameters of 2 and 23 are the same. Also, the diameters of the optical fibers 21 and 24 at both ends on the upper side are
It is smaller than the diameter of 12, 13, 14. The core diameter is the same for all optical fibers.

The four sets of optical fibers thus combined vertically are fused and stretched by using a gas burner as a heating source . The optical fibers in the center have the same cladding diameter in the upper and lower parts, whereas the upper and lower optical fibers on both sides have a difference in the cladding diameter. Despite being strong against
The characteristics of the obtained four optical fiber couplers can be made uniform.

A specific example will be described. Optical fiber 1
As 1, 12, 13, and 14, four-core tape-shaped optical fibers were used. The outer diameter of the coating of each core wire is 250 μm,
The clad diameter is 125 μm. Optical fibers 22, 23
Used the same optical fiber core wire having a clad diameter of 125 μm. Further, the optical fibers 21 and 24 at the end portions have a cladding diameter of 123 μm, which is smaller by 2 μm. Each optical fiber core wire is a 1.33 μm band communication optical fiber.

When one of the optical fibers has a clad diameter of 125 μm and the optical fiber at the center of the other optical fiber row has a clad diameter of 125 μm, the optical fiber of the other optical fiber row is also used. The cladding diameter of the optical fiber at the end is 115 μm or more and less than 125 μm.

The arrangement of the optical fiber cores was carried out by fusion-bonding stretching so that the distance between the optical fiber strands was 250 μm. The binding degree at a wavelength of 1.33 μm thus obtained was measured. FIG. 2 is a diagram showing the measurement results. The optical fiber cores of a four-core tape-shaped optical fiber are plotted on the horizontal axis from the outer side, and the saturation coupling degree of the manufactured optical fiber coupler is plotted on the vertical axis. Was 50 ± 2%, and an optical fiber coupler having uniform characteristics was obtained.

As a comparative example, the one shown in FIG. 2 is more uniform than the one shown in FIG. 3, which shows the measurement result of the optical fiber coupler manufactured by using all the optical fibers having the same cladding diameter of 125 μm. It turns out that it is good.

A four-core tape-shaped optical fiber can also be used as the upper optical fiber. In this case,
It is preferable to set the clad diameter of each core of the tape-shaped optical fiber to a value designed in advance. When using a tape-shaped optical fiber having the same clad diameter for each core, it is necessary to reduce the clad diameter of the optical fibers on both sides by hydrogen fluoride or the like.

In the above description, four tape-shaped optical fibers are used, but four or more optical fiber couplers can be manufactured at the same time by using more multi-fiber optical fibers.

In the above embodiment, the lower optical fiber, that is, the optical fiber on one side,
All have the same cladding diameter, and the optical fiber core wires on the other side have different diameters. However, the optical fibers on one side may also have different diameters.

[0025]

[0026]

As is apparent from the above description, according to the present invention, a plurality of optical fiber couplers having the same characteristics can be manufactured at the same time, and thereby the productivity of the optical fiber coupler can be dramatically improved. There is an effect.

[Brief description of drawings]

FIG. 1 is an explanatory view of a method for manufacturing an optical fiber coupler of the present invention.

FIG. 2 is a diagram showing a measurement result of an example.

FIG. 3 is a diagram showing a measurement result of a comparative example.

FIG. 4 is a diagram showing a tendency of temperature distribution of a gas burner.

FIG. 5 is a graph showing changes in the amount of fusion.

FIG. 6 is an explanatory diagram of a fusion amount.

FIG. 7 is a diagram showing the experimental results of measuring the saturation coupling degree of fiber couplers manufactured by changing the fusion amount.

FIG. 8 is a diagram showing an example of the relationship between the difference in cladding diameters of two optical fibers and the degree of saturation coupling when the fusion amount is constant.

[Explanation of symbols]

11, 12, 13, 14 ... Lower optical fiber 21, 22, 23, 24 ... Upper optical fiber.

─────────────────────────────────────────────────── ─── Continuation of front page (72) Inventor Yoichi Ishiguro 1 Taya-cho, Sakae-ku, Yokohama-shi, Kanagawa Sumitomo Electric Industries, Ltd. Yokohama Works (72) Inventor Shigeru Semura 1-tani, Sakae-ku, Yokohama, Kanagawa Sumitomo Electric Kogyo Co., Ltd. (56) Reference JP-A-6-148461 (JP, A) JP-A-6-148462 (JP, A) JP-A-1-236509 (JP, A) JP-A-2-24607 (JP, A) JP-A-63-205615 (JP, A) (58) Fields investigated (Int. Cl. ⁷ , DB name) G02B 6/28-6/293 G02B 6/24-6/255

Claims (2)

(57) [Claims] 1. A plurality of optical fibers are fused and stretched by using a gas burner as a heating source in a state where two rows of optical fibers are arranged vertically and a plurality of rows of optical fibers are arranged horizontally. In the method of manufacturing an optical fiber coupler for manufacturing an optical fiber coupler at the same time, as the optical fiber, an optical fiber coupler having a uniform difference in the cladding diameters of the upper and lower optical fibers in at least the fused portion can be obtained.
As described above, the method for manufacturing an optical fiber coupler is characterized in that the optical fibers are arranged such that the ends are large and the central part is small. 2. A multi-core tape-shaped optical fiber is used as the optical fibers arranged vertically.
A method for manufacturing the optical fiber coupler described in.