JPH11258451A - Manufacture for optical fiber coupler - Google Patents

Abstract

PROBLEM TO BE SOLVED: To facilitate manufacture of an optical fiber coupler with various branching ratio in manufacturing a wavelength independence type optical fiber coupler using optical fibers of the same kind. SOLUTION: In this manufacturing method, covering is removed in the middle parts of two optical fibers of the same kind to expose the glass fiber parts, in reducing the diameter of the glass fiber part of one or two optical fibers by preliminary elongating, according to the conditions set according to the relationship between the branching ratio in the case of taking the previosly measured fusion time as a fixed value and the outside diameter difference due to preliminary elongation, preliminary elongation is performed, according to the fusion time, the glass fiber parts of two optical fibers are fused, and two optical fibers are simultaneously elongated to manufacture an optical fiber coupler.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a method of manufacturing a wavelength-independent optical fiber coupler having a constant branching ratio over a wide wavelength range.

[0002]

2. Description of the Related Art An optical fiber coupler is an optical component for splitting and coupling light between a plurality of optical fibers. As a typical method for manufacturing an optical fiber coupler, there are a melt drawing method and a polishing method. As a method for manufacturing an optical fiber coupler for a single mode, the melt drawing method is used as the most suitable method. In this fusion drawing method, a part of the coating is removed at an intermediate portion of a plurality of coated optical fibers, and the fibers are heated and fused in a state of being arranged in parallel. The stretching is stopped when the characteristics such as the above reach a desired value to form a joint.

When an optical fiber coupler is manufactured by a melt drawing method using two optical fibers of the same type, the branching characteristics of light greatly vary depending on the wavelength. In this case, two optical fibers having different cladding outer diameters are used, or two optical fibers having different mode field diameters are used.
By manufacturing by a melt drawing method, a wavelength-independent optical fiber coupler having a constant branching ratio in a wide wavelength range has been obtained. Note that the branching ratio is a ratio of light power indicating how much light transmitted through one optical fiber is branched to another optical fiber side at the fusion drawing portion.

When a wavelength-independent optical fiber coupler is manufactured by the above method, it is necessary to prepare different types of optical fibers in advance, and as an alternative to these methods, an optical fiber having the same structure is used. Are prepared, and one of them is pre-stretched prior to fusion to reduce the diameter of the glass fiber portion, and then to fuse the two in parallel with the other optical fibers which are not reduced in diameter. There is a method of stretching simultaneously.

FIG. 4 shows an example of an apparatus conventionally used for fusion drawing of an optical fiber coupler, and FIG. 5 is a view for explaining the procedure. 4 and 5, 1, 2
Is an optical fiber, 1a and 2a are glass fiber exposed portions from which the coating of the optical fibers 1 and 2 is removed, 3 is a slider device having a chuck 3a, 4 is a heating burner, and 5 is a chuck 3a of two slider devices 3 respectively. The thread for applying the moving tension, 6 is a weight.

In manufacturing a wavelength-independent optical fiber coupler, first, as shown in FIG. 5A, a coating is removed at an intermediate portion between two optical fibers 1 and 2 to form glass fibers 1a and 2a. Expose. Then, while holding the coated portions on both sides of the optical fiber 1 with the chuck 3a of the slider device 3 and heating the glass fiber 1a with the heating burner 4, the yarn 5 is moved in a direction in which the chucks 3a of the two slider devices 3 are separated. Then, the optical fiber 1 is preliminarily stretched by applying tension by the weight 6 to move the optical fiber 1 to a desired outer diameter at a portion to be a fusion-stretched portion. FIG. 5B shows that the glass fiber 1a of the optical fiber 1 has a thinner outer diameter of about 10 μm and is in a pre-drawn state. The optical fiber 2 is not pre-drawn.

Subsequently, as shown in FIG. 4, the glass fiber portions of the optical fibers 1 and 2 are made parallel to each other and held by the chuck 3a, and the space between the two glass fiber fibers 1a and 2a is pressed in the direction of arrow 7. The two are heated close to each other to fuse them together. Next, the chucks 3a of the two slider devices 3
Are driven by the weight 6 in the direction in which they are separated from each other, and the two optical fibers 1 and 2 are simultaneously drawn. FIG. 5C shows a state in which the two optical fibers 1 and 2 are fused and drawn.

[0008]

Conventionally, when an optical fiber coupler having various branching ratios is to be manufactured, first, two optical fibers are prepared, and one of them is preliminarily drawn to form a fused and drawn portion. Reduce the outer diameter of the part. After that, by repeating trial and error, the relationship between the fusion time and the branching ratio was determined by repeating trial and error to determine how much fusion time the optical fiber coupler can be obtained using the two optical fibers. And produced optical fiber couplers having various desired branching ratios according to the conditions. However, in this method, the degree of pre-drawing of the two prepared optical fibers changes every production lot, and the relationship between the fusion time and the branching ratio changes accordingly. As a result of repeated mistakes, it took a considerable amount of time to obtain manufacturing conditions. An object of the present invention is to provide a method of manufacturing an optical fiber coupler which solves the above-mentioned disadvantages of the conventional technique and which can easily set conditions even when a desired branching ratio changes.

[0009]

According to the present invention, there is provided a method of manufacturing an optical fiber coupler in which a coating is removed at an intermediate portion between two optical fibers of the same type to expose a glass fiber portion. The glass fiber portion of one or two of the optical fibers is reduced in diameter by pre-drawing so that the drawn portion of the glass fiber has an outer diameter difference between the two optical fibers. A method of manufacturing an optical fiber coupler by fusing a glass fiber portion and then simultaneously stretching two glass fiber portions, wherein the pre-stretching and fusing are performed when a previously measured fusing time is set to a constant value. This is performed according to conditions set based on the relationship between the branching ratio and the difference in outer diameter due to pre-stretching.

In addition, instead of calculating the difference in outer diameter of the glass fiber drawn portion in the pre-drawing according to the desired branching ratio and performing the pre-drawing, the drawing length difference in the pre-drawing is determined according to the desired branching ratio. It is also possible to perform pre-stretching so that the difference in stretching length is obtained. In addition, it is easier to measure the stretching length compared to the difficulty of accurately measuring the outer diameter of the stretching portion, and it is relatively easy to increase the measurement accuracy. It is more preferable to control by the difference in stretching length than to control by the difference.

Further, even if the difference in the stretching length is determined in accordance with the desired branching ratio and the preliminary stretching is performed, the difference in the actual stretching length slightly deviates from the design value. If the fusion operation is performed for a predetermined fusion time as it is, the branching ratio may deviate from a desired value. Therefore, if the deviation from the design value of the actual stretching length difference is checked, the fusion time is corrected according to the deviation, and the fusion is performed in accordance with the corrected fusion time. Further, the branching ratio can be made closer to a desired value.

[0012]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS A process for finding a solution based on the present invention described above and an embodiment of the present invention will be described.
The branching ratio of a wavelength-independent optical fiber coupler is determined by the outer diameter difference and the fusion time due to pre-stretching of the two optical fibers. When the fusion time is fixed, the branching ratio and the outer diameter difference of the pre-stretching are determined. Have a relationship as shown in FIG. The present invention focuses on the relationship of FIG. 1, and is suitable for the case where optical fiber couplers having desired branching ratios of various values are manufactured one after another.

First, the fusing time was previously set to a constant value, and FIG.
Alternatively, the outer diameter difference of the pre-stretching corresponding to the desired branching ratio is obtained from a graph corresponding thereto. FIG. 1 is a graph showing the relationship between the branching ratio and the outer diameter difference of the pre-stretching when the fusion time is set to 100 seconds. It is also possible to obtain the relationship with the diameter difference in advance and use it. When the outer diameter difference is determined, one or two optical fibers are pre-drawn so as to have the outer diameter difference, and are fusion-bonded according to a predetermined time, and then drawn. The manufacturing error of the branching ratio is ± 0.2 d
B is often required to be within B, and in that case, the manufacturing error of the pre-stretched outer diameter difference should be within ± 0.2 μm.

The outer diameter of the stretched portion in the pre-stretching is measured by a non-contact type measuring device. However, there is a heating burner and the like, so that there is considerable difficulty in the installation place of the measuring device. Therefore, paying attention to the relationship of FIG. 2 between the outer diameter difference of the pre-stretching and the stretching length, a difference in the stretching length corresponding to a desired branching ratio is determined using FIGS. 1 and 2. Then, instead of the difference in the outer diameter, the difference in the stretching length is measured. In order to keep the manufacturing error of the outer diameter difference within ± 0.2 μm, the manufacturing error of the stretching length difference needs to be within ± 20 μm. When two separate pre-stretching are performed, the manufacturing error of each stretching length needs to be within ± 10 μm.

In the case of stretching using a slider device equipped with a chuck as shown in FIG. 4, the stretching length is determined by fixing a reflector to the chuck, reflecting light from the reflector, and calculating the round-trip time difference of the reflected light. If the measurement is performed by measuring the displacement of the reflector, the measurement accuracy can be made extremely high, and there is no particular problem in determining that the deviation is within the above-described manufacturing error. FIGS. 1 and 2 show an example in which the fusion time is set to 100 seconds. Therefore, when the fusion time is set in advance to another value, the graphs corresponding to FIGS. 1 and 2 are prepared accordingly. To use.

Further, since the pre-stretching is performed by applying tension while heating, the actual stretching length may be deviated from the designed stretching length even if the pre-stretching of a predetermined stretching length is performed. In such a case, the actual branch ratio of the optical fiber coupler may deviate from the design value due to the deviation of the extension length. In order to avoid this, using the relationship shown in FIG. 3, according to the deviation from the design value of the actual drawing length difference in the pre-drawing, a correction is made to a predetermined fusing time for fusing two optical fibers. Add. Then, by performing the fusion in accordance with the corrected fusion time, the deviation of the branching ratio can be corrected. FIG. 3 shows that the branching ratio is 3.5 dB.
Is used as a standard, so a similar graph may be created for other branching ratios and used.

In the above description, an example is described in which the optical fiber coupler is formed by using two optical fibers of the same type. It is also possible to prepare two wires and make an optical fiber coupler between the corresponding cores of the two tape cores. FIG. 6 shows an example of such a multi-core optical fiber coupler. In this case, the glass fiber is exposed by removing the coating at the intermediate portion of the tape core 8, and both sides of the tape core are gripped. Pre-stretching, a difference in outer diameter is caused by pre-stretching between one tape core wire and the other tape core wire, and then the corresponding optical fibers are fused and drawn to obtain a multi-core optical fiber. A fiber coupler can be obtained.

[0018]

The method of manufacturing an optical fiber coupler according to the present invention is a manufacturing method in which the outer diameter of an optical fiber is made to be fusion-stretched by pre-stretching. When the optical fiber couplers having various branching ratios are manufactured, the branching ratio is determined according to the condition set based on the relationship between the branching ratio when the arrival time is set to a constant value and the outer diameter difference due to pre-stretching. Each time is changed, the preparation for setting the conditions is simplified.

Further, instead of performing the pre-drawing by determining the outer diameter difference of the glass fiber drawn part in the pre-drawing according to the desired branching ratio, the drawing length difference of the pre-drawing is determined according to the desired branching ratio. If the pre-stretching is performed so that the difference in the stretching length is obtained, the measurement becomes easy, and it is relatively easy to increase the measurement accuracy.

Further, a design value of the stretching length difference is determined according to a desired branching ratio, pre-stretching is performed, and a deviation from an actual stretching length difference from the design value is checked. Is corrected and the fusion is performed in accordance with the corrected fusion time, it is possible to further reduce the manufacturing error of the branching ratio.

[Brief description of the drawings]

FIG. 1 is a graph showing a relationship between a branching ratio and an outer diameter difference of a stretched portion by pre-stretching.

FIG. 2 is a graph showing a relationship between a difference in outer diameter of a stretched portion and a difference in stretch length by pre-stretching.

FIG. 3 is a graph showing a relationship between a deviation of a stretching length in pre-stretching and a correction value of a fusing time.

FIG. 4 is a front view illustrating an apparatus for manufacturing an optical fiber coupler.

FIGS. 5A, 5B, and 5C are diagrams illustrating a procedure for manufacturing a wavelength-independent optical fiber coupler.

FIG. 6 is a perspective view showing an example of an optical fiber coupler using a tape core.

[Explanation of symbols]

 1: First set slider device 1a, 2a: Chuck 2: Second set slider device 3: First optical fiber 3a, 4a: Glass fiber 4: Second optical fiber 5: Heating burner 6: Proximity direction 7, 9: Yarn 8, 10: Weight

Claims (3)

[Claims] 1. A glass fiber portion is prepared by removing a coating at an intermediate portion between two optical fibers of the same type to expose a glass fiber portion, and one or two of the glass fiber portions are reserved. The diameter is reduced by stretching, so that the stretched portion of the glass fiber has an outer diameter difference between the two optical fibers, and then the glass fiber portions of the two optical fibers are fused, and then the two are simultaneously stretched. A method of manufacturing an optical fiber coupler by doing, the pre-stretching and fusion, based on the relationship between the branching ratio and the outer diameter difference due to pre-stretching when the fusion time measured in advance is a constant value. A method for manufacturing an optical fiber coupler, wherein the method is performed according to set conditions. 2. A glass fiber portion is prepared by removing a coating at an intermediate portion between two optical fibers of the same type and exposing a glass fiber portion, and one or two of the glass fiber portions are reserved. The diameter is reduced by stretching, so that the stretched portion of the glass fiber has an outer diameter difference between the two optical fibers, and then the glass fiber portions of the two optical fibers are fused, and then the two are simultaneously stretched. A method for manufacturing an optical fiber coupler by doing, the pre-stretching and fusion, based on the relationship between the branching ratio and the stretching length difference by pre-stretching when the fusion time measured in advance is a constant value. A method for manufacturing an optical fiber coupler, wherein the method is performed according to set conditions. 3. A glass fiber portion is prepared by removing a coating at an intermediate portion between two optical fibers of the same type and exposing a glass fiber portion, and one or two of the glass fiber portions are reserved. The diameter is reduced by stretching, so that the stretched portion of the glass fiber has an outer diameter difference between the two optical fibers, and then the glass fiber portions of the two optical fibers are fused, and then the two are simultaneously stretched. In the method for manufacturing an optical fiber coupler by doing, the pre-stretching is set based on the relationship between the branching ratio and the stretching length difference due to the pre-stretching when the pre-measured fusion time is set to a constant value. Performed in accordance with the stretching length difference, the fusion time is corrected from a predetermined constant value according to the amount of deviation between the set stretching length difference and the measured stretching length difference to determine a corrected fusion time, and then corrected. At the time of fusion A method for manufacturing an optical fiber coupler, wherein fusion is performed in time.