JP2003167155A - Optical fiber coupler and its manufacturing method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an optical fiber coupler that is highly protective while suppressing fluctuation of polarization characteristics. <P>SOLUTION: In the optical fiber coupler, two optical fibers are welded in a fused part and split in a branching part situated at both ends of the fused part. The adhesive that fixes the fused part and the branching part of the optical fiber in a case is characterized by having a Young's modulus of 50-1000 N/mm<SP>2</SP>at least in the area where the adhesive is in direct contact with the optical fiber with the coating removed. <P>COPYRIGHT: (C)2003,JPO

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an optical fiber type coupler and a method of manufacturing the same, and more particularly to optical branching and coupling,
Alternatively, the present invention relates to a protection method for an optical fiber coupler that performs demultiplexing and multiplexing.

[0002]

2. Description of the Related Art An optical fiber type coupler is a device that splits and couples light between a plurality of optical fibers. After removing a part of the coating of a plurality of optical fibers and bringing them into contact with each other, they are heated. By doing so, fusion-bonding and stretching are carried out to manufacture. In the sealed and stretched portion, the bare fiber is exposed and the fiber diameter is small, so it is necessary to protect the taper portion by housing it in a case.

Conventionally, in order to form an optical fiber coupler having stable characteristics against environmental changes, as shown in FIGS. 5 (a) to 5 (d), the optical fiber coupler is inserted into the case 6 and the covering portion is formed. 7 is fixed by the first adhesive member 104 having high hardness, and the bare fiber portion is the second adhesive member 1 having low hardness.
A method of fixing with 05 has been proposed (Japanese Patent Laid-Open No. Hei 5)
No. 19137). In this method, by fixing the covering portion 7 with an adhesive having a high hardness, it is possible to prevent characteristic variations due to vibration and the like, and by bonding the bare fiber portion with the adhesive 105 having a low hardness, the bare fiber portion is bare. The stress applied to the fiber portion can be made extremely small, and the fluctuation of the polarization characteristics can be neglected. 5A is an upper side view, FIG. 5B is a top view, FIG. 5C is a sectional view taken along line CC, and FIG. 5D is a sectional view taken along line DD.

Secondly, it is intended to provide a protective structure and a protective method capable of increasing the fixing strength to the case and significantly reducing the stress applied to the bare fiber, and FIG. A fixing method as shown is also proposed (Japanese Patent Laid-Open No. 5-150140).

In this method, as shown in FIGS. 6A to 6E, a case 6 for accommodating a bare fiber which is not stretched when the optical fiber coupler F is fused and stretched, and this bare fiber portion are fixed. A first adhesive member 204 and a second adhesive member 205 that covers the first adhesive member and fixes the bare fiber portion to the case are provided, and the second adhesive member 204 is the first adhesive member 205. It is characterized by being formed of a material having higher hardness. 6A is a perspective view, FIG. 6B is a BB sectional view, FIG. 6C is a CC sectional view, FIG. 6D is a DD sectional view, and FIG. 6E is an EE sectional view. Is.

Thirdly, a method of fixing the glass portion to the case with an adhesive has been proposed (Japanese Patent Laid-Open No. 8-146).
245). In this example, as shown in FIG. 7, both ends of the non-fusion extended portion 12B extending outward from the fusion extended portion 12A of the coupler body 12 are bonded to the base 11 with the first adhesive 13, The second adhesive 14 adheres to the base 11. Then, as the first adhesive 13, one having a high viscosity and low hardness over a wide temperature range and a low softening temperature is used, and as the second adhesive 14, one having a high hardness over a wide temperature range and a high softening temperature is used. ing.

[0007]

In the case of the above-mentioned first method, if the glass is covered with a soft adhesive, the pigtail is easily broken when pulled.
This is because the fused part of the optical fiber is actually fused only in some places, so when pulling, stress concentrates on the small part that is fused, and if any one of them is torn, It is thought that this is due to breakage.

Further, the second method has a problem that the polarization characteristic is not sufficient. It is considered that this is because the entire bare fiber portion is covered with the hard first adhesive member 204.

Further, in the case of the third method, if the bare fiber portion is covered over a long region only with the hard adhesive, the polarization coupler cannot obtain the target polarization characteristic even at room temperature. is there. This is due to the stress at the time of curing and shrinkage of the adhesive, and it is considered that the shrinkage stress is large when the Young's modulus is large.

The present invention has been made in view of the above circumstances, and an object thereof is to provide an optical fiber type coupler having high protection while suppressing fluctuations in polarization characteristics.

[0011]

In the present invention, therefore, there is provided an optical fiber type coupler which is branched at a fused portion in which at least two optical fibers are fused and branch portions located at both ends of the fused portion. Then, at least in the region where the adhesive for fixing the fusion-bonded portion and the branched portion of the optical fiber in the case is in direct contact with the peeled portion of the optical fiber, the Young's modulus is 50 to 1000 N / mm ^2. Is characterized in that. According to such a configuration, the area directly contacting the peeled portion of the optical fiber has a Young's modulus of 50 to
Since it is coated with an adhesive that is 1000 N / mm ² ,
It becomes possible to fix so as to satisfy both the fixed strength and the polarization characteristic. Therefore, it is possible to obtain a highly reliable optical fiber type coupler with reduced fluctuations in polarization characteristics.

Preferably, the optical fiber type coupler is
It is a polarization maintaining type optical fiber type coupler. With this configuration, it is possible to obtain good polarization maintaining characteristics.

Preferably, the adhesive is filled in two places in the case so as to cover the branch portion and contact the inner wall of the case. According to this configuration, the adhesive having a hardness that does not affect the polarization characteristics is applied to the position where the loss does not increase. Therefore, it is possible to provide a polarization-maintaining optical fiber coupler having a target polarization characteristic without breaking the glass even when the pigtail is pulled.

Further, it is preferable that the adhesive is formed in a band shape at three or more places in the case. According to such a configuration, the optical fiber coupler is firmly fixed to the case at a large number of places, so that the tensile strength is increased, and at the same time, since it is formed in strips at intervals, deterioration of polarization characteristics is prevented. It

Preferably, the adhesive is a UV-curable acrylic adhesive or a UV-curable epoxy adhesive. According to this structure, it is possible to cure the resin efficiently by UV irradiation, and it is possible to form a highly reliable optical fiber type coupler.

Further preferably, the optical fiber has a second Young's modulus higher than that of the adhesive at the boundary between the coated portion and the peeled portion in the case.
It is characterized by being fixed by the adhesive of. According to this structure, since the covered portion is covered with the second adhesive having a high Young's modulus, it is possible to more firmly fix and improve the tensile strength without lowering the polarization characteristics. It will be possible.

Further, in the method of the present invention, a peeling step of partially peeling the outer jackets of the two fibers, a step of fusion-stretching the glass portions of each other at the peeled portions, and the fused portion in the case. And the adhesive selected to have a Young's modulus of 50 to 1000 N / mm ² so as to cover the branched portions of the optical fibers located at both ends of the fused portion and to contact the inner wall of the case. And a step of filling the agent into at least a part of the peeled portion in the case.

According to the method of the present invention, it is possible to improve the manufacturing yield in addition to the effect of the coupler described above.

[0019]

BEST MODE FOR CARRYING OUT THE INVENTION Embodiments of the present invention will be described in detail below with reference to the drawings. Embodiment 1 An optical fiber type coupler according to a first embodiment of the present invention is shown in FIG.
FIG. 2 is a perspective view and FIG. 2 is a top view. As shown in FIG. 2, at least two optical fibers 1a and 1b are fused together, and an optical fiber is branched at branch portions located at both ends of the fused portion. In the type coupler, Young's modulus is 50 to 1000 N / mm in an area where the adhesive for fixing the fused portion and the branched portion of the optical fiber in the case is in direct contact with at least a portion where the coating of the optical fiber is peeled off. It is characterized by being ² . That is, this adhesive has a Young's modulus of 51 N /
It is composed of a mm ² UV curable acrylic adhesive.

In each of the optical fibers 1a and 1b, a glass wire having a diameter of 125 μm is coated with a resin jacket to form a coating portion 7. Further, in the fusion portion 2, the optical fiber is fusion-stretched and the diameter of one glass fiber is 15 microns and the fusion length is 15 mm. In addition, this case 6
This is a square container made of quartz glass having an inner diameter of 0.7 × 0.7 × 67 mm, and is configured such that a lid 6a made of quartz glass having a diameter of 0.87 × 2 × 17 mm is attached to the central portion.

Next, a method of manufacturing this optical fiber type coupler will be described. First, as shown in FIG. 3, the coatings on the first and second optical fibers 1a and 1b are removed, and their glass portions are heated, fused and stretched.

Thereafter, as shown in FIG. 2, the first and second
A curable acrylic adhesive having a Young's modulus of 51 N / mm ² UV is applied so as to cover the branched portions 3 of the optical fibers 1a and 1b in a coating length L of 26 mm. Here, 0.013 cc is applied to each end of the case 6 at each location.

After that, the lid 6a is placed, and the U of 120 mW is placed.
Irradiate with V light for 20 minutes to cure the adhesive. Thus, the optical fiber type coupler as shown in FIGS. 1 and 2 is completed.

The optical fiber type coupler thus formed was pulled one by one in a direction parallel to the case with a pigtail by a tensile tester called Tensilon.
Here, the state of fiber breakage was examined by pulling up to 10 N at a pulling speed of 10 mm / min. As a result, it did not break at 10 N, and it passed. The polarization crosstalk of the optical fiber type coupler formed in this manner was measured by an extinction ratio monitor VPMM-100 manufactured by Suruga Seiki. As a result, it was 31 dB, which was a pass. (Here, 18 dB or more is regarded as a pass).

As described above, the optical fiber type coupler according to the first embodiment of the present invention has a high reliability with no deterioration in polarization characteristics and an excellent tensile strength.

Next, the adhesive strength was changed variously, and the tensile strength and the polarization crosstalk were measured for each optical fiber type coupler. The results are shown in the table below.

[0027] A: UV curable acrylic adhesive: Young's modulus 9 N / mm ² B: UV curable acrylic adhesive: Young's modulus 51 N / m
m ² C: UV curable epoxy adhesive: Young's modulus 210 N / m
m ² D: UV curable epoxy adhesive: Young's modulus 940 N / m
m ² E: UV curable acrylic adhesive: Young's modulus 1240 N /
It was formed so that the coating length L was 26 mm at two places including the branched portion in all of mm ² .

When the Young's modulus of the adhesive was less than 50 N / mm ² , the tensile strength was not sufficient, as is clear from Comparative Example 4. Also, the Young's modulus of the adhesive is 1000
When it exceeded N / mm ^2, as is apparent from Comparative Example 5, the polarization characteristics deteriorated. It is considered that this is because the polarization characteristics change due to non-uniform stress and the target polarization characteristics cannot be obtained.

From the above experimental results, it was found that good results can be obtained in both tensile strength and polarization characteristics when the Young's modulus of the adhesive is 50 to 1000 N / mm ² .

Embodiment 2 Next, an optical fiber type coupler according to a second embodiment of the present invention will be described. In the first embodiment, the hard adhesive is formed only on a part of the branch portion. However, in this example, as shown in FIG. 6, a coated portion inside the case 6 and a portion where the coating is peeled off are further formed. Young's modulus 2500 N / m at the boundary of
m ² UV curable acrylic adhesive (second adhesive) 5
Is applied.

Other parts were formed in exactly the same manner as in the first embodiment. According to such a configuration, it becomes possible to obtain a stronger fixed state, and it is possible to obtain a hard second
Since the area to which the adhesive is applied is the covered portion, it does not affect the polarization characteristics.

[0032]

As described above, in the optical fiber type coupler of the present invention, at least the coating of the optical fiber is peeled off by the adhesive for fixing the fused portion and the branched portion of the optical fiber in the case. Since the Young's modulus is set to 50 to 1000 N / mm ² in the region that directly contacts the open portion, it is possible to enhance the protection property and reduce the fluctuation of the polarization characteristic.

In the method of the present invention, Young's modulus is 50 to 1
Since the adhesive selected to be 000 N / mm ² is filled in at least a part of the peeled portion in the case, fluctuations in polarization characteristics are reduced, and a highly reliable optical fiber type A coupler can be provided.

[Brief description of drawings]

FIG. 1 is a diagram showing an optical fiber type coupler according to a first embodiment of the present invention.

FIG. 2 is a diagram showing a manufacturing process of the optical fiber type coupler according to the first embodiment of the present invention.

FIG. 3 is a diagram showing a manufacturing process of the optical fiber type coupler according to the first embodiment of the present invention.

FIG. 4 is a diagram showing an optical fiber type coupler according to a second embodiment of the present invention.

FIG. 5 is a diagram showing a conventional optical fiber type coupler.

FIG. 6 is a diagram showing a conventional optical fiber type coupler.

FIG. 7 is a diagram showing a conventional optical fiber type coupler.

[Explanation of symbols]

1a, 1b optical fiber 2 Fusion part 3 branches 4 adhesive 5 Second adhesive 6 cases 6a lid 7 Cover 104 First adhesive member 105 Second adhesive member 204 First adhesive member 205 Second adhesive member 11 bases 12 Coupler body 12A fusion splicing part 12B Non-fusing extension part 13 First adhesive 14 Second adhesive

   ─────────────────────────────────────────────────── ─── Continued front page    (72) Inventor Maki Ike             Sumitomoden 1 Taya-cho, Sakae-ku, Yokohama-shi, Kanagawa             Ki Industry Co., Ltd. Yokohama Works

Claims (5)

[Claims] 1. An optical fiber type coupler in which at least two optical fibers are fused and a branch portion located at both ends of the fused portion is branched. The Young's modulus is 50 at least in the region where the adhesive for fixing the attachment part and the branch part in the case is in direct contact with at least the part where the coating of the optical fiber is peeled off.
An optical fiber type coupler characterized in that it is up to 1000 N / mm ² . 2. The optical fiber type coupler is a polarization maintaining type optical fiber type coupler.
The optical fiber type coupler described in. 3. The optical fiber according to claim 1, wherein the adhesive is filled in two places in the case so as to cover the branch portion and come into contact with the inner wall of the case. Type coupler. 4. The optical fiber is fixed in the case by a second adhesive having a Young's modulus higher than that of the adhesive at the boundary between the covered portion and the peeled portion in the case. The optical fiber type coupler according to any one of claims 1 to 3, wherein 5. A peeling step of partially peeling the jackets of the two fibers, a step of fusion-stretching the glass portions of each other at the peeling portion, and arranging the fused portions in a case. The Young's modulus is 5 so as to cover the branched portions of the optical fibers located at both ends of the fused portion and to contact the inner wall of the case.
Filling at least a part of the peeled portion in the case with an adhesive selected to be 0 to 1000 N / mm ² .