JP3010113B2 - 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 fusion drawing type optical fiber coupler, and more particularly to an optical fiber coupler having an excellent waterproof effect.

[0002]

2. Description of the Related Art Conventionally, a fusion-stretched optical fiber coupler is formed by fusing and extending a plurality of optical fibers to form a fusion-stretched portion, and splits light propagating through one optical fiber. It is used as a component for converging light that enters and propagates from a plurality of optical fiber terminals, and is used for optical communication and optical measurement using an optical fiber as a transmission medium.

[0003] This fusion-stretched optical fiber coupler 1
As shown in FIGS. 7 to 9, a coupler body 3 obtained by fusing and stretching a plurality of optical fibers on a base material called a protective case 2 is fixed using an adhesive and housed. It has a structure. The protective case 2 is formed by joining two members to form a hollow cylindrical or prismatic shape. Then, the coupler body 3 and the protective case 2 are fixed at both ends of the protective case 2 so that the adhesive is not applied to the fusion-stretched portion 5.

Incidentally, such an optical fiber coupler 1
When used outdoors, water resistance is required. In the optical fiber coupler 1 having the conventional structure,
There is a possibility that moisture may enter the inside of the protective case 2 due to a capillary phenomenon from a gap formed between the joint portions 6 of the two members constituting the protective case 2.

[0005] The infiltration of water by such a capillary phenomenon is as follows.
Appears remarkably when the capillary pressure is high. A factor determining the capillary pressure is a capillary radius, and it is known that the smaller the capillary radius, the higher the capillary pressure. For this reason, if the gap formed between the joining parts 6 is sufficiently small, there is a possibility that moisture may enter the inner end 7 of the joining part 6. Further, since the adhesive layer 4 formed of the adhesive is in contact with the inner side end 7 of the joint 6, moisture that has entered from the joint 6 is naturally absorbed by the adhesive layer 4, and In addition to the increase in the volume of the entirety 4, the shape of the adhesive layer 4 changes, and due to the change in the shape, stress is applied to the fusion-bonded stretched portion 5, and the fusion-bonded stretched portion 5 may be bent. Was. As a result, the bending of the fusion-spread portion 5 causes a problem such as leakage of light energy, a change in the distribution ratio of light energy, and the like, deteriorating the optical characteristics of the optical fiber coupler 1. there were.

[0006]

SUMMARY OF THE INVENTION The present invention has been made in view of the above circumstances, and an optical fiber coupler which is excellent in waterproofness and can maintain good optical characteristics for a long time even when used in water. It is intended to provide.

[0007]

SUMMARY OF THE INVENTION An object of the present invention is to provide an optical fiber coupler in which a fusion-stretched coupler body is housed in a coupler case, wherein the coupler case has a recess formed therein for housing the coupler body. And a lid that covers the opening of the container, the coupler case and the coupler body are fixed with an adhesive, and the adhesive layer formed by solidifying the adhesive is a second adhesive layer close to both end portions of the coupler case. The first adhesive layer is divided into a first adhesive layer and a second adhesive layer closer to the fusion-stretched portion than the first adhesive layer.
It filled rather between, the second adhesive layer, Orazu in contact with the junction between the lid and the housing portion of the coupler case, and the first
The problem is solved when the gap between the adhesive layer and the second adhesive layer is 0.5 mm or more . In addition, it is preferable that the outer diameter of the lid and the container is substantially the same, and the thickness of the peripheral wall of the container is 0.2 mm or more than the thickness of the peripheral wall of the lid. Further, it is also possible to solve the problem by using a groove having a width of 0.2 mm or more formed at the bottom of the concave portion of the housing and housing the fusion-stretched portion of the coupler body in this groove.

[0008]

According to the optical fiber coupler of the present invention, since the second adhesive layer is not in contact with the joint portion between the lid of the coupler case and the housing, the portion from the inner side end of the joint portion to the second adhesive layer is formed. Is formed with a gap portion larger than the gap formed between the joining portions, and the capillary pressure decreases rapidly from the inner end of the joining portion toward the inside of the coupler case. Further, as a coupler case, the outer diameter of the lid and the container is almost the same, and the thickness of the peripheral wall of the container is thicker than the thickness of the peripheral wall of the lid, or a fused extension is provided at the bottom of the concave portion of the container. Since the groove in which the accommodating groove is formed is used, it is easy to form an adhesive layer so that the adhesive does not come into contact with the joining portion,
In addition, a gap can be reliably formed between the joint portion and the second adhesive layer. Further, since the second adhesive layer is separated from the first adhesive layer, even if the first adhesive layer absorbs moisture and expands, the second adhesive layer is not affected by the expansion. In addition, it is possible to prevent stress applied to the fusion-stretched portion.

[0009]

Next, the optical fiber coupler of the present invention will be described in detail. 1 to 3 show an example of an optical fiber coupler 10 according to the present invention. The optical fiber coupler 10 generally has a structure in which a fusion-stretched type coupler body 11 is housed in a base material called a coupler case 12.

The coupler case 12 comprises a housing 13 and a lid 14 for covering the opening of the housing 13 and is formed by joining these with an adhesive or the like to form a cylindrical outer shape. is there. The container 13 and the lid 14
Each of them has an outer shape obtained by dividing a hollow cylindrical member into two in the longitudinal direction, and further has a concave portion 15 having a semicircular cross section in the longitudinal direction. The thickness of the container 13 and the lid 14 is formed so that the thickness of the container 13 is greater than the thickness of the lid 14. Therefore, by joining the container 13 and the lid 14, the coupler case is formed. Inside 12 is formed a void portion 16 whose cross section in the short direction has an inverted convex shape.

The housing 13 of such a coupler case 12
The fusion extending portion 17 of the coupler body 11 and the vicinity of the fusion extending portion 17 are accommodated therein. Further, the coupler case 12 and the coupler body 11 are fixed with an adhesive at both ends of the coupler case 12 and portions thereof on the side of the fusion extending portion 17 therefrom. Here, an adhesive layer formed by solidifying the adhesive applied to both ends of the coupler case 12 is hereinafter referred to as a first adhesive layer 18, and an adhesive obtained by solidifying the adhesive applied to the fusion-stretched portion 17 is referred to as an adhesive layer. The layer is referred to as a second adhesive layer 19.

The first adhesive layer 18 is formed on the coupler case 1.
2 are formed without gaps in the gaps 16 formed therein. On the other hand, as shown in FIG. 3, the second adhesive layer 19 is formed so as to fit in the recess 15 of the housing 13. The amount of the adhesive applied to form the first adhesive layer 18 and the second adhesive layer 19 is not particularly limited.
And the second adhesive layer 19 does not come in contact with
The second adhesive layer 19 is a joint portion 2 between the container 13 and the lid 14.
If it does not touch 0, it can be any amount.

The first adhesive layer 18 and the second adhesive layer 1
9 is separated by 0.5 mm or more . This is 0.5mm
If it is less than 1, when the first adhesive layer 18 expands by absorbing moisture, the first adhesive layer 18 comes into contact with the second adhesive layer 19 to bend the fusion-stretched portion 17, which may cause deterioration of optical characteristics. Because there is. Further, as the kind of the adhesive forming the first adhesive layer 18 and the second adhesive layer 19, those having low water absorption are preferable, and for example, epoxy adhesive, urethane adhesive and the like are preferable.

The difference between the thickness of the housing 13 and the thickness of the lid 14 is 0.2 mm or more . The horizontal portion 21 shown in FIG. 3 is formed by the difference in the thickness. When the horizontal portion 21 is less than 0.2 mm, the second portion 21 is formed so as not to contact the joint portion 20 between the containers 13 and 14. It is difficult to form the adhesive layer 19 of the above, and when moisture invades, the possibility that the moisture reaches the second adhesive layer 19 and the fusion-stretched portion 17 increases, and the arrival time also increases. This is because it becomes shorter.

In addition, the coupler case 12 shown in FIG. 4 can be used. This is a prismatic container 13 having a recess 15 formed in the longitudinal direction,
And a plate-like lid 14 for closing the opening of the housing 13. Further, a groove 22 having a rectangular cross section in the longitudinal direction is formed at the bottom of the concave portion 15 of the container 13.
Are formed. As shown in FIG. 5, the coupler body 11 is housed in the groove 22 and fixed with an adhesive. The formation position of the adhesive layer formed by solidification of the adhesive, the type of the adhesive, and the like are the same as those in the previous example. Further, the storage body 13 and the lid 14 of the coupler case 12 of this example may have the same thickness. Further, the groove 22 is 0.2 mm from both inner peripheral walls of the concave portion 15 of the container 13.
It is preferable that they are formed apart from each other. this is,
This is for the same reason that the horizontal portion 21 of the previous example is formed with a width of 0.2 mm or more.

In such an optical fiber coupler 10, a joint portion 20 between the lid 14 of the coupler case 12 and the container 13 is provided.
Does not come into contact with the second adhesive layer 19 and the horizontal portion 21 is formed when the lid 14 and the container 13 are joined, so that the second adhesive layer 19, a gap portion 16 is formed, and the capillary pressure is rapidly reduced. Therefore, the amount of water entering through a gap formed between the joint portion 20 of the lid 14 and the container 13 is significantly reduced, and the waterproof property is reduced. Thus, the optical fiber coupler 10 is excellent. Further, since the second adhesive layer 19 is separated from the first adhesive layer 18, the fusion-stretched portion 17 is not affected by swelling due to moisture absorption of the first adhesive layer 18. , 19 are not bent and the optical fiber coupler 10 has good optical characteristics.

(Embodiments) Hereinafter, specific examples will be shown to clarify the effects of the present invention. An optical fiber coupler 10 having the structure shown in FIGS. 1 to 3 was manufactured. The coupler body 11 has a core diameter of 8.0 μm, a cladding diameter of 125 μm, and a coating diameter of 250 μm.
The optical fiber was prepared by preparing two optical fibers having a length of 3 m and a length of 3 m, contacting the coating-removed portions from which a part of the coating had been removed with each other, and subjecting the contacted portion to heat fusion stretching by a burner.

The coupler case 12 has a length of 60 m.
m, a cylinder having an outer diameter of 4 mm was prepared. The thickness of the lid 14 of the coupler case 12 was 0.5 mm, and the thickness of the container 13 was 1.5 mm. Also,
The coupler case 12 and the coupler body 11 were fixed with epoxy adhesive at all four places.

The optical fiber coupler 10 is set at 40 ° C.
Into a water tank filled with hot water, the output optical power relative to the incident optical power was measured, and the variation in insertion loss was measured. As a result, as shown in FIG. 6, the optical fiber coupler 10 of the present invention only showed an increase in the insertion loss of 0.1 dB after 55 hours.

(Conventional Example) An optical fiber coupler 1 having the structure shown in FIGS. 7 to 9 was manufactured. The optical characteristics of the coupler body 3 are the same as those of the embodiment, except that the protective case 2 is a hollow cylindrical one having a length of 60 mm, an outer diameter of 4 mm, and both a lid and a container having a thickness of 1.0 mm. A similar experiment was performed using the same one. As a result, as shown in FIG. 6, in the conventional optical fiber coupler 1, an insertion loss of 0.1 dB was observed after 10 hours.

When the results of the example and the comparative example were compared, the elapsed time until an increase of the insertion loss of 0.1 dB was observed was 5.5 times that of the example. Therefore,
The optical fiber coupler 10 of the present invention is superior in waterproofness to the conventional optical fiber coupler 1 and can maintain good optical characteristics even when used in water for a long time.

[0022]

As described above, the optical fiber coupler of the present invention is an optical fiber coupler in which a fusion-stretched type coupler main body is accommodated in a coupler case, wherein the coupler case has a recess for accommodating the coupler main body. Is formed, a lid that covers the opening of the container, the coupler case and the coupler body are fixed with an adhesive, the adhesive layer formed by solidifying the adhesive, The first adhesive layer is closer to both sides of the coupler case and the second adhesive layer is closer to the fusion-stretched portion than the first adhesive layer.
Since the gaps in the case are filled without gaps and the second adhesive layer is not in contact with the combined site of the lid and the housing of the coupler case, the gap formed between the joints is formed inside the coupler case. A larger gap is formed, and the capillary pressure drops sharply from the inner side end of the joining portion toward the inside of the coupler case, so that the infiltration of moisture due to the capillary phenomenon is greatly reduced, and the waterproofness is excellent. It becomes an optical fiber coupler.
In addition, the second adhesive layer is 0.5 mm or more with the first adhesive layer.
Even if the first adhesive layer absorbs moisture and expands , the first adhesive layer is not affected by the separation, and the fusion-stretched portion does not bend due to the expansion of the first adhesive layer. There is no leakage of the light energy involved, and the optical fiber coupler has excellent optical characteristics. Further, as the coupler case, the outer diameter of the lid and the container is almost the same, and the thickness of the peripheral wall of the container is 0.2 mm or more than the thickness of the peripheral wall of the lid. Since a groove having a width of 0.2 mm or more for accommodating the fused extension portion of the coupler body is formed at the bottom, it is easy to form an adhesive layer so that the adhesive does not come into contact with the bonding site. And the second from the joint
Since the gap can be reliably formed between the adhesive layer and the adhesive layer, effects such as more remarkable waterproofness can be obtained.

[Brief description of the drawings]

FIG. 1 is a cross-sectional view of an optical fiber coupler of the present invention cut at a joint portion between a lid and a container.

FIG. 2 is a cross-sectional view of the optical fiber coupler of the present invention cut along an axis passing through the center of a lid and a housing.

FIG. 3 shows an embodiment of the optical fiber coupler of the present invention in FIG.
FIG. 2 is a cross-sectional view taken along the line II shown in FIG.

FIG. 4 is a perspective view showing one embodiment of a coupler case used for the optical fiber coupler of the present invention.

5 is a cross-sectional view of the optical fiber coupler using the coupler case shown in FIG. 4, which is cut in the vicinity of the center of a second adhesive layer.

FIG. 6 is a graph showing experimental results of an example and a comparative example.

FIG. 7 is a cross-sectional view of a conventional optical fiber coupler cut at a joint portion between two members.

FIG. 8 is a cross-sectional view taken along an axis passing through the centers of two members of a conventional optical fiber coupler.

FIG. 9 is a cross-sectional view of one example of a conventional optical fiber coupler cut along a line II-II shown in FIG.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 10 ... Optical fiber coupler, 11 ... Coupler main body, 12 ... Coupler case, 13 ... Container, 14 ... Lid, 18 ... First adhesive layer, 19 ... Second adhesive layer, 22 ... Groove

────────────────────────────────────────────────── ─── Continuation of front page (56) References JP-A-4-281407 (JP, A) JP-A-4-313709 (JP, A) JP-A-4-40203 (JP, U) (58) Investigated Field (Int.Cl. ⁷ , DB name) G02B 6/28-6/293

Claims (3)

(57) [Claims] 1. An optical fiber coupler in which a fusion-stretched coupler body is housed in a coupler case, wherein the coupler case has a housing having a recess for housing the coupler body, and an opening of the housing. It consists of a lid that covers, and the coupler case and the coupler body is fixed by an adhesive, the adhesive layer wherein the adhesive is solidified in a first adhesive layer close to the both ends of the coupler case, this bisected more second adhesive layer close to the fused and extended portion, the first adhesive layer
The gap in the coupler case is filled without gaps, the second adhesive layer is not in contact with the joint portion between the lid of the coupler case and the container , and the first adhesive layer and the second adhesive layer Between
An optical fiber coupler having a distance of 0.5 mm or more . 2. The optical fiber coupler according to claim 1, wherein the outer diameter of the lid is substantially the same as that of the housing, and the thickness of the peripheral wall of the housing is larger than the thickness of the peripheral wall of the lid. An optical fiber coupler having a thickness of 0.2 mm or more . 3. The optical fiber coupler according to claim 1, wherein a groove having a width of 0.2 mm or more is formed at the bottom of a concave portion of the housing as the coupler case, and the coupler main body is formed in the groove. An optical fiber coupler accommodating a fusion-stretched portion of (1).