JPH08201643A - Juncture of optical fibers and method for connecting the same - Google Patents

Abstract

PURPOSE: To provide a juncture of optical fibers with which reflection and gap loss are suppressed and a method for connecting these fibers. CONSTITUTION: The end faces 4 of at least one optical fibers 3 of the optical fibers 3 butted against each other in this juncture of the optical fibers formed by butting the end faces 4 of the optical fibers 3 against each other are formed to a projecting shape. The parts where the end faces 4 are butted against each other are provided with a greasy thermoplastic material 5.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an optical fiber connecting portion in which end faces of optical fibers are connected to each other and a connecting method thereof. More specifically, the present invention relates to optical fiber connecting members for various measurements of optical fibers. The present invention relates to a connecting portion of an optical fiber that is temporarily connected and a connecting method thereof.

[0002]

2. Description of the Related Art In measuring the connection loss of an optical fiber, a technique is employed in which an optical fiber for measurement and an optical fiber to be measured are butted and optically temporarily connected.
Specifically, connection with a connector, V provided on the board
Connections and the like via grooves are known. In both of these two methods, first, the connecting end face of the optical fiber (hereinafter simply referred to as the end face) is processed into a mirror surface, and the core is made into an optical connector or V
Accurate positioning with grooves so that axis misalignment hardly occurs. Next, the both ends of the optical fiber are brought closer to each other little by little, and the cores are butted against each other and optically connected.

However, when the optical fibers are temporarily connected to each other in measuring the connection loss of the optical fibers, the optical fiber on the master side (optical fiber for measurement) corresponding to the optical fiber to be measured has a life of its end face. Therefore, in order to avoid damage to the end faces, it is necessary to open a predetermined gap between both end faces. However, if nothing is done in this gap, it causes gap loss and reflection, which has an adverse optical effect. No effective preventive measure can be found for the gap loss except to make the gap between the end faces as small as possible.
There are several possible measures against reflection. Three representative ones are described below.

(1) A refractive index matching agent having the same refractive index as that of the core is filled between the end faces. (2) Make an antireflection film on the end face of the fiber. (3) Make the butt end faces diagonal.

Explaining the above three in detail, the method (1) of using a refractive index matching agent is the most commonly used method, and a core portion such as silicone oil is formed in the gap between the end faces of both optical fibers. It satisfies the refractive index matching agent having the same refractive index. By doing so, reflection does not occur at the boundary surface of the end faces, and the connection loss is reduced.

In the method (2), a film of metal or the like is vapor-deposited on the end face of the optical fiber to form a unidirectional transmission film, and the unidirectional transmission film prevents reflection at the end face boundary surface. The method (3) prevents the reflection by cutting the end face diagonally so that the direction of reflection does not coincide with the core axis of the optical fiber. These three types are well known as connection technologies for antireflection.

[0007]

The above-mentioned three connection techniques have the following problems, respectively. The method of using the refractive index matching agent of (1) can exert a great effect on antireflection.

However, even in the case of temporary connection for measuring the connection loss of the optical fiber, it is necessary to inject the refractive index matching agent into the abutting portion each time the connection is made. Therefore, a pump for injection and a tank for storing the matching agent are required. Further, if the matching agent is volatile, there is no problem even if it is left as it is after connection, but if it is a non-volatile matching agent, liquid treatment after connection is troublesome. Like this (1)
This method is inefficient in work.

In the case of the method (2) of forming an antireflection film, the antireflection film is formed by combining various kinds of metals, so that its design and manufacture are difficult. Further, since the antireflection film itself is a unidirectional transmission film, it cannot be used for optical measurement such as OTDR measurement that requires bidirectional transmission.

The method (3) of cutting the end face diagonally is effective for preventing reflection because the reflected light does not return to the core, but the light emitted from the end face is also bent by refraction. As a result, the situation becomes the same as when the axis shift occurs and the connection loss increases. Therefore, this method is not suitable for measuring connection loss.

SUMMARY OF THE INVENTION It is an object of the present invention to solve the above problems and provide an optical fiber connecting portion and a connecting method thereof in which reflection and gap loss are suppressed.

[0012]

The present invention has the following means in order to solve the above problems.

According to a first aspect of the present invention, an optical fiber connecting portion is an optical fiber connecting portion in which end faces of the optical fibers are butted to each other, and at least one of the optical fibers has a convex end face. And a grease-like thermoplastic substance is provided at the abutting portion of the end faces.

According to a second aspect of the present invention, the connecting portion of the optical fiber is characterized in that the convex end surface is spherical or conical.

A method of connecting optical fibers according to a third aspect of the present invention, which is a method of connecting optical fibers in which end faces of at least one of the optical fibers are convex, the end faces of the optical fibers are butted against each other. A grease-like thermoplastic substance is adhered to the end face of at least one of the optical fibers to be combined, and the end face of the other optical fiber is inserted into this grease-like thermoplastic substance so that the end faces of the optical fibers are joined together. It is characterized by butt connection.

[0016]

According to the optical fiber connecting portion and the optical fiber connecting method of the present invention, the end faces of at least one of the optical fibers are first formed in a convex shape. It becomes a form that dries a grease-like thermoplastic. Therefore, the thermoplastic resin can cover and protect the optical fiber tip coating removal portion. Also, since at least one of the end faces of the optical fiber has a convex shape, when connecting the end faces to each other,
The optical fiber easily dives into the thermoplastic material. In addition, a large impact force is applied to the optical fiber in the axial direction during the connecting work, but this impact force is also greatly reduced because the end faces of the optical fiber come into contact with each other while receiving the resistance of the thermoplastic material.

Further, regarding the provision of a light passage, since the tip of the optical fiber is a convex surface, the thermoplastic material is always pushed away and the center of the convex surface comes into contact. Moreover, since a force is applied to both optical fibers in the abutting direction (axial direction of the optical fibers), the core portions are elastically deformed and both core portions come into contact with each other. Since there is no gap at the contacted portion, reflection does not occur here, and there is no gap loss, so that low loss connection is possible. When the temporary connection for measuring the splice loss is completed, one optical fiber is pulled out from the thermoplastic material, but the other optical fiber end has a hole where one optical fiber is pulled out. The remaining thermoplastic material will remain attached. By applying heat to the remaining thermoplastic material by a suitable heating means, the thermoplastic material softens and returns to its original shape with the holes closed. Therefore, if the end face of another optical fiber is then inserted into the thermoplastic, a temporary connection such as a splice loss measurement can be achieved again quickly.

[0018]

The present invention will be described below in detail with reference to examples.

An embodiment of the connecting portion of the optical fiber of the present invention will be described with reference to FIG. In FIG. 1, 1 is an optical fiber core wire. The coating 2 at the end of the optical fiber core wire 1 is removed by a predetermined length to expose the optical fiber 3. The exposed end surface 4 of the optical fiber 3 is, for example, a convex surface formed in a spherical shape. The optical fibers 3 whose end faces 4 are convex surfaces are butt-connected to each other with the convex surfaces in contact with each other. A grease-like thermoplastic material 5 is provided on the outer periphery of the butted portion including the butted end faces 4.

The above-mentioned connecting portion of the optical fiber is formed as follows. 2 to 5 show an embodiment of the optical fiber connecting method of the present invention. As shown in FIG. 2, the end face 4
The two optical fibers 3 having a spherical surface and having a convex surface are set at the abutting positions so that the axes of the respective core portions 6 coincide with each other. At this time, the grease-like thermoplastic substance 5 is previously attached to the tip coating removal portion of the optical fiber 3 on the right side in the figure. This grease-like thermoplastic 5
As the material, silicon grease, solder grease, gum, or the like can be used. Thereafter, as shown in FIG. 3, the optical fiber 3 (the optical fiber 3 on the left side in the figure) to be butt-connected is brought close to each other and inserted into the grease-like thermoplastic substance 5.
At this time, since the end surface 4 of the optical fiber 3 has a spherical shape, the thermoplastic material 5 is pushed away to proceed. For the advancing optical fiber 3, the pushing away of the thermoplastic material 5 directly becomes a resistance, so that the impact at the time of contact between the end faces 4 of the optical fiber 3 is greatly alleviated.

Since the optical connection is a contact between spherical surfaces as shown in FIG. 1, it goes without saying that the center of the spherical surface, which is the contact point, is in contact. Further, since both optical fibers 3 receive a force in the abutting direction, they are elastically deformed and the core portions 6 come into contact with each other almost completely. Therefore, in this connection portion, no gap can be formed between the core portions 6, so that no reflection or gap loss occurs. After the measurement such as the splice loss measurement, as shown in FIG.
Is pulled out from the thermoplastic material 5, but the shape of the optical fiber 3 remains as it is, and when another optical fiber is connected for the next measurement or the like, when the end faces 4 of the optical fiber 3 come into contact with each other. Can not absorb the impact of.

Therefore, heat is applied to the thermoplastic material 5 to soften it by an appropriate heating device (not shown), and the thermoplastic material 5 is returned to the initial state as shown in FIG. On the other hand, instead of the pulled-out optical fiber 3, another optical fiber 3 is butted and connected. When the connection is not made, the thermoplastic material 5 covers the uncovered portion of the optical fiber 3 and thus serves to protect the uncovered portion. If, for example, a material having a refractive index similar to that of the core portion 6 is used as the thermoplastic material 5, even if the core portion 6 does not come into complete contact with the thermoplastic resin 5 even if the contact force is insufficient, Since the substance 5 also acts as a refractive index matching agent, it has an effect of preventing reflection and can realize a low loss connection. Further, it is more preferable if the thermoplastic substance 5 has a good transmittance.

Another embodiment of the optical fiber connecting portion of the present invention will be described with reference to FIG. In FIG. 6, 1A is an optical fiber core wire. The coating 2 at the end of the optical fiber core wire 1A is removed by a predetermined length to expose the optical fiber 3A. The exposed end surface 4A of the optical fiber 3A is a convex surface formed in a conical shape. Optical fibers 3A each having a conical end surface 4A are butt-connected with their convex surfaces in contact with each other. A grease-like thermoplastic material 5 is provided on the outer periphery of the butted portion including the butted end surface 4A. The above-mentioned connecting portion of the optical fiber shown in FIG.
The detailed description will be omitted because it is formed by the same procedure as in FIG.

[0024]

As described above, according to the optical fiber splicing portion and the optical fiber splicing method of the present invention, the end faces are first formed in a convex shape. Since the fiber is shaped so as to dive in the grease-like thermoplastic material, the optical fiber tip coating removal portion can be protected. Further, since the end faces are convex, the optical fiber is likely to dive into the thermoplastic material when the end faces are butt-joined and connected. In addition, since the optical fiber progresses while receiving a large force in the axial direction, that is, the facing direction, during the connection work, the optical fiber receives a large impact when the convex surfaces of the end faces come into contact with each other, but receives the resistance of the thermoplastic material. This impact is softened due to the contact.

Further, in order to secure the passage of light, since the tip of the optical fiber is a convex surface, the thermoplastic material is always pushed away and the center of the convex surface comes into contact. Moreover, since a force is applied to both optical fibers in the direction of butting, the core portion is elastically deformed and both cores come into contact with each other. Since there is no gap in the contact area, reflection does not occur here,
Since there is no gap loss, low loss connection is possible. Also,
When temporary connection such as splice loss measurement is completed, one of the optical fibers is pulled out from the thermoplastic material, but the other end of the optical fiber is a thermoplastic with a hole in which one optical fiber is pulled out. The substance will remain. By applying heat to the remaining thermoplastic material by a suitable heating means, the thermoplastic material softens and returns to its original shape with the holes closed. Therefore, a temporary connection, such as a splice loss measurement, can again be accomplished quickly by inserting the end of another optical fiber into the thermoplastic.

[Brief description of drawings]

FIG. 1 is a front view showing an embodiment of an optical fiber connecting portion of the present invention.

FIG. 2 is a front view showing a part of the process of an embodiment of the optical fiber connecting method of the present invention.

FIG. 3 is a front view showing another part of the process of the embodiment of the optical fiber connecting method of the present invention.

FIG. 4 is a front view showing another part of the process of the embodiment of the optical fiber connecting method of the present invention.

FIG. 5 is a front view showing another part of the process of the embodiment of the optical fiber connecting method of the present invention.

FIG. 6 is a front view showing another embodiment of the connecting portion of the optical fiber of the present invention.

[Explanation of symbols]

 1 Optical Fiber Core 1A Optical Fiber Core 2 Coating 3 Optical Fiber 3A Optical Fiber 4 End Face 4A End Face 5 Thermoplastic Material

Claims (3)

[Claims] 1. A connection portion of optical fibers in which end faces of optical fibers are butted to each other, wherein at least one of the butted optical fibers has a convex end face, and the end faces of the optical fibers are butted to each other. Optical fiber splicing part characterized in that a grease-like thermoplastic material is provided in the part. 2. The optical fiber connecting portion according to claim 1, wherein the convex end surface is spherical or conical. 3. A method of connecting optical fibers in which end faces of at least one of the optical fibers are in a convex shape, and the end faces of the optical fibers are in contact with each other. A grease-like thermoplastic substance is attached to the end face, and the end face of the other optical fiber is inserted into this grease-like thermoplastic substance and the end faces of the optical fiber are butt-joined to each other and connected. How to connect.