JP2005284150A - Method of manufacturing core-expanded optical fiber, optical fiber, and optical connector - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To prevent optical characteristics of light loss, a reflection attenuation quantity, etc., from deteriorating even if fault events such as a flaw, a stain, and dirt are generated on an optical connector end surface, particularly on an optical fiber end surface, to make an optical connection with excellent optical characteristics under small influence of a flaw and dirt at a connection part, to facilitate alignment of an optical fiber with an optical component, and to provide a new method for manufacturing a core-expanded optical fiber which facilitates manufacture. <P>SOLUTION: While the center part of a multi-mode optical fiber 1 is heated, both ends are clamped and drawn to the right and left to cut the center part. The core diameter on one end surface is the core diameter (d) of a single-mode optical fiber and the diameter is increased in a tapered shape toward the other end, and two core-expanded optical fibers 3 having a core diameter D of the multi-mode optical fiber on the other end surface are obtained. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to a method of manufacturing a core-expanded optical fiber whose core diameter expands in a taper shape along the longitudinal direction of the optical fiber, an optical fiber using the core-expanded optical fiber by this manufacturing method, and this The present invention relates to an optical connector with an optical fiber.

For optical communication lines such as subscriber-side lines, backbone networks, and measurement diameters for testing lines, when connecting optical fibers with optical connectors, an optical connector incorporating an optical ferrule with an optical fiber inserted and fixed is used. Although used, as a means to achieve low connection loss in this type of optical connector connection, the tip surface of the optical ferrule is PC-polished, and the PC polished surfaces (connection end surfaces) of the optical ferrule are in physical contact with each other. The method of making it is common.
Further, when an optical fiber is connected to a light emitting element (light source), a light receiving element, an optical element or other optical components, the connection is performed after aligning the optical fiber and aligning the optical axis with the optical component. In this case, the optical component may be connected with an optical connector attached to the optical fiber.

In addition, the core diameter near the end face of a single-mode optical fiber has been increased in a tapered shape as an optical fiber that can reduce connection loss when connecting different types of optical fibers or connecting optical components with optical fibers. Core expansion optical fibers are known. In general, this type of conventional core-enlarging optical fiber manufacturing method generally distributes and heats the vicinity of the connection end face of a single-mode optical fiber to diffuse the doping agent added to the core, thereby expanding the core diameter into a tapered shape. The distributed heating diffusion method is adopted. This type of core-expanded optical fiber is generally also called a TEC fiber (Thermally-diffused Expanded Core Fiber) (see Patent Document 1 and Patent Document 2).
Paragraph number [0009] of JP-A-11-109185, etc. Paragraph number [0029] of Japanese Patent Laid-Open No. 5-119235

In FTTH, an optical ferrule for PC polishing is frequently used. However, an optical connector for PC connection tends to be scratched on the connection end surface of the optical ferrule when the optical connector is attached or detached. If scratches occur, optical connection loss increases.
Also, with this type of optical ferrule, if there are scratches or dust on the connection end face of the optical ferrule, when the scratch or dust is exposed to strong light, the scratched part will burn and the end face condition may deteriorate. There is sex. This further increases the optical connection loss. In such a case, the optical connector that has been precisely polished is expensive, so it is not discarded and the end face of the optical ferrule is again subjected to high scratch-free polishing. Scratchless polishing is often difficult.

  In addition to optical connector applications, when an optical fiber is connected to an optical element such as an LD or PD or other optical component, alignment work for aligning the optical axis of the optical fiber with respect to the optical component is not easy, and time is required. And productivity is low.

  As for the core-enlarged optical fiber, the above-described conventional manufacturing method has a problem that accurate control of the distributed heating is difficult when the optical fiber is distributed and heated with a burner, and the manufacturing is difficult and the yield is poor.

  The present invention has been made to eliminate the above-mentioned conventional drawbacks. Even if an optical connector end face, particularly an optical fiber end face, is damaged, such as scratches, dirt, dust, etc., light loss, return loss, etc. This makes it possible to prevent deterioration of characteristics, and enables optical connection with good optical characteristics with little influence of scratches and dust on the connection part even when a strong optical connection is made. The purpose is to facilitate alignment. Furthermore, it aims at providing the manufacturing method of the novel core expansion optical fiber with easy manufacture.

  The method of manufacturing a core-enlarged optical fiber according to claim 1, which solves the above-described problem, forms a softened portion by heating and softening a part of the optical fiber, and pulls and stretches at least one side of the softened portion, thereby A taper part centering on the part is formed, and then the core diameter of the cutting part is made smaller than the core diameters other than the cutting part by cutting the middle part of the taper part.

  The optical fiber of claim 2 has a core diameter smaller than that of the first optical fiber as the material, with the end surface on the narrow diameter side of the core-enlarged optical fiber manufactured by the method of claim 1 using the first optical fiber as the material. The second optical fiber is fusion spliced.

  According to a third aspect of the present invention, in the optical fiber according to the second aspect, the core diameter of the narrow diameter portion of the first optical fiber is the same as the core diameter of the second optical fiber.

  According to a fourth aspect of the present invention, in the optical fiber according to the second to third aspects, the first optical fiber is a multimode optical fiber, and the second optical fiber is a single mode optical fiber.

  An optical connector according to a fifth aspect is characterized in that at least the core expansion optical fiber portion of the optical fiber according to the fourth aspect is internally fixed to the front end side of the optical ferrule.

  According to the method for manufacturing a core-enlarged optical fiber according to claim 1, at least one side is stretched while heating a part (intermediate part) of the optical fiber to form a tapered portion, and the portion having a small diameter is cut. As a result, the core-enlarged optical fiber can be obtained, so that it is less difficult to control and easier to manufacture the core-enlarged optical fiber than the conventional distributed heating diffusion method that requires precise control of the distributed heating using a burner. . Moreover, productivity is high compared with the conventional method also in the point that two core expansion optical fibers are obtained simultaneously.

According to the optical fiber according to any one of claims 2 to 4 or the optical connector according to claim 5, when the optical connector is connected, the core diameter at the connection end face is large. Light loss is reduced. In addition, since the light intensity per unit area becomes weak, it is possible to avoid the problem that the fiber end face is burned by high heat and the end face is deteriorated even if there are scratches or dust on the end face. For this reason, it can be applied in the case of performing a high-strength optical connection.
Also, when connecting optical connectors between single mode optical fibers, the core diameter of the connection end faces of the optical connectors is large, and the accuracy required for positional displacement during the connection becomes loose. Connection becomes easy.

In addition, when connecting an optical connector between a multimode optical fiber and a single mode optical fiber, the core diameter at the connection end face is the same. However, it is possible to make an optical connector connection with little connection loss.
Also, the core-enlarged optical fiber according to the present invention is usually 125 μm in clad diameter like a general optical fiber. Therefore, any optical ferrule for an optical fiber hole diameter of 125 μm can be used regardless of shape, size, and material. The core expansion optical fiber according to the invention can be applied.

  Furthermore, when the optical fiber of the present invention is directly connected to a light emitting element, a light receiving element, an optical element, or other optical components, the core diameter of the connecting end face of the optical fiber is large, so that the alignment work for the optical components is easy. The same applies to the case where an optical connector is attached to an optical fiber to connect with an optical component.

  Hereinafter, a manufacturing method of a core expansion optical fiber, an optical fiber, and an optical connector which carried out the present invention are explained with reference to drawings.

The manufacturing method of the core expansion optical fiber of Claim 1 is demonstrated with reference to FIG. In the figure, reference numeral 1 denotes a short first optical fiber cut into an appropriate length, for example, a multimode optical fiber (hereinafter, the first optical fiber may be referred to as a multimode optical fiber). 1a is a core and 1b is a clad. The multimode optical fiber 1 is a general multimode optical fiber having a quartz diameter, and has, for example, a core diameter D of 50 μm and a cladding diameter of 125 μm.
A central portion of the optical fiber 1 is heated (schematically shown) by an appropriate heating means to form a softened portion, and both ends are gripped by the clamp means 2 around the softened portion, and at least one side is pulled. Preferably, the left and right clamps 2 are simultaneously pulled to the left and right ((A) in the figure). Then, a taper is formed. The core diameter d of the thinnest part at the center is a second optical fiber having a diameter smaller than the core diameter of the multimode optical fiber (hereinafter, the second optical fiber may be referred to as a single mode optical fiber). It is close to the core diameter. More preferably, it is the same as the core diameter of the single mode optical fiber ((b) in the figure). Next, the portion having the smallest diameter is cut (FIG. 3C). As a result, the core diameter at one end surface is the core diameter d of the single mode optical fiber, and the diameter is increased in a tapered shape toward the other end side. 2), two core expansion optical fibers 3 having a core diameter D of the multimode optical fiber are obtained. Note that the cutting position is arbitrary corresponding to the required core diameter, but when the core diameter on the narrow diameter side of the core expansion optical fiber 3 obtained in this way is smaller than the core diameter d of the single mode optical fiber, It is also conceivable to recut at the position of the core diameter d.

  In the manufacturing method of the above-described core-enlarging optical fiber, the core-enlarging optical fiber 3 can be obtained simply by cutting the thinned portion while heating the central portion of the optical fiber 1. Compared to the conventional distributed heating diffusion method that requires control of distributed heating, there is less difficulty in control and it is easy to manufacture a core-enlarged optical fiber. In particular, by pulling from both sides with the heating part as the center, a symmetrical core expansion optical fiber with the heating part as the center can be obtained.

  As shown in FIG. 2, the core-enlarged optical fiber 3 can be formed into a single optical fiber 5 by fusion-splicing to the single mode optical fiber 4 with the end face on the small diameter side as the inside. 4a is a core of the single mode optical fiber 4, and 4b is a clad. The fusion splicing method may be a general fusion splicing method. The core diameter d of the single mode optical fiber 4 is, for example, 10 μm, and the cladding diameter is 125 μm, as in the multimode optical fiber.

  FIG. 3 shows an optical connector 7 with an optical fiber in which the optical fiber 5 is attached to an optical ferrule 6. The portion of the core-enlarging optical fiber 3 in the optical fiber 5 is the tip side of the optical ferrule 6, and the optical fiber 5 including the tip portion 4c of the single mode optical fiber 4 is inserted into and fixed to the optical fiber hole 6a. Next, end face polishing is performed to form a connection end face 6b whose tip end of the optical fiber is spherically polished for, for example, PC connection, thereby completing the optical connector 7 with the optical fiber.

This optical connector 7 with an optical fiber can be connected to another optical connector, for example, as schematically shown in FIG. In the figure, the optical ferrule 6 of the optical connector 7 is accommodated in a connector housing 10, and the optical ferrule 6 of the optical connector 7 with both optical fibers is fitted into a sleeve 11 of an adapter (not shown) from both sides. And make a butt connection.
FIG. 5 shows another embodiment of the present invention, in which an optical connector 7 having an optical ferrule 6 attached to the tip of the optical fiber 5 and an optical ferrule 6 'to which an optical fiber 13 having a full length multimode optical fiber is fixed. The connector 17 is connected. The optical connector of the present invention can be used to connect an optical connector for a single mode optical fiber and an optical connector for a multimode optical fiber.

In this optical connector connection, since the core diameter at the connection end face a is the core diameter D of the multimode optical fiber, the light intensity per unit area is weaker than in the case of optical connection with a single mode optical fiber. . Therefore, the energy per unit area of the light emitted from the end face is reduced, and even if there are scratches or dust adhering to the end face, the fiber end face is burnt due to the intense light generating high heat in the scratched part or dust. The problem of degradation of optical characteristics can be avoided. For this reason, it can be applied in the case of performing a high-strength optical connection.
Moreover, in this optical connector 7 with an optical fiber, since the clad diameter at the tip of the core expansion optical fiber 3 is the same as the clad diameter of the single mode optical fiber, the optical ferrule and housing of the conventional general optical connector are used as they are. Therefore, the workability of the handling can be equivalent to that of the conventional optical connector.

Moreover, the optical fiber 5 of FIG. 2 mentioned above can be used for the optical system in an optical module (optical transmission / reception apparatus), for example, as shown in FIG. In this figure, 31 is an optical communication device, and 32 is an optical element connected to the optical communication device, for example, a light receiving element (PD). In this case, even if most of the optical fiber 5 is a single mode optical fiber, the core diameter D at the tip end face thereof, that is, the connection end face with the optical element 32 is large. In comparison, alignment work for aligning the optical axes of the optical element 32 and the optical fiber is facilitated. Even if the intensity of the light emitted to the optical element 32 is high, as described above, the core diameter at the connection end face is large and the light intensity per unit area is low, so that the influence of scratches and dust on the fiber end face is affected. Less is.
It can also be used in the same way for connection to optical elements such as lenses and other optical components.

It is a figure explaining one Example of the manufacturing method of the core expansion optical fiber of invention of Claim 1 according to the process order of (A), (B), (C). It is a figure of the optical fiber produced using the core expansion optical fiber obtained with the manufacturing method of FIG. It is sectional drawing of the optical fiber with an optical connector produced using the optical fiber of FIG. It is sectional drawing which shows the optical connector connection structure using the optical fiber with an optical connector of FIG. It is sectional drawing which shows the optical connector connection structure of a single mode optical fiber and a multimode optical fiber performed using the optical connector with an optical fiber of FIG. It is a figure explaining the case where the optical fiber of FIG. 2 is used for connection with optical components, such as an optical element of an optical module.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 1st optical fiber 1a, 1'a Core 1b, 1'b Clad 2 Clamp means 3 Core expansion optical fiber 3a Core 3b Clad 4 Single mode optical fiber (2nd optical fiber)
4a Core 4b Clad 5 Optical fiber 6 Optical ferrule 7, 17 Optical fiber with optical connector 8 Optical connector 10 Connector housing 11 Sleeve 13 Multimode optical fiber 13a Core 13b Clad 31 Optical communication equipment 32 Optical element (light receiving element)

Claims (5)

  A part of the optical fiber is heated and softened to form a softened part, and at least one side of the softened part is stretched to form a tapered part centered on the softened part, and then in the middle of the tapered part A method for producing a core-enlarged optical fiber, wherein the core diameter of the cut portion is reduced more than the core diameter other than the cut portion by cutting the core.   The end surface on the narrow diameter side of the core expansion optical fiber manufactured by the method of claim 1 using the first optical fiber as a material is fused to a second optical fiber having a core diameter smaller than that of the first optical fiber as the material. An optical fiber characterized by being connected.   The optical fiber according to claim 2, wherein the core diameter of the narrow diameter portion of the first optical fiber is the same as the core diameter of the second optical fiber.   4. The optical fiber according to claim 2, wherein the first optical fiber is a multimode optical fiber, and the second optical fiber is a single mode optical fiber.   An optical connector, wherein at least a core expansion optical fiber portion of the optical fiber according to claim 4 is internally fixed to the tip side of the optical ferrule.

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