JP2005084607A - Manufacturing method of optical fiber multiplexing/demultiplexing element - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To solve the problem in the manufacture of an optical fiber multiplexing/demultiplexing element, the problem in which, in the case of connection between an optical fiber on the incident side and an elongation part of a branching optical fiber, the core of the incident optical fiber and the core/clad of the elongation part of the branching optical fiber are to correspond to each other, so that for example light from the incident optical fiber entering the branching optical fiber is simultaneously made incident to the clad part of the branching optical fiber, generating a clad mode in the branching optical fiber and causing an undesirable effect in transmitting light. <P>SOLUTION: The elongation part of the branching optical fiber 3 is cut off in a manner containing a core 1. As a result, no core at the cut part is separated by the clad, which, in the connection with the optical fiber 5, makes the core of the optical fiber 5 integrally connect to the core of the elongation part of the branching optical fiber 3. Thus, no clad mode is generated, eliminating leakage of the clad mode as well as a possibility of accidents. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

  The present invention relates to a method of manufacturing an optical fiber multiplexer / demultiplexer, and more particularly to a method of manufacturing an optical fiber multiplexer / demultiplexer so that incident light from an incident optical fiber does not leak into a cladding.

  In recent years, with the development of optical fiber communication networks, various optical fiber-related elements have been used. Among them, many optical fiber multiplexing / demultiplexing elements are conventionally used, such as multiplexing a plurality of different signals into one optical fiber or demultiplexing one optical signal into a plurality of optical signals.

  Conventionally, several optical fiber multiplexing / demultiplexing devices or optical fiber multiplexing / demultiplexing device manufacturing methods are known as shown in FIG. That is, in FIG. 2A, two optical fibers 21 and 22 are prepared, and after aligning the two optical fibers 21 and 22, the intermediate portion 23 is fused and integrated while being heated and stretched. This is a method of manufacturing a fiber multiplexing / demultiplexing device (see, for example, Patent Document 1).

  FIG. 2B shows the arrangement of a plurality of optical fibers 21 and 22, and the aligned intermediate portion 23 is heat-sealed and then cut at the fused portion to place another optical fiber 24 at the cut portion. This is an optical fiber multiplexing / demultiplexing element that is fusion spliced (for example, see Patent Document 2).

  Further, FIG. 2 (c) is similar to FIG. 2 (b), in which a plurality of optical fibers 21 and 22 are aligned, and the aligned intermediate portion 23 is heat-fused and then cut at the fused portion to obtain the cut portion. The optical fiber multiplexing / demultiplexing element has a mixer rod 25 disposed between the cut portion and the optical fiber to be fusion-bonded when another optical fiber 24 is fusion-connected (for example, see Patent Document 3).

  FIG. 2D is an optical fiber multiplexing / demultiplexing device obtained by cutting one of the optical fibers 21 and 22 on the incident side of the optical fiber multiplexing / demultiplexing device manufactured by the method shown in FIG. (For example, refer to Patent Document 4).

In the conventional optical fiber multiplexer / demultiplexer as described above, a plurality of optical fibers are aligned and then stretched by heating and fusing the intermediate portion, but the stretched portion of other optical fibers to be fused is stretched. Since it is the same as the outer diameter, the core diameter is similarly reduced. However, no matter how thin it is, the configuration consisting of the core and the surrounding clad does not change.

  Therefore, as shown in FIG. 3, the cross section of the extended portion is composed of the cores 31a and 31b and the cladding 32 around the core. FIG. 3A shows a case where the cores 31a and 31b are circular, and FIG. 3B shows a case where the cores 31a and 31b are semicircular.

JP-A-5-307128 Japanese Utility Model Publication No. 64-36805 Japanese Utility Model Publication No. 63-107404 JP-A-7-198987

  By the way, the conventional techniques as described above have the following problems to be solved.

  That is, conventionally, as described above, after aligning a plurality of optical fibers, the intermediate portion is heated and fused to be stretched, the stretched portion is cut, and another optical fiber is fused and connected to the cut portion. When the incident side optical fiber is connected to the extension portion of the branching optical fiber, the core of the incident optical fiber corresponds to the core and cladding of the extension portion of the branching optical fiber. This means that, for example, when light from the incident optical fiber enters the branching optical fiber, the light also enters the cladding portion of the branching optical fiber.

  Therefore, a cladding mode is generated in the branching optical fiber, which is not preferable for transmitting light. Especially when high power light such as YAG laser is incident, the clad mode also becomes high power. If the clad mode leaks to the outside, it may lead to an accident even if the leak rate is low. Is concerned.

  From the above situation, branching of high-power laser light such as YAG laser processing has been conventionally performed by a system combining a mirror and a lens.

  The present invention has been made paying attention to the above points, and provides a method capable of manufacturing an optical fiber multiplexing / demultiplexing element that does not cause generation of a cladding mode or leakage in an optical fiber element that multiplexes / demultiplexes incident light. Is.

<Configuration 1>
One optical fiber composed of a core having a high refractive index and a clad having a low refractive index around it is bent into a U-shape to form an optical fiber for branching, and a glass rod is attached to the U-shaped portion bent into the U-shape of the optical fiber for branching. And the U-shaped portion is stretched by the glass rod, and then the stretched U-shaped portion is cut at a location where the core of the U-shaped portion is not separated by the cladding, and then the cut location. A method of manufacturing an optical fiber multiplexing / demultiplexing device, wherein another optical fiber is fused and connected to the optical fiber.

  When the U-shaped portion where the glass rod is fusion-bonded is extended, a portion where the core is not separated by the clad is formed. Here, when other optical fibers are fusion-connected, a connection portion that does not sandwich the clad is formed. Therefore, an optical fiber multiplexing / demultiplexing device in which the influence of the cladding mode is reduced can be manufactured.

<Configuration 2>
The straight portions 3A and 3B other than the U-shaped portion 3C of the branching optical fiber 3 are shaped so as to be substantially parallel, and the glass rod 4 is substantially parallel to the straight portions 3A and 3B of the branching optical fiber 3. The end of the glass rod 4 is fusion bonded to the substantially central side surface of the U-shaped portion 3C, and the U-shaped portion 3C is applied while applying a tensile force in a direction substantially parallel to the direction of the glass rod 4. The structure according to the first aspect, wherein the clad 2 on the side surface of the U-shaped portion 3C and the core 1 of the U-shaped portion 3C are bent into a pine needle shape by heating to provide a portion where the core is not separated by the clad. Manufacturing method of optical fiber multiplexing / demultiplexing element.

  The straight portions 3A and 3B are held substantially in parallel so that when a tensile force is applied by heating, the cross-section of the U-shaped portion 3C can be shaped into a pine needle shape with a substantially perfect circle and no distortion. The orientation of the glass rod 4 is also selected so that it is substantially parallel to the straight portions 3A, 3B of the branching optical fiber 3. When a U-shaped portion 3C is extended by applying a pulling force in a direction substantially parallel to the direction of the glass rod 4, ideal shaping can be performed.

<Configuration 3>
The cut portion of the U-shaped portion and the optical fiber are fusion-bonded so that the core diameter of the U-shaped portion of the branching optical fiber matches the core diameter of another optical fiber connected to the U-shaped portion. A method of manufacturing an optical fiber multiplexer / demultiplexer according to Configuration 1, wherein:

  Since the core diameters coincide at the cut portion of the branching optical fiber, that is, at the connection point between the branching optical fiber and another optical fiber, and the core is not separated by the cladding, the influence of the cladding mode is eliminated.

<Configuration 4>
A portion in which the core diameter of the other optical fiber 5 to be connected and the diameter of the core 1 of the cut surface of the U-shaped portion 3C are substantially the same, and the cross section of the core 1 of the cut surface is substantially circular Is selected as a cutting point. A method for manufacturing an optical fiber multiplexer / demultiplexer.

  By the shaping process as described above, the section of the core 1 of the cut surface of the U-shaped portion 3C is formed with a substantially circular portion, and another optical fiber 5 is connected to the portion so that the core diameter is substantially matched. Thus, it is possible to manufacture an optical fiber multiplexing / demultiplexing device having extremely good characteristics.

  Hereinafter, embodiments of the present invention will be described using specific examples.

  FIG. 1 shows a method for manufacturing an optical fiber multiplexer / demultiplexer according to the present invention. That is, as shown in FIG. 1A, a single optical fiber 3 is prepared that includes a core 1 having a high refractive index and its periphery, and includes a clad 2 having a refractive index lower than that of the core 1. The center of the optical fiber 3 is bent into a U shape to form a branching optical fiber. Next, as shown in FIG. 1B, one end face of the glass rod 4 is fused and connected to a portion bent into a U shape (hereinafter referred to as a U-shaped portion 3C). Thereafter, as shown in FIG. 1C, the glass rod 4 is pulled while the portion where the glass rod 4 is fused and the vicinity of the U-shaped portion 3C is heated, and the U-shaped portion 3C of the branching optical fiber 3 is extended. To do. And as shown in FIG.1 (d), the said expansion | extension part is cut | disconnected by a broken-line part. Finally, as shown in FIG. 1 (e), the cut portion and another optical fiber 5 are fusion-spliced.

  In the above operation, both end portions of the branching optical fiber 3, that is, the straight portions 3A and 3B other than the U-shaped portion 3C are shaped so as to be substantially parallel and fixed with an appropriate jig. Further, the direction of the glass rod 4 is selected so as to be substantially parallel to the straight portions 3A and 3B of the branching optical fiber 3, and the end surface of the glass rod 4 is fusion-bonded to the substantially central side surface of the U-shaped portion 3C. To do. The pulling direction is substantially parallel to the directions of the glass rod 4 and the straight portions 3A and 3B of the branching optical fiber 3. Thus, when the side surface of the U-shaped portion 3C of the branching optical fiber 3 is stretched while applying a pulling force, the U-shaped portion 3C is bent into a pine needle shape. When the clad 2 on the side surface of the U-shaped portion 3C is pulled, the core 1 is also pulled in the same direction while being bent.

  As shown in FIG. 1 (f), the result is a plane W passing through a broken line parallel to the end face of the glass rod 4 in the U-shaped portion 3C of the branching optical fiber 3 bent in a pine needle shape. When cut, the cross-sectional shape is as shown in FIG. That is, the core 1 exists in the center, the layer of the clad 2 surrounds the outer periphery thereof, and the core is not separated by the clad. As described above, the core is not separated by the clad, and the core diameter of the other optical fiber to be connected to the cut portion is substantially the same as the diameter of the core 1 of the cut surface. A portion having a substantially circular cross section may be selected as a cutting portion.

  As described above, even when another optical fiber 5 is connected to the cut surface, the core of the optical fiber 5 and the core of the extending portion of the branching optical fiber 3 are connected so as to be optically continuous as an integral core. Will be. That is, the cladding layer is not sandwiched. Further, when cutting the above-described extension portion, if the core diameter of the cut portion is made to be substantially the same as the core diameter of the optical fiber to be spliced, incident light enters the clad after the connection due to the mismatch of the core diameters. Therefore, the clad mode does not occur, and there is no possibility of an accident or the like without the clad mode leakage.

It is a figure showing embodiment of this invention. It is a figure explaining the manufacturing method of the conventional optical fiber multiplexing / demultiplexing element. It is a figure showing the cross section of the branch part of the conventional optical fiber multiplexing / demultiplexing element.

Explanation of symbols

1 core 2 clad 3 branching optical fiber 4 glass rod 5 optical fiber

Claims (4)

  One optical fiber composed of a core having a high refractive index and a cladding having a low refractive index around the core is bent into a U-shape to form an optical fiber for branching, and a glass rod is placed on the U-shaped portion bent into the U-shape of the optical fiber for branching. And the U-shaped portion is stretched by the glass rod, and then the stretched U-shaped portion is cut at a location where the core of the U-shaped portion is not separated by the clad, and then the cut location. A method of manufacturing an optical fiber multiplexing / demultiplexing device, wherein another optical fiber is fused and connected to the optical fiber.   The straight portions 3A and 3B other than the U-shaped portion 3C of the branching optical fiber 3 are shaped so as to be substantially parallel, and the glass rod 4 is substantially parallel to the straight portions 3A and 3B of the branching optical fiber 3. The end of the glass rod 4 is fused and connected to the substantially central side surface of the U-shaped portion 3C, and the U-shaped portion 3C is applied while applying a tensile force in a direction substantially parallel to the direction of the glass rod 4. The clad 2 on the side surface of the U-shaped part 3C and the core 1 of the U-shaped part 3C are bent into a pine needle shape by heating, and a portion where the core is not separated by the clad is provided. Manufacturing method of the optical fiber multiplexing / demultiplexing device.   The cut portion of the U-shaped portion and the optical fiber are fusion-spliced so that the core diameter of the U-shaped portion of the branching optical fiber matches the core diameter of another optical fiber connected to the U-shaped portion. The method of manufacturing an optical fiber multiplexer / demultiplexer according to claim 1.   A portion where the core diameter of the other optical fiber 5 to be connected and the diameter of the core 1 of the cut surface of the U-shaped portion 3C are substantially the same, and the cross section of the core 1 of the cut surface is substantially circular Is selected as a cutting point. A method for manufacturing an optical fiber multiplexer / demultiplexer.

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