JP2007094156A - Optical fiber coupler and its manufacturing method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an optical fiber coupler capable of maintaining satisfactory transmission characteristic with a simple structure. <P>SOLUTION: The coupler 1 has a two-layered structure composed of core parts 11, 21 extending along center axes CL1, CL2 and clad parts 12, 22 covering the circumference of the core parts. In addition, the coupler is equipped with a pair of optical fibers 10, 20 each having a planar shaped cross section 13, 23 formed by machining on a part of the side face, wherein the cross sections 13, 23 are made to form a joined part 2 by joining to each other. Since the cross sections 13, 23 of the optical fibers 10, 20 are designed to be mechanically joined without applying heat, no thermal contraction nor change in quality is caused in the core parts 11, 21. As a result, it is possible to synthesize optical fluxes propagating each of the optical fibers 10, 20 or to proportionate the optical flux propagating one of the optical fibers 10, 20 to the other fiber. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to an optical fiber coupler that distributes or combines light beams propagating in an optical fiber, and a method for manufacturing the same.

  Generally, an optical fiber made of plastic or glass is used as an optical signal transmission path. Conventionally, a plastic optical fiber has a transmission loss larger than that of a glass optical fiber, so that its application has been limited to illumination and a display. However, in recent years, loss reduction has progressed, and the use of plastic optical fibers in the information communication field has begun to spread. Compared with glass optical fiber, the advantage of plastic optical fiber is its total cost including ease of handling, material cost and processing cost. For this reason, recently, for example, adoption in a control system such as an optical LAN or automobile equipment in a small-scale area has been studied, or a part of the system has begun to be introduced.

In constructing such an optical communication network, since it is necessary to distribute or combine optical signals, an optical fiber coupler is used. As this optical fiber coupler, there are a plurality of plastic optical fibers fused and stretched by discharge heating (for example, refer to Patent Document 1) and those fused by ultrasonic waves (for example, refer to Patent Document 2).
JP 59-7921 A JP 2001-166178 A

  However, in the optical fiber coupler that has been connected by fusion as described above, there is a concern about the influence of heat on the plastic optical fiber. Specifically, the core portion of the plastic optical fiber is contracted or altered by heat, which may increase transmission loss. Recently, in addition to a single mode (SM) type plastic optical fiber, a graded index (GI) type plastic optical fiber having a continuous refractive index profile, which has been difficult to manufacture, has been developed. If the core plastic optical fiber undergoes thermal contraction or alteration of the core, it is difficult to maintain the original refractive index distribution, and the transmission characteristics cannot be fully exhibited. In addition, in order to manufacture the above-described fusion spliced optical fiber coupler, a predetermined fusion device is required and the operation is complicated.

  The present invention has been made in view of such problems, and an object of the present invention is to provide an optical fiber coupler capable of maintaining good transmission characteristics with a simple configuration, and to provide such an optical fiber coupler more. An object of the present invention is to provide an optical fiber coupler manufacturing method that can be easily manufactured.

  The first optical fiber coupler of the present invention has a two-layer structure of a core portion extending along the central axis and a clad portion covering the periphery of the core portion, and is formed by machining on a part of the side surface. A pair of optical fibers each having a planar processed cross section including a core part and a clad part are provided, and the processed cross sections are joined together to form a joined part. A side surface here means the surface along the propagation direction of the light beam which passes a core part. The processed cross section includes a core portion and a clad portion and refers to a cross section along the central axis of the core portion.

  In the first optical fiber coupler of the present invention, since the processing cross sections of the two optical fibers are mechanically joined without applying heat, the core portions of each other can be produced without causing thermal contraction or alteration of the core portions. Can be synthesized, or the light beam propagating through one core can be distributed to the other. In addition, since the processed cross-sections of both optical fibers extend along the propagation direction of the light beam, efficient light transmission / reception can be performed and transmission loss can be reduced.

  The second optical fiber coupler of the present invention has a two-layer structure composed of a core portion extending along the central axis and a cladding portion covering the periphery thereof, and a predetermined distance from the first end surface along the side surface. A first optical fiber and a second optical fiber each having a planar processed cross section including a core portion and a clad portion, and a third optical fiber having a second end face, The processed cross sections of the first and second optical fibers are joined to each other, and the first end face and the second end face are joined to each other to form a Y shape. The term “end face” as used herein means a cross section orthogonal to the central axis of the core portion or a cross section that crosses the optical fiber in the radial direction.

  In the second optical fiber coupler of the present invention, the processed cross sections of the first and second optical fibers and the first and second end faces are mechanically joined without applying heat, respectively. The light beams propagating through the first and second optical fibers can be combined without causing thermal contraction or alteration of the core portion, or the light beams propagating through the third optical fiber can be distributed to the other. In addition, since the processed cross sections of the first and second optical fibers extend over a predetermined distance along the propagation direction of the light beam, efficient light exchange can be performed and transmission loss can be reduced. it can.

  In the method of manufacturing an optical fiber coupler of the present invention, an optical fiber having a two-layer structure of a core portion extending along the central axis and a clad portion covering the periphery of the core portion is placed around a columnar member having a constant diameter. After winding, forming a processed cross section including both the core part and the clad part by collectively machining a part of the side surface of the optical fiber, and dividing the optical fiber into a plurality of parts, The method includes a step of forming a plurality of optical fiber elements including a processed cross section and a step of forming a joint portion by bonding the processed cross sections of the optical fiber elements.

  In the manufacturing method of the optical fiber coupler of the present invention, since the processing cross sections of the two optical fiber elements are mechanically joined without applying heat, the cores of each other can be produced without causing thermal contraction or alteration of the core portion. An optical fiber coupler capable of combining the light beams propagating through the portion or distributing the light beam propagating through one core portion to the other is obtained. Further, the processed cross section of both optical fibers extends along the direction of propagation of the light beam, so that an efficient transmission / reception of light is performed and an optical fiber coupler capable of reducing transmission loss is obtained. Furthermore, after the optical fiber is wound around a columnar member having a certain diameter, a part of the side surface of the optical fiber is machined together to form a processed cross section. The optical fiber element having the same shape can be obtained easily and in large quantities.

  According to the first optical fiber coupler of the present invention, each of the pair of optical fibers has a planar processed cross section including both the core portion and the clad portion formed by machining on a part of the side surface, Since the joining portion is formed by joining the processed cross sections, it is possible to synthesize or distribute the light beams while maintaining a good transmission characteristic with a simple configuration.

  According to the second optical fiber coupler of the present invention, the first processed cross section including the core portion and the clad portion formed by machining along the side surface from the first end surface over a predetermined distance is included. A first optical fiber, a second optical fiber, and a third optical fiber having a second end face, wherein the processed cross sections of the first and second optical fibers are joined to each other, and the first and second end faces are joined to each other. Therefore, the light beam can be combined or distributed while maintaining a good transmission characteristic with a simple configuration.

  According to the method for manufacturing an optical fiber coupler of the present invention, after winding an optical fiber having a two-layer structure of a core part and a clad part around a columnar member having a certain diameter, a part of the side surface of the optical fiber is collectively Forming a processed cross section including both the core portion and the clad portion by machining, and further dividing the optical fiber into a plurality of optical fiber elements including at least one processed cross section, Since the joints are formed by joining the processed cross sections of the fiber elements, an optical fiber coupler that can synthesize or distribute light beams while maintaining good transmission characteristics with a simple configuration is easy. And it can be manufactured in large quantities.

  Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings.

  First, the configuration of an optical fiber coupler according to an embodiment of the present invention will be described with reference to FIGS. FIG. 1 is a partially cutaway view showing a perspective configuration of an optical fiber coupler 1 (hereinafter simply referred to as a coupler 1) of the present embodiment. The coupler 1 includes a pair of optical fibers 10 and 20 that are joined with each other in contact with each other at the joint portion 2 and a holding member 3 that holds the optical fibers 10 and 20.

  FIG. 2 is an exploded cross-sectional view of the optical fibers 10 and 20. The optical fibers 10 and 20 extend linearly along the central axes CL1 and CL2, respectively, and core portions 11 and 21 serving as optical paths (light guide paths) through which light beams propagate, and cladding portions 12 and 22 covering the periphery thereof. It has a two-layer structure. The core parts 11 and 21 and the clad parts 12 and 22 are both made of plastic, but the core parts 11 and 21 have a higher refractive index than the clad parts 12 and 22. As a result, the light beam incident on the core portions 11 and 21 propagates through the core portions 11 and 21 while repeating total reflection at the boundary surfaces between the core portions 11 and 21 and the cladding portions 12 and 22. When the optical fibers 10 and 20 are single mode (SM) type optical fibers, the refractive indexes of the core parts 11 and 21 are constant, and when the optical fibers 10 and 20 are graded index (GI) type optical fibers, The refractive index of 21 has a distribution. In the present embodiment, as the optical fibers 10 and 20, the same type of SM type optical fiber and GI type optical fiber are used, and the refractive indexes (or refractive index distributions) of the core portions 11 and 21 are equal to each other. Is used. Although not shown here, the optical fibers 10 and 20 may have a coating layer such as an ultraviolet curable resin around the cladding portions 12 and 22.

  Furthermore, the optical fibers 10 and 20 each have a cross section 13 extending in the direction along the central axes CL1 and CL2 (that is, the light propagation direction) so as to include both the core portions 11 and 21 and the cladding portions 12 and 22, respectively. , 23 and are joined to each other to form a joint portion 2. The cross sections 13 and 23 are formed by machining such as polishing and cutting. Here, the cross sections 13 and 23 are collectively referred to as a joint surface 2S. The light beam propagating through the optical fiber 10 can enter the optical fiber 20 and the light beam propagating through the optical fiber 20 can enter the optical fiber 10 through the bonding surface 2S.

  FIG. 3 shows an enlarged cross-sectional configuration of the joint portion 2. As shown in FIG. 3, a transparent matching oil 71 having a refractive index equivalent to that of the core portions 11 and 21 is interposed between the cross section 13 and the cross section 23. Alternatively, instead of the matching oil 71, a transparent adhesive having a refractive index equivalent to that of the core portions 11 and 21 may be interposed to bond the cross section 13 and the cross section 23 together. The refractive index equivalent to the core portions 11 and 21 here is equal to or higher than the refractive index of the core portions 11 and 21 when the optical fibers 10 and 20 are SM type optical fibers, and in the cross sections 13 and 23. It means that the light beam propagating through the core parts 11 and 21 has a refractive index that does not cause total reflection. On the other hand, when the optical fibers 10 and 20 are GI type optical fibers, the light flux propagating through the core parts 11 and 21 in the cross sections 13 and 23 is totally reflected, which is larger than the average refractive index of the core parts 11 and 21. This means that the refractive index is such that it does not cause any problem. With such a configuration, the joint 2 can behave as if it is a single optical fiber. In particular, if the cross sections 13 and 23 include the central axes CL1 and CL2 of the core portions 11 and 21, the cross-sectional dimensions of the joint portion 2 are substantially the same as those of the optical fibers 10 and 20 other than the joint portion 2. preferable.

  The holding member 3 has a housing part 30 and a lid 40. As shown in FIG. 4, the accommodating portion 30 is formed with a recess 36 having the same planar shape as the contour of the joint portion 2. The recessed part 36 has the branch parts 31-34 and the junction part 35 where they merge. The recess 36 has a depth corresponding to the diameter of the optical fibers 10 and 20 throughout. The optical fiber 10 is accommodated in the branch portion 31, the junction portion 35 and the branch portion 33, and the optical fiber 20 is accommodated in the branch portion 32, the junction portion 35 and the branch portion 34. Moreover, the accommodating part 30 is comprised by elastic bodies, such as hard rubber, for example, and deform | transforms according to external force.

  The lid 40 covers the opening surface 36K of the recess 36 and urges the joint 2 in the direction in which the cross sections of the optical fibers 10 and 20 are pressed against each other (X-axis direction). Hereinafter, the configuration of the lid 40 will be described with reference to FIGS. 5A and 5B are cross-sectional views corresponding to the arrow direction of the VV cutting line shown in FIG. As shown in FIG. 5A, the lid 40 includes a main body 41 and a pair of gripping portions 42A and 42B that are provided at both ends of the main body 41 and face each other. Here, the pair of gripping portions 42A and 42B is configured to exhibit elasticity in a direction (X-axis direction) facing each other. Therefore, when the lid 40 and the accommodating portion 30 are combined so that the main body 41 covers the opening surface 36K of the recess 36 in which the optical fibers 10 and 20 are accommodated, as shown in FIG. The biasing force P perpendicular to the cross sections 13 and 23 is applied by 42B. As a result, the cross sections 13 and 23 of the optical fibers 10 and 20 are reliably held in a joined state.

  Next, the operation of the coupler 1 will be described.

  As shown in FIG. 6, when the light beam φ <b> 1 enters from the end 10 </ b> A side of the optical fiber 10, the light beam φ <b> 1 propagates through the core portion 11 and reaches the joint portion 2. After reaching the joint portion 2, the light beam φ1 is distributed into a light beam φ3 toward the end portion 10B and a light beam φ4 toward the end portion 20B. Here, since the cross section 13 and the cross section 23 form the joint surface 2S via the matching oil 71 having a predetermined refractive index, the propagation mode and intensity of the light beam φ1 are maintained, and the light beams φ3 and φ4 are the light beam φ1. It has the same propagation mode and intensity. Similarly, when the light beam φ2 is incident from the end 20A side of the optical fiber 20, the light beam φ3 toward the end 10B and the light beam toward the end 20B while maintaining the propagation mode and intensity of the light beam φ2. can be distributed to φ4.

  Further, when the light beam φ1 is incident from the end portion 10A and the light beam φ2 is incident from the end portion 20A, the light beam φ1 and the light beam φ2 are combined at the joint portion 2, and the combined light is combined with the light beams φ3 and φ4 to the end portions 10B and 20B. Are each distributed as

  Thus, according to the coupler 1 of the present embodiment, each of the two-layer structures of the core parts 11 and 21 and the clad parts 12 and 22 has a planar cross section 13 formed by machining on a part of the side surface. , 23 and the cross-sections 13 and 23 are joined to each other to form the joint 2, so that a good transmission characteristic is maintained while having a simple configuration. The light beam can be synthesized or distributed as it is. In particular, since the joint portion 2 is accommodated in the holding member 3, the joint state between the cross sections 13 and 23 can be reliably maintained, and the reliability in characteristics is improved.

  Next, a method for manufacturing the coupler 1 will be described.

  First, as shown in FIG. 7, an optical fiber 5 is wound around a cylindrical drum 4 having a certain diameter. After that, a part of the side surface of the optical fiber 5 is machined collectively to form a processed cross section 5S as shown in FIG. As shown in the partial cross-sectional view of FIG. 8B, the processed cross-section 5S includes both the core portion 51 and the clad portion 52.

  After forming the processed cross section 5S, a plurality of optical fiber elements are formed by cutting the optical fiber 5 into a plurality for each processed cross section 5S. Thereby, the optical fibers 10 and 20 shown in FIG. 1, FIG. 2, etc. are obtained. Subsequently, as shown in FIG. 9, the joint portion 2 is formed by joining the cross sections 13 and 23 of the optical fibers 10 and 20, and then the joined optical fibers 10 and 20 are accommodated in the housing portion shown in FIG. 4. The coupler 1 is completed by being accommodated in the 30 recesses 36 and further covered with a lid 40. When forming the joint 2, the matching oil 71 or a predetermined adhesive is applied to one or both of the cross sections 13 and 23. Or after accommodating both the optical fibers 10 and 20 in the recessed part 36, you may make it flow the matching oil 71 or a predetermined adhesive agent between the cross section 13 and the cross section 23. FIG.

  As described above, according to the method for manufacturing the coupler 1 in the present embodiment, the optical fiber 5 having the two-layer structure of the core portion 51 and the cladding portion 52 is wound around the drum 4 having a certain diameter, and then the optical fiber 5 is wound. By machining a part of the side surface of the fiber 5 collectively, a processed cross section 5S is formed, and further, the optical fiber 5 is cut at each processed cross section 5S, thereby forming the optical fibers 10 having the cross sections 13 and 23 formed therein. After the optical fiber is divided into a plurality of optical fibers 20, the cross-sections 13 and 23 are joined together to form the joint 2, so that the light beam is synthesized while maintaining a good transmission characteristic with a simple configuration. Or the coupler 1 which can perform distribution can be manufactured easily and in large quantities.

  Although the present invention has been described with reference to the embodiment and the modifications, the present invention is not limited to the above embodiment and the examples, and various modifications can be made. For example, in the present embodiment, the X-shaped coupler 1 has been described. However, the present invention is not limited to this, and the Y-shape formed of the optical fibers 10, 20, and 60 as in the modification shown in FIG. The coupler 1A may be used. Here, the optical fibers 10, 20, 60 include core portions 11, 21, 61 extending along the central axes CL <b> 1 to CL <b> 3 and clad portions 12, 22, 62 covering the periphery of the core portions 11, 21, 61. Each has a two-layer structure. The optical fibers 10 and 20 have a first end face T1 orthogonal to the central axes CL1 and CL2, and planar cross sections formed by machining along the side surface from the first end face T1 over a predetermined distance. Has a bonding surface 2S formed by bonding. One optical fiber 60 has a second end face T2 orthogonal to the central axis CL3. In FIG. 10, a gap is provided between the first end face T1 and the second end face T2 in order to clearly show them, but they are actually joined so that the light beam is transmitted. In order to manufacture such a coupler 1, as described in the above embodiment, the cross-sections 13 and 23 are joined to form the joint 2, and then the joint 2 is cut to obtain the central axis CL 1. A first end face T1 orthogonal to CL2 may be formed and joined to the first end face T1 and the second end face T2 of the optical fiber 60.

1 is a partially cutaway view showing a perspective configuration of an optical fiber coupler as an embodiment of the present invention. It is sectional drawing showing the structure of the optical fiber in the optical fiber coupler shown in FIG. FIG. 2 is an enlarged cross-sectional view in which a main part of the optical fiber coupler shown in FIG. 1 is enlarged. It is a top view showing the structure of the accommodating part in the optical fiber coupler shown in FIG. It is sectional drawing showing the cross-sectional structure in the VV cutting | disconnection line of the optical fiber coupler shown in FIG. It is explanatory drawing for demonstrating the effect | action of the optical fiber coupler shown in FIG. It is a perspective view for demonstrating one process in the manufacturing method of the coupler as one embodiment of this invention. FIG. 8 is a perspective view and an enlarged cross-sectional view for explaining one process following FIG. 7. FIG. 9 is a cross-sectional view for explaining a step subsequent to FIG. 8. It is sectional drawing showing the cross-sectional structure of the optical fiber coupler as a modification of this invention.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 ... Optical fiber coupler, 2 ... Contact part, 2S ... Contact surface, 3 ... Holding member, 4 ... Drum, 5 ... Optical fiber, 10, 20 ... Optical fiber, 11, 21, 51, 61 ... Core part, 12, 22, 52, 62 ... clad part, 30 ... accommodating part, 36 ... concave part, 40 ... lid, 71 ... matching oil.

Claims (11)

The core part and the clad part each having a two-layer structure of a core part extending along the central axis and a clad part covering the periphery of the core part, and formed by machining on a part of the side surface Comprising a pair of optical fibers each having a planar processing cross section including:
The processed cross-sections are joined together to form a joined portion. The optical fiber coupler according to claim 1, wherein the processed cross section includes a central axis of the core portion. The optical fiber coupler according to claim 1, further comprising a holding member that holds a bonded state between the processed cross sections of the optical fibers. The transparent matching oil which has a refractive index equivalent to the said core part interposes between the process cross sections of the said optical fiber pair. The Claim 1 characterized by the above-mentioned. Optical fiber coupler. 4. The optical fiber according to claim 1, wherein the cross sections of the optical fiber pair are bonded to each other by a transparent adhesive having a refractive index equivalent to that of the core portion. Coupler. The holding member is
An accommodating portion made of an elastic body and including a concave portion having the same planar shape as the outline of the joint portion;
6. The lid according to claim 1, further comprising: a lid that covers the opening surface of the recess and urges the pair of optical fibers in the joining direction of the processed cross section. Optical fiber coupler. The optical fiber coupler according to claim 6, wherein the recess has a depth corresponding to the diameter of the optical fiber. Each has a two-layer structure of a core portion extending along the central axis and a clad portion covering the periphery of the core portion, and is formed by machining along a side surface from the first end surface over a predetermined distance. A first optical fiber and a second optical fiber each having a planar processed cross section including the core portion and the clad portion;
A third optical fiber having a second end face;
The processing cross sections of the first and second optical fibers are bonded to each other, and the first end surface and the second end surface are bonded to each other to form a Y shape. Optical fiber coupler. After winding an optical fiber having a two-layer structure of a core portion extending along the central axis and a clad portion covering the periphery of the core portion around a columnar member, a part of the side surface of the optical fiber is collectively Forming a processed cross section including both the core part and the clad part by machining;
Forming a plurality of optical fiber elements including at least one processed cross section by dividing the optical fiber into a plurality of parts;
Forming a joint by joining the processed cross-sections of the optical fiber element to each other. The method of manufacturing an optical fiber coupler according to claim 9, wherein the processed cross section is formed so as to include a central axis of the core portion. Furthermore, after forming the end face orthogonal to the central axis by cutting the joint portion, a Y-shaped optical fiber coupler is formed by joining with the end face of another optical fiber. Or the manufacturing method of the optical fiber coupler of Claim 10.

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