JP2013160869A - Optical fiber sheet - Google Patents

Abstract

PROBLEM TO BE SOLVED: To solve such a problem that upon implementing optical fibers or optical fiber sheets by bending, which is frequently performed, a bending loss of an optical fiber increases if a radius of curvature of the optical fiber is decreased to be smaller than the allowable radius of curvature of the optical fiber.SOLUTION: An optical fiber sheet including an optical fiber and a pair of sheet materials interposing the optical fiber has a ribbon portion where the optical fiber protrudes from an end of the sheet material. The ribbon portion has a concavo-convex structure in which a plurality of projections and recesses are alternately formed in a longitudinal direction of the optical fiber and projections abut to each other when the ribbon portion is bent. The projections interfere with each other when the fiber is bent, which can maintain the optical fiber ribbon portion in a loosely bent state with a larger radius of curvature than the allowable radius of curvature of the optical fiber.

Description

  The present invention relates to an optical fiber and an optical fiber sheet for optically connecting optical elements, optical circuits, optical devices and the like.

  In recent years, information processing apparatuses such as servers, routers, and storages have been required to improve the backplane transmission speed. Furthermore, the equipment throughput is larger than the trend of transmission speed, and it is necessary to increase the wiring density. In the conventional electrical transmission, there is a limit to the improvement of the transmission speed and transmission density, so the application of optical interconnect technology in the equipment is considered. Has been.

  In order to perform optical transmission of the backplane, an optical fiber sheet in which a plurality of optical fiber wirings are integrated into a sheet shape is used. The sheet is made of polyimide or other soft resin and has a structure in which an optical fiber is sandwiched between two sheet materials. In general, several optical fibers are drawn from the edge of the optical fiber sheet, and an optical connector is attached to the end of the optical fiber.

  For example, Japanese Patent Application Laid-Open Nos. 2001-255491 (Patent Document 1) and 2002-303740 (Patent Document 2) describe structures for preventing buckling of an optical fiber sheet, protecting an optical fiber, and mechanically reinforcing the optical fiber sheet. It has become.

JP 2001-255491 A JP 2002-303740 A

  Several optical fibers are pulled out from the edge of the optical fiber sheet, and an optical connector is attached to the end of the optical fiber sheet (hereinafter referred to as an optical fiber ribbon). When connecting the optical fiber ribbon and the backplane connector, In this case, since the backplane connector is disposed at a position perpendicular to the optical fiber sheet, it is necessary to bend the optical fiber ribbon portion at a substantially right angle (90 °) during assembly. However, the optical fiber only needs to be bent little by little. However, when the curvature of the optical fiber ribbon is locally increased and becomes smaller than the allowable curvature radius of the optical fiber, there is a problem that the optical characteristic (bending loss) of the optical fiber increases. .

  In addition, when an optical connector is attached to the tip of the optical fiber ribbon, it is necessary to secure a certain length of the optical fiber ribbon from the viewpoint of workability within the polishing process of the optical connector tip. Depending on the fitting position of the connector, an excess portion is generated in the optical fiber ribbon, and the bending radius of the optical fiber becomes small.

  Further, when a plurality of optical fiber sheets are mounted in an overlapped manner, if the rigidity of the optical fiber ribbon portion is low, there is a risk that the optical fiber is buckled during assembly and the optical fiber is broken.

  In view of the above, it is desirable to introduce a method for fixing the optical fiber ribbon portion with an allowable radius of curvature of the optical fiber or more when fixing the optical fiber ribbon portion drawn from the optical fiber sheet.

  In order to achieve the above object, the present invention provides an optical fiber sheet including an optical fiber and a pair of sheet materials sandwiching the optical fiber, the optical fiber having a ribbon portion protruding from an end of the sheet material, A plurality of convex portions and concave portions are alternately formed in the length direction of the optical fiber, and the ribbon portion has a concavo-convex structure in which the convex portions come into contact with each other when the ribbon portion is bent.

  As described above, according to the present invention, the bending radius of the optical fiber ribbon portion can be fixed more gently than the allowable curvature radius, and the optical fiber ribbon portion can be fixed without increasing the bending loss of the optical fiber. .

It is a perspective view of the backplane concerning one example of the present invention. It is sectional drawing of the backplane concerning one Example of this invention. It is a top view of the optical fiber sheet concerning one example of the present invention. (A) (b) is a top view of the ribbon part of the optical fiber sheet which concerns on one Example of this invention. (A) is sectional drawing of the ribbon part of the optical fiber sheet which concerns on one Example of this invention, (b) is the enlarged view. (A) (b) is sectional drawing of the ribbon part of the optical fiber sheet which concerns on one Example of this invention. (A) is sectional drawing of the ribbon part of the optical fiber sheet which concerns on one Example of this invention, (b) is the enlarged view. (A) (b) is a top view of the ribbon part of the optical fiber sheet which concerns on the other Example of this invention. (A) is sectional drawing of the ribbon part of the optical fiber sheet which concerns on the other Example of this invention, (b) is the enlarged view. It is sectional drawing of the ribbon part of the optical fiber sheet which concerns on the other Example of this invention. It is a top view of the ribbon part of the optical fiber sheet which concerns on the other Example of this invention. It is a figure of the optical fiber which concerns on the other Example of this invention.

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

  FIG. 1 shows a backplane of a server as an example in which the optical fiber sheet of the present embodiment is fixed and used. A switch board 102 and a blade board 103 are attached to the backplane board 101 on the front and back sides. The switch substrate 102 and the blade 103 are connected by electrical wiring (not shown) and an optical fiber 1 described later, and the LSI includes elements 102a and 103a such as light emitting / receiving elements on the substrate.

  FIG. 2 shows a cross-sectional view of a backplane provided with an optical fiber sheet according to an embodiment of the present invention. On both surfaces of the backplane substrate 101, a switch substrate 102 and a blade substrate 103 are provided substantially perpendicular to the backplane substrate 101, respectively. The switch substrate 102 and the blade substrate 103 are optically connected via a backplane connector 104 and an optical fiber sheet 105.

  A plurality of optical fiber sheets 105 are stacked and fixed on the backplane substrate 101. The optical fiber ribbon portion 1 drawn out from the optical fiber sheet 105 is perpendicular (90 °) at a predetermined position so as to be fitted to the switch board 102 and the backplane connector 104 mounted on the blade board 103. It is bent and mounted.

  In FIG. 3, the schematic of the optical fiber sheet 105 is shown. The optical fiber sheet 105 includes two sheet members 7 and the optical fiber 1 sandwiched therebetween. Although simplified in the drawing, the optical fiber 1 is actually a bundle of optical fibers in which a plurality of optical fibers are bundled. The optical fiber sheet is provided with an opening hole 2 for connecting a backplane connector, and the optical fiber ribbon portion 1 can be bent to both the front and back of the optical fiber sheet 105 from the opening hole 2. . The ribbon portion 1 has a bundle of optical fibers 5 inside thereof, and the width of the sheet material 7 is smaller than the other portions in order to bend the bundle of optical fibers 5 individually. Further, the optical fibers 1 are arranged in parallel or intersecting with each other depending on the connection destination. By attaching the optical fiber sheet 105 to the backplane 101, optical connection to the switch substrate 102 and the blade substrate 103 mounted on both sides of the backplane 101 can be realized. The optical fiber sheet 105 is designed by changing the length and width, the number of built-in optical fibers, and the shape of the sheet according to the apparatus to be mounted. Further, the optical fiber sheet 105 often has a structure of being stacked in multiple layers. In this case, the positions of the ribbon portions 1 are made different from each other so that the ribbon portion 1 for taking out the optical fibers does not interfere.

  FIG. 4 is a plan view showing a bent portion of the ribbon portion 1 of the optical fiber sheet 105. 4A is a surface that becomes the inner side when the ribbon portion 1 is bent, and FIG. 4B is an opposite surface that is a surface that becomes the outer side. The ribbon portion 1 of the optical fiber sheet 105 has a structure in which one or more optical fibers 5 are adjacent to each other in a horizontal line and integrated with two sheet materials 7 made of polyimide or other soft resin. Further, an optical connector 3 for attaching to a connector (not shown) on the apparatus side is attached to the end of the optical fiber ribbon portion 1. Bending direction guiding members 4 are attached to the front and back of the optical fiber ribbon portion 1. The relationship between the length a of the bending direction guiding member 4a in the direction to be bent (inside refraction) and the length b of the bending direction guiding member 4b on the back surface (outside of refraction) is a <b. Further, one or more bending direction guiding members 4c are attached at the bent portion of the optical fiber ribbon portion 1.

  5A shows a cross-sectional view of the optical fiber sheet 105, and FIG. 5B shows an enlarged cross-sectional view of the bent portion. In the bent portion, the bending direction guiding member 4a and the bending direction guiding member 4b are provided side by side, and the bending direction guiding member 4c is disposed with a gap at the tip of the bending direction guiding member 4a. In order to bend the curvature of the optical fiber 5 greatly, the bending direction guiding member 4a and the bending direction guiding member 4c are arranged so as to interfere with each other during bending. Therefore, the optical fiber 5 can be prevented from being bent from the allowable radius of curvature, and deterioration of the optical characteristics of the optical fiber can be suppressed.

  6A and 6B are cross-sectional views of the ribbon portion 1. A plurality of optical fibers 5 are provided between the two sheet materials 7. In FIG. 6A, the bending direction guide member 4 is provided inside the sheet material 7, that is, between the sheet material 7 and the optical fiber 5. In the ribbon portion 1, the bending direction guide member 4 provided on the sheet material that is on the outer side when bent is on the inner side than the sheet material 7, and thus the curvature of the ribbon portion 1 is limited by the unevenness.

  In FIG. 6B, the bending direction guiding member 4 is provided outside the sheet material 7, that is, on the opposite side of the optical fiber 5 with respect to the sheet material 7. In this ribbon portion, the bending direction guide member 4 provided on the sheet material that is on the inner side when bent is further on the inner side than the sheet material 7, and thus the curvature of the ribbon portion 1 is limited by the unevenness.

  As described above, regardless of whether the bending direction guiding member 4 is formed on the inner side or the outer side of the sheet material 7, there is an effect of limiting the curvature. If the bending direction guiding member 4 is provided on the inner side in the bending direction with respect to the sheet material 7, the effect of limiting the curvature is obtained. When the direction in which the ribbon portion 1 is bent is determined in advance, the guide member 4 that limits the curvature may be provided on only one sheet material or on both sheet materials.

  The bending direction guiding member 4c can take various shapes as long as the optical fiber ribbon portion 1 is a structure that interferes with the optical fiber 5 so that it does not bend below the allowable radius of curvature when the optical fiber ribbon portion 1 is bent. FIGS. 7A and 7B show the shape when a plurality of bending direction guiding members 4c are attached in the vicinity of the bent portion. In this case, a plurality of gaps are formed between the plurality of guide members 4c arranged in the length direction of the optical fiber. When bent, these gaps are reduced, and when all the gaps are eliminated, the bending angle is further increased. No longer grows.

  In addition, since the bending direction induction | guidance | derivation member 4c uses a sheet | seat with constant thickness as the sheet | seat material 7, although another member is attached to the sheet | seat material 7, even if it has a structure integrated with the bending direction induction | guidance | derivation member 4a. Good.

  Further, as a material of the bending direction guiding member 4, a soft resin (polyimide), polyethylene terephthalate, polyethylene, polyester, polypropylene, or the like having higher rigidity than the sheet material 7 is desirable. When limiting the curvature, the bending direction guiding member 4 is not hollow but solid so that the convex portion is not crushed.

  A second embodiment of the present invention will be described with reference to FIGS. In addition to the form of the first embodiment, FIG. 8 shows an optical fiber ribbon portion in which a shape holding member 6 having rigidity higher than that of the sheet material 7 is wired at both ends of the optical fiber ribbon portion 1 and the end of the sheet material near the ribbon portion. 1 is a structure which can hold | maintain a shape at the time of bending. The shape maintaining member 6 maintains its bending angle once bent. The material of the shape holding member 6 is desirably a metal, a soft resin (polyimide), polyethylene terephthalate, polyethylene, polyester, polypropylene, or the like that is higher in rigidity than the optical fiber ribbon portion 1.

  FIG. 9 is a cross-sectional view of the bent portion of the optical fiber ribbon portion 1 when a function equivalent to that of the bending direction guiding member 4 is given to the shape holding member 6. The bent portion is provided with a concavo-convex structure 6a so that the optical fiber 5 is not bent below the allowable radius of curvature and is easily bent in a predetermined direction, thereby providing a curvature limiting function equivalent to that of the bending direction guiding member 4. It was realized. This concavo-convex structure may be integrally formed, a separate member may be attached, or a recess may be formed by cutting. Further, in the case of the present embodiment, only the shape holding member 6 may be used without arranging the bending direction guiding member 4.

  FIG. 10 shows a cross-sectional view of the optical fiber ribbon portion 1. The shape holding member 6 is preferably disposed at both ends where the optical fibers 5 are wired adjacent to each other in a horizontal row. In addition, by setting the cross-sectional dimensions c and d to c> d, the optical fiber ribbon portion 1 can be easily bent in the direction d. Further, the bending direction guiding member 4 may be disposed in the optical fiber sheet, on the cover film of the optical fiber sheet 105, or may be omitted.

  FIG. 8 shows an embodiment in which the optical connector 3 is not attached to the tip of the optical fiber ribbon portion 1. It is not essential to attach the optical connector 3 to the tip of the optical fiber ribbon 1. For example, when optically connecting to a waveguide or a backplane connector with a lens, the tip of the shape memory member 6 can be used as the positioning protrusion 8. is there.

  FIG. 12 is a diagram of an optical fiber according to one embodiment of the present invention. The optical fiber has a concavo-convex structure 6a on its side surface. This concavo-convex structure can be formed of a covering material or the like that is recessed around the optical fiber body 5 formed of a transparent material such as glass.

  Also in this embodiment, when the optical fiber is bent, the convex portions of the concavo-convex structure interfere with each other and the curvature of the optical fiber can be restricted, so that an increase in bending loss can be suppressed. In the drawing, the concavo-convex structure 6a is provided only in part, but it may be provided over the entire surface of the optical fiber, or may be provided only in part if the position to be bent is known in advance.

DESCRIPTION OF SYMBOLS 1 ... Optical fiber ribbon part, 2 ... Opening hole, 3 ... Optical connector, 4 ... Bending direction guide member, 5 ... Optical fiber, 6 ... Shape holding member, 7 ... Optical fiber sheet cover material, 8 ... positioning protrusion, 101 ... backplane, 102 ... switch board, 103 ... blade board, 104 ... backplane connector, 105 ... optical fiber sheet .

Claims (14)

Optical fiber,
A pair of sheet materials sandwiching the optical fiber;
In an optical fiber sheet comprising:
The optical fiber has a ribbon portion protruding from an end of the sheet material;
An optical fiber, wherein a plurality of convex portions and concave portions are alternately formed in the length direction of the optical fiber, and the ribbon portion has a concavo-convex structure in which the convex portions abut each other when the ribbon portion is bent. Sheet. In claim 1,
The concavo-convex structure limits the curvature of the ribbon portion when the plurality of convex portions come into contact with each other. In claim 1 or 2,
In the concavo-convex structure, convex portions and concave portions extending in a direction along the surface direction of the sheet material and intersecting the length direction of the optical fiber are alternately formed in the length direction of the optical fiber. An optical fiber sheet characterized by the above. In any one of Claims 1 thru | or 3,
The concave-convex structure is provided on the sheet material. In claim 4,
The concavo-convex structure is formed on the opposite side of the sheet material from the optical fiber. In claim 4 or 5,
The concavo-convex structure is formed on the surface of the sheet material facing the optical fiber side. In any one of Claims 1 thru | or 6.
The ribbon portion has a shape holding member that defines a bending direction of the ribbon portion,
The concavo-convex structure is provided on the shape holding member. In any one of Claims 1 thru | or 7,
The optical fiber sheet, wherein the concavo-convex structure is formed by providing a bending induction material on the sheet material or shape maintaining member on which the concavo-convex structure is provided. In claim 8,
The concavo-convex structure is formed by providing a plurality of the bending induction materials apart from each other. In claim 8,
An optical fiber sheet, wherein the concave-convex structure is formed by forming a concave portion in the bending induction material. In any one of Claims 1 thru | or 7,
The optical fiber sheet, wherein the concavo-convex structure is integrally formed with the sheet material or shape holding member on which the concavo-convex structure is provided. In any one of Claims 1 thru | or 11,
An optical fiber sheet comprising a connector at a tip of an optical fiber of the ribbon portion. A first substrate;
The optical fiber sheet according to any one of claims 1 to 12, provided on the first substrate;
In the electronic device comprising the second substrate attached to the first substrate and optically connected to the optical fiber of the optical fiber sheet,
The optical fiber sheet is provided with a bent portion of the ribbon portion having a concavo-convex structure. An optical fiber body;
A concavo-convex structure having a plurality of convex portions and concave portions formed around the optical fiber main body and alternately arranged in the length direction;
When the optical fiber main body is bent, the curvature of the optical fiber main body is limited by the plurality of convex portions coming into contact with each other.

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