JP2014142495A - Connection structure and connection method for multi-core optical fiber - Google Patents

Abstract

PROBLEM TO BE SOLVED: To easily connect a pair of multi-core optical fibers.SOLUTION: A connection structure C for a multi-core optical fiber includes a pair of multi-core optical fibers 11 each having a flat surface on the outer periphery thereof and a mechanical splice 21 for butting the end surfaces of the pair of multi-core optical fibers 11 against each other, to connect them. The mechanical splice 21 includes a fiber guide part 26 guiding each of the pair of multi-core optical fibers 11 along a length direction, and rotation regulation parts 26a and 26b coming into contact with the flat surface 11c possessed by the outer periphery of each of the pair of multi-core optical fibers 11, to regulate the axial rotation of the multi-core optical fibers 11.

Description

  The present invention relates to a multi-core optical fiber connection structure and a connection method.

  As a mechanical splice for butting and connecting optical fibers, a pair of optical fibers are supported in the V-groove of the V-groove substrate so that they are supported at two points and opposed to each other, and axial alignment is performed. What is connected by the V-groove method and what is connected by the sleeve method in which the optical fiber is inserted and abutted from both sides of the sleeve having an inner diameter slightly larger than the outer diameter of the optical fiber are connected. .

  Patent Document 1 discloses that a multi-core optical fiber having a plurality of cores is butted and spliced.

JP 2011-209702 A

When connecting multi-core optical fibers, not only axial alignment but also alignment in the axial rotation direction is necessary to connect all the cores.

  The subject of this invention is enabling it to connect a pair of multi-core optical fiber easily.

  The present invention is a multi-core optical fiber connection structure comprising a pair of multi-core optical fibers each having a flat surface on the outer periphery, and a mechanical splice that connects the end faces of the pair of multi-core optical fibers by abutting each other. The splice contacts the flat surface of the outer periphery of each of the pair of multi-core optical fibers and guides each of the pair of multi-core optical fibers along the length direction, and rotates the axis of the multi-core optical fibers. A rotation restricting portion for restricting the rotation.

  The present invention is a method of connecting a pair of multi-core optical fibers each having a flat surface on the outer periphery, and the pair of multi-core optical fibers are connected to a fiber guide portion for guiding them along the length direction. The multi-core optical fibers are opposed to each other, and each of the rotation guides is in contact with a flat surface on the outer periphery to restrict axial rotation, and at least one of the pair of multi-core optical fibers is provided with the fiber guide. And abutting the end faces of the pair of multi-core optical fibers by moving along the length direction by guiding the part.

  According to the present invention, each of the pair of multi-core optical fibers is guided along the length direction by the fiber guide portion, and the rotation restricting portion is brought into contact with the flat surface of the outer periphery of the multi-core optical fiber so as to restrict the shaft rotation. Alignment in the axial rotation direction can be performed together with alignment, and a pair of multi-core optical fibers can be easily connected.

1 is a perspective view of a multi-core optical fiber connection structure according to Embodiment 1. FIG. (A) is IIa-IIa sectional drawing in FIG. 1, (b) is IIb-IIb sectional drawing in FIG. It is a principal part enlarged view in Fig.2 (a). It is a perspective view of a multi-core optical fiber core wire. It is a perspective view of the mechanical splice of the connection structure of the multi-core optical fiber which concerns on Embodiment 1. FIG. (A) is a figure which shows the connection method of the multi-core optical fiber which concerns on Embodiment 1, (b) is VIb-VIb sectional drawing in Fig.6 (a). It is sectional drawing corresponding to FIG. 3 of the modification 1-1 of the connection structure of the multi-core optical fiber which concerns on Embodiment 1. FIG. It is sectional drawing corresponding to FIG. 3 of the modification 1-2 of the connection structure of the multi-core optical fiber which concerns on Embodiment 1. FIG. It is sectional drawing corresponding to FIG. 3 of the modification 1-3 of the connection structure of the multi-core optical fiber which concerns on Embodiment 1. FIG. It is sectional drawing corresponding to FIG. 3 of the modification 1-4 of the connection structure of the multi-core optical fiber which concerns on Embodiment 1. FIG. 6 is a perspective view of a multi-core optical fiber connection structure according to Embodiment 2. FIG. (A) is XIIa-XIIa sectional drawing in FIG. 11, (b) is XIIb-XIIb sectional drawing in FIG. It is a principal part enlarged view in Fig.12 (a). It is a perspective view of the mechanical splice of the connection structure of the multi-core optical fiber which concerns on Embodiment 2. FIG. It is sectional drawing corresponding to FIG. 13 of the modification 2-1 of the connection structure of the multi-core optical fiber which concerns on Embodiment 2. FIG. It is sectional drawing corresponding to FIG. 13 of the modification 2-2 of the connection structure of the multi-core optical fiber which concerns on Embodiment 2. FIG. (A) It is a perspective view which shows the modification of the mechanical splice of the connection structure of the multi-core optical fiber which concerns on Embodiment 2, (b) is XVIIb-XVIIb sectional drawing in Fig.17 (a).

  Hereinafter, embodiments will be described in detail based on the drawings.

(Embodiment 1)
1, FIG. 2 (a) and (b), and FIG. 3 show the connection structure C of the multi-core optical fiber 11 according to the first embodiment. In the connection structure C according to the first embodiment, a pair of multi-core optical fiber core wires 10 are connected by a mechanical splice 20.

  FIG. 4 shows a multi-core optical fiber core wire 10.

  The multi-core optical fiber core 10 includes a multi-core optical fiber 11 and a coating layer 12 that covers the multi-core optical fiber 11. The outer diameter of the multi-core optical fiber core 10 is, for example, 250 μm.

  The multi-core optical fiber 11 is made of, for example, quartz glass and has a regular hexagonal cross section. The maximum outer diameter of the multi-core optical fiber 11 is, for example, 125 to 200 μm.

  The multi-core optical fiber 11 has seven cores 11a and a clad 11b that covers them.

  Each of the seven cores 11a is doped with a dopant such as germanium and has a relatively high refractive index. The seven cores 11a are provided with six cores 11a so as to form a regular hexagon around one core 11a at the center in the cross section, and form a triangular lattice as a whole. Each of the six surrounding cores 11a is provided on a line connecting the center and the apex in the cross section, and therefore the six surrounding cores 11a are equivalent. The diameter of the core 11a is, for example, 8 to 11 μm. The interval between the adjacent cores 11a is, for example, 20 to 50 μm. In addition, the number of cores 11a includes 19 and 37 in addition to the seven shown in FIG. 4, and may be 2 to 50, for example. In addition to the triangular lattice shown in FIG. 4, the core 11a may be arranged to form a square lattice, may be arranged rotationally or line-symmetrically, and has regularity. It may be arranged without. The diameter of the core 11a may be the same as shown in FIG. 4, or different ones may be mixed.

  The cladding 11b is not doped with a dopant, or is doped with a dopant such as fluorine that lowers the refractive index, and has a relatively low refractive index.

  The covering layer 12 is made of, for example, an ultraviolet curable urethane acrylic resin. The thickness of the coating layer 12 is, for example, 25 to 62.5 μm.

  FIG. 5 shows a mechanical splice 20.

  The mechanical splice 20 includes an elongated groove forming member 21, a fiber pressing member 22, a pair of core wire pressing members 23, a fiber fitting member 24 and a core wire fitting member 25. The fiber pressing member 22 and the pair of core wire pressing members 23 are provided on the groove forming member 21 so as to sandwich the fiber pressing member 22 between the pair of core wire pressing members 23 along the length direction thereof. The fiber fitting member 24 is provided so as to fit the groove forming member 21 and the fiber pressing member 22 from the side. The core wire fitting member 25 is provided so as to fit the groove forming member 21 and the core wire pressing member 23 from the side.

  The groove forming member 21 is formed in an elongated rectangular plate shape using, for example, PPS resin or the like. At the center in the width direction of the upper surface of the groove forming member 21, a fiber holding groove 26 corresponding to the fiber pressing member 22 is formed at the center in the length direction so as to extend in the length direction. The cross-sectional shape of the fiber holding groove 26 is a trapezoid in which the bottom surface 26a side is formed into a narrow trapezoid, and the bottom portion of the groove is a trapezoid in which the cross-sectional shape of the multicore optical fiber 11 is divided into two between two opposing vertices. It is formed in the same shape. The depth of the fiber holding groove 26 is slightly smaller than the distance between opposing sides in the hexagonal cross section of the multicore optical fiber 11. The opening angle of both side surfaces 26b forming the fiber holding groove 26 is 60 °. Further, in the center of the upper surface of the groove forming member 21 in the width direction, there is a core wire holding groove 27 constituted by a V groove corresponding to the core wire pressing member 23 continuously to both ends of the fiber holding groove 26. It is formed to extend in the length direction.

  Each of the fiber pressing member 22 and the core wire pressing member 23 is formed in an elongated rectangular flat plate shape having the same width as that of the groove forming member 21 with, for example, PPS resin. On the side of the lower surface of the fiber pressing member 22 where the fiber fitting member 24 is not provided, a pair of missing portions 28 are formed at intervals in the length direction. A missing portion 28 is also formed on the side of the lower surface of the core wire pressing member 23 where the core wire fitting member 25 is not provided.

  Each of the fiber fitting member 24 and the core wire fitting member 25 is formed in a U-shaped cross section with a metal such as stainless steel.

  At both ends of the mechanical splice 20, fiber insertion ports 29 formed by laminating a groove forming member 21 and a core wire holding member 23 are formed. The fiber insertion port 29 is formed in a shape with an opening extending outward so that the multi-core optical fiber 11 can be easily introduced.

  In the connection structure C of the multicore optical fiber 11 according to the first embodiment, the coating layer 12 is peeled off at one end of each of the pair of multicore optical fiber cores 10. One end of the pair of multi-core optical fiber cores 10 is inserted from one end and the other end of the mechanical splice 20, respectively. The multi-core optical fiber 11 exposed by peeling off the coating layer 12 is fitted into the fiber holding groove 26 of the groove forming member 21, and the elasticity of the fiber fitting member 24 through the fiber pressing member 22 placed thereon. It is sandwiched and held by pressing force. Of the one end portion inserted into the mechanical splice 20, the portion covered with the coating layer 12 on the proximal end side of the exposed multi-core optical fiber 11 has two points on both side surfaces of the groove forming member 21 forming the core wire holding groove 27. It is supported by a three-point support that is supported by a pressing force of the elastic force of the core wire fitting member 25 via a core wire pressing member 23 placed thereon. The multi-core optical fiber 11 of the pair of multi-core optical fiber cores 10 has an end face abutted on the fiber holding groove 26 in the mechanical splice 20, and therefore the seven cores 11a are also abutted. Further, the pair of multi-core optical fiber cores 10 are respectively held between the groove forming member 21 and the fiber pressing member 22 of the multi-core optical fiber 11 by the elastic force of the fiber fitting member 24 and the elasticity of the core wire fitting member 25. The multi-core optical fiber core wire 10 is attached and fixed to the mechanical splice 20 by holding the multi-core optical fiber core wire 10 between the groove forming member 21 and the core wire pressing member 23 by force.

  Here, in the connection structure C of the multicore optical fiber 11 according to the first embodiment, each multicore optical fiber 11 is guided along the length direction by the fiber holding groove 26 of the groove forming member 21. Accordingly, the fiber holding groove 26 of the groove forming member 21 constitutes a fiber guide portion that guides each of the pair of multi-core optical fibers 11 along the length direction. In addition, as shown in FIG. 3, the cross-sectional shape of the multi-core optical fiber 11 is divided into two halves between two opposing vertices, and the cross-section of the groove bottom side portion of the fiber holding groove 26 of the groove forming member 21. Since the trapezoidal shape is the same, the lower half of each multi-core optical fiber 11 is fitted into the fiber holding groove 26 of the groove forming member 21, and the three flat surfaces 11 c that the outer periphery of the multi-core optical fiber 11 has are grooves. The bottom surface 26a and both side surfaces 26b of the forming member 21 forming the fiber holding groove 26 are brought into contact with each other, whereby the multi-core optical fiber 11 is restricted from rotating axially. Accordingly, the bottom surface 26a and both side surfaces 26b forming the fiber holding groove 26 of the groove forming member 21 are in contact with the flat surface 11c of the outer periphery of each of the pair of multicore optical fibers 11 to restrict axial rotation of the multicore optical fiber 11. The rotation restricting portion is configured. The upper portion of the multi-core optical fiber 11 slightly protrudes from the fiber holding groove 26 and faces the flat surface 11 c that contacts the bottom surface 26 a that forms the fiber holding groove 26 of the groove forming member 21 on the outer periphery of the multi-core optical fiber 11. The flat surface 11c of the upper surface to be pressed comes into contact with and pressed by the fiber pressing member 22, thereby restricting the separation of the groove forming member 21 of the multi-core optical fiber 11 from the fiber holding groove 26.

  Next, a method for connecting the multi-core optical fiber 11 according to the first embodiment will be described.

  First, for each of the pair of multi-core optical fibers 10, the coating layer 12 at one end is peeled to expose the multi-core optical fiber 11, and the end surface of the multi-core optical fiber 11 is cut to cut the end face. Process into a mirror surface. At this time, the covering layer 12 is preferably peeled off so that the sum of the exposed lengths of both the multi-core optical fibers 11 is the same as or slightly longer than the length of the fiber holding groove 26 of the mechanical splice 20.

  Next, as shown in FIGS. 6A and 6B, the wedge member W is inserted into the defective portion 28 of the mechanical splice 20 to resist the elastic force of the fiber fitting member 24 and the pair of core wire fitting members 25. Thus, the gap between the groove forming member 21, the fiber pressing member 22, and the pair of core wire pressing members 23 is widened.

  Subsequently, one end of the multi-core optical fiber 10 is inserted from both sides of the mechanical splice 20, and the end faces of the multi-core optical fiber 11 are butted together on the fiber holding groove 26. At this time, each of the pair of multicore optical fiber cores 10 is guided along the length direction by the core wire holding groove 27, and each of the pair of multicore optical fibers 11 is lengthwise by the fiber holding groove 26. Will be guided along. Each multi-core optical fiber 11 has its bottom surface 26 a and both side surfaces 26 b forming the fiber holding groove 26 of the groove forming member 21 in contact with the outer flat surface 11 c, so that the shaft rotation is restricted. In addition, it is preferable to inject a refractive index matching agent into the fiber holding groove 26 of the groove forming member 21 in advance.

  Then, the wedge member W is removed, and the pair of multi-core optical fibers 11 abutted on the fiber holding groove 26 are sandwiched and fixed with the groove forming member 21 by the fiber pressing member 22, and the core wires are held on both sides thereof. The multi-core optical fiber core wire 10 on the groove 27 is sandwiched and fixed between the core wire pressing member 23 and the groove forming member 21.

  According to the connection structure C of the multi-core optical fiber 11 according to the first embodiment described above, each of the pair of multi-core optical fibers 11 is guided along the length direction by the fiber holding groove 26 constituting the fiber guide portion, and Since the bottom surface 26a and both side surfaces 26b forming the fiber holding groove 26 constituting the rotation restricting portion are brought into contact with the flat surface 11c provided on the outer periphery of the multi-core optical fiber 11, the shaft rotation is restricted. Position alignment can also be performed, and a pair of multi-core optical fibers 11 can be easily connected.

<Modification 1-1>
FIG. 7 shows a modified example 1-1 of the connection structure C of the multi-core optical fiber 11 according to the first embodiment. In addition, the part of the same name as the above is shown with the same code | symbol as the above.

  In the connection structure C of the modified example 1-1, the fiber holding groove 26 formed in the groove forming member 21 is configured by a V groove having an opening angle of 60 °. As shown in FIG. 7, the two flat surfaces 11 c on both sides of the flat surface 11 c on the lower surface of the outer periphery of the multi-core optical fiber 11 come into contact with both side surfaces 26 b forming the fiber holding grooves 26 of the groove forming member 21. Further, the lower half of the multi-core optical fiber 11 is fitted in the fiber holding groove 26 of the groove forming member 21.

  In the connection structure C of the modified example 1-1, the multi-core optical fiber 11 is guided along the length direction by the fiber holding groove 26 of the groove forming member 21. Accordingly, the fiber holding groove 26 of the groove forming member 21 constitutes a fiber guide portion that guides each of the pair of multi-core optical fibers 11 along the length direction. In addition, as shown in FIG. 7, the two flat surfaces 11 c on both sides of the flat surface 11 c on the lower surface of the outer periphery of the multicore optical fiber 11 come into contact with both side surfaces 26 b forming the fiber holding groove 26 of the groove forming member 21. Thereby, the shaft rotation of the multi-core optical fiber 11 is restricted. Accordingly, both side surfaces 26b forming the fiber holding groove 26 of the groove forming member 21 come into contact with the flat surface 11c of the outer periphery of each of the pair of multi-core optical fibers 11 to restrict the axial rotation of the multi-core optical fiber 11. Parts. The upper portion of the multi-core optical fiber 11 slightly protrudes from the fiber holding groove 26, and the flat surface 11c on the upper surface of the outer periphery of the multi-core optical fiber 11 is pressed in contact with the fiber pressing member 22, thereby the multi-core optical fiber. The separation of the 11 groove forming members 21 from the fiber holding grooves 26 is restricted.

<Modification 1-2>
FIG. 8 shows a modified example 1-2 of the connection structure C of the multi-core optical fiber 11 according to the first embodiment. In addition, the part of the same name as the above is shown with the same code | symbol as the above.

  In the connection structure C of the modified example 1-2, the cross-sectional shape of the multi-core optical fiber 11 is formed in a square shape. Nine cores 11a are provided, and these nine cores 11a are arranged so as to form 3 rows and 3 columns (3 × 3) with respect to any side in the cross section, and are square as a whole. A lattice is formed. The fiber holding groove 26 formed in the groove forming member 21 is a V groove having an opening angle of 90 °. Then, as shown in FIG. 8, the multicore optical fiber 11 has two adjacent flat surfaces 11 c on the outer periphery of the multicore optical fiber 11 in contact with both side surfaces 26 b forming the fiber holding grooves 26 of the groove forming member 21. The half of the cross-sectional shape is divided into two diagonal lines, and is fitted into the fiber holding groove 26 of the groove forming member 21.

  Further, in the connection structure C of the modified example 1-2, the multi-core optical fiber 11 is guided along the length direction by the fiber holding groove 26 of the groove forming member 21. Accordingly, the fiber holding groove 26 of the groove forming member 21 constitutes a fiber guide portion that guides each of the pair of multi-core optical fibers 11 along the length direction. In addition, as shown in FIG. 8, two adjacent flat surfaces 11c of the outer periphery of the multi-core optical fiber 11 are in contact with both side surfaces 26b forming the fiber holding groove 26 of the groove forming member 21, and thereby the multi-core optical fiber 11, shaft rotation is restricted. Accordingly, both side surfaces 26b forming the fiber holding groove 26 of the groove forming member 21 come into contact with the flat surface 11c of the outer periphery of each of the pair of multi-core optical fibers 11 to restrict the axial rotation of the multi-core optical fiber 11. Parts. The upper portion of the multicore optical fiber 11 slightly protrudes from the fiber holding groove 26, and the apex angle at the outer periphery of the multicore optical fiber 11 is pressed against the fiber pressing member 22, whereby the groove of the multicore optical fiber 11 is pressed. The separation of the forming member 21 from the fiber holding groove 26 is restricted.

<Modification 1-3>
FIG. 9 shows a modification 1-3 of the connection structure C of the multi-core optical fiber 11 according to the first embodiment. In addition, the part of the same name as the above is shown with the same code | symbol as the above.

  In the connection structure C of Modification 1-3, the outer periphery of the multi-core optical fiber 11 has one flat surface 11c, and the other outer periphery is a curved surface having an arc shape in the cross section, and the cross section shape is circular. It is formed in a so-called D shape in which the bow shape is deleted from. The cross-sectional shape of the fiber holding groove 26 of the groove forming member 21 of the mechanical splice 20 is formed in a trapezoid with a narrow bottom side. The width of the bottom surface 26 a that forms the fiber holding groove 26 is slightly wider than the width of the flat surface 11 c that the outer periphery of the multi-core optical fiber 11 has. The opening angle of both side surfaces 26b forming the fiber holding groove 26 is such that when the flat surface 11c of the multicore optical fiber 11 is in contact with the bottom surface 26a forming the fiber holding groove 26, the outer periphery of the multicore optical fiber 11 Is set so as to contact both side surfaces 26b forming the fiber holding groove 26. As shown in FIG. 9, the flat surface 11 c of the multicore optical fiber 11 contacts the bottom surface 26 a that forms the fiber holding groove 26, and the outer periphery of the multicore optical fiber 11 forms both side surfaces 26 b that form the fiber holding groove 26. A portion on the flat surface 11 c side of the multi-core optical fiber 11 is fitted in the fiber holding groove 26 of the groove forming member 21 so as to be in contact with each other and to have a gap in the fiber holding groove 26.

  In the connection structure C of Modification 1-3, the multicore optical fiber 11 is fitted in the fiber holding groove 26 of the groove forming member 21, and both sides of the multicore optical fiber 11 forming the fiber holding groove 26 of the groove forming member 21. The line 26 is in line contact with the surface 26 b and the lateral movement is restricted, and the multi-core optical fiber 11 is guided along the length direction by the fiber holding groove 26 of the groove forming member 21. Accordingly, the fiber holding groove 26 of the groove forming member 21 constitutes a fiber guide portion that guides each of the pair of multi-core optical fibers 11 along the length direction. In addition, as shown in FIG. 9, the flat surface 11 c of the outer periphery of the multi-core optical fiber 11 comes into contact with the bottom surface 26 a that forms the fiber holding groove 26 of the groove forming member 21, thereby causing the multi-core optical fiber 11 to rotate axially. Be regulated. Therefore, the bottom surface 26a that forms the fiber holding groove 26 of the groove forming member 21 that the flat surface 11c that the outer periphery of the multicore optical fiber 11 has contacts the flat surface 11c that the outer periphery of each of the pair of multicore optical fibers 11 has. Thus, a rotation restricting portion that restricts the shaft rotation of the multi-core optical fiber 11 is configured. The upper portion of the multi-core optical fiber 11 slightly protrudes from the fiber holding groove 26, and the top of the curved surface on the outer periphery of the multi-core optical fiber 11 comes into contact with and presses the fiber holding member 22, thereby the multi-core optical fiber 11. The separation of the groove forming member 21 from the fiber holding groove 26 is restricted.

  Furthermore, in the connection structure C of Modification 1-3, the seven cores 11a of the multi-core optical fiber 11 have six cores so as to form a regular hexagon around the one core 11a at the center in the cross section. 11a is provided and forms a triangular lattice as a whole. Two of the six surrounding cores 11a are provided close to the outer peripheral flat surface 11c. Therefore, as in the connection structure C of Modification 1-3, if there is a mutually independent symmetry between the symmetry of the cross-sectional shape of the multi-core optical fiber 11 and the symmetry of the core 11a in the cross-section, For example, there is a symmetry axis that is symmetric in the cross-sectional shape of the multi-core optical fiber 11 but not in the core 11a in the cross-section, and is not symmetric in the cross-sectional shape of the multi-core optical fiber 11 but symmetric in the core 11a in the cross-section. If there is a certain axis of symmetry, the core 11a can be distinguished and used properly based on one of the cores 11a without making the core 11a equivalent.

<Modification 1-4>
FIG. 10 shows a modified example 1-4 of the connection structure C of the multi-core optical fiber 11 according to the first embodiment. In addition, the part of the same name as the above is shown with the same code | symbol as the above.

  In the connection structure C of this modified example 1-4, similarly to the modified example 1-3, the outer periphery of the multi-core optical fiber 11 has one flat surface 11c, and the outer periphery of the other outer periphery is a circular arc in the cross section. The cross-sectional shape is formed in a so-called D shape in which an arc shape is removed from a circular shape. The cross-sectional shape of the fiber holding groove 26 of the groove forming member 21 of the mechanical splice 20 is a V-groove having an opening angle of 60 °, for example. Then, as shown in FIG. 10, the flat surface 11 c on the outer periphery of the multi-core optical fiber 11 is in contact with the lower surface 22 a of the fiber pressing member 22, and two portions where the outer cross section is an arc are the grooves forming member 21. A portion of the multi-core optical fiber 11 opposite to the flat surface 11 c side is fitted in the fiber holding groove 26 of the groove forming member 21 so as to contact both side surfaces 26 b forming the fiber holding groove 26.

  Further, in the connection structure C of the modified example 1-4, the multi-core optical fiber 11 is fitted into the fiber holding groove 26 of the groove forming member 21, and the both sides on which the multi-core optical fiber 11 forms the fiber holding groove 26 of the groove forming member 21. The line 26 is in line contact with the surface 26 b and the lateral movement is restricted, and the multi-core optical fiber 11 is guided along the length direction by the fiber holding groove 26 of the groove forming member 21. Accordingly, the fiber holding groove 26 of the groove forming member 21 constitutes a fiber guide portion that guides each of the pair of multi-core optical fibers 11 along the length direction. In addition, as shown in FIG. 10, the flat surface 11 c on the outer periphery of the multi-core optical fiber 11 contacts the lower surface 22 a of the fiber pressing member 22, thereby restricting the axial rotation of the multi-core optical fiber 11. Accordingly, the lower surface 22a of the fiber holding member 22 that contacts the outer flat surface 11c of the multi-core optical fiber 11 contacts the flat surface 11c of the outer periphery of each of the pair of multi-core optical fibers 11 and rotates the multi-core optical fiber. A rotation restricting portion to be restricted is configured. The upper portion of the multi-core optical fiber 11 slightly protrudes from the fiber holding groove 26, and the flat surface 11c on the outer periphery of the multi-core optical fiber 11 contacts and is pressed against the lower surface 22a of the fiber holding member 22, thereby The separation of the groove forming member 21 of the fiber 11 from the fiber holding groove 26 is restricted.

  Furthermore, in the connection structure C of Modification 1-4, the seven solids 111a of the multi-core optical fiber 11 have six cores so as to form a regular hexagon around the one core 11a at the center in the cross section. 11a is provided and forms a triangular lattice as a whole. Two of the surrounding six cores 11a are provided close to the outer peripheral flat surface 11c. Therefore, as in the connection structure C of Modification 1-4, if there is a mutually independent symmetry between the symmetry of the cross-sectional shape of the multi-core optical fiber 11 and the symmetry of the core 11a in the cross-section, For example, there is a symmetry axis that is symmetric in the cross-sectional shape of the multi-core optical fiber 11 but not in the core 11a in the cross-section, and is not symmetric in the cross-sectional shape of the multi-core optical fiber 11 but symmetric in the core 11a in the cross-section. If there is a certain axis of symmetry, the core 11a can be distinguished and used properly based on one of the cores 11a without making the core 11a equivalent.

(Embodiment 2)
11, FIG. 12 (a) and (b), and FIG. 13 show the connection structure C of the multi-core optical fiber 11 according to the second embodiment. In the connection structure C according to the second embodiment, a pair of multi-core optical fiber core wires 10 are connected by a mechanical splice 30. Portions common to the first embodiment are denoted by the same reference numerals as those in the first embodiment.

  The multi-core optical fiber core 10 has the same configuration as that of the first embodiment shown in FIG. Therefore, the cross-sectional shape of the multi-core optical fiber 11 is a regular hexagon.

  FIG. 14 shows a mechanical splice 30.

  The mechanical splice 30 includes an outer fixed sleeve 31 and an inner connection sleeve 32 fitted therein.

  The fixing sleeve 31 is formed in a cylindrical shape. The material of the fixing sleeve 31 is preferably a glass-based material because it is desired that the difference in coefficient of linear expansion of the multi-core optical fiber 11 due to temperature changes is small. In the case of using a curable adhesive, a transparent glass-based material is preferable. Further, when the fixing to the multi-core optical fiber core 10 is performed by caulking, the material of the fixing sleeve 31 is preferably a metal such as aluminum. The length of the fixing sleeve 31 is 20 to 60 mm, for example. The outer diameter of the fixed sleeve 31 is, for example, 1 to 4 mm. The outer shape of the cross-section of the circular hole of the fixing sleeve 31 is formed in a circular shape similar to the cross-sectional shape so that the multi-core optical fiber core wire 10 is fitted therein. Therefore, the inner diameter of the fixing sleeve 31 is For example, the outer diameter of the multi-core optical fiber core 10 is 250 μm.

  The connection sleeve 32 is formed in a cylindrical shape from a metal such as aluminum or quartz glass. The length of the connection sleeve 32 is shorter than the fixed sleeve 31 and is, for example, 2 to 20 mm. The outer shape in the cross section of the connection sleeve 32 is formed in the same circular shape as the cross section shape of the circular hole so as to be fitted in the fixing sleeve 31. Therefore, the outer diameter of the connection sleeve 32 is fixed. The inner diameter of the sleeve 31 and the outer diameter of the multi-core optical fiber core 10 are, for example, 250 μm. A fiber holding hole 33 for inserting the multi-core optical fiber 11 is formed in the connection sleeve 32, and the outer shape in the cross section thereof is the same as that of the cross section so that the multi-core optical fiber 11 is fitted inside. It is formed in a regular hexagon. Note that both ends of the fiber holding hole 33 are subjected to a countersink process in which an opening is widened outward so that the multi-core optical fiber 11 can be easily introduced.

  In the connection structure C of the multicore optical fiber 11 according to the second embodiment, the coating layer 12 is peeled off at one end of each of the pair of multicore optical fiber cores 10. One end of one of the multi-core optical fibers 10 is inserted from one end of the mechanical splice 30, and the multi-core optical fiber 11 exposed by peeling off the coating layer 12 is inserted into the fiber holding hole 33 of the connection sleeve 32 so that a gap is formed. The portion covered with the coating layer 12 on the base end side is fitted into the fixing sleeve 31. Also, one end of the other multi-core optical fiber core 10 is inserted from the other end of the mechanical splice 30, and the multi-core optical fiber 11 exposed by peeling off the coating layer 12 is inserted into the fiber holding hole 33 of the connection sleeve 32. The portion covered with the coating layer 12 on the base end side is fitted into the fixed sleeve 31. The multi-core optical fiber 11 of the pair of multi-core optical fibers 10 has an end face butted in the connection sleeve 32 in the mechanical splice 30, and therefore the seven cores 11a are also butted. The pair of multi-core optical fiber cores 10 are fixedly attached to the mechanical splice 30 by being bonded to the fixing sleeve 31 with an adhesive or by caulking the fixing sleeve 31, respectively.

  Here, in the connection structure C of the multi-core optical fiber 11 according to the second embodiment, the multi-core optical fiber 11 is guided along the length direction by the fiber holding hole 33 of the connection sleeve 32. Accordingly, the fiber holding hole 33 of the connection sleeve 32 constitutes a fiber guide portion that guides each of the pair of multi-core optical fibers 11 along the length direction. In addition, as shown in FIG. 14, the cross-sectional shape of the multi-core optical fiber 11 and the outer shape of the cross-section of the fiber holding hole 33 of the connection sleeve 32 are formed in the same regular hexagon. Is fitted into the fiber holding hole 33 of the connection sleeve 32, and any of the six flat surfaces 11c on the outer periphery of the multi-core optical fiber 11 contacts the corresponding inner wall surface 33a of the fiber holding hole 33 of the connection sleeve 32, thereby The multi-core optical fiber 11 is restricted in shaft rotation. Accordingly, any of the six inner wall surfaces 33a of the fiber holding hole 33 of the connection sleeve 32 contacts the flat surface 11c of the outer periphery of each of the pair of multicore optical fibers 11 to restrict the axial rotation of the multicore optical fiber 11. A rotation restricting portion is configured. The multi-core optical fiber 11 is fitted in the fiber holding hole 33 of the connection sleeve 32, so that not only axial rotation but also movement in any direction in the axial direction is restricted.

  Next, a method for connecting the multi-core optical fiber 11 according to the second embodiment will be described.

  First, for each of the pair of multi-core optical fibers 10, the coating layer 12 at one end is peeled to expose the multi-core optical fiber 11, and the end surface of the multi-core optical fiber 11 is cut to cut the end face. Process into a mirror surface. At this time, the coating layer 12 is preferably peeled off so that the sum of the exposed lengths of both the multi-core optical fibers 11 is the same as or slightly longer than the length of the connection sleeve 32 of the mechanical splice 30.

  Next, for each of the pair of multi-core optical fiber cores 10, one multi-core optical fiber core wire 10 is inserted through the fixing sleeve 31 of the mechanical splice 30.

  Subsequently, the exposed multi-core optical fiber 11 at one end of the multi-core optical fiber core 10 is inserted into the fiber holding hole 33 of the connection sleeve 32 of the mechanical splice 30 from both sides. Match. At this time, each of the pair of multi-core optical fibers 11 is guided along the length direction by the fiber holding hole 33 of the connection sleeve 32. In addition, each multi-core optical fiber 11 is restricted from rotating axially when any of the six inner wall surfaces 33a of the fiber holding hole 33 of the connection sleeve 32 is in contact with the outer flat surface 11c. Note that it is preferable to inject a refractive index matching agent into the fiber holding hole 33 of the connection sleeve 32 in advance.

  Then, the fixing sleeve 31 is slid to cover the connection sleeve 32 into which the multi-core optical fiber 11 is inserted from both sides, and both end portions of the fixing sleeve 31 are bonded to the multi-core optical fiber core wire 10 or fixed by caulking. .

  According to the connection structure C of the multi-core optical fiber 11 according to the second embodiment, each of the pair of multi-core optical fibers 11 is guided along the length direction by the fiber holding hole 33 constituting the fiber guide portion, and Since the inner wall surface 33a of the fiber holding hole 33 constituting the rotation restricting portion is brought into contact with the flat surface 11c provided on the outer periphery of the multi-core optical fiber 11, the shaft rotation is restricted. The pair of multi-core optical fibers 11 can be easily connected.

<Modification 2-1>
FIG. 15 shows a modified example 2-1 of the connection structure C of the multi-core optical fiber 11 according to the second embodiment. In addition, the part of the same name as the above is shown with the same code as the above.

  In the connection structure C of the modified example 2-1, the cross-sectional shape of the multi-core optical fiber 11 is a regular pentagon. The outer shape of the cross section of the fiber holding hole 33 of the connection sleeve 32 of the mechanical splice 30 is formed in the same regular pentagon as that of the multi-core optical fiber 11. Then, as shown in FIG. 15, the multicore optical fiber 11 is fitted in the fiber holding hole 33 of the connection sleeve 32, in which the outer shape of the cross section is the same regular pentagon as that of the multicore optical fiber 11. ing.

  Further, in the connection structure C of the modified example 2-1, the multi-core optical fiber 11 is guided along the length direction by the fiber holding hole 33 of the connection sleeve 32. Accordingly, the fiber holding hole 33 of the connection sleeve 32 constitutes a fiber guide portion that guides each of the pair of multi-core optical fibers 11 along the length direction. In addition, as shown in FIG. 15, any of the five flat surfaces 11 c on the outer periphery of the multi-core optical fiber 11 contacts the corresponding inner wall surface 33 a of the fiber holding hole 33 of the connection sleeve 32, thereby causing the multi-core optical fiber 11. The shaft rotation is restricted. Accordingly, any of the five inner wall surfaces 33a of the fiber holding hole 33 of the connection sleeve 32 is in contact with the flat surface 11c of the outer periphery of each of the pair of multicore optical fibers 11, thereby restricting the axial rotation of the multicore optical fiber 11. A rotation restricting portion is configured. The multi-core optical fiber 11 is fitted in the fiber holding hole 33 of the connection sleeve 32, so that not only axial rotation but also movement in any direction in the axial direction is restricted.

  Furthermore, in the connection structure C of the modified example 2-1, the seven cores 11a of the multi-core optical fiber 11 have six cores so as to form a regular hexagon around the one core 11a at the center in the cross section. 11a is provided and forms a triangular lattice as a whole. And only one of the surrounding six cores 11a is provided on a line connecting the center and the apex in the cross section, so that the pair of multi-core optical fibers 11 are also aligned in the axial rotation direction. Is performed and inserted into the connection sleeve 32 of the mechanical splice 30. Therefore, in the connection structure C of the modified example 2-1, since there is an independent symmetry between the symmetry of the cross-sectional shape of the multi-core optical fiber 11 and the symmetry of the core 11a in the cross-section, the core 11a Without being equivalent to each other, the core 11a can be distinguished and used on the basis of any one of the cores 11a.

<Modification 2-2>
FIG. 16 shows a modification 2-2 of the connection structure C of the multi-core optical fiber 11 according to the second embodiment. In addition, the part of the same name as the above is shown with the same code | symbol as the above.

  In the connection structure C of the modified example 2-2, the outer periphery of the multi-core optical fiber 11 has one flat surface 11c, and the other outer periphery is a curved surface having an arc shape in the cross section, and the cross section shape is circular. It is formed in a so-called D shape in which the bow shape is deleted from. The fiber holding hole 33 of the connection sleeve 32 of the mechanical splice 30 is formed in the same D shape as the cross-sectional shape of the multi-core optical fiber 11. Then, as shown in FIG. 16, the multicore optical fiber 11 is fitted in the fiber holding hole 33 of the connection sleeve 32 formed in the same D shape as the cross sectional shape of the multicore optical fiber 11. ing.

  In the connection structure C of the modification 2-2, the multi-core optical fiber 11 is guided along the length direction by the fiber holding hole 33 of the connection sleeve 32. Accordingly, the fiber holding hole 33 of the connection sleeve 32 constitutes a fiber guide portion that guides each of the pair of multi-core optical fibers 11 along the length direction. In addition, as shown in FIG. 16, the flat surface 11 c of the outer periphery of the multi-core optical fiber 11 comes into contact with the corresponding inner wall surface 33 a of the fiber holding hole 33 of the connection sleeve 32, thereby causing the multi-core optical fiber 11 to rotate axially. Be regulated. Accordingly, the inner wall surface 33a of the fiber holding hole 33 of the connection sleeve 32 corresponding to the flat surface 11c of the outer periphery of the multi-core optical fiber 11 comes into contact with the flat surface 11c of the outer periphery of the pair of multi-core optical fibers 11 and multi-core. A rotation restricting portion that restricts the shaft rotation of the optical fiber 11 is configured. The multi-core optical fiber 11 is fitted in the fiber holding hole 33 of the connection sleeve 32, so that not only axial rotation but also movement in any direction in the axial direction is restricted.

  Furthermore, in the connection structure C of the modification 2-2, the seven cores 11a of the multi-core optical fiber 11 have six cores so as to form a regular hexagon around the one core 11a at the center in the cross section. 11a is provided and forms a triangular lattice as a whole. And two of the surrounding six cores 11a are provided close to the outer peripheral flat surface 11c. Therefore, in the connection structure C of the modified example 2-2, since there is an independent symmetry between the symmetry of the cross-sectional shape of the multi-core optical fiber 11 and the symmetry of the core 11a in the cross-section, the core 11a Without being equivalent to each other, the core 11a can be distinguished and used on the basis of any one of the cores 11a.

(Other embodiments)
In the first and second embodiments and the modifications thereof, the cross-sectional shape of the multi-core optical fiber 11 is a regular hexagon, a regular pentagon, a square, and a D shape. It may be non-circular such as a polygon.

  In the second embodiment, the mechanical splice 30 includes the fixed sleeve 31 and the connection sleeve 32. However, the present invention is not limited to this, and a single member is used as shown in FIGS. 17 (a) and 17 (b). The mechanical splice 30 comprised by these may be sufficient. In this case, in order to configure the connection structure C, for each of the pair of multi-core optical fibers 10, the coating layer 12 at one end is peeled and the multi-core optical fiber 11 is exposed so as to protrude, Then, they are inserted from both sides of the mechanical splice 30 and the end faces thereof are butted together at the fiber holding hole 33 in the mechanical splice 30, and the mechanical splice 30 is attached to each of the pair of multi-core optical fiber cores 10 by bonding or caulking. Fix it.

  The present invention is useful for a connection structure and a connection method of a multi-core optical fiber.

C Multi-core optical fiber connection structure W Wedge member 10 Multi-core optical fiber core wire 11 Multi-core optical fiber 11a Core 11b Clad 11c Flat surface 12 Coating layer 20, 30 Mechanical splice 21 Groove forming member 22 Fiber holding member 23 Core wire holding member 24 Fiber Insertion member 25 Core wire attachment member 26 Fiber holding groove 26a Bottom surface 26b Side surface 27 Core wire holding groove 28 Defect portion 29 Fiber insertion port 31 Fixing sleeve 32 Connection sleeve 33 Fiber holding hole 33a Inner wall surface

Claims (6)

A pair of multi-core optical fibers each having a flat surface on the outer periphery;
A mechanical splice that connects the end faces of the pair of multi-core optical fibers by abutting each other;
A multi-core optical fiber connection structure comprising:
The mechanical splice is
A fiber guide for guiding each of the pair of multi-core optical fibers along the length direction;
A rotation restricting portion for restricting axial rotation of the multicore optical fiber in contact with a flat surface of each of the pair of multicore optical fibers;
A multi-core optical fiber connection structure comprising: The multi-core optical fiber connection structure according to claim 1,
A multi-core optical fiber connection structure in which the fiber guide portion is constituted by a fiber holding groove. In the connection structure of the multi-core optical fiber according to claim 2,
A multi-core optical fiber connection structure in which the rotation restricting portion is configured by a surface forming the fiber holding groove. The multi-core optical fiber connection structure according to claim 1,
A multi-core optical fiber connection structure in which the fiber guide portion is constituted by a fiber holding hole. In the multi-core optical fiber connection structure according to claim 4,
A multi-core optical fiber connection structure in which the rotation restricting portion is configured by an inner wall surface of the fiber holding hole. A method of connecting a pair of multi-core optical fibers each having a flat surface on the outer periphery,
The end surfaces of the pair of multicore optical fibers are opposed to the fiber guide portions that guide the pair of multicore optical fibers along the length direction, and the rotation restricting portions are in contact with the outer flat surfaces. Providing the shaft rotation to be regulated;
Abutting the end faces of the pair of multicore optical fibers by moving at least one of the pair of multicore optical fibers along the length direction by guiding the fiber guide; and
Multi-core optical fiber connection method including:

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