JP2012215695A - Multi-core fiber - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a multi-core fiber that can be relatively easily manufactured and has reduced crosstalk.SOLUTION: A multi-core fiber 1 comprises: a plurality of first cores 11 with first optical characteristics; a plurality of second cores 12 with second optical characteristics different from the first optical characteristics; a clad 14 for forming holes 13 and covering the plurality of first cores 11 and the plurality of second cores 12. The holes 13 are positioned on line segments connecting adjacent cores with the same optical characteristics among the plurality of first cores 11 and the plurality of second cores 12.

Description

  The present invention relates to a multi-core fiber.

  In recent years, a technique using a multi-core fiber, which is an optical fiber having a plurality of cores, as a transmission fiber has been proposed. By using a multi-core fiber, the transmission capacity can be made larger than when an optical fiber having a single core is used.

  As such a multi-core fiber, one having a hole assist structure in which holes are provided around each core is known (for example, Patent Document 1). According to this multicore fiber, crosstalk between cores can be reduced by holes around each core.

JP 2011-18013 A

  However, the multi-core fiber described in Patent Document 1 has a problem that it is difficult to manufacture due to the large number of holes and the complexity of arrangement.

  Accordingly, one of the objects of the present invention is to provide a multi-core fiber with reduced crosstalk that can be manufactured relatively easily by reducing the number of holes.

  In one embodiment of the present invention, a plurality of first cores having a first optical characteristic, a plurality of second cores having a second optical characteristic different from the first optical characteristic, and a hole are formed And providing a multi-core fiber including a clad covering the plurality of first cores and the plurality of second cores. The hole is located on a line segment connecting adjacent cores having the same optical characteristics among the plurality of first cores and the plurality of second cores.

  In the multi-core fiber, it is preferable that all the holes are located on a line segment that connects adjacent cores having the same optical characteristics.

  In the multi-core fiber, it is preferable that one hole is located on a line connecting a pair of adjacent cores having the same optical characteristics.

  Moreover, it is preferable that the said hole is located on the midpoint of the line segment which connects the said cores which have the same optical characteristic adjacent.

  Further, in the multicore fiber, in the cross section of the multicore fiber, the plurality of first cores and the plurality of second cores are alternately arranged in a square lattice shape, and the holes are formed in the square lattice. It is preferable to be located at the center of the unit cell.

  In the multi-core fiber, for example, since one or both of the refractive index and the effective area of the first core and the second core are different, the first optical characteristic and the second optical characteristic are different. Different.

  According to the present invention, it is possible to provide a multi-core fiber with reduced crosstalk that can be manufactured relatively easily.

FIG. 1 is a cross-sectional view of a multi-core fiber according to the first embodiment of the present invention. FIG. 2 is a cross-sectional view of the multi-core fiber taken along line II-II in FIG. FIGS. 3A and 3B are cross-sectional views of multicore fibers according to the second and third embodiments of the present invention.

Embodiment
FIG. 1 is a cross-sectional view of a multi-core fiber 1 according to the first embodiment of the present invention. The multi-core fiber 1 includes a plurality of first cores 11 (11a to 11e) having a first optical characteristic, a plurality of second cores 12 (12a to 12d) having a second optical characteristic, the cores 11 and 11 12, and a plurality of holes 13 (13 a to 13 d) formed in the cladding 14.

  The first optical characteristic of the first core 11 and the second optical characteristic of the second core 12 are different. For example, when the refractive index and effective area of the first core 11 and the second core 12 are different, the first optical characteristic and the second optical characteristic are different. The first core 11 and the second core 12 are different in one or both of the refractive index and the effective area.

  FIG. 1 shows a first core 11 and a second core 12 having different effective indices but the same effective cross-sectional area. In this case, the diameters of the first core 11 and the second core 12 are, for example, 10 μm. Moreover, although the cross-sectional area of the 1st core 11 and the refractive index of a 2nd core are the same, when the effective cross-sectional area differs, the diameter of the 1st core 11 and the 2nd core 12 is each, for example 5-7 μm, 8-16 μm.

  The inner diameter of the air holes 13 is, for example, 10 μm. The cross-sectional shape of the air holes 13 is not limited to a circle. The air holes 13 do not contact the first core 11 and the second core 12. Therefore, if the interval between the center lines of the adjacent first cores 11 is L1, and the diameter of the cross section of the first core 11 in the direction of the interval L1 is A1, the diameter D1 of the hole 13 in the direction of the interval L1 is D1. The relationship of <L1-A1 is satisfied. Further, when the interval between the center lines of the adjacent second cores 12 is L2, and the diameter of the cross section of the second core 12 in the direction of the interval L2 is A2, the diameter D2 of the hole 13 in the direction of the interval L2 is D2 <The relationship of L2-A2 is satisfied.

  As shown in FIG. 1, in one cross section of the multi-core fiber 1, the first core 11 and the second core 12 are arranged on lattice points of a square lattice (square lattice or rectangular lattice). Further, the first core 11 and the second core 12 are preferably arranged alternately so that cores having the same optical characteristics are separated as much as possible.

  Moreover, the void | hole 13 is located on the line segment which connects the core which has the same optical characteristic which adjoins. Specifically, the hole 13a is located on the line segment connecting the first cores 11a and 11c, the hole 13b is located on the line segment connecting the first cores 11b and 11c, and the first The hole 13c is located on the line segment connecting the cores 11c and 11d, and the hole 13d is located on the line segment connecting the first cores 11c and 11e.

  Further, a hole 13a is located on a line segment connecting the second cores 12a and 12b, a hole 13b is located on a line segment connecting the second cores 12a and 12c, and the second core 12b Hole 13c is located on the line connecting 12d, and hole 13d is located on the line connecting the second cores 12c and 12d.

  Generally, in a multicore fiber, when cores having the same optical characteristics are adjacent to each other, crosstalk occurs between the cores. Further, when cores having different optical characteristics are adjacent to each other, crosstalk between the cores is small.

  In the multi-core fiber 1 according to the present embodiment, since cores having different optical characteristics are used, crosstalk between them is suppressed. Further, since the holes 13 are formed on the line segment connecting the adjacent cores having the same optical characteristics, the refractive index between the cores is greatly changed, the electromagnetic waves generated between the cores are reduced, and the adjacent optical characteristics are the same. Crosstalk between cores having the same is also reduced.

  Note that all the holes 13 are located on a line segment connecting adjacent cores having the same optical characteristics, that is, there are no holes 13 located on a line segment connecting adjacent cores having the same optical characteristics. Preferably not. Further, it is preferable that only one hole 13 is located on a line connecting a pair of adjacent cores having the same optical characteristics. Furthermore, it is preferable that the hole 13 is located on the midpoint of a line segment connecting adjacent cores having the same optical characteristics. That is, as shown in FIG. 1, when the first core 11 and the second core 12 are arranged on lattice points of a square lattice, the hole 13 is positioned at the center of the unit lattice of the square lattice. It is preferable to do.

  With these structures, crosstalk can be effectively reduced by a small number of holes 13. If the number of the holes 13 is small, the multi-core fiber 1 can be easily manufactured.

  The refractive index of the first core 11 and the refractive index of the second core 12 are higher than the refractive index of the cladding 14. For example, the first core 11 and the second core 12 are made of quartz glass to which impurities such as germanium (Ge) are added, and the cladding 14 is made of pure quartz glass. For example, the first core 11 and the second core 12 are made of a single mode optical fiber (SMF).

  Moreover, it is preferable that the shortest distance between the outer peripheral surface of the clad 14 and the outer peripheral surface of each core in the multi-core fiber 1 is 25 μm or more, for example, in the range of 25 to 60 μm. Thereby, the tolerance with respect to the bending of the multi-core fiber 1 can be improved, and microbending loss can be suppressed.

  FIG. 2 is a cross-sectional view of the multi-core fiber 1 taken along line II-II in FIG. As shown in FIG. 2, the holes 13 are formed along the length direction of the multi-core fiber 1. The air holes 13 are preferably formed continuously along the length direction of the multicore fiber 1, but may not be completely continuous.

  The number and arrangement of the first cores 11 and the second cores 12 are not limited to those shown in FIG.

  FIGS. 3A and 3B are cross-sectional views of the multi-core fibers of the second and third embodiments, in which the first core 11 and the second core 12 are arranged in a staggered pattern, respectively. The

  The multi-core fiber 1 shown in FIG. 3A is formed in a first core 11 (11f to 11h), a second core 12 (12e to 12h), a clad 14 covering these cores, and the clad 14. In addition, the holes 13 (13e to 13h) are included.

  In one cross section of the multi-core fiber 1, a hole 13e is located on a line segment connecting the first cores 11f and 11g, and a hole 13h is located on a line segment connecting the first cores 11g and 11h.

  In addition, a hole 13e is located on a line segment connecting the second cores 12e and 12f, a hole 13f is located on a line segment connecting the second cores 12e and 12g, and the second core 12f Hole 13g is located on the line connecting 12h, and hole 13h is located on the line connecting the second cores 12g and 12h.

  The multi-core fiber 1 shown in FIG. 3B is formed in a first core 11 (11i to 11l), a second core 12 (12i to 12k), a clad 14 covering these cores, and the clad 14. Including holes 13 (13i to 13k).

  A hole 13i is located on the line segment connecting the first cores 11i and 11j, a hole 13j is located on the line segment connecting the first cores 11j and 11k, and the first cores 11j and 11l Hole 13k is located on the line segment connecting the two.

  Further, a hole 13i is located on a line segment connecting the second cores 12i and 12j, a hole 13j is located on a line segment connecting the second cores 12i and 12k, and the second core 12j Hole 13k is located on the line connecting 12k.

  In addition, since the space | interval between the 1st cores 11i and 11k, the 1st cores 11i and 11l, and the 1st cores 11k and 11l is comparatively large, a void | hole is not formed among these, but cross You may form in order to reduce talk more.

(Effect of embodiment)
According to the first to third embodiments of the present invention, since the first core 11 and the second core 12 having different optical characteristics are used, the first core 11 and the second core 12 are adjacent to each other. Crosstalk between them is suppressed when they match.

  Moreover, since the void | hole 13 is formed on the line segment which ties the adjacent core (the two adjacent 1st cores 11 or the 2nd adjacent 2nd cores 12) which has the same optical characteristic, these Electromagnetic waves generated between the cores are reduced, and crosstalk between adjacent cores having the same optical characteristics is also reduced.

  Since the crosstalk can be reduced more effectively than the conventional multi-core fiber, the number of cores can be increased as compared with the conventional multi-core fiber.

  Moreover, since the crosstalk can be reduced by a small number of holes 13, the multi-core fiber 1 can be easily manufactured, and the yield can be improved.

  While the embodiments of the present invention have been described above, the embodiments described above do not limit the invention according to the claims. In addition, it should be noted that not all the combinations of features described in the embodiments are essential to the means for solving the problems of the invention.

1 Multi-core fiber 11a to 11l First core 12a to 12k Second core 13a to 13k Hole 14 Cladding

Claims (6)

A plurality of first cores having a first optical characteristic;
A plurality of second cores having a second optical characteristic different from the first optical characteristic;
A clad formed with holes and covering the plurality of first cores and the plurality of second cores;
The hole is located on a line segment connecting adjacent cores having the same optical characteristics among the plurality of first cores and the plurality of second cores.
Multi-core fiber. The holes are all located on a line segment connecting the adjacent cores having the same optical characteristics,
The multi-core fiber according to claim 1. One hole is located on a line segment connecting a pair of adjacent cores having the same optical characteristics,
The multi-core fiber according to claim 1 or 2. The hole is located on the midpoint of a line segment connecting the adjacent cores having the same optical characteristics,
The multi-core fiber according to any one of claims 1 to 3. In one cross section of the multi-core fiber, the plurality of first cores and the plurality of second cores are alternately arranged in a square lattice shape, and the hole is located at the center of the unit lattice of the square lattice. ,
The multi-core fiber according to any one of claims 1 to 4. The first optical characteristic and the second optical characteristic are different because one or both of the refractive index and effective area of the first core and the second core are different.
The multi-core fiber according to any one of claims 1 to 5.

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