Fiber connecting body, optical communication system, optical device, and method for manufacturing fiber connecting body

1 . A fiber connected body comprising:

a plurality of multi-core fibers including a first multi-core fiber, a second multi-core fiber, and

a third-multi-core fiber, each of which comprises:

a cladding;

a marker disposed in the cladding; and

cores disposed in the cladding at different distances from the marker, wherein in a coupling state of the fiber connected body, one end surface of the second multi-core fiber

is connected to one end surface of the first multi-core fiber such that:

each of the cores in the second multi-core fiber is connected to a respective one of the cores in the first multi-core fiber, and

the marker of the second multi-core fiber is connected to a part of the first multi-core fiber other than the marker thereof, or the marker of the first multi-core fiber is connected to a part of the second multi-core fiber other than the marker thereof,

in the coupling state, one end surface of the third multi-core fiber is connected to the other end surface of the second multi-core fiber such that:

each of the cores in the third multi-core fiber is connected to a respective one of the cores in the second multi-core fiber, and

the marker of the third multi-core fiber is connected to a part of the second multi-core fiber other than the marker thereof, or the marker of the second multi-core fiber is connected to a part of the third multi-core fiber other than the marker thereof,

the fiber connected body is configured such that, in a state where the second multi-core fiber is rotated about its axis:

the one end surface of the rotated second multi-core fiber is connected to the one end surface of the first multi-core fiber,

the other end surface of the rotated second multi-core fiber is connected to the one end surface of the third multi-core fiber,

each of the cores in the rotated second multi-core fiber is connected to a respective one of the cores in the first multi-core fiber,

the marker in the rotated second multi-core fiber is connected to a part of the marker in the first multi-core fiber, or the marker in the first multi-core fiber is connected to a part of the marker in the rotated second multi-core fiber,

each of the cores in the third multi-core fiber is connected to a respective one of the cores in the rotated second multi-core fiber, and

the marker in the third multi-core fiber is connected to a part of the marker in the rotated second multi-core fiber, or the marker in the rotated second multi-core fiber is connected to a part of the marker in the third multi-core fiber,

a total number of the cores in the first multi-core fiber and a total number of the cores in the third multi-core fiber are both n, where the n is a natural number greater than or equal to three,

in each of the first multi-core fiber, the second multi-core fiber, and the third-multi-core fiber, the cores are arranged in order from closest to farthest from the marker, and

in the coupling state, an i-th core arranged in order in the third multi-core fiber is connected to one of the cores in the second multi-core fiber that is connected to an i-th core arranged in order in the first multi-core fiber, where i is a natural number greater than or equal to one and less than or equal to n.

2 . The fiber connected body as set forth in claim 1 , wherein in both end surfaces of the fiber connected body, cores used for input of an optical signal are disposed to be diagonal to each other and cores used for output of an optical signal are disposed to be diagonal to each other.

3 . A fiber connected body comprising:

four or more multi-core fibers connected to each other, each comprising:

a cladding;

cores disposed in the cladding to be axisymmetric with respect to imaginary symmetry axes in a cross section of each of the four or more multi-core fibers; and

a marker disposed in the cladding different distances from respective ones of the cores; and

junctions at which two adjacent multi-core fibers of the four or more multi-core fibers are connected to each other such that a first end surface of one of the two adjacent multi-core fibers is connected to a second end surface of the other of the two adjacent multi-core fibers, wherein

the imaginary symmetry axes in the cross section of each of the four or more multi-core fibers include a specific imaginary symmetry axis, wherein the specific imaginary symmetry axis has a common positional relationship with the cores and the marker among the four or more multi-core fibers,

in an odd number of three or more junctions among the junctions:

each of the cores in the first end surface overlaps a respective one of the cores in the second end surface,

a first core closest to the marker in the first end surface overlaps a second core in the second end surface that is axisymmetric, with respect to the specific imaginary symmetry axis in the other of the two adjacent multi-core fibers, to a third core closest to the marker in the second end surface, and

a fourth core in the first end surface that is axisymmetric, with respect to the specific imaginary symmetry axis in the one of the two adjacent multi-core fibers, to the first core overlaps the third core.

4 . The fiber connected body as set forth in claim 3 , wherein the cores are disposed at locations that do not overlap the specific imaginary symmetry axis.

5 . The fiber connected body as set forth in claim 3 , wherein in both end surfaces of the fiber connected body, cores used for input of an optical signal are disposed to be diagonal to each other and cores used for output of an optical signal are disposed to be diagonal to each other.

6 . The fiber connected body as set forth in claim 3 , wherein

the four or more multi-core fibers include:

a first multi-core fiber disposed at one end of the fiber connected body; and

a second multi-core fiber disposed at the other end of the fiber connected body,

a total number of the cores in the first multi-core fiber and a total number of the cores in the second multi-core fiber are both n, where the n is a natural number greater than or equal to two,

in each of the first multi-core fiber and the second multi-core fiber, the cores are arranged in order from closest to farthest from the marker, and

an i-th core arranged in order in the first multi-core fiber is optically coupled to a core in the second multi-core fiber that is axisymmetric, with respect to the specific imaginary symmetry axis in the second multi-core fiber, to an i-th core arranged in order in the second multi-core fiber, where i is a natural number greater than or equal to one and less than or equal to n.