Multicore fiber with different-mode interaction section

A multicore fiber comprising:

• a first core that propagates light of up to an x-th order LP mode (here, x is an integer of “2” or more);
• and
• a second core that propagates light of up to a y-th order LP mode (here, y is an integer of “1” or more),
• wherein a different-mode interaction section in which a propagation constant of light of an x1-th order LP mode of the first core (here, x1 is an integer of “1” or more and x or less) and a propagation constant of light of a y1-th order LP mode of the second core (here, y1 is an integer of “1” or more and y or less other than x1) coincide with each other and a different-mode non-interaction section in which a propagation constant of light of each LP mode of the first core and a propagation constant of light of each LP mode of the second core are configured not to coincide with each other are arranged,
• wherein the multicore fiber further comprising:
• a third core that propagates light of up to a z-th order LP mode (here, z is an integer or “1” or more),
• wherein x is an integer of “3” or more,
• in the different-mode interaction section, a propagation constant of light of an x2-th order LP mode of the first core (here, x2 is an integer of “1” or more and x or less other than x1) and a propagation constant of light of a z1-th order LP mode of the third core (here, z1 is an integer of “1” or more and z or less other than x1 and x2) coincide with each other, and
• in the different-mode non-interaction section, a propagation constant of light of each LP mode of the first core and a propagation constant of light of each LP mode of the third core do not coincide with each other.

A multicore fiber comprising:

• a first core that propagates light of up to an x-th order LP mode (here, x is an integer of “2” or more);
• a second core that propagates light of up to a y-th order LP mode (here, y is an integer of “1” or more);
• and
• a common cladding surrounding the first core and the second core,
• wherein a different-mode interaction section in which a propagation constant of light of an x1-th order LP mode of the first core (here, x1 is an integer of “1” or more and x or less) and a propagation constant of light of a y1-th order LP mode of the second core (here, y1 is an integer of “1” or more and y or less other than x1) coincide with each other and a different-mode noninteraction section in which a propagation constant of light of each LP mode of the first core and a propagation constant of light of each LP mode of the second core are configured not to coincide with each other are arranged,
• wherein the first core is positioned at the center of the common cladding,
• wherein a cutoff wavelength of the LP21 mode of the first core is larger than a cutoff wavelength of the LP21 mode of the second core in the different-mode non-interaction section.