Optical fiber

An optical fiber comprising:

• a core group composed of a plurality of cores extending along a fiber axis;
• a common cladding including the core group;
• and a coating covering an outer periphery of the common cladding,
• wherein in a cross section of the optical fiber perpendicular to the fiber axis, the common cladding has a circular outer peripheral shape and a core group constellation indicative of a constellation of the plurality of cores has symmetry, and
• wherein the optical fiber satisfies either one of first and second configurations,
• the first configuration being defined in that:
• in the cross section, core group symmetry being the symmetry of the core group constellation is at least one of line symmetry and rotational symmetry;
• and
• in the cross section, a core group position in the common cladding is separated in a predetermined separation direction from a cladding center of the common cladding and, as a result, all types of cladding symmetry featuring a structure of the common cladding including the core group constellation are broken,
• the second configuration being defined in that:
• in the cross section, the cladding symmetry is symmetry defined by only a line symmetry axis of one axis;
• and
• the coating is provided with a distinguishing marker for distinguishment of a fiber end.