Multi-core optical fiber and multi-core optical fiber cable

A multi-core optical fiber comprising:

• multiple cores each extending along a central axis;
• a common cladding covering each of the multiple cores, and having a refractive index lower than each refractive index of the multiple cores;
• and
• a resin coating provided on an outer periphery of the common cladding, wherein
• on a cross-section of the multi-core optical fiber, the cross-section being orthogonal to the central axis, the multiple cores are arranged such that no adjacent relationship is established between cores each having an adjacent relationship with any core,
• on the cross-section, the multiple cores are respectively arranged at positions of line symmetry with respect to an axis that serves as a symmetric axis, that passes through a center of the common cladding intersecting with the central axis, and that intersects with none of the multiple cores,
• an outer diameter of the resin coating defined on the cross-section falls within a range of 235 μm or more and 265 μm or less,
• a diameter CD [μm] of the common cladding defined on the cross-section falls within a range of a value of CDnominal−1 μm or more and a value of CDnominal+1 μm with a value of 146 μm or more and 195 μm or less used as a nominal value CDnominal [μm],
• a mode field diameter MFD [μm] of light at a wavelength of 1310 nm guided by the each core of the multiple cores falls within a range of a value of a wavelength reference value−0.4 μm or more and a value of the wavelength reference value+0.4 μm or less with a value of 8.2 μm or more used as the wavelength reference value,
• a shortest distance dcoat [μm] of respective distances from an interface between the resin coating and the common cladding to centers of the multiple cores, a mode field diameter MFD [μm] of light at a wavelength of 1310 nm, and a cable cutoff wavelength λcc [μm] satisfies a following Formula (1):
• dcoat≥2.88MFD/λcc+5.36 (1),
• the multi-core optical fiber has a structure satisfying one of a first condition and a second condition, and has an optical characteristic satisfying any one of a third condition to a sixth condition,
• the first condition is that the each core of the multiple cores is in direct contact with the common cladding,
• the second condition is that optical claddings respectively corresponding to the multiple cores are respectively disposed between the multiple cores and the common cladding, and the optical claddings each have a relative refractive index difference Δ2 of −0.1% or more and 0.1% or less with respect to the common cladding,
• the third condition is that the multiple cores include 12 cores, for each of the 12 cores, a total crosstalk corresponding to the fiber length of 10 km from the cores having the adjacent relationship at a wavelength of 1360 nm is −6.8 dB or less, and a center-to-center interval Λ between the cores having the adjacent relationship satisfies a following Formula (2):
• Λ≥2.34MFD/λcc+12.1 (2), and
• the multi-core optical fiber satisfies a following Formula (3):
• CDnominal≥13.15MFD/λcc+54.25 (3),
• the fourth condition is that the multiple cores include 12 cores, for each of the 12 cores, the total crosstalk corresponding to the fiber length of 10 km from the cores having the adjacent relationship at the wavelength of 1360 nm is −16.8 dB or less, and the center-to-center interval Λ between the cores having the adjacent relationship satisfies a following Formula (4):
• Λ≥2.73MFD/λcc+12.7 (4), and
• the multi-core optical fiber satisfies a following Formula (5):
• CDnominal≥14.07MFD/λcc+55.59 (5),
• the fifth condition is that the multiple cores include 16 cores, for each of the 16 cores, a total crosstalk corresponding to the fiber length of 10 km from the cores having the adjacent relationship at the wavelength of 1360 nm is −6.8 dB or less, and the center-to-center interval Λ between the cores having the adjacent relationship satisfies a following Formula (6):
• Λ≥2.34MFD/λcc+12.1 (6), and,
• the multi-core optical fiber satisfies a following Formula (7):
• CDnominal≥15.77MFD/λcc+68.58 (7), and
• the sixth condition is that the multiple cores include 16 cores, for each of the 16 cores, the total crosstalk corresponding to the fiber length of 10 km from the cores having the adjacent relationship at the wavelength of 1360 nm is −16.8 dB or less, and the center-to-center interval Λ between the cores having the adjacent relationship satisfies a following Formula (8):
• Λ≥2.73MFD/λcc+12.7 (8) and
• the multi-core optical fiber satisfies a following Formula (9):
• CDnominal≥17.01MFD/λcc+70.37 (9).