Patent ID: 8811785

Claim:
A multi-core optical fiber comprising a plurality of cores, the multi-core optical fiber satisfying at least one of first to third conditions, wherein the first condition is defined by satisfying at least either of relations of Expressions (1) and (2) below at a wavelength of 1550 nm, when a first core represents a core with a largest crosstalk from other core, D [ps/(nm·km)] represents a chromatic dispersion of the first core, A eff [μm 2 ] represents an effective area of the first core, α dB [dB/km] represents a transmission loss of the first core, η WC [/km] represents a sum of power coupling coefficients to the first core from the other cores, μ X,WC [dB] [dB] represents a sum of statistical averages of crosstalks to the first core from the other cores after 80 km propagation, η WC ≤ 1.57 × 10 - 5 [ 0.71 - 1.39 ⁢ ( 10 10 ⁢ α d ⁢ ⁢ B - 1 ) (  D  ⁢ A eff 2 ⁢ α d ⁢ ⁢ B ⁢ 10 10 ⁢ α d ⁢ ⁢ B ) 1 3 ] ( 1 ) - 49.3 ≤ 10 3 ⁢ log 10 [  D  ⁢ A eff 2 ⁢ α d ⁢ ⁢ B ⁢ 10 8 ⁢ α d ⁢ ⁢ B ( 10 8 ⁢ α d ⁢ ⁢ B - 1 ) 3 ] + μ X , WC [ d ⁢ ⁢ B ] ≤ - 31.8 , ( 2 ) wherein the second condition is defined by: a fundamental mode in each of the plurality of cores having an effective area of not less than 120 μm 2 at the wavelength of 1550 nm, a transmission loss of not more than 0.195 dB/km at the wavelength of 1550 nm, a chromatic dispersion of not less than about 17 ps/(nm·km) at the wavelength of 1550 nm, and a bending loss per 100 turns of not more than 0.5 dB in a bending radius of 30 mm at a wavelength of 1625 nm; a difference of the transmission loss of the fundamental mode at the wavelength of 1550 nm between different cores out of the plurality of cores, the difference being at most 0.02 dB/km or less; and a sum of statistical averages of crosstalks to a core from other cores out of the plurality of cores after 80 km propagation, the sum being not more than −32.9 dB, and wherein the third condition is defined by: a fundamental mode in each of the plurality of cores having an effective area of not less than 80 μm 2 at the wavelength of 1550 nm, a transmission loss of not more than 0.195 dB/km at the wavelength of 1550 nm, a chromatic dispersion of not less than about 17 ps/(nm·km) at the wavelength of 1550 nm, and a bending loss per 100 turns of not more than 0.5 dB in a bending radius of 30 mm at the wavelength of 1625 nm; a difference of the transmission loss of the fundamental mode at the wavelength of 1550 nm between different cores out of the plurality of cores, the difference being at most 0.02 dB/km or less; and a sum of statistical averages of crosstalks to a certain core from other cores out of the plurality of cores after 80 km propagation, the certain core representing a core with a largest crosstalk from other cores, the sum being not less than −53.4 dB and not more than −33.9 dB.