Patent ID: 8867881

Claim:
A multicore optical fiber which comprises: a plurality of cores extending along a predetermined axis while being arranged like a hexagonal lattice on a cross section perpendicular to the axis; and a cladding region surrounding each of the plurality of cores, all of core portions, each constituting at least a part of the associated one of the plurality of cores, having substantially the same structure; wherein, letting κ be the mode-coupling coefficient between cores, β be the propagation constant of each of the plurality of cores, Λ be the core pitch, R th be the radius of curvature of the fiber, L F be the fiber length, XT μ be the average value of a crosstalk distribution after propagation over the fiber length L F , XT s be the maximum permissible XT μ , Λ th be the minimum permissible Λ, and R th be the maximum permissible R, the multicore optical fiber satisfies any of the following expressions (1) to (3), whereby XT μ is XT s or less: 6.2 ⁢ κ 2 β ⁢ R Λ ⁢ L F ≤ X ⁢ ⁢ T S ( 1 ) Λ ≥ 12 ⁢ κ 2 β ⁢ R ⁢ L F X ⁢ ⁢ T S = Λ th ( 2 ) R ≤ 1 12 ⁢ β κ 2 ⁢ Λ ⁢ X ⁢ ⁢ T S L F = R th . ( 3 )