Patent ID: 8718429

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 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, XT S be the permissible maximum XT μ , Λ th be the minimum permissible Λ, and R th be the permissible maximum R, the multicore optical fiber satisfies any of the following expressions (1) to (3): XT μ = 6 · 2 ⁢ κ 2 β ⁢ R Λ ⁢ L F ≤ XT S ( 1 ) Λ ≥ 12 ⁢ κ 2 β ⁢ R ⁢ L F XT S = Λ th ( 2 ) R ≤ 1 12 ⁢ β κ 2 ⁢ Λ ⁢ XT S L F = R th . ( 3 )