Patent ID: 9588284
Date: 2017-03-07
CPC Classifications: G02B

Claim:
1. A multi-core fiber comprising: nine or more core elements each including a core that propagates light of at least up to a second-order LP mode in a C band and an L band, an inner cladding layer that surrounds an outer circumferential face of the core and has a refractive index lower than a refractive index of the core, and a trench layer that surrounds an outer circumferential face of the inner cladding layer and has a refractive index lower than the refractive index of the inner cladding layer; and an outer cladding that surrounds outer circumferential faces of the trench layers and has a refractive index higher than the refractive index of the trench layer and lower than the refractive index of the core, wherein effective refractive indices of light propagating through cores adjacent to each other are different from each other such that a magnitude of crosstalk of light of a highest-order LP mode commonly propagating through the cores adjacent to each other between the cores adjacent to each other becomes a peak at a bending diameter smaller than a diameter of 100 mm, and wherein the core has a higher refractive index in an area including a center axis than in an area disposed on an outer circumferential side such that a differential mode group delay of the core is 700 picoseconds/km or less.