Multicore optical fiber and optical transmission system
A multi-core optical fiber includes: a pair of cores; and a cladding that covers both of the pair of cores. A diameter of the cladding is 124 μm or more and 126 μm or less. A distance between centers of the pair of cores is 46.5 μm or less. Cross talk between counter-propagating cores at a wavelength of 1550 nm is −30 dB/100 km or less.
1 . An uncoupled multi-core optical fiber comprising:
a pair of cores, wherein diameters, materials, additive elements, or refractive index distributions of the pair of cores are different from each other, such that propagation constants of light waves propagating through the pair of cores are different from each other;
a cladding that covers both of the pair of cores; and
a low refractive index portion disposed between the pair of cores, being spaced apart from the pair of cores, and having a refractive index lower than a refractive index of the cladding and a diameter of at least 0.5 times a diameter of each of the pair of cores,
wherein a diameter of the cladding is 124 μm or more and 126 μm or less,
a distance between centers of the pair of cores is 46.5 μm or less, and
cross talk between counter-propagating cores at a wavelength of 1550 nm is −30 dB/100 km or less.
2 . The uncoupled multi-core optical fiber according to claim 1 , wherein a bending loss at a wavelength of 1625 nm when wound in an annular shape with a radius of 30 mm is 0.25 dB/100 turns or less.
3 . The uncoupled multi-core optical fiber according to claim 1 , wherein a cable cut-off wavelength is 1530 nm or less.
4 . The uncoupled multi-core optical fiber according to claim 1 , wherein the cladding comprises:
an optical cladding covering the pair of cores; and
a physical cladding surrounding the optical cladding and having a refractive index greater than or equal to a refractive index of the optical cladding.
5 . The uncoupled multi-core optical fiber according to claim 4 , wherein a relative refractive index difference of the physical cladding with respect to the optical cladding is 0.1% or more 0.4% or less.
6 . An optical transmission system comprising:
the uncoupled multi-core optical fiber according to claim 1 ; and
an optical transmitter and an optical receiver connected to both ends of each of the pair of cores.