Abstract: An optical transmission system includes an optical transmitting unit that outputs at least one optical signal having a wavelength included in an operation wavelength band and a holey fiber that is connected to the optical transmitting unit. The holey fiber includes a core and a cladding formed around the core. The cladding includes a plurality of holes formed around the core in a triangular lattice shape. The holey fiber transmits the optical signal in a single mode. A bending loss of the holey fiber is equal to or less than 5 dB/m at a wavelength within the operation wavelength band when the holey fiber is wound at a diameter of 20 millimeters.

Abstract: A multi-core optical fiber includes: a plurality of core portions; and a cladding portion positioned around the plurality of core portions and including a marker for identifying a position of a specific one of the plurality of core portions.

Abstract: A multi-core optical fiber includes: a plurality of core portions; and a cladding portion positioned so as to surround each of the core portions, wherein each core portion includes a center core portion that has a refractive index greater than that of the cladding portion, a second core portion that is formed so as to surround the center core portion and that has a refractive index less than that of the center core portion, and a depressed portion that is formed so as to surround the second core portion and that has a refractive index less than those of the second core portion and the cladding portion, and an interval distance between the adjacent core portions is set such that optical cross-talk between the core portions for a total length of the multi-core optical fiber is equal to or less than ?30 dB at a wavelength of 1.55 ?m.

Abstract: A multi-core optical fiber includes: a plurality of core portions; and a cladding portion positioned around the plurality of core portions and including a marker for identifying a position of a specific one of the plurality of core portions.

Abstract: A multi-core holey fiber with suppression of crosstalk deterioration among transmitted optical signals in a plurality of cores, and an optical transmission system using the fiber are disclosed. The multi-core holey fiber comprises a plurality of cores arranged separately from each other, and a cladding surrounding the plurality of cores wherein the cladding has plurality of holes arranged in a triangular lattice shape to create hole layers around the plurality of cores. Additionally, d/? is not more than 0.5, where ? [?m] is lattice constant of the triangular lattice, d [?m] is diameter of each of the holes; a distance between adjacent cores is equivalent to not less than six hole layers; the cores arranged farthest from the center of the multi-core holey fiber is surrounded by not less three hole layers; and the sum of the coupling coefficients between the adjacent cores is not more than 1.6×10?5/m.

Abstract: A multi-core optical fiber includes: a plurality of core portions; and a cladding portion positioned around the plurality of core portions and including a marker for identifying a position of a specific one of the plurality of core portions.

Abstract: A multi-core optical fiber includes a plurality of core portions. The diameter of each of the core portions is 12 micrometers or smaller, the relative refractive-index difference of the core portions with respect to the cladding portion is 0.2% or larger, the cut-off wavelength is 1.53 micrometers or smaller, the bending loss at a 1.55-micrometer wavelength is 10 dB/m or smaller, the effective core area at a 1.55-micrometer wavelength is 30 ?m2 or larger, and the cross-talk of light between the core portions is ?35 decibels or smaller.

Abstract: A multi-core optical fiber which has a plurality of core portions arranged separately from one another in a cross-section perpendicular to a longitudinal direction, and a cladding portion located around the core portions, the multi-core optical fiber comprises a cylindrical portion of which diameter is even, and a reverse-tapered portion gradually expanding toward at least one edge in the longitudinal direction, wherein a gap between each adjacent ones of the core portions in the reverse-tapered portion is greater than that in the cylindrical portion.

Abstract: A holey fiber with significantly large effective core area is provided. The holey fiber comprises a core portion and a cladding portion at the circumference of the core portion. The cladding portion has plurality of holes distributed to shape triangular lattices around the core portion; wherein d/? is less than or equal to 0.42, the diameter of the holey fiber is larger than or equal to 580 ?m, an effective core area is larger than or equal to 15000 ?m2 at 1064 nm and a confinement loss is less than or equal to 0.1 dB/m at 1064 nm; where d is the hole diameter in ?m and ? is a lattice constant of the triangular lattice in ?m.

Abstract: A holey fiber with significantly large effective core area is provided. The holey fiber comprises a core portion and a cladding portion at the circumference of the core portion. The cladding portion has plurality of holes distributed to shape triangular lattices around the core portion; wherein d/? is less than or equal to 0.42, the diameter of the holey fiber is larger than or equal to 580 ?m, an effective core area is larger than or equal to 15000 ?m2 at 1064 nm and a confinement loss is less than or equal to 0.1 dB/m at 1064 nm; where d is the hole diameter in ?m and ? is a lattice constant of the triangular lattice in ?m.

Abstract: A multi-core optical fiber includes: a plurality of core portions; and a cladding portion positioned around the plurality of core portions and including a marker for identifying a position of a specific one of the plurality of core portions.

Abstract: A multi-core optical fiber includes: a plurality of core portions; and a cladding portion positioned around the plurality of core portions and including, in a cross section of the cladding portion, a flat portion in at least a part of an outer periphery of the cladding portion and a remaining portion of the outer periphery that is circular, the cross section being perpendicular to a longitudinal direction of the cladding portion.

Abstract: An optical fiber transmits at least a signal light having a wavelength of 1550 nanometers in a fundamental propagation mode. The optical fiber has a cutoff wavelength equal to or longer than a wavelength of 1550 nanometers, a wavelength dispersion in the fundamental propagation mode at the wavelength of 1550 nanometers larger than 0 ps/nm/km, and a dispersion slope in the fundamental propagation mode at the wavelength of the signal light equal to or smaller than ?0.05 ps/nm2/km.

Abstract: A silica-based optical fiber includes a core and a cladding that is formed on an outer circumference of the core. The core includes three or more layers including a layer doped with at least one of germanium and fluorine, and a concentration of the germanium or the fluorine in each of the layers is controlled in such a manner that a Brillouin gain spectral peak is spread into a plurality of peaks on a Brillouin gain spectrum. With this scheme, an optical fiber is provided, which has stable characteristics in the longitudinal direction, and which has a high SBS threshold so that generation of the SBS can be effectively suppressed.

Abstract: A holey fiber includes a core portion and a cladding portion positioned around a periphery of the core portion. The cladding portion includes 12 to 36 holes that are arranged circularly at a radius of 36 to 48 micrometers around a center of the core portion and that each have a hole diameter of 2.0 to 11.0 micrometers. At a wavelength of 1064 nanometers the holey fiber substantially performs a single-mode operation and has an effective core area equal to or greater than 1500 ?m2.

Abstract: A holey fiber, which has a zero-dispersion wavelength of less than 700 nm and operates as single mode under its zero-dispersion wavelength, is provided. The holey fiber according to the present invention comprises a core region that is formed at a center of the holey fiber; and a cladding region, formed at the circumference of the core region, which has a plurality of holes distributed as triangle lattice around the core region; wherein the holey fiber has a fundamental mode of less than 700 nm, a higher order mode, and the fundamental mode and the higher order mode confinement losses of less than 0.1 dB/m and more than 10 dB/m, respectively, at the zero-dispersion wavelength.

Abstract: A multi-core holey fiber with suppression of crosstalk deterioration among transmitted optical signals in a plurality of cores, and an optical transmission system using the fiber are disclosed. The multi-core holey fiber comprises a plurality of cores arranged separately from each other, and a cladding surrounding the plurality of cores wherein the cladding has plurality of holes arranged in a triangular lattice shape to create hole layers around the plurality of cores. Additionally, d/? is not more than 0.5, where ? [?m] is lattice constant of the triangular lattice, d [?m] is diameter of each of the holes; a distance between adjacent cores is equivalent to not less than six hole layers; the cores arranged farthest from the center of the multi-core holey fiber is surrounded by not less three hole layers; and the sum of the coupling coefficients between the adjacent cores is not more than 1.6×10?5/m.

Abstract: A photonic bandgap fiber includes a hollow core formed along a center axis of the photonic bandgap fiber, through which a light propagates and a cladding region made of silica glass. The cladding region includes air holes forming a triangular lattice arranged around the hollow core. A lattice constant of the triangular lattice of the air holes ? is equal to or smaller than 2.1 ?m. Confinement loss in a predetermined wavelength range including a center wavelength of a photonic bandgap is lower than scattering loss.

Abstract: An optical transmission system includes an optical transmitting unit that outputs at least one optical signal having a wavelength included in an operation wavelength band and a holey fiber that is connected to the optical transmitting unit. The holey fiber includes a core and a cladding formed around the core. The cladding includes a plurality of holes formed around the core in a triangular lattice shape. The holey fiber transmits the optical signal in a single mode. A bending loss of the holey fiber is equal to or less than 5 dB/m at a wavelength within the operation wavelength band when the holey fiber is wound at a diameter of 20 millimeters.

Abstract: An optical fiber that transmits a signal light in a fundamental propagation mode has a cutoff wavelength longer than a wavelength of the signal light, a wavelength dispersion of the fundamental propagation mode of ?5 ps/nm/km to ?1 ps/nm/km at a wavelength of 1550 nanometers, an effective core area of the fundamental propagation mode larger than 45 ?m2 at the wavelength of 1550 nanometers, and a dispersion slope of the fundamental propagation mode smaller than 0.03 ps/nm2/km at the wavelength of 1550 nanometers.