Abstract: An optical fiber includes a core portion and a cladding portion that is formed around an outer periphery of the core portion and has a refractive index lower than a maximum refractive index of the core portion. As characteristics at a wavelength of 1550 nm, an effective core area in a fundamental propagation mode is 120 ?m2 or larger, an effective core area in a first higher-order propagation mode is 150 ?m2 or larger, an effective core area in a second higher-order propagation mode is 180 ?m2 or larger. An effective refractive index in the second higher-order propagation mode is larger than the refractive index of the cladding portion by 0.0002 or more, and an effective refractive index in a third higher-order propagation mode is less than the refractive index of the cladding portion.

Abstract: An optical fiber that propagates light over a use wavelength bandwidth of 100 nm or wider in a plurality of propagation modes is provided. The optical fiber has: a confinement loss equal to or less than 1 dB/km in each of the plurality of propagation modes over the use wavelength bandwidth; and a bending loss equal to or less than 100 dB/m in each of the plurality of propagation modes over the use wavelength bandwidth when the optical fiber is bent at a diameter of 20 mm.

Abstract: An optical fiber includes a core portion that confines light therein and guides the light therethrough and a cladding portion that is formed around an outer circumference of the core portion. The cladding portion contains a hole which is formed at a position a distance away from the core portion such that the hole does not substantially affect an effective core area or a chromatic dispersion characteristic of the optical fiber. The hole decreases a microbending loss of the optical fiber.

Abstract: A holey fiber includes: a core portion; an inner-cladding portion positioned at an outer periphery of the core portion, the inner-cladding portion having a plurality of inner holes formed in a layered structure around the core portion; and an outer-cladding portion positioned at an outer periphery of the inner-cladding portion, the outer-cladding portion having a plurality of outer holes formed in a layered structure around the inner-cladding portion. The inner holes are disposed to form a triangular lattice of which lattice constant ?1 is equal to or smaller than 2.0 ?m and to form equal to or greater than two layers. The outer holes are disposed to form a triangular lattice of which lattice constant ?2 is greater than the ?1 and equal to or larger than 3.0 ?m and to form equal to or greater than two layers. The overlap index is equal to or greater than 2.0%.

Abstract: A multi-core optical fiber includes a plurality of core portions, and a cladding portion positioned at outer peripheries of the plurality of core portions, the cladding portion having a refractive index lower than a maximum refractive index of each of the core portions, in which each of the core portions propagates light only with predetermined number, which is equal to or greater than 2, of propagation modes, and an effective core area at wavelength of 1550 nm of each of the propagation modes is equal to or greater than 120 ?m2.

Abstract: A holey fiber includes a core portion and a cladding portion in which holes located in the outer periphery of the core portion and arranged around the core portion in layers, and a low refractive index layer having an internal diameter that is equal to or larger than four times a mode field radius of light in the core portion and having a refractive index lower than the core portion are formed.

Abstract: An optical fiber includes a core portion and a cladding portion that is formed on an outer periphery of the core portion and has a refractive index lower than a maximum refractive index of the core portion. Characteristics at a wavelength of 1550 nm are an effective core area of a fundamental propagation mode of equal to or larger than 120 ?m2, an effective core area of a first higher-order propagation mode of equal to or larger than 170 ?m2, and an effective refractive index of the first higher-order propagation mode of larger than the refractive index of the cladding portion by equal to or larger than 0.0005.

Abstract: A method of manufacturing a photonic bandgap fiber, which includes: a core portion; and a cladding portion that is formed around the core portion and has holes arranged to form a photonic crystal in which the core portion is a crystal defect, includes: forming a preform by inserting, into a jacket tube, hexagonal capillary tubes having tube-holes shapes and outer shapes that are both approximately hexagonal; and drawing the preform.

Abstract: A manufacturing method of a photonic band gap fiber which includes measuring a hole diameter d0 and a distance-between-holes ?0 in a preliminary experiment capillary body by first drawing a preliminary experiment preform, calculating a confinement loss to a normalized wavelength ?/? being a wavelength ? normalized by an optional distance-between-holes ? using a ratio d0/?0 and the optional distance-between-holes ? as design parameters, setting a distance-between-holes by calculating the set distance-between-holes ?1 to a desired transmission wavelength ?1 of a photonic band gap fiber to be manufactured using a value of the normalized wavelength ?/? in which the confinement loss becomes about a minimum value, and second drawing a preform for a photonic band gap fiber by using the same members as those of the preliminary experiment preform and by setting a distance-between-holes to the set distance-between-holes ?1, in a drawing temperature condition used for the first drawing.

Abstract: An optical fiber includes a core portion and a cladding portion that is formed around an outer periphery of the core portion and has a refractive index lower than a maximum refractive index of the core portion. As characteristics at a wavelength of 1550 nm, an effective core area in a fundamental propagation mode is 120 ?m2 or larger, an effective core area in a first higher-order propagation mode is 150 ?m2 or larger, an effective core area in a second higher-order propagation mode is 180 ?m2 or larger. An effective refractive index in the second higher-order propagation mode is larger than the refractive index of the cladding portion by 0.0002 or more, and an effective refractive index in a third higher-order propagation mode is less than the refractive index of the cladding portion.

Abstract: A holey fiber includes a core portion located at a center of the holey fiber, and a cladding portion located around the core portion, the cladding portion having holes formed in layers around the core portion. The holes are arranged so as to form a triangular lattice while d/? is within a range of 0.33 to 0.43, ? is within a range of 10.5 micrometers to 15 micrometers when a hole diameter is d in micrometer and a lattice constant of the triangular lattice is ? in micrometer, and in a wavelength of 1550 nanometer, an effective core-area is equal to or greater than 130 ?m2, a bending loss in a case of bending the holey fiber at a bend diameter of 20 millimeters is equal to or less than 200 dB/m, and the holey fiber demonstrates a single-mode operation.

Abstract: An optical fiber that propagates light over a use wavelength bandwidth of 100 nm or wider in a plurality of propagation modes is provided. The optical fiber has: a confinement loss equal to or less than 1 dB/km in each of the plurality of propagation modes over the use wavelength bandwidth; and a bending loss equal to or less than 100 dB/m in each of the plurality of propagation modes over the use wavelength bandwidth when the optical fiber is bent at a diameter of 20 mm.

Abstract: An optical fiber includes a center core portion; an inner core layer formed around an outer circumference of the center core portion, a refractive index of which is less than that of the center core portion; an outer core layer formed around an outer circumference of the inner core layer, a refractive index of which is less than that of the inner core layer; and a cladding portion formed around an outer circumference of the outer core layer. A refractive index of the cladding portion is substantially equal to that of the inner core layer. At a wavelength of 1550 nm, an effective core area is equal to or larger than 130 ?m2 and a bending loss is equal to or less than 100 dB/m when the optical fiber is bent with a diameter of 20 mm. A cable cut-off wavelength is equal to or less than 1530 nm.

Abstract: An optical fiber includes a center core portion; an inner core layer formed around an outer circumference of the center core portion, a refractive index of which is less than that of the center core portion; an outer core layer formed around an outer circumference of the inner core layer, a refractive index of which is less than that of the inner core layer; and a cladding portion formed around an outer circumference of the outer core layer. A refractive index of the cladding portion is substantially equal to that of the inner core layer. At a wavelength of 1550 nm, an effective core area is equal to or larger than 130 ?m2 and a bending loss is equal to or less than 100 dB/m when the optical fiber is bent with a diameter of 20 mm. A cable cut-off wavelength is equal to or less than 1530 nm.

Abstract: A method of manufacturing a holey fiber includes forming a preform and drawing the preform. The forming includes arranging a core rod at a center of a jacket tube and arranging capillary tubes having hollows around the core rod inside the jacket tube. The drawing includes heat melting the preform in a heating furnace while controlling at least one of a gas pressure to be applied to insides of the hollows of the capillary tubes, a temperature of the heating furnace, and a drawing speed, based on a structure of air holes to be formed in a first layer from the core region.

Abstract: An optical fiber includes a core portion that confines light therein and guides the light therethrough and a cladding portion that is formed around an outer circumference of the core portion. The cladding portion contains a hole which is formed at a position a distance away from the core portion such that the hole does not substantially affect an effective core area or a chromatic dispersion characteristic of the optical fiber. The hole decreases a microbending loss of the optical fiber.

Abstract: A holey fiber includes a core portion located at a center of the holey fiber, and a cladding portion located around the core portion, the cladding portion having holes formed in layers around the core portion. The holes are arranged so as to form a triangular lattice while d/? is within a range of 0.33 to 0.43, ? is within a range of 10.5 micrometers to 15 micrometers when a hole diameter is d in micrometer and a lattice constant of the triangular lattice is ? in micrometer, and in a wavelength of 1550 nanometer, an effective core-area is equal to or greater than 130 ?m2, a bending loss in a case of bending the holey fiber at a bend diameter of 20 millimeters is equal to or less than 200 dB/m, and the holey fiber demonstrates a single-mode operation.

Abstract: A manufacturing method of a photonic band gap fiber which includes measuring a hole diameter d0 and a distance-between-holes ?0 in a preliminary experiment capillary body by first drawing a preliminary experiment preform, calculating a confinement loss to a normalized wavelength ?/? being a wavelength ? normalized by an optional distance-between-holes ? using a ratio d0/?0 and the optional distance-between-holes ? as design parameters, setting a distance-between-holes by calculating the set distance-between-holes ?1 to a desired transmission wavelength ?1 of a photonic band gap fiber to be manufactured using a value of the normalized wavelength ?/? in which the confinement loss becomes about a minimum value, and second drawing a preform for a photonic band gap fiber by using the same members as those of the preliminary experiment preform and by setting a distance-between-holes to the set distance-between-holes ?1, in a drawing temperature condition used for the first drawing.

Abstract: Optical fibers and optical transmission systems, which are capable of broadband and large capacity single-mode optical transmission, and have low macrobends are provided. The optical fiber made from pure silica comprising a core region, a cladding region at the circumference of the core region a coating layer made from a resin at the circumference of the cladding region, and having a cutoff wavelength of shorter than 1530 nm, and positive dispersion at 1550 nm, bending loss of less than 10 dB/m at a bending diameter of 20 mm, and an effective core area of 120 ?m2.

Abstract: An optical fiber manufacturing method comprises preparing first base materials each of which includes at least one core forming part to form a core and a cladding forming part to form a cladding; performing a first elongating to form second base materials by forming a first bundle by bundling two or more base materials including at least one of the first base materials having been prepared at the preparing and by thermally elongating the first bundle; and performing a second elongating at least once to form a second bundle by bundling two or more base materials including at least one of the second base materials and by thermally elongating the second bundle, wherein the second bundle is thermally elongated up until the point when the optical fiber is formed at the second elongating.