Abstract: An optical fiber includes: a central core portion; an intermediate layer formed around an outer circumference of the central core portion; a trench layer formed around an outer circumference of the intermediate layer; and a cladding portion formed around an outer circumference of the trench layer. Further, when, relative to the cladding portion, a relative refractive-index difference of the central core portion is ?1, a relative refractive-index difference of the intermediate layer is ?2, and a relative refractive-index difference of the trench layer is ?3, relationships ?1>?2>?3 and 0>?3 are satisfied and ?1 is equal to or greater than 0.34% and equal to or less than 0.40%, |?3| is equal to or less than 0.25%, and ?1×|?3| is less than 0.08%2.

Abstract: A multi-core fiber includes: a plurality of cores; and a cladding portion formed around outer peripheries of the cores. Further, the cores each have a propagation characteristic conforming to any one of a plurality of standards for optical propagation characteristics, and of the cores, cores that are closest to each other conform to standards different from each other.

Abstract: An optical fiber includes: a core portion made of glass; and a cladding portion made of glass, having a refractive index lower than the refractive index of the core portion, and positioned on an outer periphery of the core portion. Further, the cladding portion has an outer diameter smaller than 100 ?m, and the core portion has a relative refractive-index difference of 0.32% to 0.40% with respect to the cladding portion.

Abstract: An optical fiber includes: a core made of silica based glass; a cladding made of silica based glass, the cladding having a refractive index that is lower than a maximum refractive index of the core; and a coating including a primary coating layer, and a secondary coating layer. An outer diameter of the cladding is less than 100 ?m. A thickness of the primary coating layer is larger than or equal to 15 ?m. A mode field diameter at a wavelength of 1310 nm is larger than or equal to 8.6 ?m and smaller than or equal to 9.2 ?m. An effective cutoff wavelength is smaller than or equal to 1260 ?m. A bending loss at a wavelength of 1550 nm when bending is made at a diameter of 60 mm is smaller than or equal to 0.1 dB/100 turn.

Abstract: An optical fiber includes: a core portion made of glass; and a cladding portion made of glass, having a refractive index lower than the refractive index of the core portion, and positioned on an outer periphery of the core portion. Further, the cladding portion has an outer diameter smaller than 100 ?m, and the core portion has a relative refractive-index difference of 0.32% to 0.40% with respect to the cladding portion.

Abstract: An optical fiber includes: a core made of silica-based glass; a cladding configured to cover an outer circumference of the core and made of silica-based glass having a refractive index smaller than a maximum refractive index of the core; and a coating configured to cover an outer circumference of the cladding. The cladding has an outer diameter of 120 ?m or smaller, a mode field diameter at a wavelength of 1310 nm is 8.6 ?m to 9.2 ?m, an effective cut-off wavelength is 1260 ?m or smaller, and a bending loss at a wavelength of 1550 nm in a case of bending at a diameter of 20 mm is 0.75 dB/turn or smaller.

Abstract: An optical fiber includes: a central core portion; an intermediate layer; a trench layer; and a cladding portion. Further, relationships ?1>?2>?3 and 0>?3 are satisfied, where ?1, ?2, and ?3 are a relative refractive-index difference of the central core portion, the intermediate layer, and the trench layer, respectively, with respect to the cladding portion, ?1 is equal to or larger than 0.34% and equal to or smaller than 0.37%, |?3| is equal to or larger than 0.1% and equal to or smaller than 0.25%, ?1×|?3| is equal to or smaller than 0.08%2, a mode field diameter at a wavelength of 1310 nm is equal to or larger than 8.8 ?m, and a transmission loss at a wavelength of 1550 nm is equal to or smaller than 0.195 dB/km.

Abstract: An optical fiber includes: a central core portion; an intermediate layer; a trench layer; and a cladding portion. Further, ?1>?2>?3 and 0>?3 are satisfied, where ?1 is a relative refractive-index difference of the central core portion, ?2 is a relative refractive-index difference of the intermediate layer, and ?3 is a relative refractive-index difference of the trench layer with respect to the cladding portion, respectively, and (c?b) is smaller than 4.5 ?m when ?1 is equal to or larger than 0.36% and equal to or smaller than 0.40%, ?2 is equal to or larger than ?0.05% and equal to or smaller than 0.05%, |?3| is equal to or smaller than 0.25%, ?1×|?3| is equal to or smaller than 0.08%2, an inner diameter of the trench layer is 2b, and an outer diameter of the trench layer is 2c.

Abstract: An optical fiber includes: a core portion made of glass; a cladding portion that is located on an outer periphery of the core portion and that is made of glass having a lower refractive index than a refractive index of the core portion; and a coating portion that covers an outer periphery of the cladding portion. Further, an average value of a relative refractive-index difference of a center core of the core portion is 0.1 to 0.5%, a fiber diameter including the coating portion is equal to or smaller than 220 ?m, an effective cutoff wavelength is longer than 1260 nm and smaller than 1530 nm, and a mode field diameter of light at 1550 nm is equal to or larger than 9 ?m.

Abstract: An optical fiber includes: a central core portion; an intermediate layer formed around an outer circumference of the central core portion; a trench layer formed around an outer circumference of the intermediate layer; and a cladding portion formed around an outer circumference of the trench layer. Further, when, relative to the cladding portion, a relative refractive-index difference of the central core portion is ?1, a relative refractive-index difference of the intermediate layer is ?2, and a relative refractive-index difference of the trench layer is ?3, relationships ?1>?2>?3 and 0>?3 are satisfied and ?1 is equal to or greater than 0.34% and equal to or less than 0.40%, |?3| is equal to or less than 0.25%, and ?1×|?3| is less than 0.08%2.

Abstract: An object is to obtain an optical fiber having a small diameter and suppressing the increase of a microbending loss of the optical fiber. The optical fiber includes: a core portion made of silica glass; a cladding portion made of silica glass, the cladding portion covering the outer periphery of the core portion and having a refractive index smaller than a maximum refractive index of the core portion; and a coating portion covering the outer periphery of the cladding portion. The outer diameter of the cladding portion is 100 ?m or smaller, the relative refractive-index difference ?1 of the core portion is 0.5% or smaller, and the thickness of the coating portion is 10 ?m or larger.

Abstract: An optical fiber cable includes: a small-diameter optical fiber including a core and a cladding portion made of glass and having a cladding diameter of 120 ?m or less; a normal optical fiber that is optically connected to at least one end of the small-diameter optical fiber, includes a core and a cladding portion made of glass, and has a cladding diameter conforming to a standard of 125 ?m; an optical coupling mechanism provided between the small-diameter optical fiber and the normal optical fiber; and a sheath covering an outer periphery of the small-diameter optical fiber only, among the small-diameter optical fiber and the normal optical fiber. Further, the end of the small-diameter optical fiber is positioned outside the sheath.

Abstract: An optical fiber includes: a core portion made of glass; and a cladding portion made of glass, having a refractive index lower than the refractive index of the core portion, and positioned on an outer periphery of the core portion. Further, the cladding portion has an outer diameter smaller than 100 ?m, and the core portion has a relative refractive-index difference of 0.32% to 0.40% with respect to the cladding portion.

Abstract: A multi-core fiber includes: a plurality of cores; and a cladding portion formed around outer peripheries of the cores. Further, the cores each have a propagation characteristic conforming to any one of a plurality of standards for optical propagation characteristics, and of the cores, cores that are closest to each other conform to standards different from each other.

Abstract: A method of manufacturing a multicore fiber includes: an initial-preform forming process of forming an initial preform by arranging in an array a plurality of core rods each including a core portion and a cladding portion formed around outer periphery of the core portion; and an optical fiber manufacturing process of manufacturing an optical fiber from the initial preform. Further, the core rods include a plurality of holes, and the core rods are arranged in a manner that one hole is arranged between two core portion adjacent to each other in the initial-preform forming process.

Abstract: A tapered waveguide is optically connected to an end surface of an optical fiber bundle part, and has a tapered part that changes in outside diameter in a tapered shape. The fiber bundle part is optically connected to the end surface of the large-diameter side of the waveguide. The entire waveguide has a substantially uniform index of refraction. A delivery fiber is optically connected to the end surface on the small-diameter side of the waveguide. As with the fiber bundle part the delivery fiber passes through a hole in a capillary and is affixed. The capillaries are each affixed to a retaining member such that the fiber bundle part, the waveguide, and the delivery fiber are disposed on the same axis and optically connected. The waveguide is retained in a state floating from the retaining member, and the outside surface of the waveguide is not in contact with the retaining member.

Abstract: An optical fiber that has an air layer in a clad portion and can suppress a degradation in a transmission characteristic caused by a support member present in the air layer is provided. The optical fiber includes a core (1), tubular layers (22 to 25) concentrically arranged around the core (1) via the air layer, and support members (3a to 3l) that are arranged to the air layer and connect the core (1) with the tubular layers (22 to 25), and in the optical fiber, in a cross-sectional view of a longitudinal direction of the optical fiber, a distance between support members (3a to 3l) in a circumferential direction of the optical fiber is wider than a double thickness of the air layer in which the support members (3a to 3l) are arranged.

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: 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 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%.