Abstract: An optical fiber includes a core portion made of silica-based glass; and a cladding portion made of silica-based glass having lower maximum refractive index than the core portion, the cladding portion surrounding an outer periphery of the core portion. The core portion is doped with an alkali metal element and chlorine. An average concentration of chlorine is higher than 800 atomic ppm on a cross-section perpendicular to a longitudinal direction of the core portion. A region doped with the alkali metal element is larger than a region doped with chlorine at 800 atomic ppm or higher.

Abstract: An optical fiber includes: a core portion made of glass; a side core layer made of glass and enclosing the core portion; a cladding portion made of glass and enclosing the side core layer; and a coating layer including a primary layer made of resin and enclosing the cladding portion, and a secondary layer made of resin and enclosing the primary layer. The relationships ?1>?Clad>?2 and 0>?2 are satisfied where ?1 represents relative refractive-index difference of average maximum refractive index of the core portion with respect to average refractive index of the cladding portion, ?2 represents relative refractive-index difference of average refractive index of the side core layer with respect to average refractive index of the cladding portion, and ?Clad represents relative refractive-index difference of average refractive index of the cladding portion with respect to refractive index of pure silica glass.

Abstract: A method of producing an optical fiber preform includes a silica glass body forming step of forming a silica glass body to be at least a portion of a core portion. The method includes an alkali-metal-doped silica glass body forming step of forming an alkali-metal-doped silica glass body doped with an alkali metal around the silica glass body such that the alkali-metal-doped silica glass body contacts the silica glass body. The method further includes a diffusing step of diffusing the alkali metal from the alkali-metal-doped silica glass body to the silica glass body by a heat treatment.

Abstract: An optical amplifying fiber includes: at least one core portion including a rare earth element added therein; an inner cladding portion surrounding the at least one core portion, the inner cladding portion having a refractive index lower than a maximum refractive index of the at least one core portion; and an outer cladding portion surrounding the inner cladding portion, the outer cladding portion having a refractive index lower than the refractive index of the inner cladding portion, the inner cladding portion including different refractive index regions each having a refractive index different from a refractive index of a region adjacent to that different refractive index region.

Abstract: An optical amplifying fiber includes: at least one single core portion doped with a rare-earth element; an inner cladding portion configured to enclose the at least one core portion, the inner cladding portion having a lower refractive index than maximum refractive index of each core portion; and an outer cladding portion configured to enclose the inner cladding portion, the outer cladding portion having a lower refractive index than refractive index of the inner cladding portion, wherein the inner cladding portion includes a plurality of air bubbles.

Abstract: An optical fiber has a core to which chlorine is added and a clad to which fluorine is added, chlorine of 9000 to 13000 ppm is added to the core, a relative refractive index difference ?1 of the core to a pure silica glass is 0.09 to 0.13%, a relative refractive index difference ?2 of the clad to a pure silica glass is ?0.36 to ?0.17%, a difference (?1-?2) between the relative refractive index difference ?1 of the core and the relative refractive index difference ?2 of the clad is larger than or equal to 0.30%, a mode field diameter at wavelength 1.31 ?m is 8.8 to 9.6 ?m, and a stress difference occurring at an interface between the core and the clad is lower than or equal to 60 MPa.

Abstract: A method of producing an optical fiber preform includes a silica glass body forming step of forming a silica glass body to be at least a portion of a core portion. The method includes an alkali-metal-doped silica glass body forming step of forming an alkali-metal-doped silica glass body doped with an alkali metal around the silica glass body such that the alkali-metal-doped silica glass body contacts the silica glass body. The method further includes a diffusing step of diffusing the alkali metal from the alkali-metal-doped silica glass body to the silica glass body by a heat treatment.

Abstract: A method of producing an optical fiber preform includes: an alkali-metal-doped silica glass body forming step of forming an alkali-metal-doped silica glass body doped with an alkali metal; a silica glass body forming step of forming a silica glass body to be at least a portion of a core portion around the alkali-metal-doped silica glass body such that the silica glass body contacts the alkali-metal-doped silica glass body; and a diffusing step of diffusing the alkali metal from the alkali-metal-doped silica glass body to the silica glass body by a heat treatment.

Abstract: Provided are an optical fiber and a manufacturing method of the optical fiber that can reduce transmission loss even when drawing is performed at a high tension and a high rate. An optical fiber has a core to which chlorine is added and a clad to which fluorine is added, chlorine of 9000 to 13000 ppm is added to the core, a relative refractive index difference ?1 of the core to a pure silica glass is 0.09 to 0.13%, a relative refractive index difference ?2 of the clad to a pure silica glass is ?0.36 to ?0.17%, a difference (?1??2) between the relative refractive index difference ?1 of the core and the relative refractive index difference ?2 of the clad is larger than or equal to 0.30%, a mode field diameter at wavelength 1.31 ?m is 8.8 to 9.6 ?m, and a stress difference occurring at an interface between the core and the clad is lower than or equal to 60 MPa.

Abstract: A method of producing a glass preform including: forming a porous glass soot configured by an inner deposition soot deposited on a start material and an outer deposition soot deposited outside the inner deposition soot; and sintering, after the forming, the porous glass soot while doping with fluorine to form a glass body including an inner glass portion and an outer glass layer. An amount of the fluorine, with which the inner deposition soot is doped at the sintering, is equal to or more than 0 g/cm3 and less than an amount of the fluorine with which the outer deposition soot is doped.

Abstract: A method of producing an optical fiber preform includes: an alkali-metal-doped silica glass body forming step of forming an alkali-metal-doped silica glass body doped with an alkali metal; a silica glass body forming step of forming a silica glass body to be at least a portion of a core portion around the alkali-metal-doped silica glass body such that the silica glass body contacts the alkali-metal-doped silica glass body; and a diffusing step of diffusing the alkali metal from the alkali-metal-doped silica glass body to the silica glass body by a heat treatment.

Abstract: A multi-core amplification optical fiber includes a plurality of rare-earth-doped core portions and a cladding portion positioned at an outer periphery of the core portions and having refractive index lower than those of the core portions. When a doping concentration of the rare-earth of each of the core portions is 250 ppm to 2000 ppm, a relative refractive index difference of each of the core portions relative to the cladding portion is 0.5% to 2% at a wavelength of 1550 nm, and a core diameter of each of the core portions is 1 ?m to 5 ?m, a separation distance between each of the core portions and adjacent one of the core portions is set at equal to or larger than 30 ?m and at equal to or smaller than 60 ?m so that a light-crosstalk between the adjacent core portions is equal to or lower than ?30 dB.

Abstract: A method of producing a glass preform including: forming a porous glass soot configured by an inner deposition soot deposited on a start material and an outer deposition soot deposited outside the inner deposition soot; and sintering, after the forming, the porous glass soot while doping with fluorine to form a glass body including an inner glass portion and an outer glass layer. An amount of the fluorine, with which the inner deposition soot is doped at the sintering, is equal to or more than 0 g/cm3 and less than an amount of the fluorine with which the outer deposition soot is doped.

Abstract: A multi-core amplification optical fiber includes a plurality of rare-earth-doped core portions and a cladding portion positioned at an outer periphery of the core portions and having refractive index lower than those of the core portions. When a doping concentration of the rare-earth of each of the core portions is 250 ppm to 2000 ppm, a relative refractive index difference of each of the core portions relative to the cladding portion is 0.5% to 2% at a wavelength of 1550 nm, and a core diameter of each of the core portions is 1 ?m to 5 ?m, a separation distance between each of the core portions and adjacent one of the core portions is set at equal to or larger than 30 ?m and at equal to or smaller than 60 ?m so that a light-crosstalk between the adjacent core portions is equal to or lower than ?30 dB.

Abstract: An optical fiber has: a core made of silica glass in which a rare earth element and aluminum have been added; an inner cladding layer that is formed around the core, is made of silica glass in which at least any one of an alkali metal and an alkali earth metal has been added, and has a refractive index lower than a refractive index of the core; and an outer cladding layer that is formed around the inner cladding layer and has a refractive index lower than the refractive index of the inner cladding layer.

Abstract: A method of producing a glass preform by depositing silica powder that contains silica particles on a starting material includes a transferring step, a disaggregating step, and a depositing step. The transferring step includes transferring the silica powder. The disaggregating step includes disaggregating and dispersing agglomerates of the silica particles contained in the silica powder while being transferred in the transferring step. The depositing step includes depositing the silica powder, which is transferred and is obtained by disaggregating and dispersing the agglomerates of the silica particles, on the starting material.

Abstract: An optical fiber includes a core region having a first refractive index and a cladding region having a second refractive index lower than the first refractive index on an outer circumference of the core region. The cladding region includes four holes formed to have a four-fold rotational symmetry with respect to a center axis around the core region in a longitudinal direction, such that a zero-dispersion wavelength is 900 nm to 1150 nm and a cutoff wavelength is equal to or shorter than 950 nm.

Abstract: An optical fiber includes a core region having a first refractive index and a cladding region having a second refractive index lower than the first refractive index on an outer circumference of the core region. The cladding region includes four holes formed to have a four-fold rotational symmetry with respect to a center axis around the core region in a longitudinal direction, such that a zero-dispersion wavelength is 900 nm to 1150 nm and a cutoff wavelength is equal to or shorter than 950 nm.

Abstract: An optical fiber includes a core region having a first refractive index and a cladding region having a second refractive index lower than the first refractive index on an outer circumference of the core region. The cladding region includes four holes formed to have a four-fold rotational symmetry with respect to a center axis around the core region in a longitudinal direction, such that a zero-dispersion wavelength is 900 nm to 1150 nm and a cutoff wavelength is equal to or shorter than 950 nm.

Abstract: By optimizing the refractive index profile, the absorption coefficient of a rare earth element doped optical fiber can be enlarged and nonlinear effect can be suppressed. Thus, according to the present invention, the optical fiber, which is suitable for wide band optical amplification, can be realized. Moreover, in the present invention, the optical fiber of W-shape profile comprising a core, the first cladding having a refractive index smaller than that of said core surrounding said core, and the second cladding having a refractive index smaller than that of said core and larger than that of said first cladding surrounding said first cladding is prepared and are suitable for the wide band optical amplification.