Abstract: A hole-assisted optical fiber includes a core portion and a cladding portion that includes an inner cladding layer, an outer cladding layer, and holes formed around the core portion. A diameter of the core portion is 3 ?m to 9.8 ?m, a relative refractive index difference of the core portion relative to the outer cladding layer is 0.11% to 0.45%, an outside diameter of the inner cladding layer is 53 ?m or less, a relative refractive index difference of the inner cladding layer relative to the outer cladding layer is a negative value, ?0.30% or more, a diameter of each hole is 2.4 ?m to 4.0 ?m, a hole occupancy rate is 17% to 48%, a bending loss at a wavelength of 1625 nm when bent at a radius of 5 mm is 1 dB/turn or less, and a cut-off wavelength is 1550 nm or less.

Abstract: An optical fiber suitable for high-capacity transmission having a large effective core area, a low bending loss, and capable of single mode operation at 1550 nm is provided. The optical fiber 10 has an effective core area ?175 ?m2 at 1550 nm, a bending loss ?10 dB/m at a bending diameter of 20 mm at 1550 nm, and a cut-off wavelength ?c?1550 nm. The optical fiber has a first core 11 at the center, which has a refractive index higher than that of the cladding 13; and a second core 12 around the first core 11, which has a refractive index lower than that of the cladding 13; a primary medium portion; and secondary medium portions, which have a refractive index lower than that of the primary medium portion and the secondary medium portions have a plurality of first secondary medium portions 15 around the first core 11 and a plurality of second secondary medium portions 16 around the first core 11 and outside of the first secondary medium portions 15.

Abstract: An optical fiber preform manufacturing method includes: supporting a drilling jig in a radial direction of a preform that is cylinder-shaped; moving the drilling jig in a longitudinal direction of the preform; and forming a plurality of slits each extending in the longitudinal direction and each directed from an outer side of the preform toward a center the preform, and a plurality of holes each extending in the longitudinal direction and each connecting with an end of one of the plurality of slits in a depth direction of the one of the plurality of slits.

Abstract: An optical fiber has a refractive index profile approximated by n(r)=n1[1-2(?1/100)(r/a)^?]1/2 when 0<r?a, and n(r)=n1[1-2(?1/100)]1/2 when a<r, where n1 is refractive index at the center of a core, ?1 is relative refractive index difference between the center of the core and a cladding, a is radius of the core, ? is refractive index profile parameter, and ^ represents an exponential. ? is 1.95 to 2.15. The relative refractive index difference is 1.5% or larger. A diameter of the core is 20 ?m to 45 ?m. A diameter of the cladding is 70 ?m to 90 ?m. A bending loss at 850 nm when bending the optical fiber with a curvature radius of 5 mm is 0.1 dB/turn or lower.

Abstract: An optical fiber preform manufacturing method includes: supporting a drilling jig in a radial direction of a preform that is cylinder-shaped; moving the drilling jig in a longitudinal direction of the preform; and forming a plurality of slits each extending in the longitudinal direction and each directed from an outer side of the preform toward a center the preform, and a plurality of holes each extending in the longitudinal direction and each connecting with an end of one of the plurality of slits in a depth direction of the one of the plurality of slits.

Abstract: An optical fiber suitable for high-capacity transmission having a large effective core area, a low bending loss, and capable of single mode operation at 1550 nm is provided. The optical fiber 10 has an effective core area?175 ?m2 at 1550 nm, a bending loss?10 dB/m at a bending diameter of 20 mm at 1550 nm, and a cut-off wavelength ?c?1550 nm. The optical fiber has a first core 11 at the center, which has a refractive index higher than that of the cladding 13; and a second core 12 around the first core 11, which has a refractive index lower than that of the cladding 13; a primary medium portion; and secondary medium portions, which have a refractive index lower than that of the primary medium portion and the secondary medium portions have a plurality of first secondary medium portions 15 around the first core 11 and a plurality of second secondary medium portions 16 around the first core 11 and outside of the first secondary medium portions 15.

Abstract: An optical fiber, made of silica-based glass, comprising a core and a cladding, each of the optical fiber having a mode field diameter of 5.5 ?m or larger at a wavelength of 1100 nm, transmitting light with a wavelength of 1250 nm in a single mode, and having a bending loss of 1 dB/turn or smaller at a wavelength of 1100 nm when the optical fiber is bent with a curvature radius of 2 mm.

Abstract: A tension-absorbing cladding layer is formed around a cladding layer, with a refractive index equal to that of a center core region or higher. The center core region has a relative refractive index difference of ?0.1% to 0% with respect to a pure silica glass, a chlorine concentration of wt % to 0.10 wt %, and a fluorine concentration of 0.10 wt % to 0.30 wt %. The tension-absorbing cladding layer has a relative refractive index difference of 0% to 0.05% with respect to the pure silica glass and a chlorine concentration of 0.15 wt % or lower. A ratio of an outer diameter of the tension-absorbing cladding layer to an outer diameter of the cladding layer is 1.10 to 1.40.

Abstract: An optical fiber is made of silica-based glass, and includes a core and a cladding. The optical fiber has a mode field diameter of 5.4 micrometers or larger at a wavelength of 1300 nanometers, transmits light with a wavelength of 1250 nanometers in a single mode, and has a bending loss of 1 dB/turn or smaller at a wavelength of 1300 nanometers when the optical fiber is bent with a curvature radius of 1 millimeter.

Abstract: An optical fiber, made of silica-based glass, comprising a core and a cladding. The optical fiber having a mode field diameter of 6.5 ?m or larger at a wavelength of 1300 nm, transmitting light with a wavelength of 1250 nm in a single mode, and having a bending loss of 1 dB/turn or smaller at a wavelength of 1300 nm when the optical fiber is bent with a curvature radius of 1.5 mm.

Abstract: An optical fiber, made of silica-based glass, comprising a core and a cladding, each of the optical fiber having a mode field diameter of 5.5 ?m or larger at a wavelength of 1100 nm, transmitting light with a wavelength of 1250 nm in a single mode, and having a bending loss of 1 dB/turn or smaller at a wavelength of 1100 nm when the optical fiber is bent with a curvature radius of 2 mm.

Abstract: An optical fiber has a refractive index profile approximated by n(r)=n1[1?2(?1/100)(r/a)??]1/2 when 0<r?a, and n(r)=n1[1?2(?1/100)]1/2 when a<r, where n1 is refractive index at the center of a core, ?1 is relative refractive index difference between the center of the core and a cladding, a is radius of the core, ? is refractive index profile parameter, and ? represents an exponential. ? is 1.95 to 2.15. The relative refractive index difference is 1.5% or larger. A diameter of the core is 20 ?m to 45 ?m. A diameter of the cladding is 70 ?m to 90 ?m. A bending loss at 850 nm when bending the optical fiber with a curvature radius of 5 mm is 0.1 dB/turn or lower.

Abstract: An optical fiber is made of silica-based glass, and includes a core and a cladding. The optical fiber has a mode field diameter of 5.4 micrometers or larger at a wavelength of 1300 nanometers, transmits light with a wavelength of 1250 nanometers in a single mode, and has a bending loss of 1 dB/turn or smaller at a wavelength of nanometers when the optical fiber is bent with a curvature radius of 1 millimeter.

Abstract: A tension-absorbing cladding layer is formed around a cladding layer, with a refractive index equal to that of a center core region or higher. The center core region has a relative refractive index difference of ?0.1% to 0% with respect to a pure silica glass, a chlorine concentration of wt % to 0.10 wt %, and a fluorine concentration of 0.10 wt % to 0.30 wt %. The tension-absorbing cladding layer has a relative refractive index difference of 0% to 0.05% with respect to the pure silica glass and a chlorine concentration of 0.15 wt % or lower. A ratio of an outer diameter of the tension-absorbing cladding layer to an outer diameter of the cladding layer is 1.10 to 1.40.

Abstract: An optical fiber, made of silica-based glass, comprising a core and a cladding. The optical fiber having a mode field diameter of 6.5 ?m or larger at a wavelength of 1300 nm, transmitting light with a wavelength of 1250 nm in a single mode, and having a bending loss of 1 dB/turn or smaller at a wavelength of 1300 nm when the optical fiber is bent with a curvature radius of 1.5 mm.

Abstract: An optical fiber for forming an optical transmission line suitable for the wavelength division multiplexing transmission by connecting to a positive dispersion optical fiber is provided. Outside a first glass layer (1), a second glass layer (2), a third glass layer (3) and a fourth glass layer (4) are sequentially disposed. The fourth glass layer (4) is to be a reference layer for a standard of a refractive index. A relative refractive index difference &Dgr;1 of the first glass layer to the reference layer is set to 1.6% to 2.6%, inclusive, a relative refractive index difference &Dgr;2 of the second glass layer is set to−0.65% to −0.4%, inclusive, and a relative refractive index difference &Dgr;3 of the third glass layer is set to 0.15% to 0.5%, inclusive.

Abstract: An optical fiber for forming an optical transmission line suitable for the wavelength division multiplexing transmission by connecting to a positive dispersion optical fiber is provided. Outside a first glass layer (1), a second glass layer (2), a third glass layer (3) and a fourth glass layer (4) are sequentially disposed. The fourth glass layer (4) is to be a reference layer for a standard of a refractive index. A relative refractive indexdifference &Dgr;1 of the first glass layer to the reference layer is set 1.6% to 2.6%, inclusive, a relative refractive index difference &Dgr;2 of the second glass layer is set −0.65% to −0.4%, inclusive, and a relative refractive index difference &Dgr;3 of the third glass layer is set 0.15% to 0.5%, inclusive. A relationship among an outer diameter d1 of the first glass layer, an outer diameter d2 of the second glass layer and an outer diameter d3 of the third glass layer is set 2.5≦(d2/d1)≦3.0, and 1.5≦(d3/d2)≦3.0.

Abstract: Provided are a process for producing an optical fiber preform by depositing glass soot on the periphery of a glass rod and then sintering the glass soot to form a new transparent glass layer and also a process for producing an optical fiber preform by repeating the above procedures, wherein bubble is prevented from occurring in glass layers and interfaces between them. The process includes the steps of forming a glass soot layer by depositing glass soot on the periphery of a glass rod formed by undergoing a sintering heat treatment; and carrying out subsequently another heat treatment for the glass soot to carry out sintering thereof and transform the glass soot layer into a glass layer; wherein, provided that the glass soot is treated at a sintering temperature T′(° C.) and that the glass rod is formed at a sintering temperature T(° C.

Abstract: An optical fiber for forming an optical transmission line suitable for the wavelength division multiplexing transmission by connecting to a positive dispersion optical fiber is provided. Outside a first glass layer (1), a second glass layer (2), a third glass layer (3) and a fourth glass layer (4) are sequentially disposed. The fourth glass layer (4) is to be a reference layer for a standard of a refractive index. A relative refractive index difference &Dgr;1 of the first glass layer to the reference layer is set 1.6% to 2.6%, inclusive, a relative refractive index difference &Dgr;2 of the second glass layer is set −0.65% to −0.4%, inclusive, and a relative refractive index difference &Dgr;3 of the third glass layer is set 0.15% to 0.5%, inclusive.

Abstract: An optical fiber for forming an optical transmission line suitable for the wavelength division multiplexing transmission by connecting to a positive dispersion optical fiber is provided. Outside a first glass layer (1), a second glass layer (2), a third glass layer (3) and a fourth glass layer (4) are sequentially disposed. The fourth glass layer (4) is to be a reference layer for a standard of a refractive index. A relative refractive index difference &Dgr;1 of the first glass layer to the reference layer is set 1.6% to 2.6%, inclusive, a relative refractive index difference &Dgr;2 of the second glass layer is set −0.65% to −0.4%, inclusive, and a relative refractive index difference &Dgr;3 of the third glass layer is set 0.15% to 0.5%, inclusive. A relationship among an outer diameter d1 of the first glass layer, an outer diameter d2 of the second glass layer and an outer diameter d3 of the third glass layer is set 2.5≦(d2/d1)≦3.0, and 1.5≦(d3/d2)≦3.0.