Abstract: Provided is a holey single-mode optical fiber including a core not having holes, and a clad having holes extending in a longitudinal direction, in which a refraction index of the core is larger than that of a portion of the clad other than the holes, a radius r1 of the core is within a range of 2.2 to 3.2 ?m, a relative refraction index difference ? of the core to the clad is within a range of 0.3 to 0.56%, a distance Rin between a center of the core and an inner edge of the holes is 2.0 to 3.5 times the radius r1 of the core, an air-filling fraction F is within a range of 30 to 50%, a cable cut-off wavelength is 1.0 ?m or less, a zero-dispersion wavelength is within a range of 1260 to 1460 nm, and a bending loss characteristic at a bending radius of 10 mm is 10 dB/m or less.

Abstract: Provided is a manufacturing method for an optical fiber preform of which the core is doped with a rare earth element. The method includes: depositing glass particles within a silica tube by the modified chemical vapor deposition method, the glass particles mainly consisting of silicon dioxide; adding the rare earth element and aluminum to the glass particles within the silica tube by the solution doping method; heating the silica tube while flowing a phosphorous-containing gas into the silica tube to sinter the glass particles within the silica tube while adding the phosphorous; and heating and collapsing the silica tube to which the rare earth element, the aluminum, and the phosphorous are added.

Abstract: Provided is a multi-cladding optical fiber which includes: a core with an average refractive index n1; and a cladding including an inner cladding with an average refractive index n2 formed on the periphery of the core, an intermediate cladding with an average refractive index n3 formed on the periphery of the inner cladding, and an outer cladding with an average refractive index n4 formed on the periphery of the intermediate cladding where n1>n2>n3>n4. Two or more axisymmetric modes exist in the core at a wavelength of the signal light; the two or more axisymmetric modes including a fundamental mode and at least a high-order mode. When the fiber is bent at a predetermined bending diameter, the high-order mode in the core disperses within the inner cladding due to coupling with an inner cladding mode, so that only the fundamental mode substantially propagates through the core.

Abstract: A multi-core fiber for an optical pumping device is provided. The multi-core fiber includes a plurality of optical fibers that are inserted into holes of an alignment member. The optical fibers and the alignment member are integrated by heating. The alignment member includes a material that has a lower softening temperature than a softening temperature of the optical fibers.

Abstract: Provided is an ytterbium-doped optical fiber including a core containing at least ytterbium, aluminum and phosphorous and a clad surrounding the core, wherein a molar concentration of diphosphorus pentoxide with respect to phosphorus in the core is equal to a molar concentration of aluminum oxide with respect to aluminum in the core, wherein a ratio of a molar concentration of diphosphorus pentoxide with respect to phosphorus in the core to the molar concentration of ytterbium oxide with respect to ytterbium in the core is higher than or equal to 10 and lower than or equal to 30, and wherein a relative refractive index difference between the core and the clad is higher than or equal to 0.05% and lower than or equal to 0.30%.

Abstract: An ytterbium-doped optical fiber includes: a core which contains at least ytterbium, aluminum, and phosphorus; and a cladding which encircles the core, wherein an aluminum oxide equivalent concentration of the aluminum in the core is 0.2 mol % or more, a diphosphorus pentaoxide equivalent concentration of the phosphorus is higher than the aluminum oxide equivalent concentration, and the core either does not contain germanium or contains less than 1.1 mol % of germanium in a germanium dioxide equivalent concentration.

Abstract: An ytterbium-doped optical fiber of the present invention includes: a core which contains ytterbium, aluminum, and phosphorus and does not contain germanium; and a cladding which surrounds this core. The ytterbium concentration in the core in terms of ytterbium oxide is 0.09 to 0.68 mole percent. The molar ratio between the phosphorus concentration in the core in terms of diphosphorus pentoxide and the above ytterbium concentration in terms of ytterbium oxide is 3 to 30. The molar ratio between the aluminum concentration in the core in terms of aluminum oxide and the above ytterbium concentration in terms of ytterbium oxide is 3 to 32. The molar ratio between the above aluminum concentration in terms of aluminum oxide and the above phosphorus concentration in terms of diphosphorus pentoxide is 1 to 2.5.

Abstract: An optical pumping device is provided in which a multi-core fiber obtained by bundling up a plurality of optical fibers, which are input ports, and a double clad fiber for optical pumping are spliced through a bridge fiber composed of a double clad fiber having a tapered shape. Accordingly, it is possible to efficiently couple signal light and pumping light to the double clad fiber for optical pumping.

Abstract: A multi-core fiber for an optical pumping device is provided. The multi-core fiber includes a plurality of optical fibers that are inserted into holes of an alignment member. The optical fibers and the alignment member are integrated by heating. The alignment member includes a material that has a lower softening temperature than a softening temperature of the optical fibers.

Abstract: A rare-earth doped core multi-clad fiber includes a core that includes a rare-earth element and a plurality of cladding layers that surround the core. An outermost cladding of the plurality of cladding layers is made of a polymer cladding, the plurality of cladding layers have a polygonal inner cladding, and a shape of a boundary between a second cladding from the outside and the outermost cladding does not have two-fold rotational symmetry. As a result, it is possible to provide a rare-earth doped core multi-clad fiber for an optical amplifier and a fiber laser that has low skew and is inexpensive.

Abstract: An optical fiber comprises a center core and a cladding located at an outer periphery of the core, wherein the core comprises at least one codoped layer made from silica glass doped with germanium and fluorine, and at least one lower-concentration codoped layer made from silica glass doped with germanium, or silica glass that is doped with germanium and fluorine wherein an amount of fluorine in the lower-concentration codoped layer is smaller than an amount of fluorine in the codoped layer.

Abstract: An optical fiber has a first mode field diameter in a dominant mode of an acoustic mode generated in the optical fiber different from a second mode field diameter in a light intensity distribution of the optical fiber. Furthermore, a transmission system is configured to perform an analog signal transmission, a baseband transmission, or an optical SCM transmission by use of the optical fiber.

Abstract: An optical pumping device is provided in which a multi-core fiber obtained by bundling up a plurality of optical fibers, which are input ports, and a double clad fiber for optical pumping are spliced through a bridge fiber composed of a double clad fiber having a tapered shape. Accordingly, it is possible to efficiently couple signal light and pumping light to the double clad fiber for optical pumping.

Abstract: An optical fiber has a first mode field diameter in a dominant mode of an acoustic mode generated in the optical fiber different from a second mode field diameter in a light intensity distribution of the optical fiber. Furthermore, a transmission system is configured to perform an analog signal transmission, a baseband transmission, or an optical SCM transmission by use of the optical fiber.

Abstract: A method of measuring polarization mode dispersion (PMD) of an optical fiber, includes estimating PMD when an optical fiber is formed as an optical cable, from a beat length when the optical fiber is wound around a bobbin, and an average coupling length when the optical fiber is formed as the optical cable.

Abstract: An optical fiber comprises a center core and a cladding located at an outer periphery of the core, wherein the core comprises at least one codoped layer made from silica glass doped with germanium and fluorine, and at least one lower-concentration codoped layer made from silica glass doped with germanium, or silica glass that is doped with germanium and fluorine wherein a dope amount of the fluorine is smaller than a dope amount of the fluorine in the codoped layer.

Abstract: A method of measuring polarization mode dispersion of an optical fiber includes inputting linearly polarized pulse light into an optical fiber, separating the input linearly polarized light from backscattered light from the optical fiber, detecting a light intensity of the backscattered light as time series data since the generation of the pulse light, calculating a fluctuation of the detected light intensity in the time series data, and evaluating polarization mode dispersion in the optical fiber, based on the calculated fluctuation value.

Abstract: A method of measuring polarization mode dispersion (PMD) of an optical fiber, includes estimating PMD when an optical fiber is formed as an optical cable, from a beat length when the optical fiber is wound around a bobbin, and an average coupling length when the optical fiber is formed as the optical cable.

Abstract: Under condition that a non-circularity ratio is 5% or lower and a thermal expansion coefficient of a glass which forms the core is ?1 and a thermal expansion of a glass which forms the cladding is ?2, the difference of coefficients is controlled such that a formula ?2.5×10?7/° C.??1 ??2?1.0×10?7/° C. is satisfied so as to maintain a polarization mode dispersion to be 0.03 ps/km0.5 or lower. The difference of coefficients is further controlled such that a formula ?1.5×10?7/° C.??1??2?0/° C. is satisfied so as to maintain a polarization mode dispersion to be 0.015 ps/km0.5 or lower. By doing this, birefringence is reduced by adjusting the thermal expansion coefficient in a core and a cladding; thus providing an optical fiber, and an optical transmission path using the optical fiber, having preferable PMD for high speed transmission.

Abstract: A method of measuring polarization mode dispersion of an optical fiber includes inputting linearly polarized pulse light into an optical fiber, separating the input linearly polarized light from backscattered light from the optical fiber, detecting a light intensity of the backscattered light as time series data since the generation of the pulse light, calculating a fluctuation of the detected light intensity in the time series data, and evaluating polarization mode dispersion in the optical fiber, based on the calculated fluctuation value.