Abstract: An optical fiber measurement device includes a light source, a light detector, a direction-changing member, and a tension-applying member. The light source emits light toward an optical fiber. The light detector receives the light that has propagated through the optical fiber. The optical fiber is hung on the direction-changing member. The direction-changing member changes an extending direction of the optical fiber to extend downward, the optical fiber being optically connected to the light source and the light detector at each of two end parts of the optical fiber. The tension-applying member applies a tension to the optical fiber hanging from the direction-changing member.

Abstract: A measuring method of a longitudinal distribution of bending loss of an optical fiber includes calculating an arithmetical mean value I(x) from two backscattering light intensities of two backscattering light at a position x obtained by bidirectional OTDR measurement of the optical fiber; and obtaining a bending loss value at the position x from a mode field diameter 2W(x) and a relative refractive index difference ?(x) at the position x calculated from the arithmetical mean value.

Abstract: Provided is a method of producing a preform 10P for a coupled multi-core fiber including: an arranging process P1 for arranging a plurality of core glass bodies 11R and a clad glass body 12R in such a way that the plurality of core glass bodies 11R are surrounded by the clad glass body 12R; and a collapsing process P2 for collapsing a gap between the core glass bodies 11R and the clad glass body 12R, wherein the respective core glass bodies 11R have outer regions 16 having a predetermined thickness from the periphery surfaces and made of silica glass undoped with germanium, and the clad glass body 12R is made of silica glass having a refractive index lower than a refractive index of the outer regions of the core glass bodies 11R.

Abstract: A solid photonic band gap fiber includes: a core area located at a central portion of a cross-section with respect to a longitudinal direction of the fiber, the core area being formed of a solid substance having a low refractive index; cladding areas having base portions formed of a solid substance having a low refractive index, the cladding areas surrounding the core area; and a plurality of fine high refractive index scatterers provided in the cladding areas, and disposed in a dispersed manner so as to surround the core area, the number of fine high refractive index scatterers being formed of a solid substance having a high refractive index, wherein in a state that the solid photonic band gap fiber is held at a predetermined bending radius, propagation in a high-order mode is suppressed by using a difference in a bending loss between a fundamental mode and the high-order mode, and only the fundamental mode is substantially propagated, the fundamental mode and the high-order mode being caused by bending.

Abstract: A measuring method of a hole diameter of a holey optical fiber includes calculating an arithmetical mean value I(x) from two backscattering light intensities at a position x of two backscattering light waveforms of the holey optical fiber, in which the two backscattering light waveforms are obtained by OTDR measurement; and obtaining the hole diameter at the position x, based on a correlation between an arithmetical mean value I(x) and an hole diameter of the holey optical fiber that is obtained in advance.

Abstract: Each of a first clad region (12) and a second clad region (13) has holes (12a, 13a) which have identical diameters and are periodically formed so that the first clad region (12) and the second clad region (13) each have an effective refractive index lower than a refractive index of a core region (11), the effective refractive index of the first clad region (12) being lower than that of the second clad region (13).

Abstract: Provided is a method of producing a preform 10P for a coupled multi-core fiber including: an arranging process P1 for arranging a plurality of core glass bodies 11R and a clad glass body 12R in such a way that the plurality of core glass bodies 11R are surrounded by the clad glass body 12R; and a collapsing process P2 for collapsing a gap between the core glass bodies 11R and the clad glass body 12R, wherein the respective core glass bodies 11R have outer regions 16 having a predetermined thickness from the periphery surfaces and made of silica glass undoped with germanium, and the clad glass body 12R is made of silica glass having a refractive index lower than a refractive index of the outer regions of the core glass bodies 11R.

Abstract: A multicore fiber has a plurality of cores; and a clad which surrounds an outer peripheral surface of each of the cores, and at least one of the cores is spirally arranged such that the core rotates around a center axis of the clad. By arranging the cores in this way, it is possible to prevent crosstalk between specific cores from escalating even when the multicore fiber is disposed in a bent state.

Abstract: Provided is a method of producing a preform 10P for a coupled multi-core fiber including: an arranging process P1 for arranging a plurality of core glass bodies 11R and a clad glass body 12R in such a way that the plurality of core glass bodies 11R are surrounded by the clad glass body 12R; and a collapsing process P2 for collapsing a gap between the core glass bodies 11R and the clad glass body 12R, wherein the respective core glass bodies 11R have outer regions 16 having a predetermined thickness from the periphery surfaces and made of silica glass undoped with germanium, and the clad glass body 12R is made of silica glass having a refractive index lower than a refractive index of the outer regions of the core glass bodies 11R.

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: 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: A coupled multi-core fiber 10 includes a plurality of cores 11 and a clad 12 surrounding the plurality of cores 11, wherein the plurality of cores 11 are arranged in such a way that periphery surfaces of the adjacent cores 11 contact with each other, each of the cores 11 is made to have a refractive index higher than the clad 12 and includes: an outer region 16 having a predetermined thickness from the periphery surface; and an inner region 15 made to have a higher refractive index than the outer region 16 and surrounded by the outer region 16.

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 coupled multi-core fiber 10 includes a plurality of cores 11 and a clad 12 surrounding the plurality of cores 11, wherein the plurality of cores 11 are arranged in such a way that periphery surfaces of the adjacent cores 11 contact with each other, each of the cores 11 is made to have a refractive index higher than the clad 12 and includes: an outer region 16 having a predetermined thickness from the periphery surface; and an inner region 15 made to have a higher refractive index than the outer region 16 and surrounded by the outer region 16.

Abstract: Provided is a method of producing a preform 10P for a coupled multi-core fiber including: an arranging process P1 for arranging a plurality of core glass bodies 11R and a clad glass body 12R in such a way that the plurality of core glass bodies 11R are surrounded by the clad glass body 12R; and a collapsing process P2 for collapsing a gap between the core glass bodies 11R and the clad glass body 12R, wherein the respective core glass bodies 11R have outer regions 16 having a predetermined thickness from the periphery surfaces and made of silica glass undoped with germanium, and the clad glass body 12R is made of silica glass having a refractive index lower than a refractive index of the outer regions of the core glass bodies 11R.

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: Each of a first clad region (12) and a second clad region (13) has holes (12a, 13a) which have identical diameters and are periodically formed so that the first clad region (12) and the second clad region (13) each have an effective refractive index lower than a refractive index of a core region (11), the effective refractive index of the first clad region (12) being lower than that of the second clad region (13).

Abstract: A measuring method of a hole diameter of a holey optical fiber includes calculating an arithmetical mean value I(x) from two backscattering light intensities at a position x of two backscattering light waveforms of the holey optical fiber, in which the two backscattering light waveforms are obtained by OTDR measurement; and obtaining the hole diameter at the position x, based on a correlation between an arithmetical mean value I(x) and an hole diameter of the holey optical fiber that is obtained in advance.

Abstract: A measuring method of a longitudinal distribution of bending loss of an optical fiber includes calculating an arithmetical mean value I(x) from two backscattering light intensities of two backscattering light at a position x obtained by bidirectional OTDR measurement of the optical fiber; and obtaining a bending loss value at the position x from a mode field diameter 2W(x) and a relative refractive index difference ?(x) at the position x calculated from the arithmetical mean value.