Abstract: There is provided a method for producing a multicore optical fiber while depressurizing holes in a common cladding tube. A production method for a multicore optical fiber includes a preform forming step of forming a common cladding tube having a plurality of holes extending between a first end and a second end, an end-face working step of digging the common cladding tube from the second end to a predetermined depth to forming a third end, a connection step of connecting a glass tube to the second end, an insertion step of inserting core rods into the holes to the third end, a sealing step of sealing the first end, and a drawing step of spinning the multicore optical fiber while depressurizing the holes through the glass tube and combining the common cladding tube and the core rods from the first end.

Abstract: An embodiment of the invention enables each core in an end face to be readily identified by observation of either one end face, regardless of the presence or absence of a twist of a pertinent MCF and difference of ends. In a cross section of the MCF, a core group constellation has symmetry but each core in a core group is identifiable by breaking of all types of symmetry in a common cladding, defined by a combination of the core group constellation with the common cladding, or, by making the fiber ends distinguishable.

Abstract: A multi-core optical fiber ribbon easily optically connected to another optical component is provided. A multi-core optical fiber ribbon 1 includes a plurality of multi-core optical fibers 10 arranged parallel to one another and a common resin 20, with which the plurality of multi-core optical fibers 10 are collectively coated. A core arrangement direction in which plurality of cores in each of the plurality of multi-core optical fibers 10 are arranged is parallel to or perpendicular to the fiber arrangement direction in which the plurality of multi-core optical fibers 10 are arranged at least at both ends of the multi-core optical fiber ribbon 1.

Abstract: An embodiment of the invention enables each core in an end face to be readily identified by observation of either one end face, regardless of the presence or absence of a twist of a pertinent MCF and difference of ends. In a cross section of the MCF, a core group constellation has symmetry but each core in a core group is identifiable by breaking of all types of symmetry in a common cladding, defined by a combination of the core group constellation with the common cladding, or, by making the fiber ends distinguishable.

Abstract: An optical fiber having a composition that is most suitable from the viewpoint of filter formation time and filter properties of slanted fiber grating (SFG) is provided. An optical fiber made of silica-based glass comprises a core region, which does not contain GeO2 and includes the optical axis, and a cladding region formed around the core region. The cladding region has a refractive index smaller than that of the core region and contains GeO2 of 6.8 wt % or more. SFG made with the optical fiber enables base loss of 2 dB or less, peak wavelength shift of 1.2 nm or less, and change of 0.2 nm or less in width at half maximum.

Abstract: There is provided a multi-core fiber that can reduce both skew and crosstalk between cores. The multi-core fiber includes a plurality of cores extending along a fiber axis, and optical claddings surrounding the plurality of cores. The skew between optical signals propagating through the plurality of cores is 1 ps/m or less, and the propagation constant difference between two adjacent cores of the plurality of cores is more than 0.

Abstract: A multi-core optical fiber ribbon easily optically connected to another optical component is provided. A multi-core optical fiber ribbon 1 includes a plurality of multi-core optical fibers 10 arranged parallel to one another and a common resin 20, with which the plurality of multi-core optical fibers 10 are collectively coated. A core arrangement direction in which plurality of cores in each of the plurality of multi-core optical fibers 10 are arranged is parallel to or perpendicular to the fiber arrangement direction in which the plurality of multi-core optical fibers 10 are arranged at least at both ends of the multi-core optical fiber ribbon 1.

Abstract: A multi-core optical fiber 1A in which a plurality of cores can easily be identified even in the case where they are symmetrically arranged in its section has seven cores 10 to 16, a visual recognition marker 20, and a shared cladding 30 enclosing the seven cores 10 to 16 and the visual recognition marker 20. The cores 10 to 16, the visual recognition marker 20, and the cladding 30 are respectively made of silica glass as their main element. The cores 10 to 16 and the visual recognition marker 20 extend along the fiber-axis direction. The respective refractive index of the cores 10 to 16 is higher than the refractive index of the cladding 30. The refractive index of the visual recognition marker 20 differs from that of the cladding 30. In the cross-section perpendicular to the fiber-axis, the cores 10 to 16 are arranged such that they have 6-fold rotational symmetry and line symmetry. The visual recognition marker 20 is arranged at a position which breaks such symmetry.

Abstract: There is provided a multi-core fiber that can reduce both skew and crosstalk between cores. The multi-core fiber includes a plurality of cores extending along a fiber axis, and optical claddings surrounding the plurality of cores. The skew between optical signals propagating through the plurality of cores is 1 ps/m or less, and the propagation constant difference between two adjacent cores of the plurality of cores is more than 0.

Abstract: A multi-core optical fiber 1A in which a plurality of cores can easily be identified even in the case where they are symmetrically arranged in its section has seven cores 10 to 16, a visual recognition marker 20, and a shared cladding 30 enclosing the seven cores 10 to 16 and the visual recognition marker 20. The cores 10 to 16 and the visual recognition marker 20 extend along the fiber-axis direction. The respective refractive index of the cores 10 to 16 is higher than the refractive index of the cladding 30. The refractive index of the visual recognition marker 20 differs from that of the cladding 30. In the cross-section perpendicular to the fiber-axis, the cores 10 to 16 are arranged such that they have 6-fold rotational symmetry and line symmetry. The visual recognition marker 20 is arranged at a position which breaks such symmetry.

Abstract: The present invention provides an optical branching device and an optical communication system which are easy to connect with optical fibers. In the optical branching device, when light emitted from an optical fiber in a front stage is incident on an entrance port of a multicore optical fiber, the light propagates through a first core and then is distributed from the first core to four second cores by core-to-core crosstalk between the first and second cores. The light beams distributed to the four second cores propagate through the respective cores and are emitted to four optical waveguides optically coupled core-to-core thereto within a fan-out part at exit ports.

Abstract: An optical fiber has a plurality of holes in a cladding around a core, and has a high failure strength and small transmission loss. The core is made of glass. The cladding surrounds the core, and the holes are formed in the cladding so as to extend along a central axis of the fiber. The holes are formed with constant intervals therebetween along a circle centered on the core, and each hole has a substantially circular cross section. The cladding is sectioned into two claddings. A residual stress in an inner region that is inside a circumcircle of the holes is a compressive stress.

Abstract: A method of measuring the bending performance of an optical fiber in a simple manner is provided. Power P1 of light emitted from one end of the optical fiber when light is incident onto the other end of the optical fiber is measured under conditions where the optical fiber 1 is wound at a constant pitch by one layer on the circumferential side of a mandrel 2 and the overall circumference of the optical fiber 1 thus wound is covered with an index matching sheet 5. The refractive index of the index matching sheet 5 substantially matches with the refractive index of resin of the outermost layer of the optical fiber 1.

Abstract: An easily manufacturable optical fiber that has desired properties includes a core region made of a glass, a cladding region made of a glass surrounding the core region and having a first viscosity at a drawing temperature, and a jacket region made of a glass surrounding the cladding region and having a second viscosity that is lower than the first viscosity at the drawing temperature. A plurality of holes that are surrounded by the glass of the cladding region and the glass of the jacket region are circumferentially arranged in a cross section that is perpendicular to a fiber axis and extend along the fiber axis, and 50% or more of the glass surrounding each of the plurality of holes is the glass of the cladding region.

Abstract: A multi-core optical fibre 1A in which a plurality of cores can easily be identified even in the case where they are symmetrically arranged in its section has seven cores 10 to 16, a visual recognition marker 20, and a shared cladding 30 enclosing the seven cores 10 to 16 and the visual recognition marker 20. The cores 10 to 16 and the visual recognition marker 20 extend along the fibre-axis direction. The respective refractive index of the cores 10 to 16 is higher than the refractive index of the cladding 30. The refractive index of the visual recognition marker 20 differs from that of the cladding 30. In the cross-section perpendicular to the fibre-axis, the cores 10 to 16 are arranged such that they have 6-fold rotational symmetry and line symmetry. The visual recognition marker 20 is arranged at a position which breaks such symmetry.

Abstract: The present invention provides an optical branching device and an optical communication system which are easy to connect with optical fibers. In the optical branching device, when light emitted from an optical fiber in a front stage is incident on an entrance port of a multicore optical fiber, the light propagates through a first core and then is distributed from the first core to four second cores by core-to-core crosstalk between the first and second cores. The light beams distributed to the four second cores propagate through the respective cores and are emitted to four optical waveguides optically coupled core-to-core thereto within a fan-out part at exit ports.

Abstract: The present invention relates to a multi-core optical fiber having a structure for reducing transmission loss and nonlinearity. The multi-core optical fiber comprises plural cores extending along a center axis direction, and a cladding surrounding the peripheries of the plural cores. The cladding is comprised of silica glass doped with fluorine, and each of the plural cores is comprised of silica glass doped with chlorine or pure silica glass.

Abstract: Provided is a photonic crystal fiber capable of fusion-splicing with an ordinary optical fiber at low splicing loss and having a core region and a cladding region that surrounds the core region, wherein the cladding region is structured such that high refractive index sub-regions are periodically arranged in a two-dimensional periodic structure in the low refractive index background sub-region at a cross-section perpendicular to the fiber axis, and wherein the refractive index of the core region is higher than the refractive index of the low refractive index background sub-region. The refractive index profile of the photonic crystal fiber is uniform along the fiber axis. The effective refractive index of the core guided mode may be higher than the refractive index of the low refractive index background sub-region.

Abstract: The present invention relates to an optical waveguide manufacturing method, which excels in mass productivity of a planar optical waveguide. In an aggregating step, plural members (20), which have a rod (21) or pipe (22) shape respectively, are arranged and bundled so as to constitute a substantially similar figure to at least a part of a desired waveguide pattern on a cross-section perpendicular to the longitudinal direction of the members (20). The plural members (20) bundled in the aggregating step are, after being softened by heating, elongated in a longitudinal direction thereof in an elongating step, whereby an elongated body is formed. The elongated body formed in the elongating step is cut along a plane perpendicular to the longitudinal direction of the elongated body in a cutting step. By these steps, a planar optical waveguide, on which a waveguide pattern based on a micro-structure is formed, is manufactured.