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: A fiber fuse terminator which is used to terminate a fiber fuse, comprising: an optical fiber which includes a core and a cladding having holes extending in a longitudinal direction thereof, in which: a refractive index of the core of the optical fiber is higher than a refractive index of a portion of the cladding excepting portions of the holes; when it is assumed that a mode field diameter at a used wavelength of the optical fiber is MFD, and a distance in a cross section perpendicular to the longitudinal direction of the optical fiber between a center of the core and a position, closest to the center of the core, of the hole that is closest to the core is Rmin, a value expressed by 2×Rmin/MFD is no less than 1.2 and no more than 2.1; when it is assumed that a width, in a diameter direction, of a region where the holes present in the cladding is W, a value expressed by W/MFD is no less than 0.3; and when it is assumed that a diameter of the cladding of the optical fiber is Dfiber, W?0.

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: The multicore fiber comprises 7 or more cores, wherein diameters of the adjacent cores differ from one another, wherein each of the cores performs single-mode propagation, wherein a relative refractive index difference of each of the cores is less than 1.4%, wherein a distance between the adjacent cores is less than 50 ?m, wherein, in a case where a transmission wavelength of each of the cores is ?, the distance between the adjacent cores is , a mode field diameter of each of the cores is MFD, and a theoretical cutoff wavelength of each of the cores is ?c, (/MFD)·(2?c/(?c+?))?3.95 is satisfied, and wherein a distance between the outer circumference of the coreand an outer circumference of the clad is 2.5 or higher times as long as the mode field diameter of each of the cores.

Abstract: A fiber fuse terminator which is used to terminate a fiber fuse, comprising: an optical fiber which includes a core and a cladding having holes extending in a longitudinal direction thereof, in which: a refractive index of the core of the optical fiber is higher than a refractive index of a portion of the cladding excepting portions of the holes; when it is assumed that a mode field diameter at a used wavelength of the optical fiber is MFD, and a distance in a cross section perpendicular to the longitudinal direction of the optical fiber between a center of the core and a position, closest to the center of the core, of the hole that is closest to the core is Rmin, a value expressed by 2×Rmin/MFD is no less than 1.2 and no more than 2.1; when it is assumed that a width, in a diameter direction, of a region where the holes present in the cladding is W, a value expressed by W/MFD is no less than 0.3; and when it is assumed that a diameter of the cladding of the optical fiber is Dfiber, W?0.

Abstract: The multicore fiber comprises 7 or more cores, wherein diameters of the adjacent cores differ from one another, wherein each of the cores performs single-mode propagation, wherein a relative refractive index difference of each of the cores is less than 1.4%, wherein a distance between the adjacent cores is less than 50 ?m, wherein, in a case where a transmission wavelength of each of the cores is ?, the distance between the adjacent cores is , a mode field diameter of each of the cores is MFD, and a theoretical cutoff wavelength of each of the cores is ?c, (/MFD)·(2?c/(?c+?))?3.95 is satisfied, and wherein a distance between the outer circumference of the coreand an outer circumference of the clad is 2.5 or higher times as long as the mode field diameter of each of the cores.

Abstract: There is provided an optical fiber communication system restricting enlargement of the diameter of an optical fiber as well as enabling achievement of a large-capacity optical communication with a small number of optical fibers. An optical fiber communication system 100 includes an optical transmitter 10 transmitting a plurality of optical signals in parallel, a multicore fiber 20 in which outer circumferences of a plurality of cores are covered with a common clad, and the respective optical signals transmitted in parallel from the optical transmitter 10 are input into the cores, and an optical receiver 30 receiving the optical signals output in parallel from the respective cores of the multicore fiber, wherein the optical transmitter 10 and the optical receiver 30 perform a MIMO communication.

Abstract: A method of manufacturing a photonic band gap fiber base material includes: a forming step of continuously forming a columnar core glass body 10 and a clad glass body 20 which coats the core glass body to obtain an intermediate base material 110; a hole making step of making holes 30 in the clad glass body 20; an insertion step of inserting in the holes 30 a plurality of bilayer glass rods 40 in which an outer layer 42 which has the same refractive index as the clad glass body coats high refractive index portions 41 having a higher refractive index than a refractive index of the clad glass body 20; and a heating step of heating the intermediate base material 110 and integrating the intermediate base material 110 and the bilayer glass rods 40.

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 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: Provided is a fiber laser device capable of preventing laser light from damaging a laser oscillator even if the laser light is reflected by an object to be irradiated or at an output end.

Abstract: An extended triangular lattice type photonic bandgap fiber, includes a cladding and a capillary core, the cladding having a plurality of holes disposed within a silica glass portion in a longitudinal direction of the fiber and arranged in an extended triangular lattice shape, the capillary core having a plurality of holes arranged in a triangular lattice shape, wherein the cross-sectional area of the respective holes in the capillary core is smaller than that of the respective holes in the cladding.

Abstract: A method for measuring a multimode optical fiber includes: monitoring a temperature change within a measurement time in a DMD measurement of the multimode optical fiber, where the DMD measurement is carried out in an environment in which a magnitude of temperature change is controlled.

Abstract: A photonic bandgap fiber of the present invention functions as a polarization maintaining fiber, and includes: a core made from a solid material; a cladding provided around the core; a periodic structure region which is provided in a part of the cladding in a vicinity of the core and in which a plurality of high refractive index parts with a refractive index higher than that of the cladding are arranged in a periodic structure; a low refractive index region which is provided in another part of the cladding in a vicinity of the core and has an average refractive index lower than that of the core; and stress applying parts which are provided in a part of the low refractive index region close to the periodic structure region and have a thermal expansion coefficient different from that of another part of the low refractive index region.

Abstract: A fiber fuse terminator which is used to terminate a fiber fuse, comprising: an optical fiber which includes a core and a cladding having holes extending in a longitudinal direction thereof, in which: a refractive index of the core of the optical fiber is higher than a refractive index of a portion of the cladding excepting portions of the holes; when it is assumed that a mode field diameter at a used wavelength of the optical fiber is MFD, and a distance in a cross section perpendicular to the longitudinal direction of the optical fiber between a center of the core and a position, closest to the center of the core, of the hole that is closest to the core is Rmin, a value expressed by 2×Rmin/MFD is no less than 1.2 and no more than 2.1; when it is assumed that a width, in a diameter direction, of a region where the holes present in the cladding is W, a value expressed by W/MFD is no less than 0.3; and when it is assumed that a diameter of the cladding of the optical fiber is Dfiber, W?0.

Abstract: A photonic band gap fiber is provided having multiple air holes in a silica portion extending in the longitudinal direction of the fiber. The fiber includes a cladding containing an air hole periodic structure in an extended triangular lattice configuration, wherein first rows each having a number of air holes at a first pitch are arranged alternately in the cross section of the fiber with multiple second rows of air holes each with multiple air holes at a second pitch which is twice the first pitch. The fiber further includes an air hole core.

Abstract: An extended triangular lattice type photonic bandgap fiber, includes a cladding and a capillary core, the cladding having a plurality of holes disposed within a silica glass portion in a longitudinal direction of the fiber and arranged in an extended triangular lattice shape, the capillary core having a plurality of holes arranged in a triangular lattice shape, wherein the cross-sectional area of the respective holes in the capillary core is smaller than that of the respective holes in the cladding.

Abstract: An extended triangular lattice type photonic bandgap fiber, includes a cladding and a capillary core, the cladding having a plurality of holes disposed within a silica glass portion in a longitudinal direction of the fiber and arranged in an extended triangular lattice shape, the capillary core having a plurality of holes arranged in a triangular lattice shape, wherein the cross-sectional area of the respective holes in the capillary core is smaller than that of the respective holes in the cladding.

Abstract: A photonic band gap fiber is provided having multiple air holes in a silica portion extending in the longitudinal direction of the fiber. The fiber includes a cladding containing an air hole periodic structure in an extended triangular lattice configuration, wherein first rows each having a number of air holes at a first pitch are arranged alternately in the cross section of the fiber with multiple second rows of air holes each with multiple air holes at a second pitch which is twice the first pitch. The fiber further includes an air hole core.

Abstract: A graded-index multimode fiber includes a core made of silica glass, the core having a central region and an outer peripheral region, and a cladding which is provided at an outer periphery of the core. The central region contains one of germanium and phosphorus, and the outer peripheral region contains fluorine.