Abstract: An optical fiber bundle structure includes: plural optical fiber core wires; a crossing preventing member; and a grasping member. Further, the crossing preventing member has slits and the widths of the slits positioned at the respective sides are each equal to or larger than a difference between: a length of one side of a polygon circumscribing the plural optical fiber core wires at a hindmost end portion of the slits at the trailing end; and a length of one side of a polygon circumscribing the plural optical fiber core wires at the leading end.

Abstract: An optical fiber bundle structure includes: plural optical fiber core wires; a crossing preventing member; and a grasping member. Further, the crossing preventing member has slits and the widths of the slits positioned at the respective sides are each equal to or larger than a difference between: a length of one side of a polygon circumscribing the plural optical fiber core wires at a hindmost end portion of the slits at the trailing end; and a length of one side of a polygon circumscribing the plural optical fiber core wires at the leading end.

Abstract: A laser device includes: a seed light source configured to output a laser light having a single mode; a multicore fiber including at least one core group having at least one core, each of the core in the core group being optically coupled to neighboring cores; and an optical coupler configured to input the laser light to the core group, wherein in the multicore fiber, the laser light propagates through the core group in a super mode representing propagation mode of the core group.

Abstract: A multicore fiber includes: a plurality of core portions made of glass; and a cladding portion made of glass and configured to surround outer periphery of the plurality of core portions. The cladding portion has tensile stress of 20 MPa or lower in a region on outer periphery side than a core portion that is closest to outer periphery of the cladding portion in the plurality of core portions.

Abstract: An optical fiber bundle structure includes: a plurality of optical fiber core wires; and a capillary, wherein each of the optical fiber core wires includes a glass fiber portion including a core and a clad, and a resin coated portion, the glass fiber portions are inserted in the capillary, and d2/d1 is equal to or larger than 0.57 and smaller than 1, where d1 is a diameter of the core of each of the glass fiber portions in a rear end portion of the capillary and d2 is a diameter of the core of each of the glass fiber portions in a distal end portion of the capillary.

Abstract: A light source includes: a seed light source configured to output incoherent seed light with a predetermined bandwidth; and a booster amplifier that is a semiconductor optical amplifier configured to optically amplify the seed light input from a first facet, and output the amplified seed light as amplified light from a second facet, wherein the first facet and the second facet of the booster amplifier are subjected to a reflection reduction treatment, the booster amplifier is configured to operate in a gain saturated state, and relative intensity noise (RIN) and ripple are simultaneously suppressed in the amplified light.

Abstract: A multicore fiber includes: a plurality of first glass regions each including: a core portion; and a first cladding portion having a lower refractive index than a maximum refractive index of the core portion; and a cladding region formed on outer peripheries of the plurality of first glass regions, wherein compressive stress is applied to the plurality of first glass regions.

Abstract: An optical amplifying fiber includes: at least one core portion including a rare earth element added therein; an inner cladding portion surrounding the at least one core portion, the inner cladding portion having a refractive index lower than a maximum refractive index of the at least one core portion; and an outer cladding portion surrounding the inner cladding portion, the outer cladding portion having a refractive index lower than the refractive index of the inner cladding portion, the inner cladding portion including different refractive index regions each having a refractive index different from a refractive index of a region adjacent to that different refractive index region.

Abstract: An optical fiber amplification. system includes: a first optical fiber amplifier including a first optical amplifying fiber including a core portion doped with a first rare-earth. element, a first input unit configured to receive first signal light, an excitation-light source configured to output pump light, a pump light combiner configured to input the pump light to the first optical amplifying fiber, and a residual pump light recovery device configured to recover residual pump light; and a second optical fiber amplifier including a second optical amplifying fiber including a core portion doped with a second rare-earth. element, a second input unit configured to receive second signal light, and a residual pump light combiner configured to input, to the second optical amplifying fiber, the residual pump light recovered by the residual pump light recovery device.

Abstract: A multi-core optical amplifying fiber includes: core portions doped with a rare-earth element; an inner cladding portion; and an outer cladding portion. A mode field diameter of each core portion at a wavelength at which the rare-earth element performs optical amplification is 5 ?m to 11 ?m, a relative refractive-index difference of the maximum refractive index of each core portion with respect to the inner cladding portion is 0.35% to 2%, a core-to-core distance is set such that total inter-core crosstalk is ?40 dB/100 m or lower in an optical amplification wavelength band subjected to the optical amplification, a cladding thickness is smaller than a value obtained by adding the mode field diameter to a minimum value of the core-to-core distance, and a ratio of a total sectional area of the core portions to a sectional area of the inner cladding portion is 1.9% or more.

Abstract: An optical amplifying fiber includes: at least one single core portion doped with a rare-earth element; an inner cladding portion configured to enclose the at least one core portion, the inner cladding portion having a lower refractive index than maximum refractive index of each core portion; and an outer cladding portion configured to enclose the inner cladding portion, the outer cladding portion having a lower refractive index than refractive index of the inner cladding portion, wherein the inner cladding portion includes a plurality of air bubbles.

Abstract: A cable comprising: a plurality of optical fiber cores; and one or more optical fiber core wires including one or more of the optical fiber cores. Further, at least one of the optical fiber core wire is fixed at a plurality of positions in a longitudinal direction of the cable so as to achieve substantially no displacement in a cable radial direction, at least a pair of the optical fiber core wires are fixed in a plane perpendicular to the longitudinal direction of the cable so as to achieve substantially no displacement relative to each other, and sensing of a strain profile in the longitudinal direction of at least the pair of the optical fiber core wires leads to achievement of sensing of a shape of the cable in the longitudinal direction.

Abstract: A multi-core fiber includes: plural cores made of silica-based glass; and a cladding enclosing the plural cores and made of silica-based glass, the cladding having a refractive index lower than a maximum refractive index of the plural cores. Further, the multi-core fiber has a mode field diameter of 5.0 ?m or larger at a wavelength of 1100 nm, the multi-core fiber provides single-mode propagation at the wavelength of 1100 nm, the multi-core fiber has a bending loss of 1 dB/turn or less at the wavelength of 1100 nm when the multi-core fiber is bent at a radius of 2 mm, and the multi-core fiber has a crosstalk between cores of ?30 dB/km or less.

Abstract: An optical fiber bundle structure includes: plural optical fiber core wires; a crossing preventing member; and a grasping member. Further, the crossing preventing member has slits and the widths of the slits positioned at the respective sides are each equal to or larger than a difference between: a length of one side of a polygon circumscribing the plural optical fiber core wires at a hindmost end portion of the slits at the trailing end; and a length of one side of a polygon circumscribing the plural optical fiber core wires at the leading end.

Abstract: A multicore fiber includes: n pieces of first core regions in a circular shape with a radius r1 that are arranged about points P11 to P1n, and that has a first core portion and a first cladding portion; a second core region in a circular shape with a radius R1 that is arranged about the point a1, and that has a second core portion and a second cladding portion; and a cladding region that is formed on an outer circumferences of the first core region and the second core region. Further, abutting surfaces that are flat surfaces abutting on each other are formed in portions on the outer circumferences of the first core region and the second core region.

Abstract: A cable comprising: a plurality of optical fiber cores; and one or more optical fiber core wires including one or more of the optical fiber cores. Further, at least one of the optical fiber core wire is fixed at a plurality of positions in a longitudinal direction of the cable so as to achieve substantially no displacement in a cable radial direction, at least a pair of the optical fiber core wires are fixed in a plane perpendicular to the longitudinal direction of the cable so as to achieve substantially no displacement relative to each other, and sensing of a strain profile in the longitudinal direction of at least the pair of the optical fiber core wires leads to achievement of sensing of a shape of the cable in the longitudinal direction.

Abstract: A multicore fiber includes a plurality of unit multicore fibers each including: a plurality of core portions; and a clad portion which is formed in an outer circumference of the core portions and has a refractive index lower than a maximum refractive index of the core portions. The plurality of the core portions have substantially same refractive index profile and different group delays at same wavelength in same propagation mode. The core portions of the multicore fiber are configured so that the core portions of the plurality of the unit multicore fibers are connected in cascade, a maximum value of differential group delays between the core portions of the multicore fiber is smaller than a reduced value of a maximum value of differential group delays between the core portions of each unit multicore fiber as a value in terms of a length of the multicore fiber.

Abstract: A multi-core optical amplifying fiber device includes a plurality of multi-core optical amplifying fibers including a plurality of core portions doped with amplification medium and a cladding portion formed at outer peripheries of the plurality of core portions; and a connection portion connecting the core portions of the plurality of multi-core optical amplifying fibers to one another. The connection portion connects the core portions to restrain deviation, between every connected core portions, of amplification gain for a total length of the core portions connected one another.

Abstract: A production method of an optical fiber preform includes first preparing a first preform having a plurality of glass preforms and a first cladding portion disposed between the plurality of glass preforms, and first arranging a second cladding portion to surround the first preform. At the first arranging, a material gas and a combustion gas are ejected from a burner to produce glass particles. The first preform and the burner are moved relative to each other in a longitudinal direction of the first preform. The glass particles are deposited on the first preform.

Abstract: A multicore fiber includes a plurality of unit multicore fibers each including: a plurality of core portions; and a clad portion which is formed in an outer circumference of the core portions and has a refractive index lower than a maximum refractive index of the core portions. The plurality of the core portions have substantially same refractive index profile and different group delays at same wavelength in same propagation mode. The core portions of the multicore fiber are configured so that the core portions of the plurality of the unit multicore fibers are connected in cascade, a maximum value of differential group delays between the core portions of the multicore fiber is smaller than a reduced value of a maximum value of differential group delays between the core portions of each unit multicore fiber as a value in terms of a length of the multicore fiber.