Abstract: A multicore fiber for communication 10 which allows propagation of an optical signal includes: a clad 12; a core 11a which is arranged in a center of the clad 12; and seven to ten cores 11b which are arranged at equal intervals surrounding the core 11a, and the cladding diameter is 230 ?m, distances between centers of the mutually neighboring cores 11a and 11b are 30 ?m or more, distances between the centers of the cores 11b and an outer peripheral surface of the clad 12 are 35 ?m or more and a mode field diameter of light propagating in the cores 11a and 11b is 9 ?m to 13 ?m.

Abstract: A multicore fiber for communication 10 which allows propagation of an optical signal includes: a clad 12;a core 11a which is arranged in a center of the clad 12; and seven to ten cores 11b which are arranged at equal intervals surrounding the core 11a, and the cladding diameter is 230 ?m, distances between centers of the mutually neighboring cores 11a and 11b are 30 ?m or more, distances between the centers of the cores 11b and an outer peripheral surface of the clad 12 are 35 ?m or more and a mode field diameter of light propagating in the cores 11a and 11b is 9 ?m to 13 ?m.

Abstract: A multicore fiber for communication 10 which allows propagation of an optical signal includes: a clad 12; a core 11a which is arranged in a center of the clad 12; and seven to ten cores 11b which are arranged at equal intervals surrounding the core 11a, and the cladding diameter is 230 ?m, distances between centers of the mutually neighboring cores 11a and 11b are 30 ?m or more, distances between the centers of the cores 11b and an outer peripheral surface of the clad 12 are 35 ?m or more and a mode field diameter of light propagating in the cores 11a and 11b is 9 ?m to 13 ?m.

Abstract: A dispersion shifted optical fiber where a radius r0 of a first center segment is 0.5 ?m to 2.8 ?m, and a relative refractive index difference ?0 is 0.4% or more and 0.9% or less. A radius r1 of a first segment is 1.8 ?m or more and 4.5 ?m or less. A radius r2 of a second segment is 4.0 ?m or more and 8.0 ?m or less, and a relative refractive index difference ?2 is 0.00% or more and 0.07% or less. A radius r3 of a third segment is 4.5 ?m or more and 8.5 ?m or less, and a relative refractive index difference ?3 is 0.285% or more and 0.5% or less. A radius r4 of a fourth segment is 8.0 ?m or more and 16.0 ?m or less, and a relative refractive index difference ?4 is 0.005% or more and 0.04% or less.

Abstract: A multicore optical fiber (1) includes a plurality of cores (11 to 16) and a cladding (20) surrounding the outer circumferential surfaces of the cores (11 to 16). In the plurality of cores of the multicore optical fiber (1), a skew value (S) between a pair of cores is expressed by a predetermined expression. The multicore optical fiber (1) is bent in a specific bending direction, in which in all of the combinations of the pairs of cores in the plurality of cores, the pair of cores has the maximum absolute value of the skew value found by the expression and the skew value of the pair of cores is a minimum value.

Abstract: A multicore fiber for communication 10 which allows propagation of an optical signal includes: a clad 12; a core 11a which is arranged in a center of the clad 12; and seven to ten cores 11b which are arranged at equal intervals surrounding the core 11a, and the cladding diameter is 230 ?m, distances between centers of the mutually neighboring cores 11a and 11b are 30 ?m or more, distances between the centers of the cores 11b and an outer peripheral surface of the clad 12 are 35 ?m or more and a mode field diameter of light propagating in the cores 11a and 11b is 9 ?m to 13 ?m.

Abstract: An optical fiber includes: a core; and a clad which is formed so as to surround an outer circumference of the core concentrically with the core, the clad having at least an inner cladding layer adjacent to the outer circumference of the core and an outer cladding layer formed on an outer circumference of the inner cladding layer, wherein a refractive index of the outer cladding layer is ?3, and an outer circumference radius of the outer cladding layer is r3, a relationship of ?1max>?3>?2min is satisfied, a relationship of ?3??2min?0.08% is satisfied, a relationship of r1<r2<r3 is satisfied, a relationship of 0.35?r1/r2?0.55 is satisfied, a cable cut-off wavelength is less than or equal to 1260 nm, and an MFD at a wavelength of 1310 nm is 8.6 ?m to 9.2 ?m.

Abstract: A dispersion shifted optical fiber where a radius r0 of a first center segment is 0.5 ?m to 2.8 ?m, and a relative refractive index difference ?0 is 0.4% or more and 0.9% or less. A radius r1 of a first segment is 1.8 ?m or more and 4.5 ?m or less. A radius r2 of a second segment is 4.0 ?m or more and 8.0 ?m or less, and a relative refractive index difference ?2 is 0.00% or more and 0.07% or less. A radius r3 of a third segment is 4.5 ?m or more and 8.5 ?m or less, and a relative refractive index difference ?3 is 0.285% or more and 0.5% or less. A radius r4 of a fourth segment is 8.0 ?m or more and 16.0 ?m or less, and a relative refractive index difference ?4 is 0.005% or more and 0.04% or less.

Abstract: An optical fiber includes: a core; and a clad which is formed so as to surround an outer circumference of the core concentrically with the core, the clad having at least an inner cladding layer adjacent to the outer circumference of the core and an outer cladding layer formed on an outer circumference of the inner cladding layer, wherein a refractive index of the outer cladding layer is ?3, and an outer circumference radius of the outer cladding layer is r3, a relationship of ?1max>?3>?2min is satisfied, a relationship of ?3??2min?0.08% is satisfied, a relationship of r1<r2<r3 is satisfied, a relationship of 0.35?r1/r2?0.55 is satisfied, a cable cut-off wavelength is less than or equal to 1260 nm, and an MFD at a wavelength of 1310 nm is 8.6 ?m to 9.2 ?m.

Abstract: A multicore fiber according to an embodiment of the present invention includes a plurality of cores and a cladding that encloses the plurality of the cores. The external form of the cladding in a cross section is formed of an arc portion that is formed in an arc shape relative to the center axis of the cladding and a non-arc portion that is pinched between two ends of the arc portion and not formed in an arc shape relative to the center axis of the cladding. The non-arc portion is formed with a pair of projections projecting from two ends of the arc portion on the opposite side of the center axis relative to a straight line connecting the both ends of the arc portion and one or more of recesses pinched between the pair of the projections.

Abstract: A multicore optical fiber (1) includes a plurality of cores (11 to 16) and a cladding (20) surrounding the outer circumferential surfaces of the cores (11 to 16). In the plurality of cores of the multicore optical fiber (1), a skew value (S) between a pair of cores is expressed by a predetermined expression.

Abstract: An optical fiber for amplification includes a core having an inner core and an outer core surrounding the outer circumferential surface of the inner core. The relative refractive index difference of the inner core to a cladding is smaller than the relative refractive index difference of the outer core to the cladding. The outer core is entirely doped with erbium. The theoretical cutoff wavelength of an LP11 mode light beam is a wavelength of 1,565 nm or more. The theoretical cutoff wavelength of an LP21 mode light beam is a wavelength of 1,530 nm or less. The theoretical cutoff wavelength of the LP02 mode light beam is a wavelength of 980 nm or less.

Abstract: An amplification optical fiber operable to propagate light beams in a plurality of modes in a predetermined wavelength range through a core doped with a rare earth element, wherein Expression (1) is satisfied, where a cutoff wavelength of a propagated highest mode light beam is defined as ?max, under conditions in which the cutoff wavelength of the highest mode light beam is defined as ?c, a shortest wavelength of the wavelength range is defined as ?min, and a cutoff wavelength of a second-highest mode light beam to the highest mode light beam is ?min. ?c>0.5 ?min+0.5 ?max??(1).

Abstract: A plurality of clad rods, and a clad tube, an arrangement process for arranging the plurality of core rods and the plurality of clad rods in a tube of the clad tube, in a state in which distances between center axes of the adjacent core rods become equal to each other and a state in which parts of outer circumferential surfaces in the adjacent rods contact, and an integration process for integrating the clad tube and the plurality of core rods and the plurality of clad rods arranged in the tube, wherein a ratio of a total cross-sectional area of a direction orthogonal to a length direction in the plurality of core rods and the plurality of clad rods with respect to an internal cross-sectional area of the tube of a direction orthogonal to a length direction in the clad tube is 0.84 or more.

Abstract: An amplification optical fiber operable to propagate light beams in a plurality of modes in a predetermined wavelength range through a core doped with a rare earth element, wherein Expression (1) is satisfied, where a cutoff wavelength of a propagated highest mode light beam is defined as ?max, under conditions in which the cutoff wavelength of the highest mode light beam is defined as ?c, a shortest wavelength of the wavelength range is defined as ?min, and a cutoff wavelength of a second-highest mode light beam to the highest mode light beam is ?min. ?c>0.5 ?min+0.

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: A multicore fiber includes six or more of core elements having a core, a first clad surrounding the outer circumferential surface of the core and a second clad surrounding the outer circumferential surface of the first clad, and includes a clad surrounding the core elements. All of expressions are satisfied: n1>n2>n3, n1>n4, n3<n4, wherein the refractive index of the core is n1, the refractive index of the first clad is n2, the refractive index of the second clad is n3, and the refractive index of the clad is n4. The core elements are disposed so that the inter-center pitch between the cores adjacent to each other is disposed at regular spacing and the centers of the cores are annularly disposed.

Abstract: A multicore fiber according to the present invention includes a plurality of cores and a cladding enclosing the plurality of the cores. The plurality of the cores has two cores or greater forming a first plurality of cores linearly arranged to form a first row on one side based on a plane passed through the center axis of the cladding and three cores or greater forming a second plurality of cores arranged in parallel with the first plurality of the cores to form a second row on the other side based on the plane. The cores configuring the first plurality of the cores and the cores configuring the second plurality of the cores are disposed on lines orthogonal to the plane.

Abstract: A multicore fiber includes a plurality of cores and a cladding that encloses the plurality of the cores. The plurality of the cores is arranged and disposed on a linear line passed through the center of the cladding. A difference in the cutoff wavelength between an outer core located at the outermost position and an inner core located next to the outer core is set at a wavelength of 100 nm or less.

Abstract: A plurality of cores 51 is disposed around the center axis of a first cladding 52 in a state in which an inter-core distance ? of cores adjacent to each other is equal, a refractive index n1 of the core 51 is provided higher than a refractive index n2 of the first cladding 52, and the refractive index n2 of the first cladding 52 is provided higher than a refractive index n3 of a second cladding 53. Moreover, 5.8??/MFD(2?c/(?c+?op))?8 is satisfied, where the inter-core distance is defined as ?, a mode field diameter of the core is defined as MFD, a cutoff wavelength is defined as ?c, and a wavelength of communication light incident on the core 51 is defined as ?op.