Abstract: An optical fiber includes a core made of silica glass, and a cladding surrounding the core and made of silica glass. A product of a center wavenumber k?4 and a half width at half maximum kH4 of a peak of Raman scattered light ?4(T0) obtained by irradiating the core with excitation light having a wavelength of 532 nm is 38000 cm?2 or less.

Abstract: A glass rod manufacturing device includes: a holding portion configured to hold one end of a starting rod; a heating portion configured to heat a bent portion; and a centering jig configured to apply a force in a first direction intersecting an axis to a part of the starting rod that whirls between the bent portion and another end of the starting rod due to rotation of the starting rod about an axis. The centering jig includes: an abutment portion configured to abut against the part; an elastic displacement portion configured to elastically displace the abutment portion in the first direction according to a run-out deviation of whirl of the part; and a slide portion configured to slide the abutment portion in a second direction intersecting the axis and the first direction according to the run-out deviation of whirl of the part.

Abstract: The present disclosure relates to an optical fiber or the like that can be adapted to an optical transceiver for a short wavelength band of 850 nm or more and 1060 nm or less while maintaining compatibility with an SMF of the related art. An optical fiber of one embodiment includes a core, a cladding, and a resin coating, and has a mode field diameter of 8.2 ?m or more and 9.6 ?m or less at a wavelength of 1310 nm, a cable cutoff wavelength of an LP11 mode of 1060 nm or more and 1260 nm or less, and a cable cutoff wavelength of an LP02 mode of 1060 nm or less.

Abstract: A multi-core optical fiber includes: a pair of cores; and a cladding that covers both of the pair of cores. A diameter of the cladding is 124 ?m or more and 126 ?m or less. A distance between centers of the pair of cores is 46.5 ?m or less. Cross talk between counter-propagating cores at a wavelength of 1550 nm is ?30 dB/100 km or less.

Abstract: A multicore optical fiber of an embodiment has a structure for simultaneously realizing low transmission loss, low fusion splicing loss, and low inter-core crosstalk. The multicore optical fiber includes a plurality of cores comprised of silica glass, a common cladding comprised of silica glass and surrounding the plurality of cores, and a resin coating surrounding the common cladding. The common cladding has a refractive index lower than a refractive index of the plurality of cores. Each of the plurality of cores contains chlorine at 10000 ppm or more in at least part thereof.

Abstract: An optical fiber includes a core, an inner cladding surrounding the core, and an outer cladding surrounding the inner cladding. A mean relative refractive index difference ?1 of the core, a mean relative refractive index difference ?2 of the inner cladding, and a mean relative refractive index difference ?3 of the outer cladding satisfy a relationship of ?1>?3??2. A ratio r2/r1 of an inner cladding radius r2 to a core radius r1 is 4.5 or higher and 5.5 or lower. A minimum value ?min of a relative refractive index difference is ?0.030% or higher and ?0.010% or lower. A radius rmin at which the relative refractive index difference is the minimum value ?min satisfies a relationship of r1<rmin<r2. (?min??(r1))/(rmin?r1) is ?0.002%/?m or lower, where ?(r1) denotes the relative refractive index difference with the core radius r1.

Abstract: An MCF includes a plurality of cores each extending in a direction along a central axis and a cladding covering each of the plurality of cores. The cladding includes a low refractive index barrier. The low refractive index barrier includes an alkali metal element. A relative refractive index of the low refractive index barrier is lower than an average value of a relative refractive indices of the cladding overall. The core interval is set such that a total sum of the power coupling coefficients between a specific core among the plurality of cores and each of all remaining cores is 2.3×10?4/km or less.

Abstract: A mode-dependent loss measurement device measures a mode-dependent loss of a measurement target optical fiber including a coupled MCF. The device includes a light source, a light receiver, a mode coupled state changer, and an analysis unit. The light source inputs light to an input end of an excitation optical fiber including another coupled MCF. The light receiver detects a sum of powers of outputted light beams from a plurality of core end faces positioned on an output end of the measurement target optical fiber. The mode coupled state changer changes a mode coupled state of the excitation optical fiber. The analysis unit obtains a mode-dependent loss of the measurement target optical fiber from variations in optical powers detected by the light receiver.

Abstract: The MCF of the present disclosure suppresses occurrence of structural abnormality such as air bubbles in the vicinity of a boundary between a marker and a cladding. The MCF includes a glass optical fiber including a plurality of cores, a marker, and a cladding, and a resin coating. On a cross section of the MCF, centers of the plurality of cores and a center of the marker constitute a plane figure having a rotational symmetry of order 1 with respect to a center of the cross section. Moreover, on the cross section, the marker is disposed so as to be located on a circumference of a circle having a center coinciding with the center of the cross section and having the circumference passing through the respective centers of the plurality of cores.

Abstract: An optical fiber has a central axis. The optical fiber includes a core made of silica glass and extending along the central axis, a cladding made of silica glass and surrounding the core, the cladding extending along the central axis, and a coating layer made of resin and surrounding the cladding, the coating layer extending along the central axis. An outer diameter of the cladding varies along the central axis. A residual stress in a direction along the central axis varies along the central axis, the residual stress being averaged over the core and the cladding in a cross section perpendicular to the central axis. A deviation from an average value of the outer diameter and a deviation from an average value of the residual stress have signs opposite to each other.

Abstract: The present disclosure relates to an optical fiber or the like that can be adapted to an optical transceiver for a short wavelength band of 850 nm or more and 1060 nm or less while maintaining compatibility with an SMF of the related art. An optical fiber of one embodiment includes a core, a cladding, and a resin coating, and has a mode field diameter of 8.2 µm or more and 9.6 µm or less at a wavelength of 1310 nm, a cable cutoff wavelength of an LP11 mode of 1060 nm or more and 1260 nm or less, and a cable cutoff wavelength of an LP02 mode of 1060 nm or less.

Abstract: A gain flattening filter includes a first optical fiber that has a core, a first cladding, and a second cladding and that has a uniform composition in a length direction; and a pair of second optical fibers fused to both ends of the first optical fiber. The first optical fiber has a first section in which a slanted refractive index grating is formed and a pair of second sections connecting both ends of the first section to the pair of second optical fibers. The first cladding contains a photosensitive material whose refractive index increases upon irradiation with light having a specific wavelength. In the core, a tensile stress remains in the first section. An average MFD of the second sections is larger than an average MFD of the second optical fibers and smaller than an average MFD of the first section.

Abstract: An optical fiber includes a core, an inner cladding surrounding the core, and an outer cladding surrounding the inner cladding. A mean relative refractive index difference ?1 of the core, a mean relative refractive index difference ?2 of the inner cladding, and a mean relative refractive index difference ?3 of the outer cladding satisfy a relationship of ?1>?3??2. A ratio r2/r1 of an inner cladding radius r2 to a core radius r1 is 4.5 or higher and 5.5 or lower. A minimum value ?min of a relative refractive index difference is ?0.030% or higher and ?0.010% or lower. A radius rmin at which the relative refractive index difference is the minimum value ?min satisfies a relationship of r1<rmin<r2. (?min??(r1))/(rmin?r1) is ?0.002%/?m or lower, where ?(r1) denotes the relative refractive index difference with the core radius r1.

Abstract: The present disclosure relates to an optical fiber having a structure that has a low transmission loss and can be produced with high productivity. An optical fiber according to an embodiment includes a core and a cladding. The core is comprised of silica glass to which bromine is added, and the cladding has a refractive index lower than a maximum refractive index of the core. The core has compressive stress.

Abstract: An optical fiber line of one embodiment comprises an HNLF, an SMF, and an MFD transition portion. The MFD transition portion includes end portions of both the HNLF and the SMF facing with a fusion point thereof, and is a section in which an MFD changes such that a difference between a maximum value and a minimum value is 0.3 ?m or more for a 100 ?m-length. A splicing loss of the HNLF and the SMF at 1,550 nm is one-fifth or less than an ideal butting loss at stationary portions thereof. A total length of the MFD transition portion is 10 mm or less. In a region between one end surface of the HNLF at the fusion point and the other end surface separated from the one end surface by 50 ?m or more and 300 ?m or less, the MFD increases monotonically from the other end surface to the one end surface.

Abstract: An optical fiber according to an embodiment includes a core, a cladding, and a coating layer. At the boundary between the core and the cladding, the local sound velocity decreases in the direction from the core side toward the cladding side. At least in the cladding, the local sound velocity changes continuously in a radial direction. Further, the line width of the Brillouin gain of the light beam guided by the fundamental mode is 60 MHz or more.

Abstract: One embodiment of the present disclosure relates to an SFG (slanted fiber grating) that can easily realize a high-performance gain equalizer. The SFG includes an optical fiber comprised of silica-based glass and including a core, a first cladding containing a photosensitive material, and a second cladding. A specific section between two different points arranged along a fiber axis in the optical fiber is configured with a first region, a pair of second regions, and a third region. The first region includes a slanted Bragg grating provided in a region as the first cladding. The pair of second regions are arranged to sandwich the first region. The third region is disposed to sandwich both the first region and the pair of second regions. An MFD at a wavelength of 1.55 ?m in the third region is smaller than an MFD at a wavelength of 1.55 ?m in the first region.

Abstract: An optical fiber includes a silica-based glass. The optical fiber includes a core, an optical cladding surrounding the core, and a physical cladding surrounding the optical cladding. The optical cladding includes a first region in contact with the core and surrounding the core. A photosensitive material is added to the core and the first region. A concentration of the photosensitive material in the first region is 30% or more of a concentration of the photosensitive material in the core. A value obtained by integrating a light intensity of an LP01 mode at a wavelength of 1310 nm in a region added with the photosensitive material is 87% or more of a value obtained by integrating the light intensity in an entire region of the optical fiber.

Abstract: An optical fiber according to an embodiment includes a core and a cladding. The average value n1_ave of the refractive index of the core, the minimum value nc_min of the refractive index of the cladding, and the refractive index n0 of pure silica glass satisfy relationships of n1_ave>nc_min and nc_min<n0. The cladding contains fluorine. The fluorine concentration in the cladding is adjusted to be minimum in the outermost portion of the cladding including the outer peripheral surface of the cladding.

Abstract: An optical amplifier is provided in which adjacent ones of a plurality of cores each containing a rare-earth element and included in an amplifying multi-core optical fiber (MCF) serve as coupled cores at an amplifying wavelength, a connecting MCF is connected to the amplifying MCF, a pump light source is connected to the connecting MCF, and the pump light source pumps the rare-earth element in the amplifying MCF through the connecting MCF.