Abstract: An optical fiber has a core region, a cladding region and at least one spacer layer disposed between the core region and the cladding region. The core region is positively doped and has a positive refractive index with respect to the glass matrix of the optical fiber. The cladding region is negatively doped and has a refractive index of at most zero with respect to the glass matrix. The numerical aperture of the optical fiber is composed of variable proportions of the positively doped core region and the negatively doped cladding region and results from the refractive indices of both regions.

Abstract: Described is a modular method of making an optical fiber comprising a core and a cladding configured to support and guide a fundamental transverse mode, the cladding including (i) an outer cladding having an index nout less than the index n1 of the core, (ii) an inner cladding having an index n2<nout, (iii) a pedestal having an index n4?nout, (iv) an inner trench disposed between the inner cladding and the pedestal, the inner trench having an index n3<<n4, and (iv) an outer trench disposed between the pedestal and the outer cladding, the outer trench having an index n5<n4 and relatively close to nout. To suppress unwanted HOMs the pedestal is configured to resonantly couple at least one unwanted transverse mode of the core (other than the fundamental mode) to at least one transverse mode of the pedestal.

Abstract: Methods and systems for managing pulse energy scaling are disclosed, including generating electromagnetic radiation; coupling the electromagnetic radiation to a fiber geometrical management system comprising: a tapered fiber comprising: an elliptical or rectangular core centrally positioned within a single or double cladding shell, wherein the core comprises a fiber material and a doped gain medium; an input face wherein the doped core comprises a major axis and a minor axis, wherein the ratio of the major to minor axis at the input face ranges from about 1 to about 100; an output face wherein the doped core comprises a major axis and a minor axis, wherein the ratio of the major to minor axis at the output face ranges from about 1 to about 100; and wherein the major (minor) axis is adiabatically or linearly tapered from the input face to the output face. Other embodiments are described and claimed.

Abstract: Multi-core optical fibers are disclosed herein. According to one embodiment, a multi-core optical fiber includes a common outer cladding formed from silica-based glass and having a cladding index of refraction ncl. At least one single mode core element may be disposed in the common outer cladding. The at least one single mode core element may have a maximum index of refraction n1 sm. In addition, at least one multimode core element may be disposed in the common outer cladding, the at least one multimode core element having a maximum index of refraction n1 mm. The maximum refractive index n1 sm of the at least one single mode core element may be greater than the cladding index of refraction ncl, the maximum refractive index n1 mm of the at least one multi-mode core element may be greater than ncl, and a center-to-center spacing between adjacent core elements is greater than or equal to 25 ?m.

Abstract: One embodiment of a single mode optical fiber includes: a graded index central core region having outer radius r1 and relative refractive index ?1; a cladding region comprising (i) a first inner cladding region having an outer radius r2<10 microns and relative refractive index ?2 and 0.65?r1/r2?1; (ii) and a second inner cladding region (i.e., trench) having an outer radius r3>10 microns and comprising a minimum relative refractive index ?3, wherein said second inner cladding region has at least one region with a relative refractive index delta that becomes more negative with increasing radius; and (iii) an outer cladding region surrounding the second inner cladding region and comprising relative refractive index ?4, wherein ?1>?2>?3, ?3<?4.

Abstract: A fiber laser apparatus includes an optical amplification fiber with a multi-core structure composed of a first waveguide that pumping light enters and that transmits the pumping light; a second waveguide composed of a core containing a laser medium and for generating laser, and a clad for transmitting pumping light; and a third waveguide containing the first waveguide and the second waveguide. The optical amplification fiber is wound while the curvature radius is being changed to provide a small-size, high-power fiber laser apparatus.

Abstract: The present invention relates to a multi-core optical fiber having a structure to effectively reduce crosstalk between adjacent core regions among a plurality of core regions. The multi-core optical fiber (1) has a leakage reduction portion (50), at least a portion of which is arranged at a position on a straight line connecting adjacent core regions together among a plurality of core regions (10). The leakage reduction portion (50) reduces leakage light in the multi-core optical fiber (1) from each of the core regions (10), thereby effectively reducing crosstalk between adjacent core regions.

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 an optical waveguide comprising an optical core having transverse sides, the optical core extending along a curved path; an optical cladding on the transverse sides of the optical core, wherein the distribution of the optical cladding on the transverse sides of the optical core is asymmetric about the centre of the core.

Abstract: An apparatus for inspecting a specimen, such as a semiconductor wafer, is provided. The apparatus comprises a laser energy source, such as a deep ultraviolet (DUV) energy source and an optical fiber arrangement. The optical fiber arrangement comprises a core surrounded by a plurality of optical fibers structures used to frequency broaden energy received from the laser energy source into frequency broadened radiation. The frequency broadened radiation is employed as an illumination source for inspecting the specimen. In one aspect, the apparatus comprises a central core and a plurality of structures generally surrounding the central core, the plurality of fibers surround a hollow core fiber filled with a gas at high pressure, a tapered photonic fiber, and/or a spider web photonic crystalline fiber, configured to receive light energy and produce frequency broadened radiation for inspecting the specimen.

Abstract: To project a rectangular laser spot having a predetermined size and a high laser power density onto the surface of an object, a semiconductor manufacturing apparatus comprises a control unit for controlling power of a laser light source, an optical waveguide unit (1) including a core section (10) transmitting laser light and a clad section (11) covering the core section (10), and a lens (3) for forming the laser light output through the optical waveguide unit (1) into a laser spot having a predetermined shape, an output end surface (15) of the core section (10) has a rectangular shape with one side length of 1 ?m to 20 ?m and the other side length of 1 mm to 60 mm, and the laser source is set to make the power density of the laser spot output from the core section (10) to be 0.1 mW/?m2 or more.

Abstract: An optical fiber includes a core portion and a cladding portion that is formed on an outer periphery of the core portion and has a refractive index lower than a maximum refractive index of the core portion. Characteristics at a wavelength of 1550 nm are an effective core area of a fundamental propagation mode of equal to or larger than 120 ?m2, an effective core area of a first higher-order propagation mode of equal to or larger than 170 ?m2, and an effective refractive index of the first higher-order propagation mode of larger than the refractive index of the cladding portion by equal to or larger than 0.0005.

Abstract: An optical fiber comprising a core region embedded within a cladding. The core region of the optical fiber further comprises multiple sections, each doped with rare earth ions. The sections of the core region may be doped with different rare-earth ions or with different doping concentrations. The sections of the core region may also be made from different types of glass hosts. The optical fiber may further include multiple core regions embedded within the cladding, each core region having multiple sections doped with rare earth ions.

Abstract: A multicore fiber includes a cladding and a plurality of core elements which is provided in the cladding and includes a core, an inner cladding layer that surrounds the core, and a low-refractive index layer that surrounds the inner cladding layer and has a lower average refractive index than the cladding and the inner cladding layer. The plurality of core elements is arranged such that a specific core element is surrounded by three or more core elements, and a low-refractive index layer of a partial core element of the plurality of core elements is configured to have larger light confinement loss in the core than low-refractive index layers of the other partial core elements.

Abstract: The invention relates to a double-sheath fiber having a core region (1) and a sheath region, the sheath region having an inner region (2) and an outer region (3), which comprises a refractive index that is lower with respect to that of the inner region (2) and the core region (1), wherein the outer region (3) surrounds the inner region (2). The invention proposes an internal structure (4) of the inner region (2) which effects a spatial overlap of modes of higher order with the core region (1), which is lower than the spatial overlap of a fundamental mode with the core region (1).

Abstract: A method and apparatus for manufacturing a composite structure. A filler material with a barrier material for a channel in the filler material is formed. A composite material and the filler material with the barrier material are laid up onto a tool in a shape of the composite structure. The composite material and the filler material in the shape of the composite structure are cured.

Abstract: Light diffusing optical fibers and methods for producing light diffusing optical fibers are disclosed. In one embodiment, a light diffusing optical fiber includes a core portion formed from silica glass and comprising a plurality of helical void randomly distributed in the core portion of the optical fiber and wrapped around the long axis of the optical fiber. A pitch of the helical voids may vary along the axial length of the light diffusing optical fiber in order to achieve the desired illumination along the length of the optical fiber. A cladding may surround the core portion. Light guided by the core portion is scattered by the helical voids radially outward, through the cladding, such that the light diffusing optical fiber emits light with a predetermined intensity over an axial length of the light diffusing optical fiber, the light diffusing optical fiber having a scattering induced attenuation loss greater than about 0.2 dB/m at a wavelength of 550 nm.

Abstract: Provided is a manufacturing method for an optical waveguide in which, when the optical waveguide is cut and a contour thereof is processed, accuracy of a cut position is improved by improving visibility of an alignment mark. An undercladding layer, cores, and alignment marks are formed on a front surface of a substrate. Then, an overcladding layer is formed using a photomask so as to cover the cores with the alignment marks being exposed. After the substrate is separated to manufacture an optical waveguide body, a cut position is located with reference to the alignment marks from a rear surface side of the undercladding layer, and the undercladding layer and the overcladding layer are cut to manufacture the optical waveguide.

Abstract: A method of coupling a spliceable optical fiber includes (A) providing the spliceable optical fiber, the spliceable optical fiber including (a) a core region; and (b) a microstructured cladding region. The cladding region surrounds the core region and includes (b1) an inner cladding region having a refractive index formed by inner cladding features arranged in an inner cladding background material with a refractive index n1, the inner cladding features including thermally collapsible holes or voids, and (b2) an outer cladding region with an outer cladding background material with a refractive index n2, the spliceable optical fiber having at least one end. (B) Collapsing the thermally collapsible holes or voids by heating the at least one end of the spliceable optical fiber thereby increasing the refractive index of the inner cladding providing an expanded core. And, (C) coupling the collapsed spliceable optical fiber end to the optical component.

Abstract: A multicore fiber has a plurality of cores; and a clad which surrounds an outer peripheral surface of each of the cores, and at least one of the cores is spirally arranged such that the core rotates around a center axis of the clad. By arranging the cores in this way, it is possible to prevent crosstalk between specific cores from escalating even when the multicore fiber is disposed in a bent state.

Abstract: One embodiment of a single mode optical fiber includes: a graded index central core region having outer radius r1 and refractive index ?1; a cladding region comprising (i) a first inner cladding region having an outer radius r2<10 microns and refractive index ?2 and 0.65?r1/r2?1; (ii) and a second inner cladding region having an outer radius r3>10 microns and comprising a minimum refractive index ?3, wherein said second cladding region has at least one region with a refractive index delta that becomes more negative with increasing radius; and (iii) an outer cladding region surrounding the inner cladding region and comprising refractive index ?4, wherein ?1>?2>?3, ?3<?4.

Abstract: A graded index multimode optical fiber comprising: (a) a silica core doped with germania, and at least one co-dopant, comprising one of P2O5 or F or B2O3, the core extending to outermost core radius, r1 and having a dual alpha, ?1; (b) a low index inner cladding surrounding the core and off-set from said core; (c) an outer cladding surrounding and in contact with the inner cladding, such that at least the region of the inner cladding off-set from said core has a lower refractive index than the outer cladding. The center germania concentration at the centerline, CGe1, is greater than or equal to 0, and an outermost germania concentration in the core CGe2, at r1 is greater than or equal to 0. The core has a center co-dopant concentration at the centerline, Cc-d1, greater than or equal to 0, and an outermost co-dopant concentration Cc-d2, at r1, wherein Cc-d2 is greater than or equal to 0.

Abstract: An optical fiber includes multiple cores and a cladding. At least one of the multiple cores forms an optical waveguide and has an elongated cross-section with a narrower dimension in a fast-axis direction and a wider dimension in a slow-axis direction. The cladding surrounds the multiple cores and has a refractive index that differs from at least one refractive index of the multiple cores. The multiple cores could be stacked such that a first of the multiple cores is located at least partially over a second of the multiple cores in the fast-axis direction. The optical fiber could include an additional core within the cladding and having a substantially circular cross-section. The cores could be used to transport a high-power laser beam, an illumination laser beam, and an alignment laser beam. The optical fiber could have a length of at least two meters.

Abstract: A hybrid optical fiber integrates features of multimode optical fibers and single-mode optical fibers. The hybrid optical fiber possesses an optical core having a first core region and a second core region to provide improved optical mode coupling ratio for single-mode transmission while maintaining a broad bandwidth for multimode transmission. The hybrid optical fiber's optical core may optionally include a depressed trench positioned between the optical core's first core region and the optical core's second core region to reduce modal dispersion and to improve modal bandwidth during multimode transmissions.

Abstract: There are provided an optical waveguide including: a substrate 1; a lower clad layer 2; a core pattern 3 with a taper in thickness direction; and an upper clad layer 4, the lower clad layer, the core pattern, and the upper clad layer being sequentially laminated on the substrate 1, in which the lower clad layer 2 has a cutting part 5. There also provided with an optical waveguide including: a substrate 1; a lower clad layer 2; a core pattern 3 with a taper in thickness direction; and an upper clad layer 4, the lower clad layer, the core pattern, and the upper clad layer being sequentially laminated on the substrate 1, in which the lower clad layer 2 has a dummy part on the top. These optical waveguides can secure alignment tolerance when connected with an optical element.

Abstract: Various embodiments include large cores fibers that can propagate few modes or a single mode while introducing loss to higher order modes. Some of these fibers are holey fibers that comprising cladding features such as air-holes. Additional embodiments described herein include holey rods. The rods and fibers may be used in many optical systems including optical amplification systems, lasers, short pulse generators, Q-switched lasers, etc. and may be used for example for micromachining.

Abstract: A photonic bandgap fiber includes a core of a solid material; a first cladding provided around the core; a low-refractive-index region provided in a part of a core vicinity portion of the first cladding and whose average refractive index is lower than that of the core; and a periodic structure region that is arranged in another part of the core vicinity portion of the first cladding which is made of a great many high-refractive-index portions whose refractive index is higher than that of the first cladding arranged in a periodic structure. According to the invention, it is possible to provide a photonic bandgap fiber which, when arranged in a double-clad structure, enables pump light to efficiently pump signal light.

Abstract: A multimode optical fiber includes a central core, an inner cladding, a buried trench, and an outer cladding (e.g., an outer optical cladding). Typically, the optical fiber's central core is a glass-based central core having an alpha-index profile (i.e., a graded-index profile), an outer radius r1, and a maximum refractive index difference ?n1 with respect to the outer cladding. The central core's alpha-index profile has a minimum refractive index at the central core's outer radius r1 that corresponds to a refractive index difference ?nend with respect to the outer cladding. The inner cladding has an outer radius r2, a width w2, and a refractive index difference ?n2 with respect to the outer cladding. The buried trench has an outer radius rext, a width w3, and a refractive index difference ?n3 with respect to the outer cladding. The multimode optical fiber typically has reduced bending losses, a high bandwidth at wavelengths of both 850 nanometers and 1300 nanometers, and a reduced cladding effect.

Abstract: A single-mode transmission optical fibre includes a central core region radially outwardly from a centerline to a radius r1 and having a positive relative refractive index ?1; a first inner cladding region extending radially outwardly from the central core to a radius r2 and having a negative relative refractive index ?2; a second inner cladding region extending radially outwardly from the first inner cladding region to a radius r3 and having a non-negative relative refractive index ?3; an intermediate cladding region extending radially outwardly from the second inner cladding region to a radius r4 having a negative relative refractive index ?4 larger in absolute value than the relative refractive index ?2; and an outer cladding region extending radially outwardly from the intermediate cladding region and having a non-negative relative refractive index ?5; wherein the relative refractive index ?2 of the first inner cladding region is ?0.1·10?3 to ?1.

Abstract: An optical fiber comprising a first core, a second core, a third core, and a cladding, wherein with a refractive index of the cladding as a reference, ?1 is a maximum value of a relative refractive index difference of the first core, ?2 is a maximum value of a relative refractive index difference of the second core, ?3 is a minimum value of a relative refractive index difference of the third core, “a” is a half-value radial width for the relative refractive index difference (?1??2) of the first core, “b” is a radius of a second core/third core boundary, and “c” is a radius of a third core/cladding boundary, the expressions 0.30%??1?0.45%, ?0.05%??2?0.05%, ?0.6%??3??0.3%, 2.85?b/a, 10 ?m?b?15 ?m, and 3 ?m?c?b?5.5 ?m are satisfied, and transmission loss for a wavelength of 1550 nm when the optical fiber is wound around a mandrel with a diameter of 10 mm is no greater than 0.2 dB/turn.

Abstract: An X-ray waveguide according to the present invention includes: a core for guiding an X-ray in such a wavelength band that a real part of the refractive index of a material is 1 or less; and a cladding for confining the X-ray in the core, wherein: the cladding has a periodic structure in which multiple materials having different real parts of the refractive index are periodically arranged in two-dimensional directions perpendicular to the guiding direction of X-ray; and the periodic structure has a period of 100 nm or less.

Abstract: Various embodiments described herein include rare earth doped glass compositions that may be used in optical fiber and rods having large core sizes. Such optical fibers and rods may be employed in fiber lasers and amplifiers. The index of refraction of the glass may be substantially uniform and may be close to that of silica in some embodiments. Possible advantages to such features include reduction of formation of additional waveguides within the core, which becomes increasingly a problem with larger core sizes.

Abstract: An optical fiber having both low macrobend loss and low microbend loss. The fiber has a first inner cladding region having an outer radius r2>8 microns and refractive index ?2 and a second outer cladding region surrounding the inner cladding region having refractive index ?3, wherein ?1>?3>?2. The difference between ?3 and ?2 is greater than 0.01. The fiber exhibits a 22 m cable cutoff less than or equal to 1260 nm, and r1/r2 is greater or equal to 0.25.

Abstract: In a photonic waveguide, there is provided an undercladding layer and a waveguide core, having a cross-sectional height and width, that is disposed on the undercladding layer. The waveguide core comprises a waveguide core material having a thermo-optic coefficient. A refractive index tuning cladding layer is disposed on top of the waveguide core. The refractive index tuning cladding layer comprises a refractive index tuning cladding material having an adjustable refractive index and an absorption length at a refractive index tuning radiation wavelength. A thermo-optic coefficient compensation cladding layer is disposed on top of the refractive index tuning cladding layer. The thermo-optic coefficient compensation cladding layer comprises a thermo-optic coefficient compensation material having a thermo-optic coefficient that is of opposite sign to the thermo-optic coefficient of the waveguide core material.

Abstract: The present invention relates to a multi-core optical fiber including a plurality of cores, in each of which an effective area at the wavelength of 1550 nm, a transmission loss at the wavelength of 1550 nm, a chromatic dispersion at the wavelength of 1550 nm, a cable cutoff wavelength, and a bending loss in a bending radius of 30 mm at the wavelength of 1625 nm are set so as to increase a transmission capacity in each core in a state in which a difference of the transmission loss at the wavelength of 1550 nm between different cores is controlled to at most 0.02 dB/km or less.

Abstract: An optical fiber includes a central glass core region comprising maximum refractive index delta percent ?1, a first inner annular region surrounding said core comprising refractive index delta percent ?2, a depressed annular region surrounding said inner annular region and comprising ?3 and a third annular region surrounding the depressed annular region comprising refractive index delta percent ?4; wherein ?1MAX>?4>?2>?3. The difference between ?4 and ?2 is greater than 0.01% and profile volume, |V3| is at least 10%-?m2. The fibers exhibit an effective area at 1550 nm which is greater than 110 ?m2.

Abstract: There is provided an optical device including a first optical waveguide of a directional coupler, a second optical waveguide connected to the first optical waveguide and which guides light, and a common cladding of the first and second optical waveguides, wherein: the common cladding of the first and second optical waveguides includes a first cladding and a second cladding, the second cladding being provided on the first cladding and having a higher refractive index than the first cladding; the first optical waveguide and the second optical waveguide are formed continuously on the first cladding with a constant width and a constant height and are integrated with each other, and a cross sectional shape of each of the first and second optical waveguides is a rectangular shape that is longest in a direction orthogonal to a surface of the first cladding.

Abstract: A multi-core optical fiber includes a plurality of core portions. The diameter of each of the core portions is 12 micrometers or smaller, the relative refractive-index difference of the core portions with respect to the cladding portion is 0.2% or larger, the cut-off wavelength is 1.53 micrometers or smaller, the bending loss at a 1.55-micrometer wavelength is 10 dB/m or smaller, the effective core area at a 1.55-micrometer wavelength is 30 ?m2 or larger, and the cross-talk of light between the core portions is ?35 decibels or smaller.

Abstract: An optical fiber includes a core (1a) having an oblong rectangular or square cross section and made of quartz, a cladding (2) surrounding the core (1a), having a circular outer cross-sectional shape, having a lower refractive index than the core (1a), and made of resin, and a support layer (3) surrounding the cladding (2) and made of quartz.

Abstract: According to some embodiments, the optical fiber comprises: (i) a core having a first index of refraction n1; (ii) a cladding surrounding the core and having a second index of refraction n2, such that n1>n2, wherein cladding has at two sets of stress rods extending longitudinally through the length of the optical fiber, wherein the two sets of stress rods have CTE coefficients and/or softening points different from one another and different from that of cladding.

Abstract: A solid photonic band gap fiber includes: a core area located at a central portion of a cross-section with respect to a longitudinal direction of the fiber, the core area being formed of a solid substance having a low refractive index; cladding areas having base portions formed of a solid substance having a low refractive index, the cladding areas surrounding the core area; and a plurality of fine high refractive index scatterers provided in the cladding areas, and disposed in a dispersed manner so as to surround the core area, the number of fine high refractive index scatterers being formed of a solid substance having a high refractive index, wherein in a state that the solid photonic band gap fiber is held at a predetermined bending radius, propagation in a high-order mode is suppressed by using a difference in a bending loss between a fundamental mode and the high-order mode, and only the fundamental mode is substantially propagated, the fundamental mode and the high-order mode being caused by bending.

Abstract: An optical transmission system includes: a multi-core optical fiber having a plurality of core portions. Signal light beams having wavelengths different from each other are caused to be input to adjacent core portions of the plurality of core portions. The adjacent core portions are the most adjacent to each other in the multi-core optical fiber.

Abstract: An embodiment of an apparatus includes an optical fiber for which a complete orthogonal basis of propagating modes at an optical telecommunication frequency includes ones of the propagating modes with different angular momenta. The optical fiber has a tubular optical core and an outer optical cladding in contact with and surrounding the tubular optical core. The tubular optical core has a larger refractive index than the optical cladding. The tubular optical core is configured such that those of the propagating modes whose angular momenta have the lowest magnitude for the propagating modes have substantially the same radial intensity profile.

Abstract: An amplifying optical fiber includes a core containing oxides of elements selected from the group consisting of silicon, germanium, phosphorus, bismuth, aluminum, gallium with a concentration of bismuth oxide of 10-4-5 mol %, a total concentration of silicon and germanium oxides of 70-99.8999 mol %, a total concentration of aluminum and gallium oxides of 0.1-20 mol % wherein both aluminum and gallium oxide are present and a ratio of aluminum oxide to gallium oxide is at least two, and a concentration of phosphorus oxide from 0 to 10 mol %, and provides a maximum optical gain at least 10 times greater than the nonresonant loss factor in the optical fiber. An outside oxide glass cladding comprises fused silica. The core has an absorption band in the 1000 nm region, pumping to which region provides an increased efficiency of power conversion of pump light into luminescence light in the 1000-1700 nm range.

Abstract: An apparatus includes an optical fiber having a plurality of optical cores therein. Each optical core is located lateral in the optical fiber to the remaining one or more optical cores and is able to support a number of propagating optical modes at telecommunications wavelengths. Each number is less than seventy.

Abstract: A multi-core fiber of the present invention employs the multi-core fiber mode, which corresponds to the “uncoupled” operation aspect in which individual cores are used independently for single-mode transmission, to perform space division multiplexing transmission using a multi-core fiber in which multiple single-mode cores are stored in one optical fiber. More specifically, the multi-core fiber of the present invention forms an uncoupled multi-core fiber that makes individual cores correspond to single-mode, independent transmission channels.

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: An optical fiber has two or more core regions disposed within a common cladding region. Each of the core regions is configured to guide a respective light transmission comprising at least one optical mode along the length of the fiber. The cores are arranged within the common cladding region according to a core configuration that substantially prevents crosstalk between modes of neighboring cores in the fiber, in a deployment of the fiber in which cross-coupling between neighboring cores is affected by perturbations arising in the deployed fiber.

Abstract: An optical waveguide has: a core layer which includes at least one core portion for transmitting a light signal and at least two side cladding portions respectively provided at lateral sides of the core portion so as to be opposed to each other; and two cladding layers respectively provided at vertical sides of the core layer. The core layer is configured to have a horizontal refractive index distribution curve W in a width direction of a cross-sectional plane of the core layer. The horizontal refractive index distribution curve W has a region including at least two local minimum values, at least one first local maximum value and at least two second local maximum values smaller than the first local maximum value. A refractive index in whole of the horizontal refractive index distribution curve W continuously varies.

Abstract: An optical fiber having increased mechanical strength is provided. The optical fiber includes an over cladding layer that has a compressive stress of at least 100 MPa.