Abstract: A dispersion compensating optical fiber for NZ-DSFs, includes: an uncovered dispersion compensating optical fiber; a double-layered resin coating disposed around the uncovered dispersion compensating optical fiber; and an outer coating layer having a thickness of 3 to 7 ?m, containing silicone in an amount of 1 to 5% by weight, and disposed around the double-layered resin coating. The outer diameter of the uncovered dispersion compensating optical fiber is in a range from 90 to 125 ?m, an outer diameter of the dispersion compensating optical fiber is in a range from 180 to 250 ?m, and the amount of silicone contained in the outer coating layer is determined such that an adhesive property of the outer coating layer is 1 gf/mm or less.

Abstract: A connection method for a photonic crystal fiber for connecting the photonic crystal fiber and a fiber to be connected, the photonic crystal fiber including a cladding region having a number of microholes and a core region having a same refractive index as that of the cladding region, includes the steps of: abutting respective end faces of the photonic crystal fiber and the fiber to be connected each other; after the abutting, performing a main discharge in which an abutted portion is heated by an electric discharge under a first condition; and after the main discharge, performing an additional discharge in which the connection portion is heated by an electric discharge at least once under a second condition to increase a splice strength.

Abstract: An optical fiber includes: a core at a center; a first cladding layer; a second cladding layer; and a third cladding layer. A maximum refractive index of the core is greater than any of maximum refractive indices of the first cladding layer, the second cladding layer, and the third cladding layer, and the maximum refractive index of the second cladding layer is smaller than any of the maximum refractive indices of the first and the third cladding layer. Additionally, a ratio of a2/a1 is not less than about 2.5 and not more than about 4.5, where a1 represents the radius of the core, and a2 represents the radius of an outer periphery of the first cladding layer, and a relative refractive index difference of the core with respect to a maximum refractive index of the third cladding layer is not less than 0.20% and not more than 0.70%.

Abstract: A hole-assisted holey fiber is provided. The holey fiber includes a core region; a cladding region around the core region, and a plurality of holes in the cladding region around the core region. The core region has a higher refractive index than that of the cladding region. The holes form an inner hole layer and an outer hole layer, and the inner hole layer has the same number of holes as the number of the holes in the outer hole layer. The outer layer holes are provided in locations in which inner holes are absent when viewed from the center of the core region, and holes defining the same layer have the same diameter. A distance ?1 from a center of the core region to a center of an inner hole and a distance ?2 from the center of the core region to a center of an outer hole satisfy the relationship ?1<?2, and a diameter d1 of an inner hole and a diameter d2 of an outer hole satisfy the relationship d1?d2.

Abstract: In an optical transmission path including multimode optical fibers, modal dispersion is reduced so that signal light can be transmitted at high speed and across a broad band, at low-cost and over a long distance. To reduce modal dispersion, when the transmission path is constructed by coupling a plurality of multimode optical fibers, a length ratio for the multimode optical fibers that obtains the maximum band of the optical transmission path is determined, and the multimode optical fibers are coupled according to this length ratio. The multimode optical fibers that are used have specific refractive index profiles as mode dispersion-compensating fibers. The compensated fiber and the mode dispersion-compensating fiber are coupled with specific lengths.

Abstract: A particulate titanium oxide is obtained which has a large specific surface area and a high crystallinity with few internal defects, and thus a high photocatalytic activity as a photocatalyst is expected. Particulate titanium oxide in which the particles are box-shaped polyhedra is used as the photocatalyst. The particles are each a box-shaped polyhedron composed of one or more titanium oxide single crystalline polyhedron. When this single crystalline polyhedron has a flatness ratio of 0.33 to 3.0, the crystallinity is even higher. The particulate titanium oxide typically has a rutile transition ratio R(700-24) of not more than 7.5% and a rutile transition ratio R(500-24) of not more than 2.0%. Titanium oxide particles of these shapes are manufactured by feeding titanium tetrachloride vapor and oxygen into a reaction tube made of silica glass and applying heat from outside the tube to effect thermal oxidation.

Abstract: A method of measuring polarization mode dispersion of an optical fiber includes inputting linearly polarized pulse light into an optical fiber, separating the input linearly polarized light from backscattered light from the optical fiber, detecting a light intensity of the backscattered light as time series data since the generation of the pulse light, calculating a fluctuation of the detected light intensity in the time series data, and evaluating polarization mode dispersion in the optical fiber, based on the calculated fluctuation value.

Abstract: A dispersion compensating optical fiber includes an uncovered dispersion compensating optical fiber containing a core and a cladding, and a resin coating which is disposed around the uncovered dispersion compensating optical fiber, wherein the resin coating has an adhesive property of 10 g/mm or less, and which includes an outer coating layer which is formed to have a thickness of 3 ?m or more, and the outer diameter of the uncovered dispersion compensating optical fiber is in a range from 90 to 125 ?m, and the outer diameter of the dispersion compensating optical fiber is in a range from 180 to 250 ?m.

Abstract: A dispersion-compensated optical fiber which does not cause an increase in a loss if it is wound in a small reel and has a stable temperature characteristics is provided. A dispersion-compensated optical fiber is formed such that, in at least a wavelength between 1.53 to 1.63 ?m, a bending loss of 20 mm bending diameter is 5 dB/m or lower, a wavelength dispersion is ?120 ps/nm/km or lower, a cut-off wavelength under a usage condition is 1.53 ?m or lower, an outer diameter of the cladding is 80 to 100 ?m, an outer diameter of a coating is 160 to 200 ?m, a viscosity of a surface of a coating resin is 10 gf/mm or lower. It is set such that b/a is 1.5 to 3.5, c/b is 1.2 to 2.0, a radius of a core is 4 to 8 ?m, ?1 is +1.6% to +2.6%, ?2 is ?0.30% to ?1.4%, and ?3 is ?0.3 0% to +1.0%. Young's modulus of a first coating layer is 0.15 kgf/nun 2 or lower and its thickness is 20 to 30 ?m. Young's modulus of a second coating layer is 50 kgf/mm2 or lower and its thickness is 15 to 30 ?m.

Abstract: A dispersion compensating fiber module which, when connected to an optical fiber which exhibits, at a wavelength of 1.55 ?m, a chromatic dispersion of between +2 and +6 ps/nm/km, a dispersion slope of between +0.075 ps/nm2/km and +0.095 ps/nm2/pm, and a relative dispersion slope of between 0.016 nm?1 and 0.024 nm?1, performs compensation so that the residual dispersion of the connected optical fiber is reduced, the dispersion compensating fiber module includes a dispersion compensating fiber and at least one optical fiber fused to the dispersion compensating fiber, in which the dispersion compensating fiber module exhibits at a wavelength of 1.55 ?m, a relative dispersion slope of between 0.016 nm?1 and 0.026 nm?1; and in a wavelength range between 1.525 ?m and 1.565 ?m, a maximum residual dispersion difference, when converted per km of the transmission optical fiber, of less than or equal to 0.4 ps/nm/km.

Abstract: A dispersion compensating fiber, which has a negative dispersion slope with a large absolute value while maintaining the absolute value of the chromatic dispersion, and which has sufficient dispersion slope compensation properties even for the non-zero dispersion shifted optical fiber requiring a large RDS for dispersion compensation. In this dispersion compensating fiber, the radius of a ring core region is set in a range from 6.7 ?m to 10.7 ?m, the radius ratio of a depressed core region relative to a central core region is set in a range from 2.0 to 3.0, and the radius ratio of the ring core region relative to the depressed core region is set in a range from 1.3 to 2.0, the relative refractive index difference of the central core region relative to the cladding is set in a range from +1.00% to +1.80%, the relative refractive index difference of the depressed core region relative to the cladding is set in a range from ?1.20% to ?1.

Abstract: There is provided at low cost an optical fiber suitable for wavelength division multiplex transmissions that has strengthened the tolerance to bending loss at even smaller bending diameters. The present invention is an optical fiber whose base material is silica glass and that has a two layer structure formed by a core that has a substantially uniform refractive index and by a cladding that is located outside the core and that has a substantially uniform refractive index, wherein the optical fiber satisfies the following conditions (1) to (3): (1) an outer diameter of the core is in a range of 4 to 8 ?m, and a relative refractive index difference of the core is in a range of 0.4 to 0.8%; (2) chromatic dispersion at a wavelength of 1550 nm is in a range of 2 to 15 ps/nm/km; and (3) effective area at a wavelength of 1550 nm is 40 ?m2 or more.

Abstract: A wavelength division multiplexing system includes a wavelength division multiplexing transmission path including a multimode optical fiber that is codoped with germanium and fluorine. The wavelength division multiplexing system may further include a multiplexer and a demultiplexer, in which the multiplexer and the demultiplexer are coupled via the multimode optical fiber. The wavelength division multiplexing system may further include a first multiplexer/demultiplexer and a second multiplexer/demultiplexer, in which the first multiplexer/demultiplexer and the second multiplexer/demultiplexer are coupled via the multimode optical fiber so that a bidirectional wavelength division multiplexing is enabled.

Abstract: An optical fiber that includes a core containing a first concentration of germanium, an inner cladding arranged on the core, the inner cladding containing a second concentration of germanium and having a first diffusion coefficient, and an outer cladding arranged on the inner cladding, the outer cladding having a second diffusion coefficient, where the first diffusion coefficient is larger than the second diffusion coefficient, and where the first concentration of germanium is about 200% or more of the second concentration of germanium. An optical fiber constructed in this manner can be spliced with an optical fiber having a different MFD, such as a single-mode optical fiber or an erbium-doped optical fiber, with low splice loss and a sufficient splicing strength.

Abstract: A single-mode optical fiber has a core and a cladding, and is produced in such a way that, when the radii of layers having individual refractive indexes are varied, more than one optical properties of the core, for example, the effective core area Aeff and the dispersion slope exhibit respective limiting values within a specific range of a reference radius. Such optical fibers provide basically the same optical properties but enable to vary the chromatic dispersion within a specific range so that the single-mode optical fiber is ideally suited for use in high-speed and large capacity communication systems.

Abstract: The present invention provides an optical transmission system that enables high-speed transmission of 40 Gb/s with low residual dispersion while maintaining the yield of a dispersion compensating fiber. In the present invention, the dispersion compensating fiber is connected to each span of an optical fiber for transmission. One set of an optical transmission path is formed by this optical fiber for transmission and the dispersion compensating fiber, and this one set of optical transmission path is connected in multiple stages and connected to a transmitter and a receiver. By setting the conditions of dispersion compensation in each span comparatively leniently, managing the residual dispersion of each transmission span, and suitably arranging each transmission span, an optical transmission system is composed in which adequate dispersion compensation is performed over the entire optical transmission path.

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.

Abstract: In fusion-splicing a dispersion compensating optical fiber having a negative dispersion slope, with a connection optical fiber having a different near field pattern from that of the dispersion compensating optical fiber, if for the connection optical fiber, one is selected such that a theoretical joint loss in a used wavelength, obtained from an overlap integral of a near field pattern of the dispersion compensating optical fiber after fusion splicing and a near field pattern of the connection optical fiber after fusion splicing is presumed to be 0.3 dB or less, in an unconnected state, a construction enabling connection at a low loss results.

Abstract: A polarization-maintaining optical fiber which exhibits an excellent polarization-maintaining performance and significantly low splice loss when spliced with a polarization-maintaining optical fiber having a cladding 125 ?m in diameter even if the polarization-maintaining optical fiber has a small-diameter cladding of about 80 ?m. The polarization-maintaining optical fiber includes a core, a pair of stress-applying parts provided radially outwardly with respect to the core, and a cladding which surrounds the core and the stress-applying parts. With a diameter D of the stress-applying parts between 21 ?m and 32 ?m, a distance R between the stress-applying parts between 6 ?m and 17 ?m, and a relative refractive index difference ? between 0.3% to 0.5%, a sufficiently large mode field diameter (MFD) is obtained; thus splice loss can be reduced.

Abstract: A graded-index multimode fiber includes a core containing fluorine and a cladding which is provided at an outer periphery of the core, and the fiber has a refractive index profile which satisfies the following Formula (1): n ? ( r ) = { n 1 ? [ 1 - 2 ? ? ? ? ? ? ? ( r a ) ? ] 1 / 2 ( O ? r ? a ) n 1 ? ( 1 - 2 ? ? ? ? ) 1 / 2 ( r > a ) ( 1 ) where n(r) is a refractive index of the optical fiber at a distance “r” from the center of the core, n1 is a refractive index at the center of the core, ? is a relative refractive index difference of the center of the core with respect to the cladding, “a” is a core radius, and ? is a refractive index profile exponential parameter.