Abstract: An extended triangular lattice type photonic bandgap fiber, includes a cladding and a capillary core, the cladding having a plurality of holes disposed within a silica glass portion in a longitudinal direction of the fiber and arranged in an extended triangular lattice shape, the capillary core having a plurality of holes arranged in a triangular lattice shape, wherein the cross-sectional area of the respective holes in the capillary core is smaller than that of the respective holes in the cladding.

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: A higher order mode dispersion compensating fiber includes an optical fiber and a first loss layer which is provided within the fiber and which attenuates a lower order mode propagating through the optical fiber while not attenuating a higher order mode which is higher than the lower order mode. A dispersion compensating fiber mode converter for a higher order fiber includes a single mode fiber; a higher order mode dispersion compensating fiber; and a fused and extended portion which has been formed by fusing and extending the single mode fiber and the higher order mode fiber. The fused and extended portion converts between the LP01 mode of the single mode fiber and the LP02 mode of the higher order mode dispersion compensating fiber.

Abstract: A higher order mode dispersion compensating fiber includes an optical fiber and a first loss layer which is provided within the fiber and which attenuates a lower order mode propagating through the optical fiber while not attenuating a higher order mode which is higher than the lower order mode. A dispersion compensating fiber mode converter for a higher order fiber includes a single mode fiber; a higher order mode dispersion compensating fiber; and a fused and extended portion which has been formed by fusing and extending the single mode fiber and the higher order mode fiber. The fused and extended portion converts between the LP01 mode of the single mode fiber and the LP02 mode of the higher order mode dispersion compensating fiber.

Abstract: A single-mode optical fiber has a prescribed mode field diameter (MFD1 (?m)) at a first wavelength ?1, in which a bending loss when measured at a second wavelength ?2 (?m) and wound with a bending radius r (mm) is Lb (dB) for one bending, a connector/splice loss with an optical fiber that has a prescribed mode field diameter MFD2 (?m) at the first wavelength ?1 is Ls (dB) for one connection/splice point at the second wavelength ?2 (?m), and an mode field diameter dependence of a total loss coefficient calculated by a formula (1) has a local minimal value in a range of MFD1±0.5 ?m, with the formula (1) being as follows: L=ws·Ls+wb·Lb,??(1) ws+wb=1,??(2) ws>0, wb>0.??(3) where ws and wb in the formula (1) represent dimensionless weighting factors and are set within a range that satisfies the formulas (2) and (3).

Abstract: An optical fiber comprises a center core and a cladding located at an outer periphery of the core, wherein the core comprises at least one codoped layer made from silica glass doped with germanium and fluorine, and at least one lower-concentration codoped layer made from silica glass doped with germanium, or silica glass that is doped with germanium and fluorine wherein a dope amount of the fluorine is smaller than a dope amount of the fluorine in the codoped layer.

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: A single-mode optical fiber has a cut-off wavelength of 1260 nm or less, a zero-dispersion wavelength in the range of 1300 nm to 1324 nm, a zero-dispersion slope of 0.093 ps/nm2/km or less, a mode field diameter at a wavelength of 1310 nm in the range of 5.5 ?m to 7.9 ?m, and a bending loss of 0.5 dB or less at a wavelength of 1550 nm, the bending loss being produced when the fiber is wound around a 10-mm radius for 10 turns.

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, wherein, in a wavelength range from. 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 with a 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, and 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 ?0.30% to +1.0%. Young's modulus of a first coating layer is 0.15 kgf/mm2 or lower and its thickness is 20 to 30 ?m.

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 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: 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: An optical fiber is produced so as to have ring-shape refractive index profile such that chromatic dispersion is between +6 ps/nm/km or larger and smaller than +15 ps/nm/km in 1550 nm wavelength, the transmission loss is smaller than 0.210 dB/km, effective cross sectional area Aeff is larger than 90 ?m2, dispersion slope is in a range of 0.05 ps/nm2/km and 0.08 ps/nm2/km. By doing this, an optical fiber having ring-shaped refractive index profile, enlarged effective cross sectional area, restricted dispersion slope, and low loss characteristics can be provided.

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 method of measuring polarization mode dispersion (PMD) of an optical fiber, includes estimating PMD when an optical fiber is formed as an optical cable, from a beat length when the optical fiber is wound around a bobbin, and an average coupling length when the optical fiber is formed as the optical cable.

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: Under condition that a non-circularity ratio is 5% or lower and a thermal expansion coefficient of a glass which forms the core is ?1 and a thermal expansion of a glass which forms the cladding is ?2, the difference of coefficients is controlled such that a formula ?2.5×10?7/° C.??1 ??2?1.0×10?7/° C. is satisfied so as to maintain a polarization mode dispersion to be 0.03 ps/km0.5 or lower. The difference of coefficients is further controlled such that a formula ?1.5×10?7/° C.??1??2?0/° C. is satisfied so as to maintain a polarization mode dispersion to be 0.015 ps/km0.5 or lower. By doing this, birefringence is reduced by adjusting the thermal expansion coefficient in a core and a cladding; thus providing an optical fiber, and an optical transmission path using the optical fiber, having preferable PMD for high speed transmission.

Abstract: A single-mode optical fiber, cable, cord, and a method for ensuring a service life of the fiber are provided. The fiber has a core and a cladding, the fiber having a cut-off wavelength that exhibits a single-mode transmission in a 1.31 ?m wavelength band. A relative refractive index difference of the core with respect to the cladding is adjusted such that a bending loss, when a bend is applied in a radius smaller than a limit bending radius of the fiber, becomes greater than a detection limit value. The limit bending radius is calculated from a relationship between a bending radius applied to the optical fiber and a failure probability which occurs after a time period. The method includes measuring a loss and ensuring that a failure probability of the fiber during a service life falls within a failure probability used for setting the limit bending radius.

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.

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.