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: An optical fiber having a chromatic dispersion of +1.0 ps/nm/km or more in a 1460 nm wavelength band, a dispersion slope of 0.04 ps/nm2/km or less in a 1550 nm wavelength band, and a cutoff wavelength of 1450 nm or less, comprises a relation of an RDS, which is a value of the dispersion slope to the chromatic dispersion, to a wavelength &lgr; is −1.67×10−5&lgr;+0.0300≧RDS(&lgr;)≧−1.67×10−5&lgr;+0.0285.

Abstract: The present invention provides a polarization maintaining optical fiber of which polarization crosstalk characteristic is not deteriorated after fusing two or more polarization maintaining optical fibers, and provides a method for producing a preform thereof. The polarization maintaining optical fiber includes two stress applying portions disposed in a cladding around a core, in which an angle formed by a line connecting the center of one of the stress applying portions with the center of the core and a line connecting the center of the other stress applying portion with the center of the core is 3 degrees or less. The preform is produced by forming one insertion hole in a cladding element and then rotating the preform 180 degrees around a core element without moving the drilling tool, followed by forming the other insertion hole in the cladding element and then inserting stress applying elements into the insertion holes.

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 &mgr;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 &mgr;m2 or more.

Abstract: An optical fiber for preserving the plane of polarization including a cladding and a stress imparting part disposed in the cladding, the stress imparting part comprising a base material including B2O3. The average concentration of B2O3 in the base material of the stress imparting part is in a range between about 17 and 21 wt. %, and the maximum concentration of B2O3 in the base material is in a range between about 17 and 22 wt. %. The optical fiber has excellent polarization plane preserving properties, and no concave portion is generated in its stress imparting part even under wet heat conditions.

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 &agr;1 and a thermal expansion of a glass which forms the cladding is &agr;2, the difference of coefficients is controlled such that a formula −2.5×10−7/° C.≦&agr;1−&agr;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.≦&agr;1−&agr;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: Under condition that a non-circularity ratio is 5% or lower and a thermal expansion coefficient of a glass which forms the core is &agr;1 and a thermal expansion of a glass which forms the cladding is &agr;2, the difference of coefficients is controlled such that a formula −2.5×10−7/° C.≦&agr;1−&agr;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.≦&agr;1−&agr;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 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: 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 &mgr;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: An optical fiber having a chromatic dispersion of +1.0 ps/nm/km or more in a 1460 nm wavelength band, a dispersion slope of 0.04 ps/nm2/km or more in a 1550 nm wavelength band, and a cutoff wavelength of 1450 nm or less, comprises a relation of an RDS, which is a value of the dispersion slope to the chromatic dispersion, to a wavelength &lgr; is −1.67×10−5&lgr;+0.0300≧RDS(&lgr;)≧−1.67×10−5&lgr;+0.0285.

Abstract: An optical fiber for preserving plane of polarization including a core; and a clad disposed so as to surround the core, wherein the mode field diameter non-circularity ratio of the optical fiber which is calculated according to the equation: MFD ⁢   ⁢ non ⁢ - ⁢ circularity ⁢   ⁢ ratio ⁢   ⁢ ( % ) = Ma - Mb Ma 2 + Mb 2 2 × 100 (where MFD indicates a mode field diameter, and Ma is the maximum value and Mb is the minimum value of the mode field diameter, respectively, in a wavelength region of li

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 &mgr;m to 10.7 &mgr;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: 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: An optical fiber (10) for preserving plane of polarization including a core (11); and a clad (12) disposed so as to surround the core, wherein the mode field diameter non-circularity ratio of the optical fiber which is calculated according to the equation: 1 MFD ⁢   ⁢ non ⁢ - ⁢ circularity ⁢   ⁢ ratio ⁢   ⁢ ( % ) = Ma - Mb Ma 2 + Mb 2 2 × 100

Abstract: An improved method for manufacturing an optical fiber preform uses the CVD method in which a portion of or the whole of the optical fiber preform is formed by depositing glass on the inner wall of the starting tube. The method comprises a first step of depositing glass on the inner wall of the starting tube and collapsing the starting tube so that a silica rod is formed; a second step of removing the starting tube surrounding the silica rod or removing the starting tube and a part of synthetic glass; and a third step of depositing glass on an outer periphery of the silica rod obtained in the second step. By setting the refractive index of the cladding to be less than that of pure silica using the present method, an optical fiber having an extremely low transmission loss may be obtained.

Abstract: This dispersion compensating optical fiber comprises an uncovered dispersion compensating optical fiber which contains a core and a cladding and a resin coating which is disposed around the uncovered dispersion compensating optical fiber and which has an adhesive property of 10 g/mm or less. Alternatively, the dispersion compensating optical fiber comprises an uncovered dispersion compensating optical fiber which contains a core and a cladding and a resin coating which is disposed around the uncovered dispersion compensating optical fiber, which has an adhesive property of 1 g/mm or less, and which includes a single or double coating layer and an outer coating layer formed on the surface of the single or double coating layer to have a thickness of 3 &mgr;m or more.

Abstract: By limiting the ranges of the numerical values of a plurality of structural parameters of a dispersion compensating optical fiber which is endowed with a segmented W-shaped refractive index profile, and by suitably combining these structural parameters, it is possible to obtain a dispersion compensating optical fiber which can compensate both for chromatic dispersion and also for dispersion slope of a single mode optical fiber for transmission over a wide wavelength band which is selected from the range from 1.53 &mgr;m to 1.63 &mgr;m, and for which the value of Aeff is large, and moreover the absolute value of chromatic dispersion is large. As a result desirable transmission characteristics are obtained by being able to suppress the occurrence of nonlinearity effects, and furthermore, since the length which is required is short, the cost is low, and it is possible to produce a module which is small in size.

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: The present invention provides a polarization maintaining optical fiber of which polarization crosstalk characteristic is not deteriorated after fusing two or more polarization maintaining optical fibers, and provides a method for producing a preform thereof. The polarization maintaining optical fiber includes two stress applying portions disposed in a cladding around a core, in which an angle formed by a line connecting the center of one of the stress applying portions with the center of the core and a line connecting the center of the other stress applying portion with the center of the core is 3 degrees or less. The preform is produced by forming one insertion hole in a cladding element and then rotating the preform 180 degrees around a core element without moving the drilling tool, followed by forming the other insertion hole in the cladding element and then inserting stress applying elements into the insertion holes.

Abstract: An optical fiber for preserving the plane of polarization including a cladding and a stress imparting part disposed in the cladding, the stress imparting part comprising a base material including B2O3. The average concentration of B2O3 in the base material of the stress imparting part is in a range between about 17 and 21 wt. %, and the maximum concentration of B2O3 in the base material is in a range between about 17 and 22 wt. %. The optical fiber has excellent polarization plane preserving properties, and no concave portion is generated in its stress imparting part even under wet heat conditions.