Abstract: An optical fiber cable has a sectional area of Ac [mm2] and housing a number N of optical fibers. A transmission loss ?dB [dB/km], a mode field diameter W [?m], an effective area Aeff [?m2], an effective length Leff [km], and a wavelength dispersion D [ps/nm/km] of each of the optical fibers at a wavelength of 1550 nm satisfy a predetermined equation and the transmission loss of the optical fiber at the wavelength of 1550 nm is 0.19 dB/km or less, and the effective area of the optical fiber is in a range from 125 to 155 ?m2.

Abstract: An optical fiber having a reduced attenuation includes a silica glass core and a silica glass cladding. The silica glass core has substantially no germanium and includes a first core and a second core. The second core encloses the first core, the refractive index of the second core is larger than the refractive index of the first core, and the average value of halogen concentration of the second core is 5000 ppm or more. The silica glass cladding surrounds the second core and contains substantially no gemianium. The refractive index of the cladding is smaller than the refractive index of the first core.

Abstract: The present invention relates to a method of manufacturing an optical fiber preform for obtaining an optical fiber with low transmission loss. A core preform included in the optical fiber preform comprises three or more core portions, which are each produced by a rod-in-collapse method, and in which both their alkali metal element concentration and chlorine concentration are independently controlled. In two or more manufacturing steps of the manufacturing steps for each of the three or more core portions, an alkali metal element is added. As a result, the mean alkali metal element concentration in the whole core preform is controlled to 7 atomic ppm or more and 70 atomic ppm or less.

Abstract: The present invention relates to an optical fiber which can improve OSNR in an optical transmission system in which Raman amplification and an EDFA are combined. With respect to the optical fiber, a predetermined conditional formula is satisfied by an effective area Aeff1450 [?m2] at a wavelength of 1450 nm, a transmission loss ?1450 [/km] at a wavelength of 1450 nm, and a transmission loss ?1550_dB [dB/km] at a wavelength of 1550 nm. Further, with respect to the optical fiber, another predetermined conditional formula is satisfied by an effective area Aeff1550 [?m2] at a wavelength of 1550 nm, and a transmission loss ?1550 [/km] at a wavelength of 1550 nm.

Abstract: Provided is an optical fiber having W-shaped refractive-index distribution and in which a micro-bend loss in an actual usage waveband is reduced. The optical fiber includes a core, inner cladding that surrounds the core and has a refractive index smaller than a refractive index of the core, and outer cladding that surrounds the inner cladding and has a refractive index smaller than the refractive index of the core and larger than the refractive index of the inner cladding. When a coupling coefficient between a fundamental mode and a cladding mode is denoted by C01-CL, a coupling coefficient between the fundamental mode and a higher-order mode is denoted by C01-11, and a coupling coefficient between the higher-order mode and the cladding mode is denoted by C11-CL, Ctotal defined as Ctotal=C01-CL+C01-11C11-CL has a minimum value at a wavelength ranging between 1520 nm and 1630 nm.

Abstract: The optical fiber includes a core, the first cladding, and second cladding. The core is made of silica based glass containing Cl. The first cladding and the second cladding are made of silica based glass containing fluorine. The refractive index of the first cladding is lower than that of the core. The refractive index of the second cladding is lower than that of the core and higher than that of the first cladding. The second cladding is divided into an outer region having a uniform refractive index and an inner region having a refractive index higher than that of the outer region. The difference ?P between the maximum refractive index of the inner region and the refractive index of the outer region is 0.02% to 0.10% in terms of relative refractive index with respect to pure silica based glass. The radial thickness R of the inner region is 10 ?m to 25 ?m.

Abstract: There is provided a method for producing a low-loss alkali metal-doped silica core optical fiber having excellent hydrogen resistance. The method for producing the optical fiber according to the present invention includes a drawing step of drawing an optical fiber preform in a drawing furnace to produce a silica glass-based optical fiber including a core region containing an alkali metal with an average concentration of 0.5 atomic ppm or more and a cladding region that surrounds the core region and a heating step of heating the optical fiber in a heating furnace through which the optical fiber drawn from the drawing furnace passes.

Abstract: An optical fiber containing an alkali metal and capable of reducing Rayleigh scattering loss is provided. An optical fiber has a core and a cladding made of silica glass and enclosing the core. The cladding contains fluorine and has a refractive index lower than the refractive index of the core. The core contains first group dopants selected from the group of Na element, K element, or a compound thereof at an average concentration of 0.2 ppm or more and 10 ppm or less. The core also contains second group dopants for reducing the viscosity of silica glass and having a diffusion coefficient of 1×10?12 cm2/s or more and smaller than the diffusion coefficient of the first group dopants, by an average concentration of 0.2 ppm or more at a temperature of 2000° C. to 2300° C.

Abstract: An optical fiber cable has a sectional area of Ac [mm2] and housing a number N of optical fibers. A transmission loss ?dB [dB/km], a mode field diameter W [?m], an effective area Aeff [?m2], an effective length Leff [km], and a wavelength dispersion D [ps/nm/km] of each of the optical fibers at a wavelength of 1550 nm satisfy a predetermined, equation and the transmission loss of the optical fiber at the wavelength of 1550 nm is 0.19 dB/km or less, and the effective area of the optical fiber is in a range from 125 to 155 ?m2.

Abstract: An optical fiber cable has a sectional area of Ac [mm2] and housing a number N of optical fibers. A transmission loss ?dB [dB/km], a mode field diameter W [?m], an effective area Aeff [?m2], an effective length Leff [km], and a wavelength dispersion D [ps/nm/km] of each of the optical fibers at a wavelength of 1550 nm satisfy a predetermined, equation and the transmission loss of the optical fiber at the wavelength of 1550 nm is 0.19 dB/km or less, and the effective area of the optical fiber is in a range from 125 to 155 ?m2.

Abstract: An optical fiber cable has a sectional area of Ac [?m2] and housing a number N of optical fibers. A transmission loss ?dB [dB/km], a mode field diameter W [?m], an effective area Aeff [?m2], an effective length Leff [km], and a wavelength dispersion D [ps/nm/km] of each of the optical fibers at a wavelength of 1550 nm satisfy a predetermined equation.

Abstract: There is provided a method for producing a low-loss alkali metal-doped silica core optical fiber having excellent hydrogen resistance. The method for producing the optical fiber according to the present invention includes a drawing step of drawing an optical fiber preform in a drawing furnace to produce a silica glass-based optical fiber including a core region containing an alkali metal with an average concentration of 0.5 atomic ppm or more and a cladding region that surrounds the core region and a heating step of heating the optical fiber in a heating furnace through which the optical fiber drawn from the drawing furnace passes.

Abstract: An optical fiber containing an alkali metal element and exhibiting low attenuation as well as excellent radiation resistance is provided. The optical fiber of the present invention has a core region and a cladding region enclosing the core region. The core region contains alkali metal elements by an average concentration of 0.2 atomic ppm or more. The attenuation at a wavelength of 1550 nm after irradiating with the radiation of 0.10 Gy or more of cumulative absorbed dose increases by 0.02 dB/km or less as compared with the attenuation exhibited prior to radiation exposure.

Abstract: In order to increase the accuracy of dispensing liquid from a sealed liquid holding container without increasing device complexity, pressures inside and outside the sealed liquid holding container are measured with a pressure sensor connected to a dispensing probe, and the amount of discharge operation of a pump is corrected in accordance with the measured pressures. The amount of operation of the pump is corrected by calculating the amount of deformation of a dispensing flow passageway due to pressure change.

Abstract: An optical fiber cable has a sectional area of Ac [?m2] and housing a number N of optical fibers. A transmission loss ?dB [dB/km], a mode field diameter W [?m], an effective area Aeff [?m2], an effective length Leff[km], and a wavelength dispersion D [ps/nm/km] of each of the optical fibers at a wavelength of 1550 nm satisfy a predetermined equation.

Abstract: An optical fiber preform which can be drawn into a low attenuation optical fiber is provided with a core portion and a cladding portion surrounding the core portion. The core portion includes a first core portion and a second core portion surrounding the first core portion. The cladding portion includes a first cladding portion surrounding the second core portion and a second cladding portion surrounding the first cladding portion. The first core portion contains an alkali metal element, the concentration of oxygen molecules contained in glass is 30 mol ppb or more and 200 mol ppb or less in a part of or entire region having an alkali metal atom concentration of 100 atomic ppm or more, and the concentration of oxygen molecules contained in glass is 10 mol ppb or less in a region having an alkali metal atom concentration of 50 atomic ppm or less.

Abstract: An optical fiber containing an alkali metal element and exhibiting low attenuation as well as excellent radiation resistance is provided. The optical fiber of the present invention has a core region and a cladding region enclosing the core region. The core region contains alkali metal elements by an average concentration of 0.2 atomic ppm or more. The attenuation at a wavelength of 1550 nm after irradiating with the radiation of 0.10 Gy or more of cumulative absorbed dose increases by 0.02 dB/km or less as compared with the attenuation exhibited prior to radiation exposure.

Abstract: An optical fiber transmission line capable of minimizing the total splice loss per one span thereof. One span of an optical fiber transmission line provided between repeaters has two connection fibers and (N+1) number of optical transmission fibers. The optical connection fibers and are single mode optical fibers (SSMF) based on International standard ITU-T G.652 standard. (N+1) number of the optical transmission fibers are connected in series in order between the two optical connection fibers. The total splice loss ?sp_total of the optical fiber transmission line as calculated from the given formula is 1.4 dB or less, when the average value of the mode field diameter of the two connection fibers is W?, and the average value of the mode field diameter of (N+1) number of the optical transmission fibers is W, and the axial misalignment width at the splice point of the optical transmission fibers is d.

Abstract: An optical fiber containing an alkali metal and capable of reducing Rayleigh scattering loss is provided. An optical fiber has a core and a cladding made of silica glass and enclosing the core. The cladding contains fluorine and has a refractive index lower than the refractive index of the core. The core contains first group dopants selected from the group of Na element, K element, or a compound thereof at an average concentration of 0.2 ppm or more and 10 ppm or less. The core also contains second group dopants for reducing the viscosity of silica glass and having a diffusion coefficient of 1×10?12 cm2/s or more and smaller than the diffusion coefficient of the first group dopants, by an average concentration of 0.2 ppm or more at a temperature of 2000° C. to 2300° C.

Abstract: A method includes (1) a thermal diffusion process for using an alkali metal salt raw material having an average particle size of 1 mm or less in diameter, supplying a vapor of the alkali metal salt produced by heating the alkali metal salt raw material together with a carrier gas to the inside of a silica-based glass pipe from one end side of the glass pipe, and heating the glass pipe using a heat source which relatively moves in a longitudinal direction of the glass pipe to cause an oxidation reaction of an alkali metal and thermally diffuse the alkali metal into an inner side of the glass pipe, (2) a collapsing process for collapsing the glass pipe after the thermal diffusion process to prepare a core rod; and (3) a cladding portion addition process for adding a cladding portion around the core rod prepared in the collapsing process.