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 preform has a core portion having a first core portion including a central axis, a second core portion disposed around the first core portion, and a third core portion disposed around the second core portion. The first core portion contains 10 atomic ppm or more of an alkali metal and 10 to 600 atomic ppm of chlorine, the second core portion contains 10 atomic ppm or less of the alkali metal and 10 to 600 atomic ppm of chlorine, and the third core portion contains 10 atomic ppm or less of the alkali metal and 2,000 atomic ppm or more of chlorine. An optical fiber has a core region doped with an alkali metal and chlorine, wherein the minimum concentration of chlorine in the core region is 1,000 atomic ppm or more, and the average concentration of the alkali metal therein is 0.2 atomic ppm or more.

Abstract: There is provided a semiconductor device having a reduced number of external terminals allocated for address input to receive access from outside, while realizing a high-speed response to an access from outside. The semiconductor device employs, in order to allow other external devices to directly access resources it possesses in its own address space, in an external interface circuit, external terminals which input a part of the address signal required for access from outside, a supplementary register which supplements the upper portion of address information that has been input from the external terminals, a mode register accessible from outside, and an address control circuit which generates an address signal to access the address space in a form based on information input from the external terminals, required supplementary information, and mode information of the mode register.

Abstract: An easily producible optical fiber preform which is drawn to an optical fiber having a core containing a sufficient concentration of alkali metal is provided. An optical fiber preform 10 is composed of silica-based glass and includes a core portion 20 and a cladding portion 30. The core portion 20 includes a first core portion 21 including a central axis and a second core portion 22 disposed on the perimeter of the first core portion 21. The cladding portion 30 includes a first cladding portion 31 disposed on the perimeter of the second core portion 22 and a second cladding portion 32 disposed on the perimeter of the first cladding portion 31. The core portion 20 contains an alkali metal at an average concentration of 5 atomic ppm or more. The concentration of the OH group in the perimeter portion of the first cladding portion 31 is 200 mol ppm or more.

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: A method for making a high quality optical fiber preform includes: thermally defusing the alkali metal element into the inner side of a silica glass pipe by heating the glass pipe from the outside by a heat source while vapors of alkali metal salt generated by heating an alkali metal salt is supplied to the inside of the glass pipe from an end thereof; collapsing the glass pipe for forming a core rod; and adding a cladding part around the circumference of the core rod. At the start of the thermal diffusion, the alkali metal salt is heated at a temperature for making the vapor pressure of the alkali metal salt to be 0.1 kPa or less, and thereafter the alkali metal salt is heated up to a temperature for making the vapor pressure of the alkali metal salt to be larger than 0.1 kPa.

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 includes a core and a cladding that surrounds the core. The optical fiber has a group index of 1.465 or less at a wavelength of 1550 nm and an absolute value of chromatic dispersion of 4 ps/nm/km or less at a wavelength of 1550 nm. A relative refractive index difference between the core and pure silica ranges from ?0.1% to 0.1%. The core includes a first core disposed at the center of the optical fiber and a second core surrounding the first core. A relative refractive index difference between the first core and the cladding ranges from 0.6% to 0.9%. A relative refractive index difference between the second core and the cladding ranges from 0.02% to 0.12%. The ratio of the diameter of the second core to the diameter of the first core ranges from 2.0 to 6.0.

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.

Abstract: An optical fiber preform has a core portion having a first core portion including a central axis, a second core portion disposed around the first core portion, and a third core portion disposed around the second core portion. The first core portion contains 10 atomic ppm or more of an alkali metal and 10 to 600 atomic ppm of chlorine, the second core portion contains 10 atomic ppm or less of the alkali metal and 10 to 600 atomic ppm of chlorine, and the third core portion contains 10 atomic ppm or less of the alkali metal and 2,000 atomic ppm or more of chlorine. An optical fiber has a core region doped with an alkali metal and chlorine, wherein the minimum concentration of chlorine in the core region is 1,000 atomic ppm or more, and the average concentration of the alkali metal therein is 0.2 atomic ppm or more.

Abstract: An optical fiber preform includes a core portion, in which the core portion includes an alkali-metal-doped core glass portion doped with an alkali metal, the maximum concentration of oxygen molecules in the core portion is 30 mol ppb or more, and the average concentration of the alkali metal in the core portion is 5 atomic ppm or more. A method of manufacturing an optical fiber preform includes an alkali-metal-doping step of doping a pipe composed of silica-based glass with an alkali metal, an oxygen-molecule-doping step of doping the glass pipe with oxygen molecules, and a collapsing step of collapsing the glass pipe by heating the glass pipe, in which the optical fiber preform is manufactured.

Abstract: An alkali-metal-doped core optical fiber having high hydrogen resistance and a method for manufacturing such an optical fiber are provided. A method for manufacturing a deuterium-treated optical fiber according to the present invention includes a preform-forming step of forming a silica glass optical fiber preform having a core doped with an alkali metal element, a drawing step of drawing the optical fiber preform to form an optical fiber, and an exposing step of exposing the optical fiber to a deuterium gas atmosphere. Alkali-metal-doped core optical fibers can be manufactured by using this method. In the exposing step, the optical fiber is exposed to an atmosphere containing deuterium gas at a temperature of 20° C. or more under conditions where (deuterium gas partial pressure)×(exposure time) is 50 kPa·hour or more.

Abstract: An optical fiber having a central axis includes a core extending along the central axis and containing an alkali metal element, and a cladding having a lower refractive index than the core, wherein a radial distance with respect to the central axis is defined as r, a power of light propagating through the core at the radial distance r is defined as P(r), and a fictive temperature at a radial distance rmax at which rP(r) becomes maximum is at least 50° C. lower than a fictive temperature on the central axis.

Abstract: Provided is an optical fiber that is suitable for high-density packing and long-haul transmission. An optical fiber according to the present invention includes a core and a cladding. At a wavelength of 1550 nm, an effective area Aeff is 100 ?m2 or less and a chromatic dispersion Disp is 19.0 ps/nm/km or more and 22 ps/nm/km or less, and, when an effective length is denoted by Leff and an attenuation is denoted by cc, a figure of merit FOM represented by an expression “FOM=5 log{|Disp|·Leff}?10 log {Leff/Aeff}?100?” is 3.2 dB or more.

Abstract: An optical fiber preform has a core portion having a first core portion including a central axis, a second core portion disposed around the first core portion, and a third core portion disposed around the second core portion. The first core portion contains 10 atomic ppm or more of an alkali metal and 10 to 600 atomic ppm of chlorine, the second core portion contains 10 atomic ppm or less of the alkali metal and 10 to 600 atomic ppm of chlorine, and the third core portion contains 10 atomic ppm or less of the alkali metal and 2,000 atomic ppm or more of chlorine. An optical fiber has a core region doped with an alkali metal and chlorine, wherein the minimum concentration of chlorine in the core region is 1,000 atomic ppm or more, and the average concentration of the alkali metal therein is 0.2 atomic ppm or more.

Abstract: An easily producible optical fiber preform which is drawn to an optical fiber having a core containing a sufficient concentration of alkali metal is provided. An optical fiber preform 10 is composed of silica-based glass and includes a core portion 20 and a cladding portion 30. The core portion 20 includes a first core portion 21 including a central axis and a second core portion 22 disposed on the perimeter of the first core portion 21. The cladding portion 30 includes a first cladding portion 31 disposed on the perimeter of the second core portion 22 and a second cladding portion 32 disposed on the perimeter of the first cladding portion 31. The core portion 20 contains an alkali metal at an average concentration of 5 atomic ppm or more. The concentration of the OH group in the perimeter portion of the first cladding portion 31 is 200 mol ppm or more.

Abstract: An easily producible optical fiber preform which is drawn to an optical fiber having a core containing a sufficient concentration of alkali metal is provided. An optical fiber preform 10 is composed of silica-based glass and includes a core portion 20 and a cladding portion 30. The core portion 20 includes a first core portion 21 including a central axis and a second core portion 22 disposed on the perimeter of the first core portion 21. The cladding portion 30 includes a first cladding portion 31 disposed on the perimeter of the second core portion 22 and a second cladding portion 32 disposed on the perimeter of the first cladding portion 31. The core portion 20 contains an alkali metal at an average concentration of 5 atomic ppm or more. The concentration of the OH group in the perimeter portion of the first cladding portion 31 is 200 mol ppm or more.

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: Provided is a method for producing an optical fiber having low attenuation and including a core that contains an alkali metal element. An optical fiber preform that includes a core part and a cladding part is drawn with a drawing apparatus 1 to form an optical fiber 30, the core part having an average concentration of an alkali metal element of 5 atomic ppm or more and the cladding part containing fluorine and chlorine. The optical fiber includes a glass portion and resin coating portion and the glass portion is under residual stress that is a compressive stress of 130 MPa or less. During the drawing, the time during which an individual position of the optical fiber preform is maintained at 1500° C. or higher is 110 minutes or less.

Abstract: An optical fiber preform producing method is a method for producing an optical fiber preform including a core part and a cladding part and being composed of silica-based glass, which has: an alkali metal adding step of adding an alkali metal in a maximum concentration of not less than 500 ppm in the vicinity of an inner surface of a glass pipe composed of silica glass; an etching step of etching the inner surface of the glass pipe by vapor phase etching under flow of SF6 gas and chlorine gas through an inner hollow of the glass pipe, after the alkali metal adding step; and a collapsing step of eliminating the hollow of the glass pipe to produce a glass rod, after the etching step, wherein the optical fiber preform is produced using the glass rod produced by the collapsing step.