Abstract: A method for cleaning a vaporizer that vaporizes, at normal temperature and pressure, a source material in a liquid state, and supplies the vaporized source material to a reactor through a supply pipe, includes a cleaning step of passing the source material to the vaporizer while maintaining the source material in a liquid state to clean the vaporizer.

Abstract: A method for manufacturing an optical fiber preform includes: producing a core preform including a core portion made of transparent glass and a first cladding layer obtained by adding fluorine to the core portion; and forming, on an outer periphery of the first cladding layer, a second cladding layer made of glass having a refractive index higher than that of the first cladding layer. Further, a refractive index profile is formed in the first cladding layer due to a fluorine concentration profile, the refractive index profile being provided at least near a boundary surface with the second cladding layer and having a profile such that a refractive index difference between a refractive index of the first cladding layer and a refractive index of the second cladding layer decreases in accordance with a reduction in a distance from the boundary surface with the second cladding layer.

Abstract: A multiple tube burner for synthesizing a porous material includes three or more glass tubes are arranged coaxially with one another, the glass tubes having a substantially circular shape on a cross section perpendicular to a longitudinal direction. Out of the three or more glass tubes, a first glass tube and a second glass tube that is arranged on an outer side of the first glass tube are connected with each other on a gas introducing side, and a thickness near a joint portion of the second glass tube connected with the first glass tube is thicker than a thickness of the second glass tube on the gas spouting side.

Abstract: A method for cleaning a vaporizer that vaporizes, at normal temperature and pressure, a source material in a liquid state, and supplies the vaporized source material to a reactor through a supply pipe, includes a cleaning step of passing the source material to the vaporizer while maintaining the source material in a liquid state to clean the vaporizer.

Abstract: A method for manufacturing an optical fiber preform includes: producing a core preform including a core portion made of transparent glass and a first cladding layer obtained by adding fluorine to the core portion; and forming, on an outer periphery of the first cladding layer, a second cladding layer made of glass having a refractive index higher than that of the first cladding layer. Further, a refractive index profile is formed in the first cladding layer due to a fluorine concentration profile, the refractive index profile being provided at least near a boundary surface with the second cladding layer and having a profile such that a refractive index difference between a refractive index of the first cladding layer and a refractive index of the second cladding layer decreases in accordance with a reduction in a distance from the boundary surface with the second cladding layer.

Abstract: A multiple tube burner for synthesizing a porous material includes three or more glass tubes are arranged coaxially with one another, the glass tubes having a substantially circular shape on a cross section perpendicular to a longitudinal direction. Out of the three or more glass tubes, a first glass tube and a second glass tube that is arranged on an outer side of the first glass tube are connected with each other on a gas introducing side, and a thickness near a joint portion of the second glass tube connected with the first glass tube is thicker than a thickness of the second glass tube on the gas spouting side.

Abstract: An optical fiber preform includes: a columnar portion having an approximately constant radius of r; and a taper portion located adjacent to the columnar portion in a lengthwise direction and having a radius decreasing along the lengthwise direction. The taper portion includes: a first taper portion including a portion having a radius varying between 0.9r and 0.6r; and a second taper portion including a portion having a radius varying between 0.4r and 0.15r. A diameter of the first taper portion in the portion having the radius varying between 0.9r and 0.6r decreases so as to form a maximum angle ?1 between 40 degrees and 60 degrees with respect to the columnar portion, a diameter of the second taper portion in the portion having the radius varying between 0.4r and 0.

Abstract: An optical fiber preform includes: a columnar portion having an approximately constant radius of r; and a taper portion located adjacent to the columnar portion in a lengthwise direction and having a radius decreasing along the lengthwise direction. The taper portion includes: a first taper portion including a portion having a radius varying between 0.9r and 0.6r; and a second taper portion including a portion having a radius varying between 0.4r and 0.15r. A diameter of the first taper portion in the portion having the radius varying between 0.9r and 0.6r decreases so as to form a maximum angle ?1 between 40 degrees and 60 degrees with respect to the columnar portion, a diameter of the second taper portion in the portion having the radius varying between 0.4r and 0.

Abstract: An operator selecting device (10) stores areas that a user is scheduled to visit in association with each user identifying information that identifies the user, and stores an area in association with a language used in the area, and stores an operator in association with a language that the operator handles, and identifies, when an inquiry including user identifying information is received from a terminal used by a user, areas corresponding to the user identifying information, and identifies languages corresponding to the identified areas, and selects an operator who handles a first language and a second language of the identified languages, the first language being used in the current area of stay of the user, the second language being used in an area that the user is scheduled to visit thereafter.

Abstract: A dehydration-sintering furnace includes a muffle tube that accommodates therein the porous preform, a heater that heats the porous preform from outside of the muffle tube, a furnace body that accommodates the heater at an outer periphery of the muffle tube. When a gas required for dehydrating and sintering the porous preform is supplied in the muffle tube, and a pressure in the muffle tube is measured, an average value of the pressure in the muffle tube P0 and a standard deviation of the pressure in the muffle tube ?0 are controlled to satisfy a relation P0?3×?0>0.

Abstract: The present invention provides a method for manufacturing an optical fiber preform, which provides an optical fiber with stable transmission loss characteristics, and improves manufacturing efficiency. The method for manufacturing an optical fiber preform comprises dehydrating the optical fiber soot preform by lowering the optical fiber soot preform within the muffle tube and passing through a heating region, pulling up the dehydrated optical fiber soot preform to the predetermined position, and sintering the optical fiber soot preform by lowering the optical fiber soot preform again within the muffle tube and passing through the heating region where temperature of the heating region is higher than temperature of the heating region in dehydrating; wherein A?B is satisfied where A is pull-up speed (mm/minute) of the optical fiber soot preform during the pulling up and B is gas flow rate (mm/minute) within the muffle tube at room temperature during the pulling up. Furthermore, 1.5×A?B is satisfied.

Abstract: A dehydration-sintering furnace includes a muffle tube that accommodates therein the porous preform, a heater that heats the porous preform from outside of the muffle tube, a furnace body that accommodates the heater at an outer periphery of the muffle tube. When a gas required for dehydrating and sintering the porous preform is supplied in the muffle tube, and a pressure in the muffle tube is measured, an average value of the pressure in the muffle tube P0 and a standard deviation of the pressure in the muffle tube ?0 are controlled to satisfy a relation P0?3×?0>0.

Abstract: The present invention provides an optical fiber of which a zero dispersion wavelength falls within a range of between 1,250 nm and 1,350 nm inclusive, transmission loss at 1,550 nm is equal to or less than 0.185 dB/km, chromatic dispersion at 1,550 nm is within the range of 19±1 ps/nm·km, a dispersion slope at 1,550 nm is equal to or less than 0.06 ps/nm2·km, an effective area Aeff is equal to or more than 105 ?m2, a cable cutoff wavelength ?cc is equal to or less than 1,530 nm, polarization mode dispersion is equal to or less than 0.1 ps/km1/2, and a loss when the optical fiber is wound on a mandrel having an outer diameter of 20 mm is equal to or less than 10 dB/m.

Abstract: The present invention provides an optical fiber of which a zero dispersion wavelength falls within a range of between 1,250 nm and 1,350 nm inclusive, transmission loss at 1,550 nm is equal to or less than 0.185 dB/km, chromatic dispersion at 1,550 nm is within the range of 19±1 ps/nm·km, a dispersion slope at 1,550 nm is equal to or less than 0.06 ps/nm2·km, an effective area Aeff is equal to or more than 105 ?m2, a cable cutoff wavelength ?cc is equal to or less than 1,530 nm, polarization mode dispersion is equal to or less than 0.1 ps/km1/2, and a loss when the optical fiber is wound on a mandrel having an outer diameter of 20 mm is equal to or less than 10 dB/m.

Abstract: The present invention provides an optical fiber of which a zero dispersion wavelength falls within a range of between 1,250 nm and 1,350 nm inclusive, transmission loss at 1,550 nm is equal to or less than 0.185 dB/km, chromatic dispersion at 1,550 nm is within the range of 19±1 ps/nm·km, a dispersion slope at 1,550 nm is equal to or less than 0.06 ps/nm2·km, an effective area Aeff is equal to or more than 105 ?m2, a cable cutoff wavelength ?cc is equal to or less than 1,530 nm, polarization mode dispersion is equal to or less than 0.1 ps/km1/2, and a loss when the optical fiber is wound on a mandrel having an outer diameter of 20 mm is equal to or less than 10 dB/m.

Abstract: An optical fiber suitable for the WDM transmission in the wavelength bands of 1.31 ?m and 1.55 ?m is provided. An optical fiber is characterized by a zero dispersion wavelength of longer than 1330 nm and shorter than 1430 nm, a dispersion of not less than 6 ps/nm/km and not more than 15 ps/nm/km at a wavelength of 1550 nm, a ratio of a dispersion to a dispersion slope of not less than 200 nm and not mare than 400 nm at a wavelength of 1550 nm, a dispersion of not more than ?1 ps/nm/km and not less than?8 ps/mn/km at 1300 nm, and a cutoff wavelength of 1300 nm or shorter.

Abstract: The present invention provides an optical fiber of which a zero dispersion wavelength falls within a range of between 1,250 nm and 1,350 nm inclusive, transmission loss at 1,550 nm is equal to or less than 0.185 dB/km, chromatic dispersion at 1,550 nm is within the range of 19±1 ps/nm·km, a dispersion slope at 1,550 nm is equal to or less than 0.06 ps/nm2·km, an effective area Aeff is equal to or more than 105 ?m2, a cable cutoff wavelength ?cc is equal to or less than 1,530 nm, polarization mode dispersion is equal to or less than 0.1 ps/km1/2, and a loss when the optical fiber is wound on a mandrel having an outer diameter of 20 mm is equal to or less than 10 dB/m.

Abstract: The optical fiber includes a center core portion, a side core portion and clad portion, which has a dispersion value of 14-20 ps/nm/km at a wavelength of 1550 nm, a dispersion slope of 0.05-0.08 ps/nm2/km at a wavelength of 1550 nm and a transmission attenuation of 0.2 dB/km or less at a wavelength of 1550 nm, wherein the relative refractive index difference &Dgr;1 between the center core portion and the clad portion is 0.25-0.50%, the relative refractive index difference &Dgr;2 between the side core portion and the clad portion is 0.05-0.30%, an inequality &Dgr;2 <&Dgr;1 is satisfied, the ratio a/b between an outer diameter a of the center core portion and an outer diameter b of the side core portion is 0.3-0.7, and the effective core area Aeff at a wavelength of 1550 nm is 90 &mgr;m2 or larger.

Abstract: An optical fiber suitable for the WDM transmission in the wavelength bands of 1.31 &mgr;m and 1.55 &mgr;m is provided.

Abstract: The optical fiber which enables the optical fiber transmission stabilized in the wavelength range of the pump light also, which is not used conventionally, and suppresses the non-linear effect on the occasion of WDM transmission is offered. The optical fiber for WDM transmission has at least three or more layers wherein the first core doped with germanium is located at the center and surrounded by the second core having a refractive index lower than the first core, and cladding having a refractive index lower than the first core and higher than second core surrounds the second or last core layer.