Abstract: An optical fiber having a length of 1 km or more with average transmission loss in a wavelength band of 1383 nm being less than average transmission loss in a wavelength band of 1310 nm, wherein a maximum value of any 1 km section loss in the wavelength band of 1383 nm does not exceed the average transmission loss by 0.03 dB/km or more.

Abstract: An electric furnace extending method and apparatus for an optical fiber glass body alignment when connecting the extension use body and pulling member and making it possible to immediately start the extension after the fusing of the connection portion. A centering mechanism for centering the free end portion of the body and member on the furnace center side is provided between the furnace pipe of the electric furnace and grips of the extension use glass body and between the furnace pipe and the pulling member. The free end portion is centered by this centering mechanism, then the gripped sides of the body and member are fixed, the front ends of the two free end portions are abutted and fused and bonded at the highest temperature portion inside the electric furnace, then the highest temperature portion is moved to the extension portion of the glass body side and the extending of the glass body is commenced.

Abstract: An optical fiber characterized by a cutoff wavelength of 1310 nm or less, a transmission loss of 0.40 dB/km or less at the wavelength of 1385 nm before hydrogen ageing, a transmission loss of 0.40 dB/km or less in the wavelength range of 1310 nm to 1625 nm after hydrogen ageing, and an electron spin density of the Non-Bridging Oxygen Hole Center of 1×1013 spins/g or less measured by the electron spin resonance method after the diameter of the optical fiber is made to be about 50 ?m by etching in diluted hydrofluoric acid, that having high reliability of hydrogen-proof characteristic suitable for WDM transmission in 1310 nm to 1625 nm and the method of evaluating the optical fiber are offered.

Abstract: An optical fiber having a length of one kilometer or more with average transmission loss at a wavelength of 1383 nm being less than average transmission loss at a wavelength of 1310 nm, wherein a maximum value of a transmission loss at the wavelength of 1383 nm of any one kilometer section along the entire length of the optical fiber does not exceed the average transmission loss at the wavelength of 1383 nm along the entire length of the optical fiber by 0.03 dB/km or more.

Abstract: An optical fiber having a length of 1 km or more with average transmission loss in a wavelength band of 1383 nm being less than average transmission loss in a wavelength band of 1310 nm, wherein a maximum value of any 1 km section loss in the wavelength band of 1383 nm does not exceed the average transmission loss by 0.03 dB/km or more.

Abstract: An optical fiber characterized by a cutoff wavelength of 1310 nm or less, a transmission loss of 0.40 dB/km or less at the wavelength of 1385 nm before hydrogen ageing, a transmission loss of 0.40 dB/km or less in the wavelength range of 1310 nm to 1625 nm after hydrogen ageing, and an electron spin density of the Non-Bridging Oxygen Hole Center of 1×1013 spins/g or less measured by the electron spin resonance method after the diameter of the optical fiber is made to be about 50 ?m by etching in diluted hydrofluoric acid, that having high reliability of hydrogen-proof characteristic suitable for WDM transmission in 1310 nm to 1625 nm and the method of evaluating the optical fiber are offered.

Abstract: An optical fiber characterized by a cutoff wavelength of 1310 nm or less, a transmission loss of 0.40 dB/km or less at the wavelength of 1385 nm before hydrogen ageing, a transmission loss of 0.40 dB/km or less in the wavelength range of 1310 nm to 1625 nm after hydrogen ageing, and an electron spin density of the Non-Bridging Oxygen Hole Center of 1×1013spins/g or less measured by the electron spin resonance method after the diameter of the optical fiber is made to be about 50 ?m by etching in diluted hydrofluoric acid, that having high reliability of hydrogen-proof characteristic suitable for WDM transmission in 1310 nm to 1625 nm and the method of evaluating the optical fiber are offered.

Abstract: An apparatus for manufacturing an optical fiber soot, which comprises a core partition having an opening portion at core burner side provided on a periphery of a core burner, in a reactor of the apparatus to be used in a conventional VAD method.

Abstract: An electric furnace extending method and apparatus for an optical fiber glass body alignment when connecting the extension use body and pulling member and making it possible to immediately start the extension after the fusing of the connection portion. A centering mechanism for centering the free end portion of the body and member on the furnace center side is provided between the furnace pipe of the electric furnace and grips of the extension use glass body and between the furnace pipe and the pulling member. The free end portion is centered by this centering mechanism, then the gripped sides of the body and member are fixed, the front ends of the two free end portions are abutted and fused and bonded at the highest temperature portion inside the electric furnace, then the highest temperature portion is moved to the extension portion of the glass body side and the extending of the glass body is commenced.

Abstract: An optical fiber having a length of 1 km or more with average transmission loss in a wavelength band of 1383 nm being less than average transmission loss in a wavelength band of 1310 nm, wherein a maximum value of any 1 km section loss in the wavelength band of 1383 nm does not exceed the average transmission loss by 0.03 dB/km or more.

Abstract: An electric furnace extending method and apparatus for an optical fiber glass body alignment when connecting the extension use body and pulling member and making it possible to immediately start the extension after the fusing of the connection portion. A centering mechanism for centering the free end portion of the body and member on the furnace center side is provided between the furnace pipe of the electric furnace and grips of the extension use glass body and between the furnace pipe and the pulling member. The free end portion is centered by this centering mechanism, then the gripped sides of the body and member are fixed, the front ends of the two free end portions are abutted and fused and bonded at the highest temperature portion inside the electric furnace, then the highest temperature portion is moved to the extension portion of the glass body side and the extending of the glass body is commenced.

Abstract: An optical fiber characterized by a cutoff wavelength of 1310 nm or less, a transmission loss of 0.40 dB/km or less at the wavelength of 1385 nm before hydrogen ageing, a transmission loss of 0.40 dB/km or less in the wavelength range of 1310 nm to 1625 nm after hydrogen ageing, and an electron spin density of the Non-Bridging Oxygen Hole Center of 1×10 13 spins/g or less measured by the electron spin resonance method after the diameter of the optical fiber is made to be about 50 &mgr;m by etching in diluted hydrofluoric acid, that having high reliability of hydrogen-proof characteristic suitable for WDM transmission in 1310 nm to 1625 nm and the method of evaluating the optical fiber are offered.

Abstract: An end heating and processing method of an optical fiber preform. In this method, an optical fiber preform is processed by heating and melting an end of a vitrified optical fiber preform including a core portion and a cladding portion formed on an outer circumference thereof to process the end having a shape for drawing as an optical fiber.

Abstract: An optical fiber preform is a material used for fabricating optical fibers. The optical fiber preform has a target rod which will be the core for optical fibers and a glass layer formed around the outside thereof. A mass W (kg) of the optical fiber preform and a diameter D (cm) of the target rod satisfy a relational expression 0.4·(W)1/2<D. Satisfying this relational expression can prevent the optical fiber preform from being deformed and to have uneven diameters due to the weight thereof in the dehydrating and consolidating process in fabricating the optical fiber preform, even though it is a large-sized optical fiber preform having a diameter of 10 cm or more.

Abstract: An apparatus for manufacturing an optical fiber soot according to a VAD method, in which a cross-section shape of a combustion nozzle of a side burner for heating a core portion is rectangular. A method for manufacturing an optical fiber soot using the apparatus.

Abstract: An apparatus for manufacturing an optical fiber soot, which comprises a core partition having an opening portion at core burner side provided on a periphery of a core burner, in a reactor of the apparatus to be used in a conventional VAD method.

Abstract: An optical fiber preform is a material used for fabricating optical fibers. The optical fiber preform has a target rod which will be the core for optical fibers and a glass layer formed around the outside thereof. A mass W (kg) of the optical fiber preform and a diameter D (cm) of the target rod satisfy a relational expression 0.4·(W)1/2<D. Satisfying this relational expression can prevent the optical fiber preform from being deformed and to have uneven diameters due to the weight thereof in the dehydrating and consolidating process in fabricating the optical fiber preform, even though it is a large-sized optical fiber preform having a diameter of 10 cm or more.

Abstract: An end heating and processing method of an optical fiber preform. In this method, an optical fiber preform is processed by heating and melting an end of a vitrified optical fiber preform including a core portion and a cladding portion formed on an outer circumference thereof to process the end having a shape for drawing as an optical fiber.

Abstract: An electric furnace extending method and apparatus for an optical fiber glass body alignment when connecting the extension use body and pulling member and making it possible to immediately start the extension after the fusing of the connection portion. A centering mechanism for centering the frame and portion of the body and member on the furnace center side is provided between the furnace pipe of the electric furnaces and grips of the extension use glass body and between the furnace pipe and the pulling member. The free end portion is centered by this centering mechanism, then the gripped sides of the body and member are fixed, the front ends of the two free end portions are abutted and fused and bonded at the highest temperature portion inside the electric furnace, then the highest temperature portion is moved to the extension portion of the glass body side and the extending of the glass body is commenced.

Abstract: An electric furnace extending method and apparatus for an optical fiber glass body alignment when connecting the extension use body and pulling member and making it possible to immediately start the extension after the fusing of the connection portion. A centering mechanism for centering the free end portion of the body and member on the furnace center side is provided between the furnace pipe of the electric furnace and grips of the extension use glass body and between the furnace pipe and the pulling member. The free end portion is centered by this centering mechanism, then the gripped sides of the body and member are fixed, the front ends of the two free end portions are abutted and fused and bonded at the highest temperature portion inside the electric furnace, then the highest temperature portion is moved to the extension portion of the glass body side and the extending of the glass body is commenced.