The Furukawa Electric Co., Ltd.

Masahide Kuwabara

Yoshinori Ishida

Hideya Moridaira

Tetsuro Wada

Yukio Komura

Kazuhiko Kurusu

Kiyoshi Arima

Yasuhiro Naka

Fumio Takahashi

Sadayuki Toda

Yukio Kohmura

Shinpei Todo

Hiroyuki Wada

Akira Iino

Yukio Koumura

Satoru Ise

Kazuto Hirabayashi

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&#xd7;10spins/g or less measured by the electron spin resonance method after the diameter of the optical fiber is made to be about 50 &#x3bc;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.

Optical fiber and evaluation method thereof

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.

Optical fiber for WDM system and manufacturing method thereof

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.

Apparatus for manufacturing an optical fiber soot, and method for manufacturing an optical fiber soot using thereof

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.

Electric furnace extension method and extension apparatus for optical fiber glass preform

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.

Method of heating and processing an end of an optical fiber preform and apparatus for heating and processing an end of an optical fiber preform

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&middot;(W) <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.

Optical fiber preform

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.

An apparatus for producing an optical fiber porous glass preform using the VAD method which can stably produce a high quality optical fiber porous glass preform, wherein a target bar is only rotatably supported by a chuck and is not pulled upward, a lower tip of a soot body is detected by a laser and a photodetector, and a core burner and a cladding burner is lowered in response to the result detected. A tip position detecting drive and burners are synchronizingly lowered while the deposit of porous glass grows at the lower portion of the target bar.

Apparatus for producing an optical fiber porous glass preform

In the optical fiber, the concentration of fluorine doped in the core portion is made nonuniform in the radial direction to be greater at the center portion of the core portion and less at the outer circumferential portion of the core portion. As a result, the distribution of the refractive index of the core portion and the cladding portion before the process of transparent glassification becomes a profile which is high at the outer circumferential portion of the core portion and which is low at the center portion. The reduction of the refractive index at the outer circumferential portion of the core portion due to the dispersion of the GeO.sub.2 etc., the oxide included in the core portion, in the cladding portion in the transparent glassification processed is and as a result, the profile of the refractive index of the core portion becomes one which sticks out in a step form with respect to the cladding portion.

Growing community of inventors

Tokyo, Japan

Masahide Kuwabara