The Furukawa Electric Co., Ltd.

Nippon Telegraph and Telephone Corporation

Shigeto Matsumoto

Shinichi Arai

Takeshi Yagi

Ryuichi Sugizaki

Hiroshi Matsuura

Kazuhide Nakajima

Koichi Maeda

Tsunetoshi Saito

Keiichi Aiso

Yu Mimura

Kengo Watanabe

Ryo Miyabe

Shinichi Aozasa

Kyozo Tsujikawa

Harumi Inaba

Yukihiro Tsuchida

Youko Yamanashi

A method for screening an optical fiber core including a resin coating layer, includes: a pre-strain applying step of adding a tensile force while feeding a portion of the optical fiber core retained at both ends of the portion, and applying a pre-tensile strain larger than zero and smaller than a guaranteed tensile strain set as a guaranteed value; a guaranteed strain applying step of adding a tensile force while feeding the portion of the optical fiber core retained at both ends of the portion and applied with the pre-tensile strain, and applying the guaranteed tensile strain only for a predetermined time; and a guaranteed strain releasing step of releasing the optical fiber core from the guaranteed tensile strain.

Method and device for screening optical fiber core, and method for manufacturing optical fiber core

An optical fiber manufacturing method includes setting a first holding member and a rod inside a glass pipe, the first holding member made of glass and having plural holes formed, so that the rod is supported by the first holding member; filling glass particles between the rod and a glass pipe inner wall; holding the rod such that the rod and the filled glass particles are enclosed by the glass pipe inner wall and the first and second holding members, and sealing one end of the glass pipe and manufacturing an intermediate; and manufacturing an optical fiber from the intermediate, wherein a bulk density of the first and second holding members is set with reference to a bulk density of a filling portion made from the glass particles, and the predetermined range is determined according to a core diameter permissible variation range in its longitudinal direction.

Optical fiber manufacturing method using relative bulk densities

A multi-core amplification optical fiber includes a plurality of rare-earth-doped core portions and a cladding portion positioned at an outer periphery of the core portions and having refractive index lower than those of the core portions. When a doping concentration of the rare-earth of each of the core portions is 250 ppm to 2000 ppm, a relative refractive index difference of each of the core portions relative to the cladding portion is 0.5% to 2% at a wavelength of 1550 nm, and a core diameter of each of the core portions is 1 &#x3bc;m to 5 &#x3bc;m, a separation distance between each of the core portions and adjacent one of the core portions is set at equal to or larger than 30 &#x3bc;m and at equal to or smaller than 60 &#x3bc;m so that a light-crosstalk between the adjacent core portions is equal to or lower than &#x2212;30 dB.

Multi-core amplification optical fiber and multi-core optical fiber amplifier

An optical fiber for optical amplification has: a core portion doped with at least erbium and aluminum; a cladding portion formed around the core portion and having a refractive index smaller than that of the core portion; a peak value of absorption coefficient of 35 dB/m or greater at a wavelength around 1530 nanometers; normal dispersion characteristics and an effective core area of 20 &#x3bc;mor larger, at a wavelength of 1550 nanometers; and a power conversion efficiency of a conversion from pumping light to amplified light having a wavelength of 1550 nanometers is 30% or more.

Optical fiber for optical amplification, optical fiber amplifier, and optical fiber laser

Growing community of inventors

Tokyo, Japan

Shigeto Matsumoto