Nippon Telegraph and Telephone Public Corporation

The Furukawa Electric Co., Ltd.

Tadashi Miyashita

Masao Kawachi

Takao Edahiro

Fumiaki Hanawa

Shiro Takahashi

Tatsuo Izawa

Shintaro Sentsui

Toshiaki Kuroha

Kunio Masuno

Yasuro Furui

Masaharu Horiguchi

The invention relates to a single-mode optical fiber used in a long wavelength band range for optical telecommunication. The core and the cladding of this optical fiber contain P.sub.2 O.sub.5 as a dopant selected to lower the deposition temperature and to hasten the deposition speed so as to result in low absorption loss.

Single-mode optical fiber

A refractory starting member is rotated and, at the same time, moved along the axis of rotation. A glass raw material for the formation of the core of a porous preform and consequently an optical fiber preform is introduced into a high temperature portion near the tip of a high temperature burner from a nozzle for the core disposed in alignment with the center of rotation of one end face of the starting member. The glass raw material blown out from the nozzle for the core are caused by the flames of the high temperature burner to react to produce glass fine particles, which are deposited on abovesaid end face of the starting member at the central portion thereof in its axial direction to form a porous core. At least one nozzle for spraying a glass raw material for the formation of the cladding of the optical fiber preform is disposed opposite to the end face of the starting member but a little deviated from the axis of rotation thereof, or disposed opposite to the peripheral surface of the porous core. The glass raw material for the cladding is sprayed from the nozzle for the cladding to the high temperature portion of the high temperature burner, and caused to react to form glass fine particles, which are deposited on the end face of the starting member on the outside of the porous core or on the peripheral surface thereof at the same time as the formation of the latter, forming a porous cladding. The porous preform thus obtained is moved into a high temperature furnace provided on the path of movement of the preform for the vitrification thereof into an optical fiber preform.

Continuous optical fiber preform fabrication method

An eccentric core optical waveguide comprising at least one glass core having relatively large refraction index disposed in an outer cylindrical glass jacket having larger diameter than that of the glass core and relatively small refraction index. The one or more glass core being so arranged as to made tangential contact with the inner wall of the glass jacket or a dielectric thin film coated inside the jacket at a small area. The space between the glass core and the outer glass jacket or said thin film is filled by air.

Eccentric core optical waveguide

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Hitachi, Japan

Tadashi Miyashita