The Furukawa Electric Co., Ltd.

Yoshiyuki Sakata

Takashi Suzuki

Nobuaki Orita

Hisashi Koaizawa

Masato Oku

Toshiaki Tateishi

Tetsuya Kumada

Drawing methods and drawing furnaces for drawing an optical fiber with small non-circularity by simple drawing system are provided. An optical fiber preform is received into a muffle tube and heated by a primary heater placed to surround the muffle tube. The optical fiber preform is heated such that a starting position of a meniscus portion is higher in its position than the top of the primary heater, wherein the meniscus portion is created at the bottom portion of the optical fiber preform.

Optical fiber drawing methods and drawing furnaces

A protective cover is detachably fixed onto a spool to protect an optical fiber wound on the spool. The protective cover includes a pair of half-cylindrical cover members coupled together by a hinge and locked together by a locking mechanism. When an external force allows a pair of hinge members of the hinge to abut together, edges of the cover members are apart from each other at an angle of 2 to 7 degrees as viewed with respect to the center of the hinge. The edges of the cover members are then abut together by an additional external force to lock the locking mechanism.

Protective cover for optical fiber

An optical fiber drawing furnace capable of the prevention of entry of an ambient gas into an inner space thereof both effectively and economically, provided with a lower gas introduction portion through which inert gas is introduced into the inner space of the optical fiber drawing furnace, a chamber separated by a lower partition, and a bottom cover. The lower partition is arranged immediately below the lower gas introduction portion and has a first hole through which the chamber and the inner space are communicated. The bottom cover has a second hole through which the chamber and the atmosphere are communicated. An optical fiber is passed through the first and second holes. A controller detects a differential pressure between a pressure P,in the inner space and a pressure P,in the chamber and controls the suction flow by a pump for evacuating the gas in the chamber to maintain P,>P,The sizes of the first and second holes are defined as (L,/D,)<(L,/D,), where L,and L,are lengths of the holes and D,and D,are the diameters of the holes.

Growing community of inventors

Tokyo, Japan

Yoshiyuki Sakata