Sumitomo Electric Industries, Limited

Takenori Uchiyama

Shinji Ishikawa

Yuichi Ohga

Ichiro Tsuchiya

Katsuya Nagayama

Tatsuhiko Saitoh

An optical fiber preform having a viscosity ratio R&eegr;&equals;&eegr; /&eegr; of 2.5 or less between the core average viscosity &eegr; and the total average viscosity &eegr; is prepared, and is drawn by a drawing furnace so as to yield an optical fiber which is then heated to a temperature within a predetermined range so as to be annealed by a heating furnace disposed downstream the drawing furnace Here, upon annealing in the heating furnace the fictive temperature Tf within the optical fiber lowers, thereby reducing the Rayleigh scattering loss. At the same time, the viscosity ratio condition of R&eegr;&lE;2.5 restrains the stress from being concentrated into the core, thereby lowering the occurrence of structural asymmetry loss and the like. Hence, an optical fiber which can reduce the transmission loss caused by the Rayleigh scattering loss and the like as a whole, and a method of making the same can be obtained.

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Yokohama, Japan

Takenori Uchiyama