Sumitomo Electric Industries, Limited

Takehiko Kito

Masumi Ito

Sumio Hoshino

Takeshi Kyogoku

For an index change of an interfacial region which is formed in a boundary between core region and cladding region and which decreases its refractive indices from the core region side to the cladding region side, a change rate in relative index difference (0.5&times;&Dgr;n)/(d/r) normalized by a core radius r, obtained for a domain of change from 0.8&times;&Dgr;n to 0.3&times;&Dgr;n relative to a relative index difference &Dgr;n of the core region , is used as an index for evaluation of refractive index change and an allowable range of values thereof is set to a range of the lower limit of 0.4% to the upper limit of 4.0%, whereby a single-mode optical fiber capable of low loss phototransmission can be realized while reducing influence of a tail spread and strain in the optical fiber.

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Yokohama, Japan

Takehiko Kito