01-07-1998 дата публикации
Номер: EP0851247A2
In an optical fiber of this invention, the MFD is increased to effectively suppress the influence of nonlinear optical effects. A method of manufacturing the optical fiber effectively prevents bubble occurrence in a transparent preform, deformation of the preform, and flaws on the preform surface during the manufacture. The optical fiber has, from its center to the peripheral portion, a first core having a first refractive index n 1 , a second core having a second refractive index n 2 (< n 1 ), a first cladding having a third refractive index n 3 (< n 2 ), and a second cladding having a fourth refractive index n 4 (> n 3 , < n 2 ). The outer diameter of the second cladding is set to be 25 to 40 µm. Specifically, the refractive indices of the first and second claddings of the optical fiber preferably increase in the radial direction from the inner side thereof to the peripheral side thereof. This structure is obtained by adjusting the supply amount of a fluorine material in the manufacturing process of preform regions corresponding to first and second claddings such that the contents of fluorine decreases in the radial direction.
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