Fujikura Limited

Daiichirou Tanaka

Ryozo Yamauchi

Tetsuya Sakai

Akira Wada

Tetsuo Nozawa

A manufacturing method for erbium doped silica, having a soot formation process, in which a silica glass soot is deposited on a seed rod for forming a soot preform in a porous state on the seed rod, a dopant impregnation process, wherein the soot preform is impregnated with at least an erbium compound, and a preform formation process, wherein this soot preform impregnated with a dopant is heated and rendered transparent. The dopant impregnation process is provided with an operation in which the soot preform obtained in the soot formation process is dipped in a solution containing an erbium compound, an aluminum compound, and a phosphorus compound; this is then desiccated, and soot preform which is impregnated with the erbium compound, the aluminum compound, and the phosphorus compound is obtained.

Erbium-doped silica optical fiber preform

Solution doping of a silica preform with erbium, aluminum and phosphorus

The present invention is directed to an optical fiber comprising a core and a cladding layer wherein at least one of the constitutional parameters thereof changes along the longitudinal direction of the optical fiber. In order to present a useful optical fiber wherein the occurrence of a Brillouin scattering is prevented, an optical fiber having altered constitutional parameters is found to be effective. The constitutional parameters mean the parameters which determine the constitution of the optical fiber and is capable of influencing the condition of electromagnetic wave transmitting therethrough such as light or acoustic wave. The constitutional parameters include diameter of the core, index of refraction of the core, diameter of the optical fiber, composition of the glass, residual stress of the core. Some examples are disclosed about their manufacturing process and the test results. Much improvement was measured, especially in the use for a single mode optical fiber.

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Yotsukaido, Japan

Daiichirou Tanaka