| 摘要 |
The specification describes a VAD method for producing optical fiber preforms by depositing soot onto a solid core rod. The solid core rod preferably has a uniform composition, doped or undoped, suitable for the center core region of the preform. The primary cladding layer, and additional cladding layers if desired, are produced by depositing soot on the center core rod. The surface of the center core rod is treated with an etchant torch that traverses the center core rod in front of the soot deposition torch. This produces a clean interface between the core and primary cladding. This soot-on-center-core-rod method allows the production of sharp index profiles by reducing the diffusion of dopants into and out of the center core portion of the preform that occurs in soot-on-soot processes.
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