| 摘要 |
For fabricating porous bodies from a glass starting material, particularly in connection with the fabrication of an optical waveguide preform, it is proposed to fill powdery glass starting material under a pre-compaction into a compression mold, and to compress it thereafter. When the porous body to be formed is to have a varying composition in the radial direction, as is necessary with a view to step index optical fibers or optical waveguides having a graded index of the refractive-index profile, then differently composed powdery glass starting materials are filled one at a time, in adjacent coaxial areas, into the compression mold. This is effected with respect to each of the individual areas with the aid of a screw conveyor under a continuous, adjustable pressure and at an adjustable conveying speed. If more than two coaxially disposed areas of different composition are to result, the corresponding material is filled several times in succession into the interspace between a base body disposed in the center of the compression mold in the longitudinal direction thereof, and the inside wall of the deposited material, before the central area is filled.
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