Abstract: Apparatus for laying an optical fiber unit into one of a plurality of parallel helical or reversing helical grooves in the outer surface of a cable core conveys the core along a path. A downstream guide is freely rotatable about the core path and has an aperture for feeding the fiber unit into the groove and an inward projection for following one of the grooves to maintain registration of the downstream guide with the groove. An upstream guide is indpendently rotatable about the core path and adjacent the downstream guide, and guides the fiber from a fiber supply toward the downstream guide. A servo drive is responsive to the rotation of the downstream guide relative to the upstream guide to drive the upstream guide such as to reduce that relative angle.