Abstract: An optical cable has a grooved central filament, the grooves following helical paths, the helices changing hand along the filament. In the manufacture of the filament, plastics is extruded past a fixed die and some way downstream, the filament is held and twisted first in one direction and then in the opposite direction so that the helical paths are introduced where the plastics exits the die. Dielectric optical waveguides are disposed in the grooves and the whole is surrounded by an extruded plastic sheath to produce an optical cable.

Abstract: An optical cable is assembled by inserting dielectric optical waveguides into periodically reversing helical grooves in the surface of a central filament. The invention is concerned with minimizing longitudinal tension in the waveguides. Powered rollers draw dielectric optical waveguide from fixed reels and delivers it, in a slack condition, to a guide unit which is mounted by means of a thrust bearing. The guide unit supports rods with apertures at their ends through which dielectric optical waveguide is guided, the rod ends being disposed within the grooves so that respective dielectric optical waveguides and grooves are maintained circumferentially coincident. Cable is drawn downstream of the guide unit to pull the filament and dielectric optical waveguides together at the guide unit and also to reciprocally drive the guide unit. As the filament, with dielectric optical waveguides positioned in its grooves, exits the guide unit, it is helically wound with tape.

Abstract: An optical cable is assembled by inserting dielectric optical waveguides into a filament having periodically reversing helical grooves. Dielectric optical waveguide is unwound from fixed reels by movement of the filament past the reels. A rotatable guide unit has flexible tubes through which dielectric optical waveguide is guided, the tube ends being disposed within the grooves so that respective dielectric optical waveguides and grooves are maintained circumferentially coincident.