Method of coating optical waveguide filaments

A method of coating an optical waveguide filament comprising the steps of

• providing a coating die body defining an at least partly tapered central longitudinal aperture suitable for accommodating a waveguide filament extending from the bottom surface to the top surface of said body, said body also defining at least one radial entrance port communicating with said central longitudinal aperture intermediate said top and bottom surfaces of said body forming a junction with said central longitudinal aperture, the diameter at the exit end of said central longitudinal aperture being a function of the outside diameter of the desired coated optical waveguide filament,
• passing said optical waveguide filament through said central longitudinal aperture,
• introducing coating material into said radial port,
• flowing said coating material through said radial port into said central longitudinal aperture in an amount whereby said coating material fills said central longitudinal aperture surrounding said filament to a point substantially coincident with the top surface of said body or a point intermediate said top and bottom surfaces of said body, and
• maintaining the level of said coating material in said central longitudinal aperture at a point intermediate said top and bottom surfaces of said coating die body but not above said top surface while said filament is passed through said central longitudinal aperture and said coating material contained therein whereby said filament is coated by said coating material.