Optical light guide mfr. - by shrinking outer plastic sheath on plastic hose surrounding optical light guide fibre

摘要

An optical light guide assembly is produced by surrounding the optical light fibre by a plastic hose, e.g. of polyethylene, with a bore slightly larger than the outer dia. of the fibre. This is done either by extruding the hose around the fibre or by slitting a hose and inserting the fibre. An outer sheath e.g. of polyethylene, is now extruded on this assembly in such a way that the sheath shrinkage during the cooling period causes the plastic hose to be upset by a certain amt. which is governed by a formula quoted in the Patent. When such a light guide is wound on a cable drum, the length difference between the plastic hose and the light guide fibre ensures that the fibre elongation does not exceed 0.5% because more would lead to brittle fatigue fractures. Nor does the compression exceed 0.8%, because more would lead to microbendings and to intensified attenuation.