INTERNAL COATING OF A TUBE

摘要

For producing a fiberoptic waveguide preforms by plasma pulse-induced chemical vapor deposition (PICVD), blank glass tubes are prepared having a continuously increasing internal diameter in the direction of gas flow. This type of blank compensates for the otherwise occurring decrease in the density of the layer-forming molecules due to pressure drop, thereby permitting the formation of a uniform masswise deposition of layer-forming molecules along the length of the tube. This permits the production of collapsed preforms having a series of coating layers of substantially uniform thickness.