ALPD : Axial Lateral Plasma Deposition : From Step To Graded Index Structure

ALPD technology is a large scale industrial process which permits the manufacture of massive all silica ingots. The system works by direct fusion using a plasma flame, the deposition rate being far in excess of that achieved by other fiber manufacturing techniques. The plasma heating process involves very high temperature which promotes purification by volatilisation. No substrate is required (either tube or mandrel) and thus intermediate operations are completely avoided (collapsing of tube in internal CVD or drying, vitrification and collapsing in O.V.P.O. or V.A.D.) This combination of advantages permits the drawing of large preforms and eventually of large core step-index all silica fibers under highly economic conditions. The latest modification of the process allows index profiling of the optical interface with maintained production efficiency.