METHOD FOR MAKING OPTICAL FIBER PREFORM USING SIMULTANEOUS INSIDE AND OUTSIDE DEPOSITION

A method and apparatus for making optical fiber preforms using simultaneous plasma deposition on the inside and outside surface of a starting tube. A starting tubular member (12) is rotated, CFOT chemicals (22) are selectively injected into the plasma torch (16) and CFIT chemicals (24) are selectively injected to flow through the hollow of the tube (12). The plasma torch is traversed along the tubular member to simultaneously deposit soot on the inside and outside surface. The soot on one or both surfaces may be consolidated into a silica layer as it is deposited. The plasma torch (16) is traversed again to deposit additional soot, and/or consolidate previously deposited soot, on one or both surfaces. The process is repeated until a predetermined amount of silica is formed on the tubular member. The tubular member is then collapsed. Optionally, additional plasma deposition is performed during or after the collapsing.