Patent ID: 8028545

Claim:
A method for manufacturing a final optical fiber preform by overcladding, said method comprising the steps of: providing a primary preform ( 10 ) including a tube of pure or doped silica in which layers of silica are successively deposited so that the primary perform includes an inner cladding and a central core; positioning said primary preform ( 10 ) within at least one tube ( 20 ), wherein the at least one tube ( 20 ) partly covers the primary preform ( 10 ) to create a zone to be overcladded, being an overclad zone, which overclad zone is located on a portion of the primary preform ( 10 ) not covered by the at least one tube ( 20 ); injecting a gas into an annular space between the primary preform ( 10 ) and the at least one tube ( 20 ) under overpressure relative to the pressure outside the at least one tube ( 20 ); alternately moving the primary perform and the at least one tube relative to each other in a forward and reverse direction so that the overclad zone moves along a length of the primary preform; overcladding the primary preform ( 10 ) in the overclad zone with an overcladding material including silica particles using a plasma torch, wherein the at least one tube ( 20 ) is dimensioned to have a length between 0.3 and 0.8 times the length of the primary preform ( 10 ).