| 摘要 |
A method for making preforms by vapour phase soot deposition processes is disclosed, whereby an oxidizing atmosphere is used during at least part of the deposition process; e.g. during the deposition of the centre portion of the preform. The oxidizing atmosphere results from supplying oxygen, available to react with the fuel, in an amount which is stoichiometrically in excess of that required to fully oxidize the fuel. This results in enhanced dopant capture, reduced axial inhomogeneities (e.g. of dopant) in the consolidated preform and finished fibre, and an overall stabilization of the deposition process. A method for selecting burner flow rates which optimize the deposition process is also disclosed. The reaction deposition burner used to carry out the process has:- a first passageway (13) and second passageway (15), both of which carry at least oxygen but no fuel; a third passageway (17) to carry at least fuel and oxygen; and optionally a fourth passageway (19) to carry at least oxygen but no fuel, for shaping the flame. |
