Patent ID: 6923024

Claim:
Process for the manufacture of a preform of silica particles the soot preform having a core region and a cladding region comprising: (a) pulling a support rod; (b) simultaneously depositing core soot on the support rod and cladding soot on the core soot, wherein the core soot is deposited by: (i) forming core soot by flowing together: a flow of glass precursor gases, a flow of hydrogen, and a flow of oxygen, to form a first gas mixture, igniting the first gas mixture to form core soot, (ii) depositing the core soot on the support rod to form the core region of the preform, (iii) continuously monitoring the rate of deposition of soot in the core region to produce a core monitor signal, and the cladding soot is deposited by: (iv) forming cladding soot by flowing together: a flow of glass precursor gases, a flow of hydrogen, and a flow of oxygen, to form a second gas mixture, igniting the second gas mixture to form cladding soot, (v) depositing the cladding soot onto the core soot to form the cladding region of the preform, (vi) continuously monitoring the rate of deposition of soot in the cladding region to produce a cladding monitor signal.