The invention relates to a collapsing manufacture method with improved axial evenness for core rods of
optical fiber preforms. The method comprises the following steps: mounting a
quartz-doped liner tube on a collapsing lathe, rotating the
quartz-doped liner tube, moving a
heating furnace jacket from one end of the liner tube to the other end of the liner tube in the axial direction of the liner tube, collapsing the liner tube gradually to realize
solid burning. During the collapsing process, the two ends of the liner tube are sealed, and O2 gas is led into the liner tube. The method is characterized in that the
axial distribution condition of the sandwich layer
diameter of the liner tube after deposition is confirmed before collapsing, and an F-contained corrosive gas is led into the liner tube during the collapsing process of the liner tube to conduct different axial
corrosion on the inner wall of the liner tube, or O2 gas and the F-contained corrosive gas are led into the liner tube simultaneously after collapsing and before
solid burning to conduct different axial
corrosion on the inner wall of the liner tube. The method has the advantages that the effect that different areas in the liner tube are corroded differently is realized by adjusting the flow rate of corrosive
mixed gas, and fixed point
corrosion is realized, so that the
diameter evenness of the core rods of the
optical fiber preforms can be improved remarkably. Therefore,
optical fiber preparation cost can be reduced; the production efficiency can be improved.