PURPOSE: To remarkably enhance the forming yields of a clad layer and a core layer by regulating the difference between the maximum value and the minimum value of the outside diameter of a quartz glass pipe over a specified length and the difference between those of the thickness to each specified value or below.
CONSTITUTION: The difference between the maximum value and the minimum value of the outside diameter of a transparent quartz glass pipe for an optical fiber over 300W1000mm length and the difference berween those of the thickness are regulated to each ≤0.2mm accuracy. As a result, the temp. distribution of the pipe heated with an oxyhydrogen flame in a CVD process is made remarkably uniform. In order to manufacture such a transparent quartz glass pipe, it is required to well control the working accuracy of an inner die or an outer die, the pipe forming temp. and atmosphere, the measuring accuracy, etc. which exert influence on the pipe diameter accuracy or the heat softening state of the pipe in forming whose state exerts influence on the pipe thickness accuracy.
SATOU HISAYOSHI
YAMADA MASAYUKI
