| 摘要 |
PURPOSE:To manufacture a precisely circular preform rod, in high reproducibility, by heating a glass tube with an oxyhydrogen burner applying a specific pressure to the tube, and compressing and collapsing the tube. CONSTITUTION:A glass layer is deposited to the inner wall of a glass tube, one end of the tube is closed, and the tube is heated and sintered under introduction of gas from the other end into the tube to obtain an optical fiber preform rod. In the above process, the glass tube is held vertically and the revolution of the main axis is kept to zero, or the external pressure P and the inner pressure P1 of the glass tube are selected to satisfy the equation II (g is the acceleration of gravity, 1/m is Poisson's ratio, w is weight of the unit volume of the glass tube, omega is angular velocity of the glass tube, 2r1 is inner diameter of the glass tube, and 2r2 is outer diameter of the tube), keeping the conditions of the equation I. By this process, the radial stress is exerted to the tube by the inner pressure, and the tangential stress caused by inner pressure and the circumferential stress caused by centrifugal force are applied to the tube, whereby an optical fiber having precisely circular core and outer circumference can be obtained. |
