| 摘要 |
PURPOSE:To make the outside diameter of a glass tube constant by providing a feedback loop of detecting the amount of the gas to be blown into the chamber for capturing the exhaust gas of a starting glass tube with a flow rate controller and the ouside diameter of the glass tube with a detector and controlling the flow rate controller according to the detection value. CONSTITUTION:A fuel gas is fed from a fuel gas supplying device 45 into a starting glass tube 41 within an optical fiber producing device of an internal CVD method, and is heated with a burner 43. The exhaust gas from the glass tube 41 is temporarily captured in a chamber 47 and is fed into an exhaust gas treating chamber 49 via a damper 48. On the other hand, the outside diameter of the glass tube is detected with an outside diameter detector 51 and is compared with the preset outside diameter in a comparator 52. The deviation thereof is amplified with an amplifier 54, is fed to a flow rate controller 55 which is turn controls the amount of the gas blown into the chamber by the feedback loop. Thereby, the pressure in the glass tube is controlled constant and the tube diameter is made constant. |
