METHOD FOR CONTROLLING SURFACE DISTANCE IN LONGITUDINAL DIRECTION OF PREFORM IN MANUFACTURING PROCESS OF OPTICAL FIBER PREFORM, AND SYSTEM FOR IMPLEMENTING THE METHOD

摘要

A method for controlling a surface distance (outer or inner diameter) of a preform uniformly during an optical fiber preform manufacturing process is provided. This method controls a surface distance uniformly along an axial direction while an optical fiber material film is repeatedly deposited on a preform deposition member layer by layer. A surface distance is measured at control response completion points to which control inputs are already applied. Then, a surface distance at a control input applying point is approximated using the measured surface distance. Subsequently, a control input for decreasing a difference between a control target surface distance and the approximated surface distance is calculated using a static response characteristic. Then, the calculated control input is applied. This method prevents distortion of a refractive index profile in an axial direction of the preform and allows easy design of a surface distance control algorithm.