PRODUCTION OF OPTICAL FIBER PREFORM

摘要

PURPOSE:To facilitate the control of the core/clad ratio in the production of an optical fiber preform by adding a dopant compound to SiO2 soot deposited on the inner wall of a glass tube, inserting the obtained core rod into a specific glass tube and collapsing the assembly. CONSTITUTION:An optical fiber preform containing a dopant compound doped exclusively at the center part of the core can be produced by the following method. A dopant compound is added to a soot composed mainly of SiO2 and deposited on the inner wall of a glass tube for forming a core, the tube is vitrified and collapsed and the product is drawn to a prescribed outer diameter to obtain a core rod. The core rod is inserted into a glass tube having the refractive index of the core rod and the assembly is collapsed. The ratio of the core diameter to the diameter of the part containing the dopant such as rare-earth compound and the core/clad ratio can be easily adjusted e.g. by grinding the outer circumference of the product provided that these ratios of the original product are larger than the desired levels.