A METHOD FOR MANUFACTURING A PRECURSOR FOR A PRIMARY PREFORM FOR OPTICAL FIBRES BY MEANS OF A PLASMA DEPOSITION PROCESS

摘要

The present invention relates to a method for producing a precursor. In other words, the present invention relates to a method for producing a precursor for a primary preform for an optical fiber through an internal plasma deposition process. The method comprises the steps of: providing a hollow base material tube having a supplying part and a discharging part; producing a primary plasma reaction region having primary reaction conditions in the hollow base material tube by means of electromagnetic radiation so as to cause the deposition of non-glass silica layers on at least a part of the internal surface of the base material tube in a reverse point of the discharging side or around the same so that the base material tube having the non-glass layers can be provided onto at least a part of the internal surface thereof; producing a secondary plasma reaction region having secondary reaction conditions in the hollow base material tube by means of electromagnetic radiation so as to cause the deposition of glass silica layers on the base material tube having the non-glass layers formed on at least a part of the internal surface thereof so that the non-glass and glass silica layers are deposited on the base material tube; and cooling the base material tube on which the non-glass and glass silica layers are deposited so as to obtain the precursor for a primary preform.