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

摘要

A method for manufacturing a precursor for a primary preform for optical fibres by an internal plasma deposition process including the steps of providing a hollow substrate tube, creating a first plasma reaction zone having first reaction conditions and depositing non-vitrified silica layers along at least a portion of the inner surface of the substrate tube, subsequently creating a second plasma reaction zone having second reaction conditions different from the first reaction conditions and depositing vitrified silica layers along at least a portion of the substrate tube, and cooling the substrate tube to produce the precursor for a primary preform.

主权项

1. A method for manufacturing a precursor for a primary preform for optical fibres by an internal plasma deposition process, comprising the steps of:
i) providing a hollow substrate tube having a supply side and a discharge side; ii) creating a first plasma reaction zone having first reaction conditions in the interior of the hollow substrate tube by means of electromagnetic radiation for effecting the deposition of non-vitrified silica layers on at least a portion of the inner surface of the substrate tube at or near a reversal point at the discharge side and depositing non-vitrified silica layers along at least a portion of the inner surface of the substrate tube; and subsequently iii) creating a second plasma reaction zone having second reaction conditions in the interior of the hollow substrate tube by means of electromagnetic radiation for effecting the deposition of vitrified silica layers and depositing vitrified silica layers along at least a portion of the inner surface of the substrate tube obtained in step ii); and iv) cooling the substrate tube obtained in step iii) to produce the precursor for a primary preform.