OPTICAL FIBER PREFORM AND METHOD FOR MANUFACTURING SUCH OPTICAL FIBER PREFORM FROM A PRIMARY PREFORM

摘要

The invention relates to an optical fiber preform (20) comprising a primary preform (21) and one or more purified silica-based overclad layers (22) surrounding said primary preform (21), the purified silica-based overclad layers (22) comprising lithium and aluminium, and having a ratio between lithium concentration [Li] and aluminium concentration [Al] satisfying the following inequality (Formula (I)). 1.103≦̸[Li]/[Al]≦̸20.103   (1)