SUBSTRATE TUBE AND PROCESS FOR PRODUCING A PREFORM FOR AN OPTICAL FIBER

ON THE BASIS OF A KNOWN PROCESS FOR THE PRODUCTION OF A PREFORM FOR AN OPTICAL FIBER FOR OPTICAL DATA TRANSMISSION TECHNOLOGY, THE PRODUCTIVITY OF THE PROCESS FOR THE PRODUCTION OF COMPLEX REFRACTIVEINDEX PROFILES IS TO BE IMPROVED BY PROVIDING A QUARTZ GLASS SUBSTRATE TUBE WHICH EXHIBITS DIFFERENT DOPIGNG IN RADIAL DIRECTION, INTRODUCIGNG A CORE GLASS MADE OF SYNTHETIC QUARTZ GLASS INTO THE SUBSTRATE TUBE AND COVERING THE SUBSTRATE TUBE WITH A JACKET TUBE. A SUBSTRATE TUBE SUITABLE THEREFOR IS ALSO BEING PROVIDED WHICH TUBE REQUIRES LESS CORE GLASS MATERIAL FOR THE PRODUCTION OF THE PREFORM, WHETHER DURING THE INTERNAL DEPOSITION OR FOR THE CORE GLASS ROD IN THE ROD-IN-TUBE TECHNIQUE. REGARDING THE PROCESS IT IS PROPOSED ACCORDING TO THE INVENTION THAT A SUBSTRATE TUBE BE USED WHICH WASOBTAINED BY VITRIFICATION OF A POROUS TUBE-SHAPED SIO₂ BLANK, THE SUBSTRATE TUBE BEING PROVIDED WITH A CORE GLASS LAYER WHICH IS PRODUCED IN THAT TO THE FIRST RADIAL PORTION OF THE SIO₂ BLANK THERE IS ADDED BEFORE THE VITRICATION A FIRST DOPANT WHICH INCREASE THE REFRACTIVE INDEX OF QUARTZ GLASS. THW SUBSTRATE TUBE TUBE ACCORDING TO THE INVENTION HAS IN THE RADIAL DIRECTION REGIONS OF DIFERENT DOPING WHEREBY IT INCORPORATES A CORE GLASS LAYER WHICH HAS A REFRACTIVE INDEX OF AT LEAST 1.459.