J-Fiber Jena

The Manufacturing Process

Since fall 2010 j-fiber group has implemented its own fused silica process for the manufacturing of ingots and components which we use for the production of our own specialty fiber preforms and supply to clients in optics and laser markets, technical applications or lithography.

In the manufacturing of quartz glass we distinguish between natural and synthetic quartz glass. Fused quartz, a natural, crystal raw material is being melted either electrically or with H2/O2 flame. Synthetic quartz glass (fused silica) is generated by the chemical reaction of a high-purity silicon compound in a CVD process step. It guarantees highest purity of the glass and therefore minimizes optical absorption.


Our method of melting fused silica has been invented by the Jenaer Glaswerk. It is based on the flame-hydrolytical decomposition of the synthetically manufactured silicon tetrachlorid (SiCl4), an ultra-pure, colorless, aggressive and highly humidity-sensitive fluid. During the hydrolytic decomposition in a hydrogen-oxygen flame, very tiny silicondioxyd particles of 50nm are generated. Due to the very high temperature of that flame (> 2700 K) the particles fuse and form an ultra-pure fused silica cylinder (ingot).

Since quartz glass shows a high viscosity even at high temperatures and in order to avoid impurities from fire resistant materials, the deposition of SiO2 particles take place crucible free on the front surface of a bait rod that is slowly withdrawn from the flame thus is forming a solid round ingot. The whole melting furnace contains additionally:

  • burner gas control
  • SiCl4- doser
  • SPS system control
  • Exhaust disposal


The melting process from ignition the multi- nozzle burner up to reaching a fused silica ingot with maximum mass takes several days and the whole process is constantly supervised.



j-fiber GmbH
Im Semmicht 1
D-07751 Jena, Germany

Tel: +49-3641-352 100
Fax: +49-3641-352 101