Fused silica tubes for fiber production

Heraeus high purity fused silica tubes are produced without forming tools and provide an excellent surface with tight geometrical tolerances. There is no alternative to our tubes when producing optical fibers. Read below more about substrate tubes and tubes of fluorine doped fused silica.

Substrate tubes

For telecommunication optical fiber the only tube-based technology for core rod production employed in large scale are CVD based methods.

Heraeus offers substrate tubes in two material grades, which differ in the specified OH content. The established industry standard of F 300® and the improved grade F 500® that is “waterfree”. For more details, please check the datasheet or contact our experts.

Tubes of fluorine doped fused silica

Fused silica is doped with fluorine to lower the refractive index of silica. The design of some single mode fibers has varying refractive index values across the fiber. For highly bend insensitive fibers, for example, a ring of silica with a lower refractive index is placed around the core to improve light guiding properties. Because the ring has a lower refractive index it is called a trench.

The RIC® process provides for an easy and therefore cost-effective solution to realize these fiber designs on a large scale. To form a ring of a different refractive index around the core, a tube is placed around the core rod before inserting it into the cylinder. Further processing is as described in the RIC® process. For RIC® customers we offer silica tubes with customer-specific dimensions and doping levels.


We manufacture tubes that play a crucial role in supporting ultra-low loss fiber, multi-mode fiber, and bend-insensitive fiber. 

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