1. Home / 
  2. Products and Solutions / 
  3. Tubes / 
  4. Multimode Fiber
Multimode Fiber

Leverage our extensive experience in tube manufacturing for multimode fiber production

Heraeus has pioneered the production of high-quality glass tubes for multimode fibers and has thus shaped the industry: Heraeus has supplied natural-quartz tubes in the early days back in the 80s and 90s and then enabled the continuous performance improvements of the fibers’ bandwidths towards OM4 and OM5 grades by introducing high-purity synthetic quartz tubes for wide use. Leveraging our extensive knowledge and expertise, we continue to serve our partners with tailor-made tube products including F-doped tubes that make state-of-the-art bend-insensitive OM4 and OM5 multimode fibers.

The Material

Synthetic quartz glass has become the material of choice for multimode fibers thanks to its superior purity and compositional homogeneity. In combination with our benchmark geometrical precision, our tubes are the indispensable for running MCVD or PCVD processes with little variations and high yields. In fiber draw, the use of our high-purity tubes minimize fiber breaks and hence maximizes yields and productivity for our customers.


Our tubes are made of pure silica (SiO2) synthesized from highly pure gaseous raw materials using an outside vapour deposition process in a clean room environment. Following this, our tubes are manufactured by a contactless thermal forming process, ensuring minimal contamination risk.  We monitor purity of our materials using mass spectroscopy and typically do not find any trace elements above the ppb-detection limits. Hence, our tubes are typically about 10000x purer than tubes made from natural quartz.

Geometrical precision

With our decade-long experience and development work on our proprietary tube draw process and equipment, we are able to offer best-in-class geometrical precisions, and a large variety of different target geometries. Thanks to our thorough quality checks of each individual tube we produce our partners can be sure that every single tube they receive meets the specifications that we have developed together with them.

Refractive index adjustments

Our Fluorine-doped synthetic quartz glass tubes are available in a wide range of refractive index levels (-0.08% to -0.45%) and can be customized in geometry, to exactly match the requirements of our partners fiber designs, targeting superior bend performance of the multimode fibers.


Due to its comparably large core-to-clad ratio and its typically complex graded refractive-index profile in the core, multimode fibers are best produced using MCVD or PCVD core rod processes and a tube-based jacketing approach. Additionally, Fluorine-doped trench tubes introduced between core rod and jacket tube are versatile building blocks to manufacture bend-insensitive multimode fibers.



Multimode fibers typically have very challenging core designs with near-parabolic graded refractive index profiles that can only be manufactured efficiently with a well-controlled layer-by-layer deposition process like MCVD and PCVD. Using Heraeus’ tubes as substrates for these processes introduces minimal variances into these processes and hence enables better process control and consequently more accurate layer-based deposition, which in the maximizes the yields of high grade multimode fibers like OM4 and OM5. The substrate tubes can also come with Fluorine-doping so required down-doped trenches are already realized.


Gap Jacket

Thanks to the versatility in Fluorine levels and geometry targets, the Heraeus F-doped tubes are practical building blocks to realise trench-assisted or even more complex fiber designs.


Synthetic quartz glass tubes used as jackets for multimode fibers ensure lowest possible fiber draw process interruptions and consistently high yields. As contamination risk from the material is minimized, fiber break rates and machine downtimes are as low as it gets.

Would you like to learn more about our pure silica tubes? Contact us now to discover how you can utilize our tubes for the production of high-quality multimode fibers. Our team possesses extensive experience and expert knowledge to provide comprehensive support and solutions. 

Telecom Fiber ExpertsCustomer Contact
Send Mail