1. Home / 
  2. Products and Solutions / 
  3. Tubes / 
  4. Ultra Low Loss Fiber

Fluorine-doped tubes from Heraeus enable today’s state-of-the-art ultra-low-loss fiber performance level

Our Fluorine-doped (“F-doped”) tubes have paved the way for a wider use of Ultra-low-loss fibers (i.e. fibers with a pure-silica core in the center) in both subsea- and terrestrial longhaul cables. Heraeus has designed its products together with our partners to match the needs of the ULL fiber market, leveraging our expertise and continuous development in response to market needs. They are now commonly used as substrate tubes for core rod making, gap jacket tubes for trench-assisted designs, and cladding tubes.

The Material

For ULL applications, the highest quality materials are necessary to achieve lowest losses and consistently good optical properties in the fiber from stable and efficient manufacturing processes. Fluorine-doped tubes from Heraeus are made from highest-purity synthetic quartz that is essentially free from trace elements. They come in a large variety of different customer-specific refractive index levels, geometries with best-in-class geometric precision and material properties, providing all necessary building blocks even for special fiber designs.


Our tubes are made of fluorine-doped pure silica (SiO2) that was deposited into cylinders utilizing the OVD method in a clean room setting. The resulting tubes are then manufactured using a contactless thermal forming method, which minimizes the danger of contamination. We use mass spectrometry to monitor the purity of our products, and we rarely find trace elements above the ppb detection limits.

Hydroxyl (OH) content

Our high quality material is free of measurable OH content thanks to a carefully designed sequence of production steps, so it can be used for ULL applications even close to the light-guiding core.


High homogeneity of Fluorine doping, different doping profiles that match the fiber design, large variety of doping levels, in the range of -0.08% to -0.42% (relative RI depression versus pure SiO2).



Heraeus tubes are ideal for use as a substrate in ULL applications to produce the core rod. Thanks tot he high purity and low OH-content the material exhibits very little excess loss which allows for direct use in close vicinity of the light-guiding portion of the fiber. In addition, the compositional homogeneity and benchmark geometrical accuracy enables a well-controlled MCVD or PCVD process with stable yields.

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.


Large-OD F-doped tubes from Heraeus have enabled preform size and hence productivity scaling of ULL fiber production. Refractive index profiles of the tubes have been adjusted to market needs, and each tube comes with accurate RI-profile data. This way, matching of core rod and jacket tube can be optimized to improve yields and reduce cost.

Heraeus tubes deliver exceptional performance in the field of ultra-low loss fibers. From the purity of materials, flexibility in doping profiles, to high-quality manufacturing processes, we provide customized solutions tailored to your needs. Click below to get in touch with our tube experts or leave a message to explore further applications of our tubes in ultra-low loss fibers.

Telecom Fiber ExpertsCustomer Contact
Send Mail