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Bend Insensitive Fiber

F-doped Trench Tubes from Heraeus: Enhancing High-Quality Bend-Insensitive Fibers

Down-doped trenches are a key ingredient to the design of high-performance bend-insensitive fibers of types G.657.A2, G.657.B3. Heraeus Fluorine-doped tubes are a flexible and highly productive solution to achieve such fiber design. Since about 20 years ago, Heraeus has shaped the industry with this solution. Especially when combined with the RIC process, Heraeus’ solution has made these types of fibers commercially feasible and scalable into large volumes. Now, bend-insensitive fibers are an essential cornerstone to the FTTx network build out.

The Material

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 (typically < 0.1 ppm) content thanks to a carefully designed sequence of production steps. Especially when combined with the RIC process, this material allows to manufacture fiber designs where the trench is comparably close to the light-guiding core without introducing OH-related losses.


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.


GAP Jacket

Typically, Heraeus' F-doped are used as an additional glass component between the core rod and the cladding glass. Heraeus’ partners benefit from the Online-RIC process, where the introduction of this additional glass component does not require an additional collapsing step, but can just be added to the assembly that directly goes to into the fiber draw furnace and is drawn into the final fiber “online”.

Ready to revolutionize your fiber designs and enhance performance? Discover the excellence of Heraeus' trench tubes today. Take action now and contact us to unlock the untapped potential of bend-insensitive fibers for even the tightest spaces. 

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