Researchers use 3D printing to make optical fibre preform

Created November 1, 2019
Applications and Research

Researchers have developed a way to use 3D printing to create a preform that can be drawn into silica glass optical fibres. This new fabrication method could not only simplify production of these fibres but also enable designs and applications that weren’t possible before.

“Making silica optical fibre involves the labour-intensive process of spinning tubes on a lathe, which requires the fibre’s core or cores to be precisely centred,” explained John Canning who led the research team from the University of Technology in Sydney. “With additive manufacturing, there’s no need for the fibre geometry to be centred. This removes one of the greatest limitations in fibre design and greatly reduces the cost of fibre manufacturing.”

In The Optical Society (OSA) journal Optics Letters, Canning’s group, in collaboration with Gang-Ding Peng’s research team at the University of New South Wales in Sydney, report the first silica glass fibres drawn from 3D printed preforms.

The new achievement builds off earlier work in which the researchers used a polymer material to demonstrate the first fibre drawn from a 3D printed preform. Applying this approach to silica has proved challenging due to immense material challenges including the high temperatures – more than 1,900° C – needed to 3D print glass.

In the new work, the researchers used a commercially available direct-light projection 3D printer. This type of additive manufacturing is extremely precise and typically used to create polymer objects by using a digital light projector to polymerise photo-reactive monomers. To create a silica object, the researchers added silica nanoparticles into the monomer at amounts of 50% or greater by weight. They designed a 3D printed cylindrical object that contained a hole for a core. They then inserted a similar mix of polymer and nanoparticles into the hole, this time adding germanosilicate to the silica nanoparticles to create a higher refractive index. In this way, the integration of a range of dopants becomes possible.

Researchers used direct-light projection to make silica fibre preforms. They fabricated preforms for a step index fibre (a) and a structured preform (b). These preforms were then placed in a draw tower (middle picture) to make the final optical fibre (right). The orange inset shows a cross section of a step index fibre. Photograph: John Canning, University of Technology in Sydney

Next, the researchers used a unique heating step called debinding to remove the polymer and leave behind only the silica nanoparticles, which are held together by intermolecular forces. Finally, raising the temperature further fused the nanoparticles into a solid structure that could be inserted into a draw tower where it is heated and pulled to create the optical fibre.

The researchers used their new technique to fabricate a preform equivalent of a standard germanosilicate fibre that could be used to create multi- or single-mode fibres, depending on drawing conditions. Although they did observe high light losses in the initial fabricated optical fibres, they have since identified the causes for these losses and are working to address them.

“The new technique worked surprisingly well and can be applied to a range of glass material processing to improve other types of optical components,” said Canning.  “With further improvements to limit the light losses, this new approach could potentially replace the conventional lathe-based method of making silica optical fibres. This would not only reduce fabrication and material costs but also lower labour costs because training and hazards are reduced.”

The researchers are interested in working with a mainstream commercial fibre fabrication company to improve and commercialise the technology. They also plan to explore other methods for accelerating 3D printing by refining it for different applications.

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This article was written
by John Williamson

John Williamson is a freelance telecommunications, IT and military communications journalist. He has also written for national and international media, and been a telecoms advisor to the World Bank.