Posted in | Fibre Optics

Direct-Light Projection Used to Produce Silica Glass Optical Fiber Preform

Scientists have designed a method to use 3D printing to produce a preform that can be made into silica glass optical fibers, which serve as the backbone of the global telecommunications network.

Researchers used a 3D printing method known as direct-light projection (DLP) to make silica fiber preforms. They fabricated preforms for a step index fiber (a) and a structured preform (b). These preforms were then placed in a draw tower (middle picture) to make the final optical fiber (right). The orange inset shows a cross section of a step index fiber. (Image credit: John Canning, University of Technology Sydney)

This new fabrication method enables such fibers to be easily produced and facilitates applications and designs that were once nonviable.

Making silica optical fiber involves the labor-intensive process of spinning tubes on a lathe, which requires the fiber’s core or cores to be precisely centered. With additive manufacturing, there’s no need for the fiber geometry to be centered. This removes one of the greatest limitations in fiber design and greatly reduces the cost of fiber manufacturing.

John Canning, University of Technology Sydney

Canning led the research team from the University of Technology Sydney.

In the Optics Letters journal published by The Optical Society (OSA), Canning’s team together with Gang-Ding Peng’s team at the University of New South Wales in Sydney reported the first silica glass fibers made from 3D printed preforms.

Additive manufacturing approaches such as 3D printing are well suited to change the entire approach to fiber design and purpose,” remarked Canning. “This could, for example, broaden the applications of fiber optic sensors, which far outperform electronic equivalents in terms of longevity, calibration and maintenance but haven’t been widely deployed due to their expensive fabrication.”

Translating Polymer 3D Printing to Glass

This new effort improves previous work where the research team used a polymer material to show the first fiber made from a 3D printed preform. The application of this approach to silica is difficult due to great material challenges, including the high temperatures (over 1900 °C) required to 3D print glass.

Thanks to a novel combination of materials and nanoparticle integration, we have shown it’s possible to 3D print a silica preform. We expect this advance to bring a flurry of activity, including other additive manufacturing approaches, to accelerate this field.

John Canning, University of Technology Sydney

As part of the new study, the scientists made use of a commercially available direct-light projection 3D printer. Additive manufacturing of this kind is very accurate and generally used to produce polymer objects with a digital light projector to polymerize photo-reactive monomers.

The scientists produced a silica object by adding silica nanoparticles into the monomer at amounts of 50% or greater by weight. They developed a 3D printed cylindrical object with a hole for a core. Later, they added a similar mixture of nanoparticles and polymer into the hole. This was done by adding germanosilicate to the silica nanoparticles to produce a higher refractive index. In doing so, the amalgamation of a range of dopants could be achieved.

Then, using an exclusive heating step known as debinding, the scientists removed the polymer, which left behind only the silica nanoparticles linked by intermolecular forces. Lastly, with a further increase in the temperature, the nanoparticles combine to form a solid structure. Perhaps this solid structure can be introduced into a draw tower where it gets heated and pulled to form the optical fiber.

Using their new method, the scientists designed a preform identical to a standard germanosilicate fiber that could be used to form multi- or single-mode fibers, based on drawing conditions. Even though they observed high light losses in the first fabricated optical fibers, they have found the reasons for these losses and are working to solve 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. With further improvements to limit the light losses, this new approach could potentially replace the conventional lathe-based method of making silica optical fibers. This would not only reduce fabrication and material costs but also lower labor costs because training and hazards are reduced.

John Canning, University of Technology Sydney

The scientists are involved in working with a mainstream commercial fiber fabrication company to optimize and commercialize the technology. They also intend to analyze other techniques for advancing 3D printing by refining it for various applications.

Source: https://www.osa.org/en-us/home/

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