Window to the future - Challenges and successes of glass fibre fabrication in space
- Paper ID
99686
- DOI
- author
- company
Flawless Photonics Sarl; University of Adelaide; Leibniz-Institute of Photonic Technology; Lukasiewicz Institute of Microelectronics and Photonics; Technical University of Denmark (DTU)
- country
Luxembourg
- year
2025
- abstract
While satellite-based internet connectivity has been a recent hot topic, most of the global internet traffic passes through intercontinental silica-based fibre-optic cables that span many thousands of kilometres. The unrelenting growth in demand for internet bandwidth and the need for redundancy means significantly more undersea cables are required. Such cables, based on current silica-based fibres, are incredibly expensive to manufacture and to operate. Despite the transmission losses of silica-based fibres being very low - 1550nm and very close to the intrinsic material loss of 0.12dB/km – the signal strength after 100 km of propagation is very weak. Multiple amplifiers are therefore embedded into the cables to repeatedly boost the signal, with each fibre requiring its own chain of dedicated amplifiers. Significant electrical power is also needed to power the amplifiers, adding to the cost. A promising alternative to silica-based fibres are fibres based on ZBLAN glass. The theoretical intrinsic loss of ZBLAN is 20 times lower at 0.006dB/km at 2300nm. This means that a good ZBLAN-based fibre-optic cable would only require amplifiers every 2000 km. Some connections, such as between Australia and New Zealand, can therefore be amplifier-free, which significantly reduces the cost while allowing near-limitless scalability. While ZBLAN development is ramping up rapidly, several challenges must be overcome to achieve its full potential. One such challenge is the tendency for ZBLAN glass to form crystals during the heating process of fibre fabrication. Such crystals induce scatter within the fibre, resulting in higher losses. Earlier studies using parabolic flights have demonstrated that gravity plays a significant role in crystal formation, with crystallisation significantly reduced in micro-gravity conditions (Tucker et. al. 2004). To take advantage of this, a space-compatible miniaturised fibre draw system was developed and installed on the International Space Station (ISS). This automated production system allowed the fabrication of different fibre compositions with different parameters. It requires minimal interaction by astronauts. Through this mission, we successfully fabricated multiple lengths of ZBLAN fibres early 2024. The total length fabricated was almost 12km, with the longest continuous length of fibre was 1141m. The fibres produced were successfully returned to Earth and were analysed by multiple institutions. We will discuss the production system, some of the challenges we faced, and solutions devised for Space operations, and present the key outcomes of the mission and measurement campaign. We conclude with an outlook on the next steps of fibre production in microgravity.