Imma Perfetto
Cosmos science journalist
Next-generation optical fibre manufactured in microgravity aboard the International Space Station has been returned safely to Earth.
Scientists at Adelaide University in South Australia are now comparing the fibres to otherwise identical Earth-made counterparts to confirm whether the space-made product is superior.
It’s thought likely that it is, but the results won’t be known for a couple of months.
The research has already delivered some interesting results: “Seven of the draws went beyond 700 meters, showcasing that it is possible to produce commercial lengths of fibre in space,” says Rob Loughan, CEO of the company that designed the fibre drawing device, Flawless Photonics.
“The longest draw went above 1,141 meters, setting a record for the longest fibre manufactured in space.”
The fibres were made of ZBLAN glass, a substance which has the potential to transmit light 20 times further than traditional silica-based fibre-optic cables.
In an optical fibre, light becomes dimmer and dimmer as it travels along the fibre. Therefore, for example, submarine fibre optics cables require amplifiers about every 100km to boost the light signal to allow it to be transmitted over long distances.
A ZBLAN optical fibre could increase distances between amplifiers, from every 100 km for silica fibres to every 2,000 km.
But this isn’t feasible yet. In practice, ZBLAN fibres perform about 10 times worse than the best silica fibres because the fabrication process introduces defects and impurities, which lower its efficiency at transmitting light.
Professor Heike Ebendorff-Heidepriem, and her team at the University of Adelaide’s Australian National Fabrication Facility’s (ANFF) are trying to solve the problem of enhanced impurities and defects in current ZBLAN glass fibres.
“The purity of the glass depends on the purity of the raw material, and it is challenging to make highly pure solid raw materials,” says Ebendorff-Heidepriem. The team is trying to completely remove one of the main reasons the defects form: gravity.
“Gravity here on Earth causes convection … If you heat up something on a hot plate, the liquid is hot at the bottom. That makes the density of the liquid at the bottom become lower, which moves this portion of the liquid up, at the top the liquid becomes cooler, making the density higher, therefore gravity pulls it down, and so on” she explains.
Ebendorff-Heidepriem partnered with Flawless Photonics which designed and operates a fibre drawing device that squeezed all the necessary technology into a 0.8m-long box for the ISS.
In June, the more than 11km of fibre returned to Earth, intact. Now, work is underway at the University of Adelaide and at 5 other organisations around the world to determine how much of an impact gravity has on ZBLAN’s ability to transmit light. They are hoping to complete their analysis by December this year.
“We will see: is it better? Is it worse? Is it the same? And no matter what result we get, I think the biggest outcome is already achieved – we can make commercial lengths of optical fibres in space.”
