An optical fibre-based synchronisation system designed by UWA ICRAR researchers has been selected for the first phase of SKA-mid, the part of the Square Kilometre Array that will be built in South Africa.
The long distances between SKA antennas means radio waves from the sky will arrive at each antenna at different times. With thousands of antennas spread over continental scales, one of the most complex technical challenges for the SKA is to synchronise the incoming signals with extreme precision before they’re combined by the SKA’s supercomputers.
“The scale of the SKA posed an engineering problem that hadn’t really been faced before by any astronomical observatory. We have to achieve a precision better than five parts in a trillion,” said André Van Es, the SaDT Engineering Project Manager supervising the consortium’s work for SKA Organisation.
To achieve this level of precision or “coherence” across the array, the SKA requires a synchronisation distribution system that suppresses these fibre fluctuations in real time.
While optical fibres are incredibly stable and suited to transport data, mechanical stresses and thermal changes can affect them, degrading the stability of the transmitted signals over long distances.
Lead designer, Dr Sascha Schediwy from ICRAR UWA said the reference signals sent by the synchronisation distribution system travel to each antenna using the optical fibre network and take into account the mechanical stresses and thermal changes.
“The system then corrects the timing difference to make sure all signals coming from the antennas are digitised synchronously with a precision better than five parts in a trillion.
“To put it another way, a clock relying on a signal of that stability would only gain or lose one second after 600,000 years and field tests have shown our system to be performing between 100 and 10,000 times better than what’s required for the SKA,” Dr Schediwy said.
The extreme accuracy of this technology could have all sorts of applications beyond discovering stars and galaxies from the early Universe.
“Astronomy is constantly pushing the boundaries in fields like precision timing, imaging and big data management, leading to new technologies like more advanced medical imaging.
“At the time of invention, we often don’t fully appreciate the extent to which these technologies can change lives and boost the economy,” Dr Schediwy said.