A collaboration of European NRENs and network equipment vendors has successfully demonstrated 1.2 Tbps (Terabit-per-second) transmission from Amsterdam, The Netherlands, to Kajaani, Finland. The test is a milestone in establishing interconnected HPC (high-performance computing) centers across Europe.
In the test, the newest generation of Nokia optical and router equipment was applied. The optical transmission link was set up between the national Dutch HPC facility in Amsterdam, operated by SURF, the research and education network (NREN) of The Netherlands, and the Finish national HPC facility in Kajaani operated by CSC, the NREN of Finland. The Kajani datacentre is home to LUMI, a major EuroHPC facility. In addition to CSC and SURF, NORDUnet and the NRENs of Sweden and Norway, Sunet and Sikt provided the network infrastructure.
“The transmission took place across the networks of the five NRENs with different optical platforms and specifications. Further, we had to coordinate things with the people at the HPC side. To run a Terabit transmission seamlessly under these conditions did require collaboration at a level that has not been seen before,” says senior network specialist Jani Myyry of CSC.
A future-proof European infrastructure
Direct terabit-level connectivity between key scienctific facilities is the next frontier for research and education networks across Europe – and globally. New research instruments along with upgrades to existing ones, demand ever-increasing bandwidth. The new generation of HPC facilities, essential for earth observation, human brain research, and other advanced scientific domains—will rely on this capacity. In parallel, the infrastructure required to support massive data repositories and computing needs for the next generation of artificial intelligence applications already has roadmaps that call for terabit connectivity in the coming years.
Meeting these needs and achieving Tbps connectivity enabling a future-proof infrastructure that supports cutting-edge research, artificial intelligence, and data-driven innovation on a continental scale is a key challenge. European NRENs working together in GÉANT Association are hard at work responding to this in a timely manner. Cross-border technology experiments, demonstrating that long-distance terabit connectivity is possible already now shows the value add of the collaboration of NRENs.
“1 Tbps is a major step up for NREN network service. When our users and connected institutions have these requirements, we can say that our demonstration from Amsterdam to Kajaani show that European NREN networks are at the level that will be required,” comments Jani Myyry.
Operating close to margins
The test took place over 2-3 weeks in May 2025.
“It is best to have a clear set of goals and to get things done over a short period of time. Not least since we had to involve quite a lot of people, not just in Kajaani and Amsterdam but also along the way. Many contributed. You cannot do something like this without encountering problems that you had not anticipated.”
Topping the list of unforeseen problems was the breakdown of an optical fiber link between Sweden and Finland just a few days into the operation. The team succeeded in finding an alternative route very quickly. However, this added some 500 km to the distance.
“We were challenged since we were already operating at close to the margins in terms of signal-to-noise ratio etc.,” says Jani Myyry.
Not strictly a record, but still..
The route from Amsterdam to Kajaani is more than 3,500 km.
“Establishing an end-to-end Terabit-level optical link over this distance is not profoundly novel, as transmissions over 5,000 km have been demonstrated by others. However, these trials are conducted on submarine cables that are optimized to a degree that almost resembles transmitting in a lab setting. You just cannot optimize terrestrial cables in a similar manner. And on top of that come the challenges involved by transmitting over different networks. So, I would say that while all aspects were not unprecedented, this is certainly a milestone in the development of the network of the future,” ends Jani Myyry.
