Heraeus Covantics, a leading innovator in advanced optical fiber technologies, has delivered key technology for LUMIRing, Europe’s largest multicore fiber (MCF) testbed. The project of University Institute of Lisbon (ISCTE) is installing a 26 km cable ring in a tunnel of the Lisbon Metro.   LUMIRing represents a milestone in optical communications, allowing research and industry to validate next-generation systems under real-world conditions.

Enabling artificial intelligence, speedy telecom networks, and low carbon footprint 

Multicore fibers contain several cores that guide the light for data transmission inside a single strand of fiber, thereby multiplying data bandwidth of a cable while enabling small form factor and weight. This allows for cost-effective expansion of data bandwidth within existing telecom ducts, avoiding trenching and new construction which are especially cumbersome in urban areas. Training of artificial intelligence models in modern data centers induces a surge of data demand that can only be targeted with a high density of optical channels, while keeping power consumption low. To preserve a healthy environment, the amount of material and thus the CO2 footprint of an optical cable is cut to a fraction by multicore technology, on top of avoiding heavy carbon impact of new network construction.

Largest multicore fiber deployment worldwide

The new testbed infrastructure integrates 74 multicore fiber strands within a 144-fiber cable, totaling more than 1,900 km across five multicore types containing four to seven cores each. In total, more than 300 26-km long loops of light-guiding cores make up over 8,000 km of optical channels in one cable – making LUMIRing the largest terrestrial multicore fiber testbed worldwide. Using numerous amplifiers in the system, these loops can be combined in many ways by connecting them at different access points along the cable, one of them being the university lab.  

Heraeus Covantics’ contribution

Heraeus Covantics contributed advanced fiber designs and leading process expertise, enabling the scaled-up production of some of the longest continuous multicore fiber strands ever manufactured. The record of more than 2,000 km of fiber drawn from a single preform was presented at OFC conference in 2024, while keeping geometrical precision at a high level. Resulting low signal loss, in combination with fewer splicing points enable high reliability and low signal loss – critical factors for scaling next-generation networks. By operating in the demanding environment of Lisbon’s metro tunnels, the testbed demonstrates fiber resilience against vibration, humidity, noise, and temperature variations, conditions far beyond laboratory trials.  

Global relevance through European collaboration

The project of the University Institute of Lisbon (ISCTE) was based on a collaboration with cable manufacturer Tratos, Lisbon Metro, the installation company, and Heraeus. The university aims to attract the attention of global players in telecom and data center space such as AT&T, Deutsche Telekom, Vodafone, Google and Meta, who are expected to use the platform for network validation and product testing.

Outlook

The public inauguration of LUMIRing will take place on 29 October 2025 in Lisbon, with large-scale testing continuing throughout 2026. With its record-breaking scale and industrial validation, the project positions Europe as a hub for next-generation optical communication networks – and Heraeus Covantics as a key enabler of this transformation.

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