MILAN, March 21(Reuters) - Prysmian, the world's biggest cable maker, has signed a long-term partnership with U.S. firm Relativity Networks to produce hollow-core optical fibre cables to meet growing demand in data centres, the two companies said on Friday.

Under the partnership, Prysmian will manufacture high-performance cables based on Relativity Networks' hollow-core fibre technology, for which the U.S. company is awaiting patent approval.

Financial details of the agreement were not provided.

"This is a technology we didn't have, and we are the partner than can give scale to the technology," Prysmian's Digital Solutions Executive Vice President Frederick Persson said.

Compared to conventional optical fibre cables, where light is guided through a solid glass core, the hollow-core version has air at its centre. This reduces light dispersion, making data transmission faster.

Rapid transmission is often a priority in high-performance environments such as data centres.

The hollow-core fibre cables will be sold at higher prices than standard fiber cables.

"We are talking about a completely different scale from standard prices due to the efficiency and quality of these cables," Persson said.

Prysmian will initially manufacture cables at a dedicated facility in the Dutch city of Eindhoven. (Reporting by Alberto Chiumento in Gdansk, Giulio Piovaccari in Milan Editing by Keith Weir and Gavin Jones)