NEC claims Japan’s longest wireless optical data link with 10km test

April 25, 2025 10:30 AM

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NEC Corp claims to have completed Japan’s longest terrestrial wireless optical communication, reaching a distance of more than 10km.

The tech giant completed a free-space optical (FSO) communication from an observation deck at Tokyo Skytree, the tallest structure in Japan, to a site on the ground some 3km away, as well as to a remote site outside of Nasushiobara City.

NEC Corporation's terrestrial wireless optical communication/free-space optical (FSO) communication test from Tokyo Skytree

FSO is a wireless method that uses tightly focused beams of light to transmit data, rather than relying on physical connections like fibre or even traditional radio spectrum.

The technology promises high-speed, high-capacity links with several advantages: beams don’t easily spread, which reduces the risk of interception and interference, and there’s no need for costly radio licences.

Despite its promise, the core challenge with FSO is maintaining stable links over long distances, particularly as atmospheric turbulence can easily disrupt the connection.

NEC said its engineers overcame these hurdles by using capture and tracking technology originally developed for satellite communications, allowing bidirectional optical beams to remain locked on target even over extended distances and across significant changes in elevation.

The demonstration took place in two parts: a long-distance test in Nasushiobara City, Tochigi Prefecture, where devices established a stable link over more than 10km; and an elevation test using Tokyo Skytree, with a beam shot from 350 metres above ground to a receiver nearly 3km away, measuring how turbulence varies with altitude.

NEC envisions the technology supporting high-speed connections in areas where laying fibre isn’t feasible, providing ship-to-shore links, and offering emergency or secure backup communications in the event of disasters.

The Japanese tech giant plans to shrink its current 2m³ setup down to a portable unit and to commercialise the technology by 2028.

The company also has its sights set on integrating quantum cryptography for even more secure communications, including, potentially, ground-to-satellite links for critical infrastructure.