Japan’s National Institute of Information and Communications Technology (NICT) has pulled off something remarkable in ultra-high-speed optical communications. They’ve managed a world-first: 2 terabits-per-second free-space optical transmission using compact terminals that could actually fit on satellites or High Altitude Platform Stations (HAPS).
Let’s dig into what they did, how it works, and why it matters for Beyond 5G and 6G non-terrestrial networks. It’s not every day you see a leap like this.
World’s First 2 Tb/s Free-Space Optical Link with Compact Terminals
NICT demonstrated a 2 terabits-per-second (Tb/s) free-space optical (FSO) communication link across a real urban landscape. Instead of relying on fiber, FSO sends data through the air using tightly focused laser beams—pretty wild, right?
The experiment ran over a 7.4-kilometer link between NICT’s main building in Koganei, Tokyo, and a spot in Chofu, Tokyo. That’s a tough, turbulence-prone route—not some cushy lab setup.
Connecting FX and ST Terminals Across Tokyo
One end had a high-performance FX transceiver. The other end used a simplified ST transponder—designed to be compact and lightweight.
The ST terminal could actually fit on a satellite or HAPS platform, where space and power are at a premium. That’s a big deal for real-world use.
Even with challenging urban atmospheric turbulence—like temperature shifts, air currents from buildings, and unpredictable weather—the system kept up stable, high-speed data transmission. That kind of resilience is exactly what non-terrestrial networks need.
How NICT Achieved 2 Tb/s in Free Space
The secret sauce? Optical multiplexing. It’s a trick borrowed from top-tier fiber networks and brought into the free-space world.
NICT’s setup used Wavelength Division Multiplexing (WDM), which basically means sending lots of different laser colors through the same path. Simple, but effective.
Wavelength Division Multiplexing for Massive Capacity
They transmitted five parallel optical channels, each running at 400 Gbit/s. Here’s the math:
What’s really impressive isn’t just the speed—it’s that they did it with compact optical terminals. Usually, you need big, heavy ground equipment for terabit speeds. NICT’s work shows you can now get that kind of performance with gear small enough for satellites or HAPS.
Enabling Beyond 5G and 6G Non-Terrestrial Networks
This isn’t just a cool lab trick. It’s a real step forward for Beyond 5G and 6G Non-Terrestrial Networks (NTNs).
NTNs mix satellites, HAPS, and ground stations to weave together seamless global connectivity. Proving that terabit-class optical links can work with compact gear in real-world conditions? That’s a foundation for future networks that reach way beyond what fiber or radio can do alone.
From Demonstration to Deployment: CubeSats and HAPS
NICT’s not stopping here. They’re already planning to miniaturize the optical terminals even more, aiming for use on a 6U CubeSat.
By 2026, they hope to pull off 10 Gbit/s optical communication between a Low Earth Orbit (LEO) satellite—about 600 kilometers up—and the ground. Sure, 10 Gbit/s is slower than the 2 Tb/s urban test, but pulling that off over hundreds of kilometers through the atmosphere and space? That’s a real technical mountain to climb, and it’s a crucial step toward making this stuff work for real-world networks.
Toward Ultra-High-Speed Global Connectivity
NICT has its sights set on more demonstrations in 2027. They’re planning to test optical links between satellites and HAPS.
HAPS platforms—think long-endurance aircraft or stratospheric balloons—cruise at about 20 km altitude. These platforms work as airborne communication hubs.
By combining:
NICT wants to open the door to ultra-high-speed global connectivity. This could boost or even skip over traditional fiber and radio networks, which is a big deal for remote or underserved places.
The recent 2 Tb/s free-space optical demo really stands out. It proves that the kind of massive capacities you’d only expect from undersea or land-based fiber can actually reach the sky.
As these systems get better, they’ll help build the backbone for Beyond 5G and 6G. It’s not just about faster internet—it’s about richer services, tougher infrastructure, and maybe, finally, a truly connected world.