Yunnan: geostationary satellite sends 1 Gbit/s with a 2-watt laser, challenging Starlink

In the mountains of Yunnan province, researchers pulled off a result that could reshape the future of satellite communications: a geostationary orbiter sent data to Earth by laser at gigabit speeds - from 36,000 kilometres away, using power that feels closer to a night light than a high-end transmitter.

Laser beam instead of radio wave: what happened in China

At the Lijiang Observatory in south-west China, a team led by researchers from the Peking University of Posts and Telecommunications and the Chinese Academy of Sciences received an optical signal coming down from space. The source was a satellite in geostationary orbit - effectively “parked” above a fixed point on Earth - at roughly 36,000 kilometres altitude.

What set the test apart was the choice of link: rather than conventional radio frequencies, the satellite used a 2-watt laser. Even with the huge range and modest power, the researchers achieved a data rate of 1 gigabit per second (1 Gbit/s). According to the study, that is around five times higher than typical Starlink downlink figures, despite Starlink satellites operating in much lower orbits.

"An HD film from Shanghai to Los Angeles in under five seconds - that’s how the team turns its measurements into an intuitive comparison."

That contrast is what makes the demonstration so striking: Starlink satellites circle Earth at altitudes of a few hundred kilometres. The Chinese orbiter transmitted from a distance more than 60 times greater - yet still delivered bandwidth in the same broad class as modern fibre connections.

The hidden final boss: Yunnan’s atmosphere

For laser communications, the real trouble is not the vacuum of space, but the last few kilometres above the ground. As the beam passes into dense atmospheric layers, turbulence and temperature gradients distort the light. The result is a signal that appears to “tremble”, fragment and blur.

The Lijiang team tackled that challenge head-on. Instead of treating the atmosphere as a minor nuisance, they designed the entire ground system around actively suppressing those distortions.

• Location: Lijiang Observatory, Yunnan province, south-west China
• Satellite altitude: approx. 36,000 km (geostationary)
• Transmit power: 2-watt laser
• Achieved data rate: 1 Gbit/s downlink
• Comparison: about five times faster than typical Starlink figures

At the heart of the ground station sat a telescope with a 1.8-metre aperture to collect the incoming beam. Behind it was a sophisticated correction stage built around 357 microscopic mirrors. Each mirror could adjust its shape in real time to compensate for distortions in the arriving light’s wavefront.

How China “reassembled” the beam on the ground

Earlier approaches to laser communications generally relied on either adaptive optics or mode diversity at the receiver. On their own, neither method was sufficient under harsh conditions with strong turbulence. The Chinese team therefore fused both techniques into a two-stage system.

Stage 1: adaptive optics smooths the laser

First, an adaptive-optics system corrected the distortions introduced by the atmosphere. The 357 micro-mirrors reshaped themselves hundreds of times per second, attempting to restore the wavefront as closely as possible to its original form.

Rather than assuming a pristine beam, the design accepts that the light arrives already damaged. The mirrors “bend” that broken-up wave into a comparatively stable structure that the rest of the receiver can work with.

Stage 2: eight channels, three winners

Next, the ground station fed the corrected light through a multi-plane light converter. This component split the signal into eight base modes - eight different spatial light patterns - each handled as its own channel.

Afterwards, the electronics selected the three strongest of the eight channels and combined them to reconstruct the data. In effect, the receiver turns what would normally be a drawback (the beam breaking into fragments) into a benefit: when one portion weakens, other paths can carry the information.

"With this AO–MDR synergy, the share of usable signals rose from 72 to 91.1 per cent - a clear jump in reliability."

The technical label for the method is AO–MDR synergy (Adaptive Optics – Mode Diversity Reception). The key idea is that the receiver no longer depends on a single “ideal” optical path, but instead exploits several real, physically available paths.

Why the great height makes this even more surprising

Geostationary satellites are often seen as dinosaurs in the communications world: dependable, but distant and subject to higher latency. A round trip takes roughly a quarter of a second. That is noticeable for voice calls and online gaming, but far less critical for backbone links and bulk data transport.

The 36,000-kilometre range brings two major drawbacks:

• High attenuation: light spreads out, so intensity falls sharply with distance.
• Long optical path: tiny disturbances accumulate over the journey, especially at the transition into the atmosphere.

That is precisely why a gigabit downlink using only 2 watts feels like a rule-breaker. Traditionally, engineers countered distance with high transmit power and large antennas. This demonstration flips the logic: keep power low and push intelligence into the receiver.

The intended use-case is also telling. The Lijiang installation looks nothing like a compact satellite dish on a balcony; it resembles a heavyweight scientific facility. The experiment is clearly aimed at backbone routes and relay stations that can ingest huge data volumes from space and then distribute them onward via fibre.

What this means for Starlink & Co.

Starlink and other low-Earth-orbit constellations still lean on radio links, relatively large antennas and dense satellite networks. Optical links - laser interconnects - are widely seen as the next step, particularly between satellites to push data laterally around the globe.

The Chinese result suggests that the downlink from very high orbits to Earth can also work via laser, provided the ground segment is sufficiently advanced. That opens up several possible directions:

• Fewer satellites required: a geostationary orbiter covers vast areas, reducing the number of platforms needed.
• Stable position: the ground antenna does not have to track constantly; the satellite appears fixed in the sky.
• Optical backbone nodes: large gateways could aggregate traffic from multiple regions.
• Competition for radio bands: lasers avoid spectrum bottlenecks and cause minimal interference to other services.

For traditional constellations, that creates a new benchmark. They win on low latency and broad availability, while geostationary laser links can appeal through high capacity and long-term stability - supported by a small number of extremely capable ground stations.

Terms worth knowing for this experiment

Adaptive optics: a technique borrowed from astronomy in which deformable mirrors counter atmospheric turbulence. It allows telescopes to achieve much sharper images. The same concept can be applied to communications beams.

Mode diversity reception: the beam is decomposed into multiple spatial modes. Each mode behaves like a separate transmission channel. If one fails, others can still carry the data, improving robustness and range.

Geostationary orbit: an orbit above the Equator in which a satellite completes one revolution every 24 hours - matching Earth’s rotation. From the ground it appears to remain stationary at the same point in the sky.

Where such laser links could matter in future

In the near term, nobody is installing 1.8-metre optics on a typical home. The technology is aimed at specialist applications with heavy data demand:

• Downlinking measurement data from large Earth-observation satellites to a small number of high-performance ground stations
• Connecting remote regions to national fibre backbones via optical relay links
• Secure high-speed routes for government and military communications
• Backup paths for critical infrastructure when undersea cables are disrupted

In parallel, teams worldwide are working on shrinking the hardware. Smaller telescopes, integrated photonics and AI-assisted correction could eventually enable more compact terminals - for ships, research outposts or large corporate sites.

One risk remains the dependence on weather: dense fog, heavy cloud or intense rain can severely weaken laser links or make them temporarily impossible. Many concepts therefore assume hybrid solutions, where radio and laser channels operate side-by-side and provide mutual resilience depending on conditions.

For now, the Yunnan experiment demonstrates one thing above all: when engineers prioritise the “last kilometres” through the air, it becomes possible to pull impressive data rates from space with surprisingly little power. That sets a new reference point for anyone aiming to use space as a data motorway - Starlink included.