China has recently announced a major milestone in satellite communications: a 1 gigabit-per-second (Gbps) laser downlink from geostationary orbit (GEO) using a 2-watt optical transmitter. The satellite demonstration was conducted over a distance of 36,000 kilometers (GEO).
The optical communication demonstration demonstrates a major step forward in optical satellite networks. A technology that will likely dominate future high data throughput satellites.
Why Laser Communications Matter
Radio frequency (RF) systems continue to dominate satellite connectivity due to their reliability and maturity. However, as RF spectrum congestion grows and the demand for higher-throughput satellites increases, the industry faces two main options: build and deploy large satellite constellations or invest in optical laser communications.
Optical laser communications allow for: higher bandwidth per link, reduced risk of interference or signal detection, Increased power efficiency, and smaller constellation sizes. These advantages are especially important for GEO satellites, which provide coverage to wide areas from a single position in orbit.
High Performance at Low Power
The research was led by Professor Wu Jian of Peking University of Posts and Telecommunications and Professor Liu Chao of the Chinese Academy of Sciences. Together, the team built what they describe as an AO–MDR synergy communications system:
Component | Function |
357 micro-mirror adaptive optics | Real-time wavefront correction through atmospheric turbulence |
Multi-Plane Light Converter (MPLC) | Splits the incoming beam into eight spatial channels |
Path-picking algorithms | Select the top three coherent modes for reconstruction and signal stability |
This processing pipeline increased the usable signal rate from 72% to 91.1%, allowing performance that previous systems could not sustain under weak-signal, high-turbulence conditions. Rather than achieving bandwidth through higher power, the advancement comes from optics and computation.
China’s GEO Laser System vs SpaceX’s Starlink
SpaceX’s Starlink network uses 3 optical inter-satellite links (ISL) for high-speed routing between satellites but relies on 5 Ku/Ka/E-band antennas for ground connectivity to the end user. China’s unnamed satellite demonstration uses optical downlink direct to Earth (DTE) from GEO, which is a distance of about 36,000 km. For comparison, SpaceX’s Starlink satellites operate in low Earth orbit (LEO) at an altitude of around 550 km.
Property | China’s GEO Laser System | SpaceX Starlink |
Orbit | GEO (36,000 km) | LEO (550 km) |
Ground link | Optical / Laser | RF (Ku/Ka/E-band) |
Demonstrated throughput to ground | 1 Gbps | 50-150 Mbps |
Latency | Higher (200-240 ms) | Lower (20-40 ms) |
Weather sensitivity | High | Lower |
Constellation size | Tens | Thousands |
These systems reflect two different philosophies. Starlink offers a low latency through dense LEO deployment and china’s demo showcases high capacity from a few powerful GEO nodes.
China’s Unnamed Laser Satellite
Although China hasn’t disclosed the satellite’s name, launch site, or launch vehicle, or shared much about its design, there are clues we can draw from past Chinese GEO missions. The level of secrecy suggests the spacecraft may have a dual-use or military-supporting purpose. Its position in geostationary orbit also points to a role in national data infrastructure, where a single satellite can quietly support vast communications networks.
Likely Bus Platform: The DFH-4 / DFH-5 GEO Bus Lineage
China’s large GEO communications satellites are built on the Dongfang Hong (DFH) platform families:
Bus | Launch Mass | Payload Power | First Flight |
DFH-4 | 5,000–5,300 kg | ~8–10 kW | 2006 |
DFH-4E | ~5,200 kg | 10 kW | 2007 |
DFH-5 | 6,500–9,000 kg | 10–30 kW | 2017 |
Shijian-20 | ~8,000 kg | 28 kW | 2019 |
It’s unlikely for China to develop an entirely use satellite bus/platform. Based in the spacecraft’s operational location, power, stability, and payload type, the most likely spacecraft bus used is the DFH-5.
Optical Communication Payload
Despite the 2-watt laser output, the payload would also need to include high-precision optics, adaptive optics computation, beam steering and thermal control, and mode-selection logic in real time. Based on previous components of similar type, the estimated electrical power consumption would be on the order of 100-200 watts and the payload mass is likely on the order of a few hundred kilograms.
Outlook
By demonstrating a stable, high-rate optical connection from GEO with minimal power, China has shown that laser communications are transitioning from experimental to operational relevance. There is no indication this system is immediately intended for consumer broadband. Instead, it appears aimed at the infrastructure layer, the backbone that future space and terrestrial communications may rely on.