A team of Chinese scientists claims a significant breakthrough in satellite communication, transmitting data at an unprecedented 1 Gbps from a geostationary satellite positioned 36,000 kilometers above Earth. What makes this achievement particularly remarkable is the use of a low-power 2-watt laser, a power level comparable to a mere nightlight. This speed is reportedly five times faster than SpaceX's Starlink, despite the Chinese satellite operating from an orbit 60 times higher.
According to reports from the South China Morning Post, the innovative "AO-MDR synergy" method developed by Professor Wu Jian and Dr. Liu Chao is key to this success. This method tackles the long-standing challenge of atmospheric turbulence, which typically distorts and scatters laser signals, making high-speed, long-distance laser communication difficult.
The AO-MDR Synergy Method: A Technical Deep Dive
The "AO-MDR synergy" method ingeniously combines adaptive optics (AO) with mode diversity reception (MDR) to counteract the disruptive effects of atmospheric turbulence. The system employs a 1.8-meter telescope equipped with 357 micro-mirrors. These micro-mirrors dynamically reshape incoming laser light, correcting distortions caused by the atmosphere. Simultaneously, a multi-plane converter splits the incoming light into eight base-mode channels. A specialized "path-picking" algorithm then selects the three strongest signals in real-time and merges them, significantly bolstering the signal strength and reliability.
The results of this synergistic approach are impressive: error rates plummeted to below 10⁻⁵ even under strong turbulence conditions, and the probability of receiving usable signals dramatically increased from 72% to 91.1%. This multiplicative effect was consistently observed across multiple experimental verifications, effectively preventing "communication quality degradation caused by extremely low signal power." This technology represents a major advancement over previous attempts that relied solely on either AO or MDR, neither of which proved sufficient in strong atmospheric turbulence.
Wu Jian's Groundbreaking Laser Achievement
Professor Wu Jian from Peking University of Posts and Telecommunications, along with Dr. Liu Chao from the Chinese Academy of Sciences, spearheaded this pioneering satellite communication experiment at the Lijiang Observatory in southwest China. Their demonstration involved targeting an unnamed satellite located 36,705 kilometers away. The successful transmission of data at 1 Gbps using a laser as dim as a candle highlights the effectiveness of their innovative method.
The implications of Wu's breakthrough are far-reaching. Such speeds could enable the transmission of high-definition movies from Shanghai to Los Angeles in under five seconds. Wu and Liu described their innovation as "a revolution" that "effectively prevents the degradation of communication quality caused by extremely low signal power." This achievement further builds upon China's previous successes in space laser technology, including a 10 Gbps laser downlink from geostationary orbit achieved in 2020 with the Shijian-20 satellite, although the power specifications for that mission remain undisclosed.
Geostationary (GEO) vs. Low Earth Orbit (LEO): A Comparative View
The distinction between Geostationary Earth Orbit (GEO) and Low Earth Orbit (LEO) satellites is crucial to understanding the significance of this Chinese advancement. GEO satellites operate at approximately 36,000 kilometers above Earth's surface, maintaining a fixed position relative to a point on the ground due to their orbital period matching Earth's rotation. This makes them ideal for applications requiring continuous coverage of specific regions, such as broadcasting and weather monitoring.
In contrast, LEO satellites, like those in SpaceX's Starlink constellation, orbit much closer to Earth, typically between 500 and 2,000 kilometers (Starlink operates around 550 kilometers). While LEO satellites offer lower latency and require less power for transmission, they orbit Earth rapidly (completing a circuit in about 90 minutes), necessitating large constellations to ensure continuous global coverage. The immense distance of GEO satellites historically introduces significant signal latency (approximately 1/4 second for a round trip) and power challenges. China's achievement of high-speed data transmission from GEO orbit is particularly noteworthy as it appears to overcome these typical distance-related limitations while retaining the positional advantages inherent to geostationary orbits.
