Miniaturised FSO tech for high-speed wireless communication

Researchers from Nanjing University have developed a miniaturised free-space optical communication (FSO) system that could optimise high-speed wireless communication. As reported in the journal Advanced Photonics Nexus, this system achieved a communication bandwidth of 9.16 gigabytes per second (GBps) over a one-kilometre link. What sets it apart is that it accomplishes such high FSO performance using readily available commercial fibre optical communication transceiver modules, with no need for optical amplification.

On a global level, FSO is crucial for establishing high-speed satellite internet projects like Starlink, while at the ground level, particularly in low-altitude scenarios, FSO is a suitable option for last-mile connections, disaster recovery efforts and military communications. The core of this miniaturised FSO system comprises a pair of FSO devices. Each device is compact, measuring 45 x 40 x 35 cm, with a weight of 9.5 kilograms and a power consumption of approximately 10 watts. Each houses an optical transceiver module, an acquisition, pointing and tracking (APT) device, and its control electronics, all sealed within a box for outdoor operation. The APT device also features a low-diffraction optical design and an efficient 4-stage closed-loop feedback control system.

The FSO system features multiple sensors and sophisticated algorithms, to enable automatic, fast and accurate acquisition and fine tracking in 10 minutes. This precision keeps the tracking error within three microradians (μrad), resulting in a low average link loss of 13.7 dB over the one-kilometre link. The FSO system can also achieve bidirectional data rates averaging 9.27 GBps over the one-kilometre link, using commercial transceiver modules.

Zhenda Xie, a professor at the NJU School of Electronic Science and Engineering, said the research highlights the potential for achieving FSO using commercially available fibre optical transceiver modules. The effective distance of one kilometre could also be extended, as the researchers also tested the optical links at up to four kilometres, where the average loss increased to 18 dB, potentially due to a foggy test environment. “With better weather conditions and optical amplification, longer FSO can be expected,” Xie said.

This miniaturised FSO discovery could enhance the potential for high-speed wireless communication virtually anywhere. These devices could also play a vital role in the future of FSO networks, offering plug-and-play configurations that can establish high-speed FSO channels in minutes.

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