Data on UV-C Transmits 1.5 Gbit/s at a Line-of-Sight Distance of 30 cm

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FAULHABER Drive Systems

A team from Berlin, Glasgow, and Cambridge has demonstrated an optical wireless link using far-UV-C LEDs. They achieved a data rate of 1.5 Gbit/s over a line-of-sight distance of 30 cm (11.8 inches). According to the team, this is a record data rate for wireless optical transmission at wavelengths below 235 nm.

Researchers at the Ferdinand Braun Institute (FBH), the University of Strathclyde, and the University of Cambridge have transmitted data at rates of up to 1.5 Gbit/s using far-UV-C micro-LEDs. The LEDs emit light at wavelengths below 235 nm. The experiment was successful over a 30-cm line of sight and under normal room lighting conditions. According to the FBH, this is a record data rate for wireless optical communication in this spectral range.

High Optical Performance and Fast Modulation

The technical approach involves limiting the LEDs as transmitters. The modulation bandwidth is limited, among other things, by the junction capacitance. For this reason, the light-emitting area was divided into smaller segments. This reduces the capacitance of the individual segments and enables faster modulation. Optical OFDM with adaptive bit and power allocation was used for transmission. An avalanche photodiode detected the UV signal on the receiving end.

“We have optimized our LEDs for optical communication in this spectral range,” says Dr. Jan Ruschel, a researcher at the Ferdinand Braun Institute, Leibniz Institute for High-Frequency Technology (FBH). “They deliver high optical power by international standards and can be modulated particularly quickly. This makes them suitable for optical data exchange both indoors and outdoors.”

Over a short distance and with a direct line of sight, a data transmission rate of 1.5 Gbit/s was achieved. The experiment therefore does not yet provide evidence of a comparable data rate over longer distances or in a practical communication system. Furthermore, several issues still need to be resolved for successful implementation, including range, alignment, energy efficiency, and the integration of the transmitter and receiver.

With regard to safety, it is important to note that far-UVC light is not the same as visible light. There is currently no evidence that its use is harmless. For exposure and safety reasons, it is essential to evaluate optical data transmission using such wavelengths.

Transmission without a Direct Line of Sight

Far-UV-C could offer a potential advantage when the transmitter and receiver are not directly aligned with each other. Air molecules scatter short-wavelength light more strongly than long-wavelength light. According to the Rayleigh model, scattering increases significantly as the wavelength decreases. As a result, part of the signal could reach a receiver via scattered paths even if the direct line of sight is obstructed. However, the reliability of non-line-of-sight connections has not yet been confirmed. It is known that scattering weakens the direct signal, and that range and reception depend on the geometry and environmental conditions.

The researchers therefore want to investigate how far-UVC communication can be used over longer distances and without a direct line of sight. Jan Ruschel emphasizes the importance of a practical data rate as a crucial first step. “In the next step, we will investigate over what distances and under what environmental conditions long-range UVC communication can actually be used—and, above all, without a direct line of sight.”

Transmitting Data via Light is Nothing New

Optical data transmission using light is not a new concept.Fraunhofer IPMS’s Li-Fi TinySpot is one example of a low-power, short-range link. At a range of around 25 cm (9.8 inches), it consumes 5 mW of electrical power.

The FBH demonstration takes a different approach. In laboratory tests, a data transfer rate of up to 1.5 Gbit/s was achieved for far-UV-C micro-LEDs at a viewing distance of 30 cm. However, the values are not directly comparable. The TinySpot is designed for low power consumption, whereas the FBH research investigates data transmission using rapidly modulatable, segmented UV emitters. 

Link: 1.5 Gbps Optical Wireless Communications Using Far-Ultraviolet-C Micro-Light Emitting Diodes. (external link)