UV-Light for Rapid Data Transfer

UV-light scattering is used for diffuse line-of-sight optical communications. (Source: X. Sun)

Military and civil authori­ties could benefit from secure optical communi­cation systems that use light to carry messages between moving vehicles. Researchers in Saudi Arabia at KAUST have now demonstrated rapid data transfer using ultra­violet-B (UV-B) light, which provides many advan­tages over visible light.

Optical communi­cations systems using visible lasers and light emitting diodes suffer from inter­ference due to the high levels of visible light in sunlight. What’s more, the trans­mitter and receiver must be aligned very precisely, which is very difficult for vehicles on the move. “Accurate beam alignment for point-to-point or line-of-sight optical communi­cation is challenging – slight movements of just a few milli­meters might break the communi­cation link,” says PhD student Xiaobin Sun who worked on the project with Boon Ooi and Slim Alouini and the Chinese Academy of Sciences in Beijing. “This problem motivates us to look for a nonline-of-sight communi­cation system.”

This is where UV-B becomes useful. UV-B from the sun is mostly absorbed by ozone in the upper atmo­sphere, so it doesn’t interfere with communi­cations. Also, UV-B gets scattered in different direc­tions by aerosols and common molecules, meaning the signal spreads out from the source to cover a wide area and accurate alignment of the beam is not required. Sun, Ooi, Alouini and coworkers are developing high-perfor­mance UV-LED sources and highly sensitive detectors that receive UV signals quickly and accu­rately. In their latest work, they used an LED to send pulsed UV-B signals to a sensor comprising two anti­reflective lenses that collect and focus the UV-B light into a photo­detector.

The team observed strong power transmission even when the angle between source and detector was increased up to 12 degrees, demon­strating that direct line-of-sight was not required. Moreover, the system trans­mitted data at a record-breaking rate of 71 megabits per second (Mbps). “Other groups have used different types of UV sources for trans­mitting relatively slow NLOS signals for communi­cations,” says Ooi. “We are the first to achieve multiple tens of Mbps trans­mission using UV-B LEDs.”

Now that they have proven their concept in a low-power system, the team plan to increase the optical power and sensi­tivity until they achieve long-distance nonline-of-sight UV communi­cations with high data transmission rates. “These inter­disciplinary colla­borative efforts between the photonics and communi­cation theory groups at KAUST are paving the way toward the next frontier for optical wireless communi­cation systems,” says Alouini. (Source: KAUST)

Reference: X. Sun et al.: 71-Mbit/s ultraviolet-B LED communication link based on 8-QAM-OFDM modulation, Opt. Exp. 25, 23267(2017); DOI: 10.1364/OE.25.023267

Link: Photonics Lab., King Abdullah Univ. of Science & Technology (KAUST), Thuwal, Saudi Arabia

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