Li-fi, a communication technology harnessing visible light for data transmission, has a potential to surpass Wi-Fi's speed by over 100 times and boasts a high bandwidth, faci­litating the simultaneous transmission of copious information. Notably, Li-fi ensures robust security by exclusively transmitting data to areas illuminated by light. Most importantly, it capitalizes on existing indoor lighting infra­structure, such as LEDs, eliminating the need for separate installa­tions. However, imple­menting visible light communi­cation (VLC) in practical lighting systems posed an issue of diminished stability and accuracy in data transmission.

Recently, a collaborative team led by Dae Sung Chung from the Pohang University of Science and Technology (Postech), with researcher Dowan Kim, Dong-Woo Jee and Hyung-Jun Park from the Ajou University, and Jeong-Hwan Lee from the Inha University, succeeded in utilizing indoor lighting for wireless communication by reducing light interference with a novel light source. When light of the same wavelength intersects, inter­ference occurs, resulting in the merging or cancellation of amplitudes. This phenomenon was observed when using LEDs as a single-color light source in VLC techno­logy. To resolve this hurdle, the team developed a novel light source to replace the conventional one. By combining red, green, and blue organic light-emitting diodes (OLEDs), they crafted a light source that mimics standard white illumination but with minimal inter­ference zones.

Furthermore, the team introduced a cavity structure to enhance the OLED’s color representation for each wavelength and incor­porated a Fabry- Pérot structure into the light-absorbing organic photodiodes (OPDs) to selectively receive specific wavelengths of light. The team’s composite white light exhibited a signi­ficantly lower bit error rate (BER) than that of conven­tional light sources. BER, representing the error ratio to the total transmitted bits, serves as a key quantifier of digital signal quality. This remarkable achievement signifies effective suppression of inter­ference among light sources, ensuring accurate information transmission.

Dae Sung Chung, the leader of the consortium, explained, “In contrast to conventional light sources, our light source, which blends three wavelengths, circum­vents interference thereby enhancing stability and accuracy in data trans­mission. We foresee this technology as a potentially beneficial tool for diverse industries, serving as a next-generation wireless communi­cation solution that utilizes conven­tional lighting systems.” (Source: Postech)

Reference: D. Kim et al.: Visible-Light Communication with Lighting: RGB Wavelength Division Multiplexing OLEDs/OPDs Platform, Adv. Mat. 36, 2309416 (2024); DOI: 10.1002/adma.202309416

Link: Dept. of Chemical Engineering, Pohang University of Science and Technology – Postech, Pohang, Republic of Korea