Sixth generation (6G) networks require high speed, low latency data transfer to handle bandwidth-hungry, real-time applications such as augmented and virtual reality, 4K and 8K high definition (HD) video streaming, and inter-rack connections in data centres, and potentially holographic displays. However, their performance is hampered by bandwidth limitations, a technological challenge also associated with light-emitting diode (LED)-based optical wireless communication (OWC) systems currently employed.
In response to this challenge, a team of innovative researchers from the LRDC and VI Systems GmbH has successfully experimented with next generation light fidelity (LiFi) technology as a means of leveraging laser-based OWC technologies to provide a viable alternative for delivering expanded bandwidth capacity. Early on, their research identified that, among the various types of laser diodes (LDs) available, vertical cavity surface emitting lasers (VCSELs) are well-suited to realising laser-based OWC, due to outstanding features such as low milliwatt (mW) power consumption, ability to support a wide range of modulation frequencies, well controlled output beam properties and compatibility with two-dimensional (2D) array fabrication. They also offer enhanced reliability and a low cost option.
The team’s subsequent work culminated in a live demonstration of a laser-based OWC link experiment, using a 940 nm single-mode (SM) vertical cavity surface emitting laser (VCSEL) operating at an average optical power of as low as 5 mW. The SM VCSEL was designed, manufactured and packaged by VI Systems, and tested at wafer level before being fully characterised for optical communication. This VCSEL features a unique mini-array structure with a compact footprint to boost the output power while maintaining the SM emission characteristic. To maximise the communication bandwidth, the light beam was coupled into a multi-mode (MM), 25 GHz fibre-coupled receiver by using a large-beam fibre collimator.
This novel approach validated the experimental proof-of-concept, achieving a record data rate in excess of 70 Gb/s, based on orthogonal frequency division multiplexing (OFDM) modulation with adaptive bit and power loading, with an optical transmit power below 5 mW, while also representing a fourfold increase in the data rate attained in previous work by the researchers. It was also verified that the proposed VCSEL-based OWC system can potentially reach data rates beyond 100 Gb/s, provided that measurement equipment with adequate analogue bandwidth is employed.
Delve deeper into this work, and read about the experimental setup and measurement results in-depth, in the following technical paper newly published in the IEEE/Optica Journal of Lightwave Technology: “Achieving 70 Gb/s Over A VCSEL-Based Optical Wireless Link Using A Multi-Mode Fiber-Coupled Receiver” by Hossein Kazemi, Member, IEEE, Isaac N O Osahon, Member, IEEE and Harald Haas Fellow, IEEE, of the LRDC, and Nikolay Ledentsov Jr, Ilya Titkov and Nikolay Ledentsov, Senior Member, IEEE, of VI Systems GmbH.