Wireless data transmission via WLAN has become increasingly important in recent years, not only in the private sphere but also in highly automated industry. This is because in the age of digitalization, in which ever larger amounts of data need to be transmitted, the cost of installing and maintaining wired networks is increasing. Wired technologies such as Ethercat or Profibus cannot be used everywhere. Wireless systems are often more suitable - especially for moving plant components or mobile machines. However, many wireless technologies such as WLAN quickly reach their limits in environments with many network participants: they are often too slow and also prone to interference. In industrial environments with many network users, safety applications with fast cycle times can therefore not be reliably operated via WLAN connections. This is because the radio signals can penetrate walls and machine housings and be intercepted by a receiving device within range.

Li-Fi (Light Fidelity) technology, i.e. data transmission using light, solves many of these problems. "Li-Fi uses the globally unregulated spectrum of light," explains Dr. Alexander Noack, Chief Developer at Fraunhofer IPMS. "The available bandwidth of this spectrum is limited solely by the opto-electronic components used for modulation or demodulation, and allows extremely high net data rates." Real-time capability is another feature of the system. Alexander Noack: "WLAN realizes packet-based and asynchronous data transmission. Li-Fi, on the other hand, sends data continuously in a stream. Applications in which data calculation and transmission must not exceed a predetermined time limit can be operated with Li-Fi. Several data links can be set up in parallel using space-division multiplexing without interference between the individual data links. This enables an interference-free industrial environment and a very high density of data transmission cells.

However, Li-Fi technology is subject to a basic requirement: Data transmission only works if the line of sight between the transmitter and receiver is clear. From a data security perspective, this is the biggest advantage. This is because light cannot penetrate walls or other obstacles. This means that data cannot be intercepted from outside.

Whether Li-Fi is an alternative for specific applications can often only be determined through tests under real application conditions. Fraunhofer IPMS offers its customers Li-Fi HotSpots as an evaluation kit for this purpose. Optical data links can thus be set up at a data rate of 1 Gbit/s over a distance of five meters. The module can be integrated into existing systems via a CAT5 cable without any additional effort. The module can be used to set up point-to-point connections in half or full duplex mode. Depending on the application, the HotSpot can be optimized and further developed in terms of size, data rate, data transmission distance and interfaces to meet specific customer requirements. Interfaces such as USB 3.0, Ethernet and Gigabit Ethernet have already been implemented in industrial applications. Various connection types such as point-to-point, point-to-multipoint or multipoint-to-multipoint can also be implemented. Possible applications can be found in moving or rotating systems and wherever cables, slip rings and connectors can only be used to a limited extent or where large amounts of data, such as video data, need to be transmitted for process control.

Embedded World 2018, Hall 3, Stand 123