Optical transmission testbed for space-division multiplexing

• Subject Area: Electrical Engineering and Information Technology
• Term: Funded in 2024
• Project identifier: Deutsche Forschungsgemeinschaft (DFG) - Project number 540872185

Optical communication systems form the backbone of the global information infrastructure. For many years, data rates in optical networks have been increasing exponentially. Most recently, the digitization of work, education and leisure, abruptly accelerated by the COVID-19 crisis, has created a further surge in demand for bandwidth. In addition, technologies such as edge computing, connected mobility concepts, and the currently being defined sixth-generation (6G) mobile communications standard will dramatically increase demand for ultra-high-capacity fiber-optic transmission links. To meet this, novel multiplexing techniques are needed that enable sustainable growth in data rates through high-dimensional parallelization of transmission paths. The use of space-division multiplexing (SDM) is one of the most promising techniques to increase data rates in optical fibers by several orders of magnitude compared to the maximum data rate in current standard optical fibers. Such optical fibers can be, for example, multicore or multimode fibers. To explore complete SDM transmission systems, highly spectral-efficient signals are generated, transmitted, and subsequently received. For the generation of coherent optical signals with high symbol rates and polarization multiplexing, an arbitrary waveform generator (AWG) with sampling rates of more than 100 GS/s and four independent data channels is required. Furthermore, laser sources with small linewidth (<100 kHz) and optical modulators with adequate electrical bandwidth are needed to convert the signals from the electrical to the optical domain. Pseudo-decorrelated signals for multiple spatial channels are generated via power splitters and delay optical fibers. Since signals in different spatial paths can couple strongly with each other during transmission, it is necessary to receive them synchronously and store them for further digital signal processing using multiple-input / multiple-output (MIMO) algorithms. Therefore, multiple coherent receivers are needed in combination with a multi-channel real-time oscilloscope. For example, five coherent receivers, a 20-channel oscilloscope and another tunable laser source as a local oscillator are required to receive signals from a strongly coupled optical fiber with five cores. An electrical bandwidth of more than 30 GHz and sampling rates of at least 80 GS/s ensure that the devices are suitable for high symbol rates. The SDM testbed applied for here should also partly consist of portable components. For example, it is planned that the receiver will be installed in a transportable rack and can thus also be used for field tests. The planned SDM testbed is unique in Germany and contributes to the profile of the University of Stuttgart as a leading research university.

• DFG Programme: Major Research Instrumentation
• Major Instrumentation: Optischer Übertragungsmessplatz für räumliche Multiplexverfahren
• Instrumentation Group: 6380 Frequenzanalysatoren, Schwingungsanalysatoren
• Applicant Institution: Universität Stuttgart
• Leader: Professor Dr.-Ing. Georg Rademacher