Performance improvement of optical high-speed short-range communication systems utilizing bandwidth extension and advanced digital signal processing

Christoph Kottke, Technische Universität Berlin, Technische Universität Berlin, Klaus Petermann
2019
High-speed short-range optical links are a key technology for data center applications. Today, they enable the transmission of huge amounts of information in a cost and energy efficient way and are typically based on simple optics and on-off keying modulation. In order to meet the world-wide increasing demand on transmission capacity for these optical links, new approaches are required to improve the currently achievable capacity. In this thesis two strategies are discussed. The first one
more » ... es a bandwidth extension concept based on analog mixing to increase the signal bandwidth beyond the limits of today's signal generators. The second one investigates the application of linear and nonlinear pre-equalization for vertical cavity surface emitting lasers (VCSEL) based links. The bandwidth extension concept is experimentally investigated for a high-speed optical link based on intensity modulation (IM) and direct detection (DD). The achieved transmission rates are well beyond 100 Gb/s showing the feasibility of such an approach. The thesis further includes a detailed investigation of the relevant components, the suitability of different modulation formats and the use of digital signal processing (DSP) to compensate for the system impairments such as inter-symbol interference and in-phase and quadrature (I/Q) imbalance. Furthermore, the demonstration of a wideband digital-analog converter based on this concept is shown. DSP will be one major aspect for future high-speed short-range optical links, enabled by the ever decreasing cost of application-specific integrated circuits (ASIC). Optical links using VCSELs, with their typically non-ideal characteristics, benefit especially from enhanced equalization schemes, which enable an error free transmission at higher symbol rates and the use of higher order modulation formats. Linear and nonlinear pre-equalization are two options to achieve this goal. In this work an optimized linear pre-equalization approach is utilized to demonstrate record high transmission rates for a [...]
doi:10.14279/depositonce-9107 fatcat:mane6ehjvrcyhfdw4vahxqxiii