Beschreibung
Besides a high data rate and the required reach, one focus of optical transport systems for data center interconnects is a high cost efficiency. In order to achieve this, two different system concepts are presented: on the one hand, single-sideband transmission with direct detection (DD) and wavelength division multiplexing and on the other hand transmission with polarization multiplexing (PolMux) and coherent detection. An optimization of the trade-off between reach and capacity, which is present in all communications systems, can only be achieved to a limited extent with conventional modulation formats such as pulse amplitude modulation (PAM) or quadrature amplitude modulation (QAM) due to their limited resolution. To allow non-integer rational values of bits per symbol, different flexible modulation formats are investigated: the multicarrier technique discrete multi-tone, time-domain hybrid PAM (TDH-PAM) and multidimensional PAM (MM-PAM). The finegranular variation of the data rate at a constant symbol rate and also the variation of the symbol rate at a fixed data rate are investigated in several experiments. For the systems with DD and optical SSBfiltering, different algorithms for the digital signal processing (DSP) are employed. Especially the compensation of nonlinear mixing terms that are caused by DD, can significantly improve the transmission quality. The KramersKronigalgorithm, which allows the reconstruction of the optical field under certain conditions, has shown to be a promising approach. A concept for the implementation of multidimensional PAM in coherent systems with PolMux is also derived and realized in several experiments. In addition, an adaptive DSP-chain is designed, which allows the compensation of different disturbances.
