Current WDM Systems in optical networks are commonly operated at 2.5 and 10 Gbit/s per wavelength. First transmission systems, offering the possibility of using 40 Gbit/s/λ transponders, are now commercially available. Transaction of various field trials over the last years indicates remarkable interest for this systems among the network operators. Potential further stages of systems at higher channel data rates e.g. 80, 100 or 160 Gbit/s/λ thus attracted more and more attention in the R&D community. Existing concepts like broadband dispersion compensation, distributed Raman amplification, bandwidth efficient and impairment tolerant modulation formats have been applied, but also new circumstances and physical impairments have to be considered, which are negligible at lower data rates. For data rates above 40 Gbit/s chromatic dispersion causes pulses to broaden extremely rapidly, so that transmission behaviour can be regarded as "quasi-linear". We will present a comprehensive overview to what extend system reach limits can be stressed for 160 Gbit/s/λ data rates when different parameters such as fiber type (standard single-mode fiber SMF and non-zero dispersion fiber NZDSF), modulation format (return to zero RZ, carrier suppressed return to zero CS-RZ, intensity modulated differential phase shift keying IM DPSK), different dispersion compensation schemes and signal power levels are optimized. Further, the benefit from using balanced instead of single ended receiver is investigated for IM DPSK.