The topic of the work presented in this thesis is fibres for 160Gbit/s transmission and above. This thesis entails three parts. First the dispersion compensation requirements and related topics are investigated. Secondly fibre non-linearity is considered with an emphasis on Raman amplification. And last system experiments have been performed. The effect of chromatic dispersion is briefly described and higher order chromatic dispersion is examined in order to establish their relative influence on transmission quality. The pulse distortions of the higher order dispersion can be understood from very simple physical considerations. Dispersion compensation is investigated in order to determine the requirements for dispersion and slope compensation. Tolerance to dispersion and slope of a system is established from basic principles deduced from the non-linear Schr¨odinger equation. Design targets for the dispersion compensating fibres in terms of slope compensation is explored. Finally the issue of determining the dispersion slope and possible curvature of the dispersion compensating fibre has been investigated. Fibre non-linearity pose a threat to system performance and is investigated. In particular Raman enhanced non-linearity is considered since distributed Raman amplification is being widely deployed in laboratories and in the field. However Raman pumping of the dispersion compensating module, i.e discrete Raman amplification, is also emerging, thus making it important to understand the effects of Raman amplification on the non-linearity. System experiments has been performed at both 40Gbit/s and 160Gbit/s using the return to zero, RZ, format. Only single channel experiments are considered in this thesis. The experiments at 160Gbit/s were done on four different types of fibres to compare the performance of the fibres. Raman amplification was tested in the 40Gbit/s experiments and 1280km of transmission was obtained with Raman.