Techniques for the planning of multi-service telecommunications networks over a multi-period scenario are proposed, based on routing optimisation to reduce network cost by removing DWDM transmission systems. A model of a medium-size national network is optimised using the various techniques, and the results presented in terms of the total number of DWDM systems required and the amount of wavelength-hops (giving an indication toward the number of optical transponders required). Traffic is taken as a mix between unprotected and 1+1 SNCP optical path protected demands. Traffic growth is applied over the 5 year planning horizon to give a tenfold increase in total traffic volume for the final year. A greenfield situation is assumed, yet since deployment occurs over several years, a present value calculation is used to estimate total cost, assuming that transponders and systems are only installed when they are due to be 'lit'.