A strategy is presented for the dispersion-compensated, flexible upgrading of existing 1310 nm-optimised interoffice fibre networks by using an optical equaliser fibre for dispersion compensation, an erbium-doped fibre amplifier for loss compensation and 1310/1550 nm WDM. This allows an upgrade to higher network capacities including long-distance, multigigabit per second SONET systems as required in future survivable interoffice networks. The feasibility of this concept is demonstrated with dispersion-free transmission at both 1310 and 1550 nm wavelengths over a 60 km conventional singlemode fibre, as well as with dispersion-compensated 1550 nm transmission over a 110 km conventional singlemode fibre at 2.5 Gbit/s.