New dynamic optical switching technologies and adaptive transmission techniques will allow increased capacity and flexibility in future core and metro networks. The Optical Networks Group at UCL has carried out research focused on these areas, in collaboration with industry and other university research groups, for over a decade. In this paper, the technical challenges to be overcome in implementing dynamic, high-capacity networks are discussed, and recent results of the group's work are presented. New network architectures based on wavelength-routing and optical burst switching have been proposed and analysed, and the experimental demonstration of burst switching using fast wavelength-tunable lasers is described. High-capacity dense wavelength division multiplexed transmission systems, using advanced regeneration and equalisation techniques, have been studied, both theoretically, and experimentally using a dynamically reconfigurable recirculating fibre loop. Research results on advanced optical signal formats, all-optical 3R regeneration at 40 Gbit/s channel rates, adaptive analogue and digital electronic processing techniques and optical finite impulse response equalisation are presented. Finally, the development of optical performance monitoring technology, a key component of future all-optical networks, is described. The paper concludes with a prediction of future trends in optical communications research.