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This thesis is concerned with the study of dynamic wavelength assignment in wavelength division multiplexed (WDM) passive optical networks (PONs), which is one option for implementing WDM in access networks. A discrete event simulation is developed using the Block Oriented Network Simulator (BONeS) package to compare a WDM PON using dynamic wavelength allocation with one utilizing fixed wavelengths. The model is used in conjunction with a traffic profile constructed using market research data to show bandwidth savings for dynamic assignment of between 4 and 20 % depending on the number of customers and the services distributed. It is shown that the alternative approach of using the Erlang laws underestimates these benefits. An upstream protocol for real-time services with a Fibre To The Cabinet (FTTCab) configuration is developed for single wavelength PONs. It is shown that using connectionbased information does not improve the performance of such a protocol. A segment based protocol which provides timing information on cell arrivals to reduce CDV is modelled and optimized. The results show that a frame of 766 ps divided into 10 segments allows the International Telecommunication Union (ITU) delay and cell delay variation (CDV) targets to be met. The protocol and modelling process is then extended to a WDM system with multiple service classes and non-negligible tuning times. A mechanism for masking tuning latencies which achieves a throughput efficiency of over 98% is designed and modeled. An improvement in performance is then demonstrated for rapid retuning at frame level compared with wavelength assignment at connection set-up. Finally, a new architecture for transferring the tunable devices from the optical network units (ONUs) to the optical line termination (OLT) is proposed. The reduction in the number of tunable components enables cost savings. The efficient transmission of broadcast and multicast traffic is demonstrated using this architecture.