  As passive optical networks (PON) are increasingly deployed to provide high
speed Internet access, it is important to understand their fundamental traffic
capacity limits. The paper discusses performance models applicable to
wavelength division multiplexing (WDM) EPONs and GPONs under the assumption
that users access the fibre via optical network units equipped with tunable
transmitters. The considered stochastic models are based on multiserver polling
systems for which explicit analytical results are not known. A large system
asymptotic, mean-field approximation, is used to derive closed form solutions
of these complex systems. Convergence of the mean field dynamics is proved in
the case of a simple network configuration. Simulation results show that, for a
realistic sized PON, the mean field approximation is accurate.
