Based on the scenario that the number of wavelengths may be fixed by upgrading the WDM metro ring networks

this paper proposes a new WDM slotted-ring architecture with nodes equipped with one fixed transmitter and a set of fixed receivers.A detailed design and analysis of node architecture and MAC protocol

which aims at achieving fairness among the nodes and efficient bandwidth utilization

is given.It is shown through theoretical analysis and simulation results how the proposed architecture and MAC protocol can achieve a good throughput

queuing delay and packet loss probability.In the case of a large number of wavelengths

or if the number of wavelengths may also increase by upgrading the networks

this paper further proposes an original design method:employing one fixed transmitter and a set of tunable receivers that can only be tuned among partial continuous wavelengths

we show this method can achieve a good tradeoff in terms of performance metrics such as network's throughput

cost and implementing complexity.