Switching Latency Impact on Star-Coupled WDM Photonic Network Pre-Allocation Protocol Performance

This paper evaluates the performance of two pre-allocation protocols when the switching latency of the wavelength tunable optical devices required for WDM networks is not negligible. The channels are pre-allocated to the nodes with the approach, where each node has a home channel that it uses either for all data packet transmissions or all data packet receptions. This approach reduces the resulting system complexity since both tunable transmitters and receivers are not required, and also has the advantage of being applicable to systems where there are many more nodes than wavelength channels. Switching latency is the time required by the tunable optical devices to tune to the required destination wavelength. The performance impact of switching latency on a generalized random access protocol is compared to an approach based on interleaved time multiplexing. Both protocols are designed to operate in a multiple-channel multiple-access environment and require each node to possess a tunable transmitter and a fixed (or slow tunable) receiver. Semi-markov analytic models are developed to investigate the performance of the two protocols. The analytic models are validated through extensive simulation. The performance is evaluated in terms of network throughput and packet delay with variations in the number of nodes, data channels, packet generation rate, and switching latency.