Cyclic polling-based dynamic wavelength and bandwidth allocation algorithm supporting differentiated classes of services in wavelength division multiplexing （WDM） passive optical networks （PONs） is proposed. In this algorithm, the optical line terminal （OLT） polls for optical network unit （ONU） requests to transmit data in a cyclic manner. Services are categorized into three classes： expedited forward （EF） priority, assured forwarding （AF） priority, and best effort （BE） priority. The OLT assigns bandwidth for different priorities with different strategies. Simulation results show that the proposed algorithm saves a lot of downstream bandwidth under low load and does not show the light-load penalty compared with the simultaneous and interleaved polling schemes.
Current generalized multi-protocol label switching （GMPLS） standards do not include adequate models for wavelength-switched optical networks （WSON） in recovery mechanisms. In this letter, GMPLS/path computation element （PCE） extensions are applied for the restoration of the lightpaths disrupted by collision or optical impairment. A reserved deflection routing scheme is proposed to achieve fast restoration. It uses the expanded PCE component to compute and assign the backup paths for lightpath recovery. Numerical results demonstrate that this scheme is effective and low cost.
We introduce a novel network-coding scheme that can be implemented in all-optical multicast 1 tworks. A simple and successful module based on the all-optical XOR gate is designed to realize the network coding scheme. The module is a key hardware component in realizing the proposed scheme. The working principle and the experimental results of the module are also presented. Experimental results show that the function of the module is sufficient in satisfying the reouirements of the orooosed network codin~ scheme.
Different multicasting schemes in optical packet switched networks are discussed, including the parallel mode, serial mode, and hybrid mode multicasting schemes. Simulated modeling technique is applied to compare the network-level performance of the three multicasting schemes. A conclusion can be drawn from the results that since the hybrid-mode multicasting scheme can increase the multicast success ratio and reduce the packet retransmission times compared with the other two schemes, it is the best choice for delivering multicasting sessions in the optical packet switched networks.
A contention resolution scheme.P-cycle auto-switching（PCAS）.is proposed in wavelength-switched optical networks（WSONs） based on generalized multi-protocol label switching（GMPLS） to solve backward blocking.This system permits the preferable request and switches the other to a backup path generated by the P-cycle.Simulation results show that the PCAS scheme is effective in mitigating backward blocking, especially under concentrated load.
