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A simple single-star multi-ring structure of multi-wavelength optical access network for enlarging network scale and protecting distribution fiber is presented. In this scheme, the ring structure enables optical network units to switch automatically to a protection link when the distribution fiber fails, and a star structure is adopted to weaken the sphere of the distribution fiber failure's influence. The simple combination of these two structures greatly increases the number of subscribers and minimizes costs of network. The network's survivability can also be better than that of a star network or ring network. In addition, it can easily be upgraded from an existing star network, so this article also proposes a method to update the existing star network. The simulation result shows the structure is of good performance.

Dynamic bandwidth allocation (DBA) is of great importance and interest to multichannel passive optical networks (PON). It plays a crucial role in efficiently and fairly allocating the bandwidth among all users. In this paper, we proposed an optimized excess bandwidth distribution algorithm. The excess distribution quota obtained from the algorithm can be adjusted adaptively and can further augment the efficiency and fairness of DBA. The proposed algorithm can effectively prevent excess distribution from bandwidth monopolization and over-allocation. Besides, we formulate a wavelength assignment scheme to eliminate the idle period and increase the bandwidth utilization of the network. Finally, we conduct detailed simulation experiments to research and analyze the performance and demonstrate the effectiveness of the proposed scheme.

WDM/TDM (wavelength-division multiplexing/ time-division multiplexing) PON (passive optical network) appears to be an attractive solution for the next generation optical access networks. Dynamic bandwidth allocation (DBA) plays a crucial role in efficiently and fairly allocating the bandwidth among all users in WDM/TDM PON. In this paper, two dynamic bandwidth allocation schemes (DBA1 and DBA2) are proposed to eliminate the idle time of polling cycles (i.e. polling interval), improve bandwidth utilization and make full use of bandwidth resources. The two DBA schemes adjust the time slot of sending request information and make fair scheduling among users to achieve the effective utilization of polling interval in WDM/TDM PON. The simulation and theoretical analyses verify that the proposed schemes outperform the conventional DBA scheme. We also make comparisons between the two schemes in terms of bandwidth utilization and average packet delay to further demonstrate the effectiveness of the scheme of DBA2.