Flexibility Level Adjustment in Reconfigurable WDM-TDM Optical Access Networks

Optical access networks have been widely adopted to support the exponential growth in bandwidth demand. To further fulfill the growth efficiently, reconfigurable wavelength division multiplexing-time division multiplexing optical access networks have been proposed in which optical network units can be reallocated to another wavelength on demand. Thus, the reconfigurability allows dynamic sharing of both wavelengths and timeslots. However, it requires a substantial addition to capital expenditure per user, which is prohibitive in access networks. This paper investigates an approach to preserve the merits of reconfigurability while significantly reducing the network complexity, thus cost by adjusting the level of flexibility. We define a parameter designated as the degree of flexibility to indicate the level of flexibility of a network. Then, we evaluate the performance of various degrees of flexibility based on the traffic capacity and the power consumption. The results suggest that introducing limited wavelength flexibility to the network significantly improves the performance in comparison to the static network while a highly or fully flexible network can further improve the performance but with smaller additional margins. Finally, we apply this result to a well-known reconfigurable architecture, the broadcast-and-select, to illustrate how the limited flexibility can help to reduce the network cost in terms of the optical power budget.