Strategies to increase spectral efficiency and energy saving with quality metric assurance in TWDM-PON

We propose a methodology for planning TWDM-PON that combines three lines of approach, known from literature, into a single approach that establishes a trade-off among them. That may support the network designer in finding a solution that can, simultaneously, meet high bandwidth demands, keep assurance of quality of service (QoS) level agreed with users, and increase energy saving of the network by taking into account the users’ activity and bandwidth sharing in the network. To develop the proposed algorithm, two bandwidth management techniques have been analyzed aiming at a possible migration of the end user equipment (optical network unit, ONU), whereas possible, in a more efficient distribution of ONU per wavelength pair (downstream-upstream). As a result, it becomes possible to switch off some management interfaces, thus assuring a degree of energy save. In parallel, two methods for providing an adaptive record of ONUs were aggregated to improve the performance of those ONUs that are migrating and/or entering the network, thus avoiding collision between signals and increasing the chance of their registration in the optical line terminal (OLT). The paper also addresses the fulfillment of the service level agreement (SLA), signed by operators and users, and proposes ways for designing a TWDM-PON that offers services with a quality metric assurance. Different scenarios with variable percentage of active users were considered and it was noticed that, in more realistic scenarios (50%, in average, of active ONUs), the network saved almost 50% of energy at the interfaces to be configured, with a migration period around 5 min. Additionally, it reached a SLA close to 100%, which is above the usual when it comes to compliance services. In addition, to meet bandwidth demand up to 1 Gb/s, the QoS was evaluated in four common Split Ratios (1:8 to 1:64) that the TWDM-PON can be configured, from the simplest to the most complex scenarios (active user, p, from 10% to 100%). In this way, it was verified that for the network to comply with satisfactory QoS, minimum percentage of time during which the target bit rate should be available for each connected user, the TWDM-PON should be planned at different activity levels, and the best planning are (p = 100%, 1:8), (p = 70%, 1:16), (p = 40%, 1:32) and (p = 20%, 1:64).