Reliable λ-tuning OLT-protection method based on backup-wavelength pre-assignment and discovery process for resilient WDM/TDM-PONs

This paper proposes a novel wavelength-tuning (λ-tuning) optical line terminal (OLT) protection method for wavelength division multiplexing/time division multiplexing-passive optical networks (WDM/TDM-PONs). Since λ-tuning OLT protection achieves redundancy of OLT ports utilizing only the λ-tunability of optical network units (ONUs) that ONUs intrinsically have for colorless operation, no additional equipment such as redundant OLT ports or optical switches is necessary for the protection. The proposed method is based on backup wavelength pre-assignment and a discovery process. Since the backup wavelengths are pre-assigned, the proposed method shortens the service outage time and balances traffic loads among the active OLT ports after OLT protection. Therefore, the proposed method achieves high-level reliability cost-effectively. Through system demonstrations using media access control boards and λ-selective burst-mode transceivers for symmetric 40-Gb/s WDM/TDM-PONs, the validity of the proposal is examined based on the link-up time and throughput measurement for λ-tuning OLT-protection.