Resilience in next generation access networks: Assessment of survivable TWDM-PONs

In addressing the requirements of next-generation passive optical networks, the time and wavelength division multiplexed PON (TWDM-PON) has been selected as the next technology solution beyond 10 Gbps PONs. Due to the increased network reach and customer base, many of which are business customers, rapid fault detection and subsequent restoration of services are critical. Fault protection for conventional PONs has previously been extensively explored. Application of these existing schemes is however inappropriate for TWDM-PONs as an increased network reach and customer base necessitate highly sensitive monitoring modules for fiber/device fault detection. The existing use of upstream transmissions as a loss of signal (LOS) indicator at the central office is also unsuitable due to the sleep/doze mode nature of the optical network units. Here, survivable TWDM-PON architectures which combine rapid fault detection and protection switching to provide resilience are proposed. These architectures do not rely on upstream transmissions for LOS activation. Each exploits highly-sensitive monitoring modules with fast-response fault detection and subsequent protection switching and requiring only very low levels of monitoring input power. The maximum achievable network reach and split ratio, and the survivability of all three schemes are analyzed and compared.