With the increasing number of services carried by Passive Optical Networks (PON), it has become crucial to quickly restore services after line failures. PON protection switching technology, as a core solution to ensure business continuity, significantly improves network reliability by reducing network interruption time to less than 50ms through intelligent redundancy mechanisms.
The essence of PON protection switching is to ensure business continuity through a dual path architecture of “primary+backup”.
Its workflow is divided into three stages: firstly, in the detection stage, the system can accurately identify fiber breakage or equipment failure within 5ms through a combination of optical power monitoring, error rate analysis, and heartbeat messages; During the switching phase, the switching action is automatically triggered based on a pre configured strategy, with a typical switching delay controlled within 30ms; Finally, in the recovery phase, seamless migration of 218 business parameters such as VLAN settings and bandwidth allocation is achieved through the configuration synchronization engine, ensuring that end users are completely unaware.
Actual deployment data shows that after adopting this technology, the annual interruption duration of PON networks can be reduced from 8.76 hours to 26 seconds, and reliability can be improved by 1200 times. The current mainstream PON protection mechanisms include four types, Type A to Type D, forming a complete technical system from basic to advanced.
Type A (Trunk Fiber Redundancy) adopts the design of dual PON ports on the OLT side sharing MAC chips. It establishes a primary and backup fiber optic link through a 2: N splitter and switches within 40ms. Its hardware transformation cost only increases by 20% of fiber resources, making it particularly suitable for short distance transmission scenarios such as campus networks. However, it should be noted that this scheme has limitations on the same board, and a single point failure of the splitter may cause dual link interruption.
The more advanced Type B (OLT port redundancy) deploys dual ports of independent MAC chips on the OLT side, supports cold/warm backup mode, and can be extended to a dual host architecture across OLTs. In the FTTH scenario test, this solution achieved synchronous migration of 128 ONUs within 50ms, with a packet loss rate of 0. It has been successfully applied to a 4K video transmission system in a provincial broadcasting and television network.
Type C (full fiber protection) is deployed through backbone/distributed fiber dual path deployment, combined with ONU dual optical module design, to provide end-to-end protection for financial trading systems. It achieved 300ms fault recovery in stock exchange stress testing, fully meeting the sub second interrupt tolerance standard of securities trading systems.
The highest level Type D (full system hot backup) adopts military grade design, with dual control and dual plane architecture for both OLT and ONU, supporting three-layer redundancy of fiber/port/power supply. A deployment case of a 5G base station backhaul network shows that the solution can still maintain 10ms level switching performance in extreme environments of -40 ℃, with an annual interruption time controlled within 32 seconds, and has passed MIL-STD-810G military standard certification.
To achieve seamless switching, two major technical challenges need to be overcome:
In terms of configuration synchronization, the system adopts differential incremental synchronization technology to ensure that 218 static parameters such as VLAN and QoS policies are consistent. At the same time, it synchronizes dynamic data such as MAC address table and DHCP lease through a fast replay mechanism, and seamlessly inherits security keys based on AES-256 encryption channel;
In the service recovery phase, a triple guarantee mechanism has been designed – using a fast discovery protocol to compress the ONU re registration time to within 3 seconds, an intelligent drainage algorithm based on SDN to achieve precise traffic scheduling, and automatic calibration of multidimensional parameters such as optical power/delay.
Post time: Jun-19-2025