Hello,
Today, I would like to share with you a special description of the PON network protection mode one of the security mechanisms of the FTTx network.
The protection modes of PON network mainly have the following four types:
1. Type A: backbone fiber redundancy protection
OLT: Adopt a single PON port, 1×2 optical switch is built in the PON port;
Optical splitter: use 2:N optical splitter;
ONU: No special requirements.
Switching action: the OLT detects the line status, and the switching is completed by the OLT.
Type A mode: backbone fiber redundancy
2. Type B: OLT PON port, backbone optical fiber redundancy protection
OLT: The standby OLT PON port is in cold standby state;
Optical splitter: use 2:N optical splitter;
ONU: no special requirements;
Switching action: The OLT detects the line status and OLT PON port status, and the switching is completed by the OLT.
Type B mode: OLT PON port redundancy
3. Type C: full protection (OLT PON port, backbone fiber, optical splitter, wiring fiber redundancy protection)
OLT: The main and standby OLT PON ports are all in working state;
Optical splitter: use two 1:N optical splitters;
ONU: Built-in optical switch device in front of the PON port;
Switching action: The ONU detects the line status and determines the main line. The switch is completed by the ONU.
Type C mode: full fiber redundancy
4. Type D: full protection (OLT PON port, backbone fiber, optical splitter, wiring fiber redundancy protection, ONU PON port)
OLT: The main and standby OLT PON ports are all in working state;
ONU: Both the primary and backup ONU PON ports are in working state, but only the primary ONU PON carries services, and the backup ONU PON only completes protocol interaction;
Optical splitter: use two 1:N optical splitters;
Switching action: The ONU detects the line status and determines the main line carrying the service. The switch is completed by the ONU.
Type D mode: ONU PON port redundancy
For the four protection modes Type A, B, C, and D, when one of the following conditions occurs, the fiber protection switch must be performed:
Loss of input optical signal (LOS);
Input channel channel degradation (SD):
The input optical signal power is too high or too low;
The bit error rate exceeds the limit;
In the EPON system, when the optical fiber protection switching is performed, the optical channel switching time of the four optical fiber protection types all meets 50ms.
The PON system provides automatic or manual return functions for protected services. For the automatic return method, after eliminating the fault that caused the switching, after a certain return waiting time (WTR), the protected service should automatically return to the original working route, and the return waiting time should be settable.
Considering the protection scope and protection cost, the current mainstream protection mode is Type B, which requires a spare PON port on the OLT, and the splitter needs to be configured with 2:N. The spare fiber is best to achieve physical routing redundancy.
You are welcome to leave a message and exchange in the comment area. Thank you!
