A high Bit Error Rate (BER) in 800G optical modules is a multifaceted and complex issue that requires a systematic approach for step-by-step troubleshooting. It is recommended to follow an order from simple to complex to efficiently locate and resolve the problem.
- Check Optical Power and Module Status
Use the command line interface (CLI) to view Digital Diagnostic Monitoring (DDM) information, focusing on transmit and receive optical power. Transmit optical power should not be too low or too high. Receive optical power should be within the range between receiver sensitivity and overload optical power. Abnormal optical power often indicates a link or module fault.
After ruling out link issues, check the equipment port for alarms such as RX-LOS (Receive Loss of Signal) or TX-FAULT (Transmit Fault), and confirm the module is compatible with the equipment. Swapping modules can help determine whether the issue lies with the module or the port.
- Troubleshoot Physical Links and Connections
Physical link and connection problems are common causes of high BER. Dust or oil contamination on the fiber endface can introduce optical loss and reflection, affecting signal quality. Use a fiber microscope to inspect and thoroughly clean the optical ports and jumper cables. Simultaneously, confirm that the fiber type matches the module (e.g., SR8 with multimode, DR8/FR4/LR4 with single-mode), and use an optical power meter to measure insertion loss, ensuring the total loss is within the budget. Also, check for any bending, crushing, or damage to the fiber.
- Verify Equipment Configuration and Firmware Version
800G optical modules often use PAM4 modulation and rely on FEC (Forward Error Correction) functionality for stability. Confirm that the FEC mode is enabled on both ends and try switching modes. Check that the port rate and negotiation mode are consistent, and try switching between auto-negotiation and forced modes. Also, check the firmware versions of both the equipment and the modules, updating them to the latest versions promptly.
- Assess Operating Environment and Perform In-Depth Diagnostics
If the above steps are ineffective, consider environmental factors and use instruments for in-depth diagnostics. 800G modules have high power consumption; poor heat dissipation can cause temperature rise, leading to performance degradation and increased BER. Monitor temperature via DDM and ensure equipment fans and airflow are normal. If the problem persists, use an oscilloscope to observe the signal eye pattern or utilize a Bit Error Rate Tester (BERT) for precise measurement to pinpoint the root cause of the fault.
In summary, addressing high BER issues in 800G modules requires comprehensive consideration of factors such as the link, module, configuration, and environment. A structured troubleshooting strategy is essential to effectively identify and resolve faults.
