Huawei NetEngine 8000 M14 Quick Installation Manual page 22

Appendix Inspecting and Cleaning
Optical Fiber Connectors and Adapters
Since the 50G optical module link uses the PAM4 encoding tech-
nology, there are higher requirements on the optical fiber and
cable quality and the link is more sensitive to multipath reflection
interference of signals. If the fiber link connector, fiber section, or
fiber splicing surface is dirty, optical signals are reflected back
and forth on the fiber link, causing interference due to co-chan-
nel noise on the receive side. As a result, the optical link is unsta-
ble or intermittently disconnected. To prevent this issue, you need
to check and clean the optical fiber connectors before installa-
tion. For details, see Installation and maintenance > Preparing for
the installation> Inspecting and Cleaning Optical Fiber Connec-
tors and Adapters in the product documentation.