Remove and reinstall the optical module. If the fault persists, collect log information and contact Huawei technical support personnel. The device management or driver software has a bug. Remove and. Optical modules are widely used in switches, network interface cards (NICs), routers, and other communication devices. Incorrect cable. This topic describes how to troubleshoot common faults in ONU abnormal state, including ONU fail to go online, fail to recover ONU configurations, mismatch of ONU profile, fail to auto discover an ONU, and ONU frequently goes offline. ONU includes HG series ONT and MDU.