The excessive attenuation between the TDC and RDC ports results in that the gain of the E3OAU cannot be set.
Product

OptiX BWS 1600G, Huawei OSN3500, Huawei MA5683T
Fault Type

Optical amplifier board
Symptom

In a new project, during network commissioning, the gain of the E3OAU board at a station needs to be enhanced. The gain value should be within the range and can be adjusted. The gain, however, cannot be set no matter through the network management system (NMS) or the command line.
Cause Analysis

According to the query, the output power at the TDC port of the E3OAU board is 10.5 dBm and the input power at the RDC port is -9.5 dBm. The attenuation between the TDC and RDC ports is 20 dB. Therefore, the gain of the board reaches the maximum and cannot be adjusted.
The reason is that the attenuation between the TDC and RDC ports is excessive.
Procedure

The on-site engineers remove the tail fiber from the DCM module between the TDC and RDC, reconnect the OAU, and then re-query the gain. The re-query shows that the attenuation between the TDC and RDC decreases to about 8 dB. Through the network management system, the gain of the board can be set normally. The fault is ratified.
Reference Information

None.