NE ESC communication interrupted because of the closure of the OTU laser.
Product

OptiX Metro 6100
OptiX Metro 6040
OptiX BWS 1600G
Fault Type

NE Offline
ECC
Optical Transponder Unit
Symptom

An OptiX Metro 6100 NE at a station is unreachable by the NMS and cannot be manually logged in to. The ESC communication is interrupted and the NMS reports the NE_COMMU_BREAK and NE_NOT_LOGIN alarms.
Cause Analysis

The OptiX Metro 6100 and OptiX BWS 1600G support two types of supervisory channel: optical supervisory channel (OSC) and electrical supervisory channel (ESC). The ESC is transmitted by any OTU. The difference between the OSC and the ESC is that the OSC is transmitted by a dedicated supervisory channel board but the ESC is transmitted by the DCC byte or subcarrier module of the OTU.
When the ESC is used for communication, in the case that only the OTUs are used for connection of two NEs, when the ALS function is enabled or the lasers on the OTUs are turned off forcibly, the communication on the remote NE is interrupted, and users cannot log in to the NE.
Procedure

Analyze the engineering document of the network and query the ECC routing table. It is confirmed that the ESC communication is used for the upstream and downstream NEs of the unreachable NE.
It is confirmed that the lasers on an OTU board on the upstream peer NE are manually turned off for engineering purposes.
An engineer must go to the station and turn on the lasers on the OTUs to restore the communication.
Reference Information

It is not recommended to use the ESC when two NEs are connected through the OTUs.
If the ESC is used for communication, engineers must turn on the lasers of the OTUs forcibly and it is recommended to set Automatic Laser Shutdown to Disabled (Automatic Laser Shutdown for some OTU boards is set to Enabled by default).