Should the Nominal Gain of the OAU1 Board Be Re-set?


DSC_6275.JPGShould the nominal gain of the OAU1 board in the OSN 6800 be re-set after the type of the DCM between TDC and RDC is changed?


OptiX OSN 6800

OptiX OSN 3800

Fault Type

DCM Module


In a OptiX OSN 6800 40-channel project, the TN11OAU101 (gain ranges from 20 dB to 31 dB and the per-channel standard output optical power is +4 dBm) is used. In the initial stage, no DCM is configured between optical interface TDC and RDC of the OAU1. The nominal gain of the OAU1 is set to 20 dB on the T2000 and the per-channel input/output optical power is -16 dBm/+4 dBm. In later stages, a DCM(B) (it compensates for 40 km dispersion and the insertion loss is 5 dB) is added between TDC and RDC of the OAU1 because of dispersion issues. In this case, engineers are wondering if the nominal gain of the OAU1 should be re-set on the T2000, so that the per-channel output optical power of the board remains +4 dBm? Or the OAU1 adjusts the gain automatically to ensure that the per-channel output optical power remains +4 dBm?

Cause Analysis



  1. Check if the DCM insertion loss meets the requirement before replacing the DCM.
  2. Allowable DCM insertion loss = Gain of the OAU1 – Nominal gain (the setting on the T2000) If the insertion loss between TDC and RDC is very large and exceeds the adjustment range of the OAU1, the OAU1 reports the VOA_ADJUST_FAIL, which is a minor alarm. In this case, check if the fiber insertion loss is very large. If it is very large, remove the fiber faults.
  3. If the DCM insertion loss meets the requirements and the fiber faults are removed, engineers do not need to re-set the nominal gain on the T2000. The OAU1 adopts the automatic gain control (AGC) mode. The OAU1 monitors the output and input optical power in real time, so that the gain (the difference between the input and output optical power) of the OAU1 keeps the same as the value set on the T2000. Whether TDC and RDC interfaces are connected directly through a fiber jumper or a DCM is added between them, the per-channel input/output optical power is always -16 dBm/+4 dBm and the gain remains 20 dB.

Reference Information


How Can I Obtain the Serial Number of a Fixed Switch?

04-Front_right 30°down 15°

How Can I Obtain the Serial Number of a Fixed Switch?

Log in to the switch through Telnet or the console interface, and then run the display elabel slot slot-id command (slot-id specifies the slot ID of the switch) in the user view to view electronic label information. In the command output, the BarCode field indicates the serial number of the switch.

<Quidway> display elabel slot 0
/$[System Integration Version]  
/$[Board Integration Version]  
/$[ArchivesInfo Version]      
[Board Properties]   

NE ESC Communication Interrupted Because of the Closure of the OTU Laser

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

Fault Type

NE Offline


Optical Transponder Unit


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.


  1. 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.
  2. It is confirmed that the lasers on an OTU board on the upstream peer NE are manually turned off for engineering purposes.
  3. 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).


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