Summary:
Short circuit occasionally occurs on the tunable dispersion compensation (TDC) modules of certain batches of 40G boards, which results in dispersion shift on these boards. Severe short circuit even causes service interruption and reporting of the OTU3_LOF alarm.
[Problem Description]
Trigger conditions:
A board listed in Boards at Risk of TDC Short Circuit is used.
Symptom:
The pre-FEC BER performance is occasionally degraded on the WDM side of the 40G boards used on the live network. More severely, the OTU3_LOF alarm is reported and services are interrupted.
Identification method:
You can identify the fault using the SmartKit inspector or manually.
- Identifying the fault using the SmartKit inspector
Use the SmartKit inspector to check the boards for TDC short circuit. For details, see the SmartKit Inspector Tool Usage Guide.
- Identifying the fault manually
In the Navigator, query the TDC status register 5 consecutive times. The query command varies according to the board type.
− For the TN52NS3, TN12LSXL, TN12LSXLR, TN11TDC, and TN11NS3 boards used on the OptiX OSN 6800/8800, run the following command:
:woptp:$bid_hex,1,83,1,f1,03,00,22,44,53,20,53,54,41,0d,0a #$bid_hex indicates the slot ID in hexadecimal notation.
The command output is as follows:
0d 0a 44 53 20 53 54 41 3a 20 4f 4b 0d 0a 3e
Select the output, right-click it, and choose Hex To ASCII:
The following result is displayed:
DS STA: ERR
− For the TN54NS3 and TN11LSQ boards used on the OptiX OSN 6800/8800, run the following command:
:woptp:$bid_hex,1,83,1,f1,03,00,1f,44,53,20,53,54,41,0d,0a #$bid_hex indicates the slot ID in hexadecimal notation.
The command output is as follows:
0d 0a 44 53 20 53 54 41 3a 20 4f 4b 0d 0a 3e
Select the output, right-click it, and choose Hex To ASCII:
The following result is displayed:
DS STA: ERR
− For the boards used on the OptiX BWS 1600G, run the following command:
:nptp: $bid_hex,fe,fe,44,53,20,53,54,41,0d #$bid_hex indicates the slot ID in hexadecimal notation.
The command output is as follows:
ncmd 0: 08 fe fe 00 00 44 53 20 53 54 41 0d 0a 44 53 20 53 54 41 3a
20 4f 4b 0d
Select the output, right-click it, and choose Hex To ASCII:
The following result is displayed:
DS STA: ERR
If “DS STA: ERR” is displayed, TDC short circuit occurs on the board. If other information is displayed, TDC short circuit does not occur on the board. The preceding commands can be run only on the boards listed in the attachment Boards at Risk of TDC Short Circuit.
[Root Cause]
During the manufacturing of the TDC modules of certain batches, the enamelled wire inside the module was damaged because of process control problems. As a result, short circuit occasionally occurs on the module during running after being powered on. Consequently, dispersion shift occurs and the pre-FEC BER performance is degraded on the WDM side. More severely, OTU3_LOF is reported and services are interrupted.
[Impact and Risk]
The pre-FEC BER performance is degraded on the WDM side of the 40G boards where short circuit occurs. In the case of severe short circuit, services are interrupted and OTU3_LOF or OTU_LOF is reported. The estimated failure rate is up to 2.7%, depending on the board batches and environment on the site.
[Measures and Solutions]
Recovery measures:
Replace the malfunctioning board.
Preventive measures:
N/A
Solution:
Identify the boards where short circuit has occurred on their TDC modules based on the information provided in “Identification Method”, and replace the boards.
For the boards used on the live network that are prone to the problem, upgrade the TDC module firmware to 5.43.tmp. For details, see the TDC Module Firmware Upgrade Guide.
The status of TDC modules can be queried and the firmware of TDC modules can be upgraded only for boards used on the following product versions.
Contact the R&D engineers if the product version used on site is not listed in the preceding table.
[Attachments]
Boards at Risk of TDC Short Circuit
TDC Module Firmware Upgrade Guide
Guide to Using SmartKit Inspector to Check for TDC Short Circuit
TDC Upgrade File
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