Keywords: WDM products, OptiX OSN 8800
Summary:
If no intra-board cross-connection from the WDM side to the client side is configured for
boards that support intra-board cross-connections, these boards may falsely report TD
alarms when their optical port lasers are turned on.
[Problem Description]
Trigger conditions:
The problem occurs on a board when the following conditions are present:
The board is listed in the table above. No intra-board cross-connection shown in Figure 1
is configured on the board. Specifically, no unidirectional cross-connection from the WDM
side to the client side is configured on the board.
Figure 1 Intra-board cross-connection
WDM side
Pluggable optical modules are used on the board and the optical port lasers are turned on.
Symptom:
TD alarms are reported.
Identification method:
The problem occurs if the trigger conditions and symptom are satisfied.
[Root Cause]
When no intra-board cross-connection shown in Figure 1 is configured on the board, the module
bias current increases. In addition, the laser transmit efficiency decreases when the ambient temperature
increases. To maintain stable module power, the bias current further increases. When the bias current
increases to a value greater than the alarm threshold, TD alarms are reported. The laser transmit efficiency
varies according to modules. Therefore, not all modules have this problem.
[Impact and Risk]
The board falsely reports TD alarms. Consequently, operators may consider that the optical modules are faulty.
[Measures and Solutions]
Recovery measures:
Take either of the following measures:
Turn off the lasers after confirming that no service is deployed.
Configure intra-board cross-connections for the related optical ports.
Workarounds:
Turn on the lasers after configuring intra-board cross-connections.
Preventive measures:
Update the related product manuals. Specifically, add descriptions in the product manuals that intra-board
cross-connections shown in Figure 1 must be configured for the boards listed in the table above if the lasers on
these boards are turned on to test light emitting.
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