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Cisco ONS 15454 DWDM Troubleshooting Guide, R7.0.1
78-17742-02
Chapter 1 General Troubleshooting
1.13.2 VOA Failure Scenarios
Note The power setpoint is generated by Cisco MetroPlanner on a case-by-case basis. During the ANS run,
the power target is provisioned on the VOA.
1.13.1.3 Phase 3: Channel Power Setpoint Locking
In Phase 3, the VOA is kept in a transient standby condition when a steady power value close enough to
the final power setpoint has been reached (nominally 3 dBm lower).
The duration of the transient standby condition is three seconds (by default) and allows safe management
of optical interfaces that have different signal rise time values or are undergoing a pulse startup
procedure compliant with the ITU-T G664 recommendation.
1.13.1.4 Phase 4: Channel Power Control Mode Fully Activated
The VOA reaches the final attenuation condition that leads the power value that is read on the photodiode
to the expected target value (VOA Power Reference). Simultaneously, the VOA operating mode switches
to power control mode.
From this point on, any further adjustment of the VOA attenuation is triggered by a variation of the value
read on the photodiode. The aim of these adjustments is to always keep the power value equal to the
power setpoint, with +/– 0.5 dBm as the minimum adjustment increment.
1.13.2 VOA Failure Scenarios
Several conditions can stop the startup procedure at an intermediate step, blocking the VOA (and the
circuit activation, as a consequence) from completing activation of the power control mode. The
scenarios in this section portray those conditions.
Root-cause identification can be performed based on the alarm raised and the power reading on the
photodiode associated with the VOA.
1.13.2.1 Scenario A: Optical Power Level of the Incoming Signal Lower Than Minimum Allowed by
MSTP Supported Optical Interfaces
This scenario is for a condition where a TXP or MXP card is directly connected to a 32MUX-O or
32WSS card where power in is expressed as Pin < –4.5 dBm.
If the incoming power level is lower than the minimum allowed, the startup procedure always stops at
Phase 1 (see Figure 1-33). This is the case even if the final VOA Power Reference reported in CTC is
reachable.
The final conditions that CTC reports are:
• A LOS-P (OCH layer) alarm on the port associated with the VOA (see Figure 1-33)
• A valid optical power value (different from the end of scale value of – 50 dBm) in the Power field,
but the value for Power is less than –33 dBm. (To view the Power field, in card view, click the
Provisioning > Parameters tabs.)
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