Dying_gasp informs the OLT that the ONU will be turning off in normal operation and that it is not from any defect in the optical
distribution network. This prevents the OLT from issuing unnecessary alarm reports.
C.2.20 Physical_equipment_error (PEE) Message: Both Directions
An OLT will send this PLOAM message once per second when it is unable to transmit GEM frames or OMCI messages.
C.2.21 PST (Protection Switch) Message: Both Directions
If protection switching is available, the OLT can switch all ONUs to the protection fibres. In this event, the OLT sends a broadcast POPUP
message to the ONUs instructing them to move to the Ranging state.
If there is no protection switching, or if the ONU has internal protection capabilities, the OLT can send a directed POPUP message to the
ONU to move it to the Operation state. While in Operation state, the OLT can test the ONU before returning it to full service.
If the ONU does not recover from the LOS or LOF alarms, it will not receive the broadcast or directed POPUP message and will move to
the Initial state following time-out.
C.2.22 Change_power_level Message: Downstream - Unicast or Broadcast
ONUs transmit at their full rated power at all times and this function is rarely if ever used.
C.2.23 PON-ID: Downstream (optional)
Identifies an OLT PON interface and indicates launch power in the message. This enables operators to compare locally measured optical
power with the source launch power in the message to distinguish between fiber plant loss from launch power variations.
C.2.24 Swift_POPUP: Downstream (optional)
The OLT forces all ONUs in the POPUP state that have cleared LOS/LOF alarms to enter Operation state.
C.2.25 Ranging_adjustment: Downstream (optional)
Incrementally adjusts the equalization delay to individual ONUs or all active ONUs simultaneously.
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