Appendix C
PLOAM Messages In G.984 G-PON
C.1 Activation Process Overview
The OLT controls the activation process that allows an inactive ONU to join or resume operations on the PON by exchanging PLOAM
messages with the ONT/ONU. It sends instructions downstream and receives data upstream from the ONT/ONU. The activation process
is as follows:
An ONU entering the activation process listens to the downstream transmission and receives
PSync and superframe synchronization.
The ONU waits for the Upstream_Overhead PLOAM message, optionally followed by
Extended_Burst_Length PLOAM messages periodically sent by the OLT.
The ONU receives PON operating parameters through the Upstream_Overhead and
Extended_Burst_Length messages.
The ONU announces its existence on the PON by sending a Serial_Number_ONU message.
This is in response to a broadcast serial number request periodically sent by the OLT.
If the ONT is accepted, the OLT will assign an ONU ID with an Assign_ONU-ID message.
The OLT will determine the ranging time (depends on span length), configure (Con
fi
gure_port- ID) and encrypt the Port ID
(Encrypted_port-ID) and BER interval.
Once the ONU is activated, the OLT assigns the ONU Allocation ID (AllocID) and may start sending bandwidth grants to the ONU
Allocation ID.
The ONU adjusts its transmission optical power level using the absence of directed messages from the OLT as a negative
acknowledgment.
The OLT discovers the serial number of a newly connected ONU and sends an Assign_ONU-ID message to assign an ONU-ID to
it.
The OLT issues a serial number request to a newly discovered ONU and times the ONU's response.
The OLT computes the individual equalization delay and assigns it to the ONU using the
Ranging_Time message.
The ONU adjusts the start of its upstream GTC frame clock based on the equalization delay.
The ONU completes activation and starts normal operation.
During normal operation, the OLT monitors the phase and BER of upstream ONU transmissions. The OLT may recalculate and
dynamically adjust an ONU’s equalization delay based on the monitored phase information. Depending on monitored BER information,
the OLT might instruct an ONU to change its optical power level.
C.2 PLOAM Messages
According to ITU-T G.984, many PLOAM messages are sent three times for extra assurance in the activation process. Some messages
require acknowledgement of receipt (ACK) or another type of response from the ONU/ONT and others are one-way messages.
Direction
Message Name
Unicast
Broadcast
ACK
3x
Down
Upstream_overhead
•
•
Down
Extended_burst_length
•
•
Up
Serial_number_ONU
Down
Assign_ONU-ID
•
•
Down
Ranging_time
•
•
Down
Request_password
•
Up
Password
•
Down
Assign_alloc-ID
•
•
•
Up
Acknowledge
Down
Con
fi
gure_port-ID
•
•
•
Down
Encrypted_port-ID
•
•
•
Down
BER Interval
•
•
•
•
MTTplus-420_User_Manual_RevC00
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