MTK solution GPON ONT/ONU registration process and OMCI analysis
Many ONU/ONT manufacturers now use MTK solutions, such as NOKIA ONT and Youhua Technology’s ONT.
OMCI (Optical Network Unit Management and Control Interface, namely ONU Management and Control Interface) is a protocol for information exchange between OLT and ONT defined in the GPON standard. It is used to manage the ONT in the GPON network, including configuration management, Fault management, performance management and safety management, etc.
As the saying goes, there is no rule without rules. Both Chinese and English have their own grammatical rules. If you receive a letter that does not conform to the grammatical rules, it will be difficult to read and understand. The same is true for the OMCI agreement.
This article aims to introduce the registration of ONT using the MTK solution and an introduction to the OMCI remote protocol.
Enter the serial port to log in: enter the following command to enable the GPON ONU OMCI message debugging command:
ONU activation overview
The activation process of the ONU is controlled by the OLT, and the activation process is roughly as follows:
- ONU receives working parameters through Upstream_Overhead message
- ONU adjusts its own parameters according to the received working parameters (such as: transmit optical power)
- The OLT discovers the serial number of the new ONU through the Serial_Number Acquisition process
- OLT assigns ONU-ID to all new ONUs
- OLT measures the balanced delay of the new ONU
- The OLT transmits the measured balanced delay to the ONU
- The ONU adjusts the starting point of its upstream frame transmission according to the equalized delay
The above activation process is completed by interacting with uplink and downlink flags (flag) and PLOAM messages
a) Initial-state (O1)
The ONU in this state has just been powered on and is still in LOS/LOF. Once downstream is received, LOS and LOF are eliminated, ONU
b) Just shift to the standby state (O2)
The ONU in this state has received the downstream stream and is waiting to receive network parameters. When the ONU receives the Upstream_Overhead message, it will perform the relevant configuration according to these network parameters (such as: delimiter, power mode, preset equalization delay) and transfer to the serial number state (O3)
c) Serial-Number-state (O3)
The OLT sends a Serial-Number Request message to all ONUs in this state to discover new ONUs and
Their serial numbers. When the OLT finds a new ONU, the ONU waits for the OLT to assign it an ONU-ID. OLT pass
Assign_ONU-ID message to assign ONU-ID. After the ONU obtains the ONU-ID, it shifts to the ranging state (O4)
Serial_Number Acquisition process:
First, the OLT suspends the authorization of the upstream bandwidth, which creates a quiet period. After waiting for a period of ranging delay, the OLT sends a Serial_Number Request. After the ONU in the Serial_Number state (O3) receives the Serial_Number Request, it waits for a period of SN-Response-Time (see Section 8.7.1) before sending a response message. After receiving the response message, the OLT sends an Assign_ONU-ID message, and the ONU enters the ranging state (O4). }
First, the OLT generates a quiet period, and then the OLT sends a Ranging Request message to all ONUs. After the ONU receives the Ranging Request message, it waits for the Ranging-Response-Time (see Section 8.7.2) before sending the Serial-Number message. The OLT sends Assign Ranging Time after receiving the Serial-Number message
Message, ONU enters the running state after receiving the Ranging Time message (O5)
d) Ranging-state (O4)
The ONUs with different Assign Ranging Time should keep synchronized when they reach the OLT. For this reason, each ONU needs an equalization delay. This parameter is measured in the ranging state. The ONU shifts to the running state (O5) after receiving the Ranging_Time message.
e) Operation-state (O5)
The ONU in this state can send uplink data and PLOAM messages under the control of the OLT.
The ONU can also establish other connections as required. After the ranging is successful, all ONUs send signals according to their respective equalization delays to keep the uplink frame synchronized. The signals sent by different ONUs will reach the OLT respectively, but each signal will appear exactly where it should appear in the upstream frame.
Suspend the running ONU: During normal operation, the OLT may cause the ONU to suspend sending signals to obtain other ONUs.
Serial number or ranging from other ONUs. The OLT stops granting all the upstream bandwidth for a period of time, and the ONU works in a normal manner. Since it does not receive the authorization, it will not send a signal, resulting in a quiet period. In this way, the OLT makes all ONUs suspend sending signals.
f) POPUP state POPUP-state (O6)
When the ONU in the running state (O5) detects LOS or LOF, it enters this state. ONU in this state
Stop sending signals immediately, so that the OLT will detect the ONU’s LOS alarm.
When the ODN fiber is interrupted, many ONUs will enter this state. Considering the reliability of the network, the following
One of the following methods:
If protection switching is enabled, all ONUs will be switched to the spare fiber. At this time, all ONUs will re-test
For this reason, the OLT sends a Broadcast POPUP message to notify all ONUs to enter the ranging state (O4).
If there is no protection switching but the ONU has internal protection capabilities, the OLT sends a Directed POPUP message to notify the ONU
Enter the running state (O5). When the ONU/ONT enters the O5 state, the OLT needs to detect the ONU first, and then
Restore the ONU’s business.
If ONU does not recover from LOS or LOF, ONU/ONT will not receive Broadcast POPUP message or
Directed POPUP message, the ONU enters the initial state (O1) after TO2 time.
g) Emergency-Stop-state (O7)
When the Disable_Serial_Number message received by the ONU has the “Disable” option, the ONU/ONT enters the emergency stop state (O7) and turns off the laser. In the O7 state, the ONU is prohibited from sending signals. If the ONU fails to enter the O7 state and the OLT can still continue to receive the signal sent by the ONU, the OLT will generate a Dfi alarm.
When the ONU’s fault is eliminated, the OLT sends a Disable_Serial_Number message with the “Enable” option to activate the ONU/ONT. After the ONU/ONT receives the message, it enters the standby state (O2), and all parameters (including serial number and ONU-ID) will be checked again