Failure to Go Online of a GPON ONU

OLT

A single ONU or some ONUs connected to an OLT fail to go online.

·         The SN or password configured on the OLT is different from the actual SN or password of the ONU; hence, the ONU fails to pass authentication and go online.

·         The actual distance between the ONU and OLT exceeds the ranging compensation distance configured on the OLT.

·         The OLT deactivates the ONU.

All the ONUs connected to a PON port of an OLT fail to go online.

·         The laser on the PON port is disabled.

·         The pluggable optical module of the PON is faulty.

·         The PON port is faulty.

All the ONUs connected to a board of an OLT fail to go online.

·         The board or the slot is faulty.

ODN

The PON port reports alarms described in ODN-Related Alarms, including:

·         0x2e11a001 The feeder fiber is broken or OLT can not receive any expected optical signals(LOS)

·         0x2e112007 The distribute fiber is broken or the OLT cannot receive expected optical signals from the ONT(LOSi/LOBi)

ODN failures are generally caused by large reflection and attenuation caused by improper optical components, design, or construction. For details, see .

·         If a single ONU or multiple ONUs fail to go online, the branch fiber and the optical component may have faults.

·         If all ONUs fail to go online, the backbone fiber and the optical component may have faults.

ONU

A single ONU or some ONUs connected to an OLT fail to go online.

·         The ONU is not powered on.

·         The information (including SN and password) for ONU authentication conflicts; hence, the later power-on ONU fails to go online.

·         A rogue ONU exists on the network and affects other ONUs.

·         The ONU hardware is faulty.

·         The optical module of the ONU is faulty.

·         The patch cord of the ONU is broken or bent excessively.

·         The ONU is incorrectly connected to another PON port.

ODN

ODN-Related Alarms, including:

·         0x2e11a001 The feeder fiber is broken or OLT can not receive any expected optical signals(LOS)

·         0x2e112007 The distribute fiber is broken or the OLT cannot receive expected optical signals from the ONT(LOSi/LOBi)

ONT

·         0x2e305015 The authentication information about the ONT is invalid

·         0x2e314021 There are illegal incursionary rogue ONTs under the port

·         0x2e314022 The ONT is rogue ONT

·         0x2e11a00b The dying-gasp of GPON ONTi (DGi) is generated

The SN configured on the OLT is different from the actual SN of the ONU; hence, the ONU fails to pass authentication and to go online.

Run the display ont info command to query the ONU information. It is found that the SN in the result is different from the actual ONU SN.

Run the ont modify command to modify the configured SN or password to be the correct one.

The actual distance between the ONU and OLT exceeds the ranging compensation distance configured on the OLT.

Run the display port info command to query the minimum logical reach (Min distance) and maximum logical reach (Max distance) configured for the GPON port. It is found that the actual distance between the ONU and OLT exceeds the ranging compensation distance.

For example, the actual length of the optical fiber between the ONU and OLT is about 25 km, which exceeds the ranging compensation distance of 0-20 km.

Run the port range command to adjust the minimum logical reach and maximum logical reach so that the actual distance between the ONU and OLT is within the ranging compensation distance.

NOTE:

·         By default, the ranging compensation distance of a GPON port is from 0 km to 20 km.

·         According to Class B+, the maximum logical reach of a GPON port must not exceed 60 km, and the difference between the minimum logical reach and maximum logical reach must not exceed 20 km.

The OLT deactivates the ONU.

Run the display ont info command to query the ONU information. It is found that Control flag is displayed as deactivated.

Run the ont activate command to activate an ONU.

NOTE:

When an ONU is activated, its optical module only receives optical signals but does not transmit optical signals.

The laser on the PON port is disabled.

Run the display port info command to query the information about the PON port. It is found that Admin State is in the Off state.

Run the port laser-switch command to enable the laser on the PON port.

NOTE:

By default, the laser on a GPON port is enabled.

The PON port is faulty.

If either of the following two situations occurs, the PON pot is faulty.

·         Run the display port state command to query the status of the PON port. It is found that abnormal items exist in the query result. For example, the laser status (Laser state) is abnormal and the transmit optical power (TX power) exceeds the normal range (1.5-5.0 dBm).

·         Migrate the service to another port. It is found that the ONU goes online normally.

Replace the optical module of the PON port or replace the board.

The board or the slot is faulty.

All the ONUs connected to the board fail to go online.

Change the board to another slot. If the fault persist, replace the board.

The optical fiber connector is not clean.

NOTE:

An unclean optical fiber connector will cause excessive attenuation and abnormal reflection.

1.    Test the backbone fiber and branch fiber by using the OTDR. It is found that the reflection and return loss are abnormal.

2.    Check the optical fiber connector on site by using the optical fiber endface detector. It is found that the optical fiber connector is not clean.

Clean the optical fiber connector. For details about how to clean the connector, see .

The optical fiber is bent excessively.

NOTE:

Optical signals attenuate seriously on an optical fiber with an excessively small bending radius.

1.    Test the backbone fiber and branch fiber by using the OTDR. It is found that abnormal return loss points exist on the optical fiber.

2.    Check the optical fiber on site. It is found that the optical fiber is bent excessively.

Route and bundle the optical fiber in a proper manner.

The quality of optical fiber splicing is poor. For example, the splicing point has air bubbles.

NOTE:

Poor optical fiber splicing leads to unstable transmission of optical signals. As a result, packet loss occurs.

1.    Test the backbone fiber and branch fiber by using the OTDR. It is found that abnormal return loss points exist on the optical fiber.

2.    Check the optical fiber splicing points by using the magnifying glass on site. It is found that the splicing points have quality problems, for example, air bubbles exist.

Splice the optical fiber again.

The optical fiber is not firmly connected or different types of optical fiber connectors are interconnected.

NOTE:

If the optical fiber is not firmly connected or different types of optical fiber connectors are interconnected, the attenuation and reflection will be excessively large.

1.    Test the backbone fiber and branch fiber by using the OTDR. It is found that abnormal return loss points exist on the optical fiber.

2.    Check the optical fiber connectors on site. It is found that the optical fiber is not firmly connected or PC connector (blue) and APC connector (green) are interconnected.

·         If the optical fiber is not firmly connected, reconnect the optical fiber firmly.

·         If different types of optical fiber connectors are interconnected, replace the incompatible connector with a compatible one or replace relevant devices, such as the optical splitter.

NOTE:

In the scenario of the CATV service, it is recommended that you use APC connectors (green) only.

The multi-mode optical fiber is used as the backbone or branch optical fiber.

NOTE:

If the multi-mode optical fiber is used as the backbone or branch optical fiber, the optical signal attenuates quickly and the return loss increases.

1.    Check the backbone fiber and branch fiber by using the OTDR. It is found that optical signals attenuate seriously.

2.    Check the optical path on site. It is found that the multi-mode optical fiber is used. The multi-mode optical fiber can be recognized by its physical features such as its color.

Replace the multi-mode optical fiber with the single-mode optical fiber.

The optical attenuation of the optical path is excessively small.

NOTE:

·         If the optical attenuation of the optical path is excessively small, the optical power received by the ONU will exceed the overload optical power of the ONU.

·         Such a situation occurs usually in labs, where the OLT and ONU may be directly connected to each other through a short optical fiber.

If either of the following two situations occurs, the optical attenuation of the optical path is excessively small.

·         Measure the receive optical power of the ONU by using the optical power meter. It is found that the actual receive optical power of the ONU is greater than -8 dBm.

·         Check the optical path between the OLT and ONU. It is found that the optical attenuation of the optical path is excessively small. The normal attenuation range is 10-25 dB.

Add an optical attenuator on the optical path between the OLT and ONU.

The ODN is not properly planned.

NOTE:

·         The split ratio of the ODN link is not determined by the number of ONTs connected but by the split ratio of optical splitters. When an optical splitter is connected to the ODN, attenuation occurs and the split ratio of the optical splitter needs to be calculated.

·         The differences between the OLT-received optical power from the two adjacent ONUs must be smaller than or equal to 15 dB.

The ODN does not meet the requirements of the ODN link plan or GPON Class B+.

·         Three-level splitting exists in the ODN.

·         The network coverage of the ODN exceeds 20 km by far.

·         The split ratio exceeds the maximum split ratio that the board allows. Assuming that the maximum split ratio of a board is 1:64. If the first-level split ratio is 1:8 and the second-level split ratio is 1:16, the actual split ratio is 1:128, which exceeds the maximum split ratio of the board.

·         The optical attenuation difference of two optical paths exceeds 15 dB.

Optimize the ODN to meet Huawei’s ODN planning requirements and protocol requirements.

The optical splitter is faulty or the connectors on the optical splitter are not clean.

Measure the input and output optical power of the optical splitter by using the optical power meter. It is found that the actual attenuation exceeds the theoretical attenuation.

NOTE:

The faults in the optical splitter cannot be located by the OTDR because the OTDR cannot penetrate the optical splitter.

Replace the faulty optical splitter or clean the connectors on the optical splitter.

A backbone fiber break occurs.

1.    Check the backbone fiber by using the OTDR. It is found that a backbone fiber break occurs.

2.    Check the optical fiber on site. It is found that the optical fiber is broken or not connected.

Reconnect the branch optical fiber.

A branch fiber break occurs.

1.    Check the branch fiber by using the OTDR. It is found that a branch fiber break occurs.

2.    Check the optical fiber on site. It is found that the optical fiber is broken or not connected.

Reconnect the branch optical fiber

The ONU is not powered on.

If either of the following two situations occurs, the ONU is not powered on.

·         The 0x2e11a00b The dying-gasp of GPON ONTi (DGi) is generated alarm is generated on the OLT, but the corresponding recovery alarm is not generated.

·         Check the power supply of the ONU. It is found that the power supply of the ONU fails or is turned off.

Restore the power supply of the ONU.

A rogue ONU exists on the network and affects other ONUs.

NOTE:

If a rogue ONU exists, the ONU that fails to go online may be a normal one and the ONU that can go online may be a rogue one.

If either of the following two situations occurs, a rogue ONU exists.

·         The 0x2e314021 There are illegal incursionary rogue ONTs under the port alarm is generated on the OLT.

·         The 0x2e314022 The ONT is rogue ONT alarm is generated on the OLT.

·         Remove the optical fiber from the OLT port and connect the optical fiber to the optical power meter for measurement. If a value can be read from the optical power meter, a continuous-mode ONU or irregular-mode ONU exists.

NOTICE:

Measuring the optical power interrupt services, Therefore, it is recommended that you measure the optical power when a PON port does not run any services, such as deployment.

Replace the rogue ONU with a normal one.

The information (SN) for ONU authentication conflicts; therefore, the power-on ONU fails to go online.

The 0x2e10a10b The GPON ONT is discovered by the OLT alarm is generated on the OLT. The alarm cause is that the authentication information (such as the SN and password) about the newly connected ONU conflicts with that of the current ONU.

Replace the ONU with conflicted SN.

The ONU is incorrectly connected to another PON port.

NOTE:

After being configured on the OLT, the ONU can only be connected to the corresponding PON port. If being connected to another PON port, the ONU fails to go online.

The ONU is incorrectly connected to another PON port if either of the following symptoms occurs:

·         The 0x2e10a10b The GPON ONT is discovered by the OLT event is generated on the OLT and the authentication information (such as the SN and password) about the ONU automatically discovered on the PON port is the same as that about the ONU connected to another PON port.

·         The 0x2e305015 The authentication information about the ONT is invalid event is generated on the OLT and the alarm cause is that the SN of the newly connected ONU is the same as that of the ONU configured.

Select one of the following two ways:

·         Retain the connection between the ONU and the PON port. On the OLT, run the ont delete command to delete ONU configurations and then run the ont confirm command to confirm the ONU on the PON port that automatically discovers the ONU.

·         Retain the configurations. Connect the ONU to the PON port that is configured with the ONU.

The ONU hardware is faulty.

If either of the following two situations occurs, the ONU hardware is faulty.

·         The LEDs of the ONU are off when the ONU is powered on.

·         After the ONU is replaced with another ONU, the new ONU is auto discovered by the OLT.

Replace the faulty ONU or the optical module of the ONU.

The optical module of the ONU is abnormal. For example, the transmit optical power of the optical module is excessively small or its receiver sensitivity is low.

Replace the faulty ONU with a normal one. It is found that the new ONU is auto discovered by the OLT.

An alternative is to locate the fault as follows:

·         Set the optical module of the ONU to the continuous mode, and measure the transmit optical power by using the optical power meter. It is found that the actual transmit optical power is beyond the normal range (0.5 dBm to 5.0 dBm).

·         Measure the receive optical power of the ONU by using the optical power meter. It is found that the actual receive optical power is within the normal range (-27 dBm to -8 dBm).

Replace the faulty ONU or the optical module of the ONU.

The patch cord of the ONU is broken or bent excessively.

Check the Patch cord of the ONU. It is found that the Patch cord is broken or bent excessively.

Replace the Patch cord of the ONU.