NGN Cases Chapter 3 GPON FTTx Cases
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54
Cause Analysi
s:
ONUs connected to other PON ports of the same GPBC board are normal and the fault
is not caused by the optical path. Therefore, the possible causes of the fault are as
follows:
1. The PON port is faulty.
2. The optical splitter is faulty.
3. The ONU is faulty.
Handling Proces
s:
1. Remove optical fibers that connect optical splitters of the first level to all optical
splitters of the second level and directly connect the ONUs to the optical splitters of the
first level. The ONUs go online normally and are stable.
2. Insert optical fibers that connect optical splitters of the first level to optical splitters of
the second level. After the optical fiber that connects an optical splitter of the first level to
an optical splitter of the second level is inserted, the fault recurs.
3. Check the ONUs connected to the optical splitter of the second level one after
another. After the optical fiber that connects the optical splitter to an ONU is removed,
the fault is rectified.
Suggestions and
Summary:
No exception alarm is generated on such faulty ONU and the fault persists after an ONU
is replaced. Therefore, the fault can be located only by excluding possible causes one
after another.
3.15 The ONT Connected to the MA5680T Goes Offline Frequently Due to the Incorrect
Connection of Optical Fibers on the Optical Splitter
Title:
The ONT Connected to the MA5680T Goes Offline Frequently Due to the Incorrect
Connection of Optical Fibers on the Optical Splitter
ID: SE0000364557
Information
Type :
Troubleshooting Cases Quality Level:
C
Keywords: Optical splitter, incorrect connection, frequently, offline
Permission
Level:
01Huawei Engineers Permission
Phenomenon De
scription:
The packet loss of the new ONU connected to the MA5680T is severe, and the ONU
goes offline frequently.
Alarm Informatio
n:
ALARM 9398 EVENT MAJOR 0x2e10700e ----- 2008-03-06 10:53:38
ALARM NAME : Alarm 2 for MAC layer frame error reach the limit
PARAMETERS : FrameID: 0, SlotID: 1, PortID: 3, ONUID: 0
DESCRIPTION : Alarm 2 for MAC layer frame error reach the limit
CAUSE : MAC layer frame error reach the limit of 1.953125*10E-6
Cause Analysi
s:
The threshold alarm for the error frames is generated because of the poor quality of the
line or the ONT.
Handling Proces
s:
1. Query the alarms. It is found that a lot of alarms that the count of the error frames
reaches the threshold are generated on the ONT. Run the display port statistics
command to query the statistics of the port. It is found that the number of the error
packets increases by 200 per second.
After the analysis, it is determined that maybe the problem is caused by the overlarge
optical attenuation or poor ONT quality; however, the distance between the ONT to the
MA5680T is less than 50 meters. Therefore, the line quality should be good.
2. Replace the ONT. It is found that the problem persists.
3. Check the optical path segment by segment. The optical fiber, through primary
splitting, is connected to the suspected ONT from the EPON port. Currently, the EPON
port is connected to only one ONT.
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