Huawei HG8245T Router Manual PDF (Setup & Configuration Guide)

Page 411 / 429 Scroll up to view Page 406 - 410

Step 4

Such a fault does not recur in the next week.

----End

Suggestion and Conclusion

It is recommended that you connect an SC/PC connector to an SC/PC connector (or an SC/APC

connector to an SC/APC connector). The biggest difference between an SC/PC connector and

an SC/APC connector lies in that the endface of an SC/PC connector is a plane but the endface

of an SC/APC connector is a slop. If an SC/PC connector is connected to an SC/APC connector,

at least 3 dB attenuation will be generated.

TC-C6208 ONU Frequent Going Online and Offline Because of a Too Small Fiber

Bend Radius

This topic describes how to troubleshoot the fault of ONU frequent going online and offline.

Fault Type

Abnormal ONU connection

Keyword

Bend radius

ONU frequent going offline

ONU frequent going online and offline

Fault Description

Network topology: Optical split level: one level; split ratio: 1:32; backbone fiber: 8.6 km long;

branch fiber: 1.5 km long

In an office, an ONU frequently goes online and offline.

Alarm Information

LOSi alarm and LOFi alarm

Possible Cause

l

The ONU receive optical power is larger than the overload optical power.

l

The ONU receive optical power is smaller than the sensitivity.

l

There is abnormal attenuation on ODN lines.

Procedure

Step 1

Test the receive optical power on ONU optical ports. It is found that the receive optical power

is only -28 dBm. This indicates that there is abnormal attenuation on ODN lines.

Step 2

Check field conditions. It is found that fibers are placed disorderly, the fiber bend radius is too

small and the fiber is almost broken, as shown in

Figure 5-22

.

EchoLife HG8010/HG8240B/HG8245T/HG8247T GPON

Terminal

Service Manual

5 Maintenance and Troubleshooting

Issue 01 (2011-10-18)

Huawei Proprietary and Confidential

403

Page 412 / 429

Figure 5-22

Too small fiber bend radius

Step 3

Replace the fiber and test the ONU receive optical power again. -18 dBm optical power is

obtained and services recover. This indicates that the too small fiber bend radius causes abnormal

attenuation on ODN lines and consequently causes the ONU to go online and offline frequently.

Step 4

Such a fault does not recur in the next week.

----End

Suggestion and Conclusion

Make sure that the fiber bend diameter is larger than 8 cm when bending a fiber.

TC-C6214 ONU Frequent Going Online and Offline Because of a Too Large Split

Ratio

This topic describes how to troubleshoot the fault of ONU frequent going online and offline.

Fault Type

Abnormal ONU connection

Keyword

Split ratio

ONU frequent going offline

ONU frequent going online and offline

Fault Description

Network topology: Originally, the system uses one-level optical split and the split ratio is 1:8.

Later, the customer connects a 1:16 optical splitter to the 1:8 optical splitter. The three ONUs

are connected to the 1:16 optical splitter.

During deployment in an office, three ONUs frequently go online and offline.

Alarm Information

None

EchoLife HG8010/HG8240B/HG8245T/HG8247T GPON

Terminal

Service Manual

5 Maintenance and Troubleshooting

Issue 01 (2011-10-18)

Huawei Proprietary and Confidential

404

Page 413 / 429

Possible Cause

l

The ONU receive optical power is larger than the overload optical power.

l

The ONU receive optical power is smaller than the sensitivity.

l

There is abnormal attenuation on ODN lines.

Procedure

Step 1

Test the ONU receive optical power. It is found that the receive optical power of the three ONUs

is approaching the sensitivity.

Step 2

Analyze the total split ratio of the three ONUs. It is found that the total split ratio is 1: (16 x 8)

= 1:128, which is too large and therefore causing too large attenuation, as shown in

Figure

5-23

.

Figure 5-23

Too large split ratio

Step 3

Change the 1:16 optical splitter to a 1:4 one. Then, the fault is rectified.

Step 4

Such a fault does not recur in the next week.

----End

Suggestion and Conclusion

Bit errors will occur on an ONU if the ONU receive optical power is approaching the sensitivity

and even the ONU may go offline. Reserve a 3 dBm attenuation margin in ODN planning.

EchoLife HG8010/HG8240B/HG8245T/HG8247T GPON

Terminal

Service Manual

5 Maintenance and Troubleshooting

Issue 01 (2011-10-18)

Huawei Proprietary and Confidential

405

Page 414 / 429

NOTE

The specifications of the optical path attenuation are as follows (the following are theoretical values and

the actual values vary with the environment):

l

The optical attenuation on the ONU GPON port should be within the range of 15 dBm to 25 dBm.

l

The attenuation on an optical fiber is about 0.3 dB per kilometer.

l

The attenuation for an optical splitter is as follows:

l

1:2 optical splitter: 3 dBm

l

1:4 optical splitter: 6 dBm

l

1:8 optical splitter: 9 dBm

l

1:16 optical splitter: 12 dBm

l

1:32 optical splitter: 15 dBm

l

1:64 optical splitter: 18 dBm

TC-C6217 ONU Frequent Going Online and Offline Caused by a Rogue ONU

This topic describes how to troubleshoot the fault of ONU frequent going online and offline.

Fault Type

Abnormal ONU connection

Keyword

Rogue ONU

ONU frequent going online and offline

ONU frequent going offline

Fault Description

All ONUs connected to a port in an office frequently go online and offline after a flood.

Alarm Information

Rogue ONU alarm

Possible Cause

l

The ONU receive optical power is larger than the overload optical power.

l

The ONU receive optical power is smaller than the sensitivity.

l

There is abnormal attenuation on ODN lines.

Procedure

Step 1

After communicating with the customer, we learn that there was once a flood in this office and

some ONUs are flooded.

Step 2

Analyze the condition. Only certain ONUs are flooded. This should not cause all ONUs to go

offline repeatedly. It is concluded that the optical modules of certain ONUs transmit signals

abnormally because of flood and the ONUs become rogue ONUs.

EchoLife HG8010/HG8240B/HG8245T/HG8247T GPON

Terminal

Service Manual

5 Maintenance and Troubleshooting

Issue 01 (2011-10-18)

Huawei Proprietary and Confidential

406

Page 415 / 429

Step 3

Check optical lines one by one near the optical splitter. It is found that one ONU works in the

continuous mode, as shown in

Figure 5-24

.

Figure 5-24

Rogue ONU

Step 4

Replace the ONU. System services recover.

Step 5

Such a fault does not recur in the next week.

----End

Suggestion and Conclusion

In normal conditions, ONU signal transmit timeslots are controlled by the OLT. A rogue ONU

is an ONU that goes out of control of the OLT and works in the continuous mode or irregular

mode. If a rogue ONU is detected, replace it in time.

5.8.5 Other ONU Faults

This topic describes how to troubleshoot other common ONU faults.

TC-C6008 Alarms About the Loss of GEM Cells Are Generated on an OLT Because

of Very Large Receive Optical Power of an ONT

This topic describes how to troubleshoot the fault when alarms about the loss of GEM cells are

generated on an OLT because the receive optical power of an ONT is very large.

Fault Type

ODN

Keyword

Optical power

Fault Description

An ONT in an office works normally and can register with an OLT normally. Alarms such as

the loss of GEM cells, however, are generated on the OLT.

EchoLife HG8010/HG8240B/HG8245T/HG8247T GPON

Terminal

Service Manual

5 Maintenance and Troubleshooting

Issue 01 (2011-10-18)

Huawei Proprietary and Confidential

407

Rate

Popular Huawei Models

Famous Router IPs

Famous Router Companies

Bookmark Our Site

Share