Huawei HG8245T Router Manual PDF (Setup & Configuration Guide)

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Suggestion and Conclusion

An ONT cannot be connected to an OLT directly. Optical attenuators or optical splitters must

be added between them to ensure that the optical path attenuation ranges from 15 dB to 25 dB.

NOTE

The specifications of the optical path attenuation (the following are theoretical values and the actual values vary

with the environment) are as follows:

l

The optical attenuation on the GPON port on the ONT should range from 15 dB to 25 dB.

l

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

l

After optical signals travel through an optical splitter, the attenuation of the optical signals is as follows:

l

3dB if the splitter is a 1:2 optical splitter.

l

6 dB if the splitter is a 1:4 optical splitter.

l

12 dB if the splitter is a 1:16 optical splitter.

l

15 dB if the splitter is a 1:32 optical splitter.

l

18 dB if the splitter is a 1:64 optical splitter.

TC-C6205 BER Threshold-crossing Alarm of the Physical Coding Sublayer Because

of Loose Fiber Connectors

This topic describes how to troubleshoot the fault when an alarm is displayed indicating that the

BER of the physical coding sublayer exceeds the threshold.

Fault Type

Abnormal ONU connection

Keyword

Physical coding

Bit error ratio

Fault Description

Network topology: Optical split level: one level; split ratio: 1:16; connector: SC/PC connector;

backbone fiber: 1 km long; branch fiber: 600 m long

One ONU of an office kept reporting a large number of the BER threshold-crossing alarm of

the physical coding sublayer in a long term.

NOTE

This troubleshooting case applies to only V800R105C03, V800R202C01, V800R007C00, and

V800R007C01.

Alarm Information

BER threshold-crossing alarm of the physical coding sublayer

Possible Cause

l

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

EchoLife HG8010/HG8240B/HG8245T/HG8247T GPON

Terminal

Service Manual

5 Maintenance and Troubleshooting

Issue 01 (2011-10-18)

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Page 422 / 429

l

The ONU receive optical power is smaller than the sensitivity.

l

There is abnormal attenuation on ODN lines.

Procedure

Step 1

Test results show that the downstream optical power and upstream optical power on the egress

of the optical splitter are -11.7 dBm and -0.3 dBm respectively, and the transmit optical power

and receive optical power of the ONU are 2.7 dBm and -14.7 dBm respectively. Branch fibers

are only 600 m long and have only one connector, but the optical attenuation is 3 dB. This

indicates that there is abnormal attenuation on optical lines, as shown in

Figure 5-25

.

Figure 5-25

Abnormal attenuation on optical lines

Step 2

Remove the inner-side optical fibers of the ONU ODF and insert them back. It is found that fiber

connectors are loose.

Step 3

Test the optical power. It is found that the ONU receive optical power changes to -12.5 dBm,

which is a normal value. Test results show that the loose connectors of the inner-side optical

fibers of the ONU ODF cause abnormal attenuation on optical line. As a result, the BER of the

physical coding sublayer exceeds the threshold.

Step 4

The alarm never occurred in the office in the next week.

----End

Suggestion and Conclusion

Insert an SC/PC fiber connector until hearing a click indicating that the connection is complete.

TC-C6206 BER Threshold-crossing of ONU Upstream Frames Because of Too

Tightly Fastened Fiber Connectors

This topic describes how to troubleshoot the fault when an alarm is displayed indicating that the

BER of upstream frames exceeds the threshold.

Fault Type

Abnormal ONU connection

Keyword

Upstream frames

BER threshold-crossing

EchoLife HG8010/HG8240B/HG8245T/HG8247T GPON

Terminal

Service Manual

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Fault Description

Network topology: Optical split level: one level; split ratio: 1:32; connector: FC/PC connector;

backbone fiber: 8 km long; branch fiber: 600 m long

In an office, an ONU repeatedly reports the BER threshold-crossing alarm of ONU upstream

frames for more than 200 times everyday.

NOTE

This troubleshooting case applies to only V800R105C03, V800R202C01, V800R007C00, and

V800R007C01.

Alarm Information

BER threshold-crossing of ONU upstream frames

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 downstream optical fiber of the optical splitter. It is found that the optical power is -15.7

dBm, which is within the normal range, indicating that the backbone fiber is normal.

Step 2

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

the transmit optical power and receive optical power are 2.5 dBm and -24 dBm respectively.

Branch fibers are only 600 m long and have only one connector, but the optical attenuation is

8.3 dB. This indicates that there is abnormal attenuation on ONU lines.

Step 3

Locate the fault by segment along ONU fibers. It is found that one FC/PC connector is used

between the ONU fibers and the DP point and it is over fastened and difficult to loosen.

Step 4

Loosen the connector and fasten it again. Then, the tested receive optical power becomes -19.3

dBm, which is within the normal range. This indicates that too tightly fastened connectors cause

the abnormal attenuation on ODN lines and consequently cause the BER threshold-crossing

alarm of ONU upstream frames.

Step 5

Such a fault does not occur in the next week.

----End

Suggestion and Conclusion

FC/PC connectors are generally difficult to fasten properly. Therefore, SC/PC connectors are

recommended.

TC-C6209 Too Many Bit Errors on an ONU Because of Poor Fiber Splicing

This topic describes how to troubleshoot the fault of too many bit errors on an ONU.

Fault Type

Abnormal ONU connection

EchoLife HG8010/HG8240B/HG8245T/HG8247T GPON

Terminal

Service Manual

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Keyword

Fiber splicing

Bit error

Fault Description

Network topology: Optical split level: one level; split ratio: 1:32; backbone fiber: 6.4 km long;

branch fiber: 1 km long

In an office, too many bit errors are detected on an ONU.

NOTE

Run the

display statistics ont-line-quality

command to query quality statistics of ONU lines. If this

command is executed for multiple times, the ONU bit error statistics increase, indicating that the ONU has

bit errors.

Alarm Information

None

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 power is -27.3 dBm. Test the downstream

optical power of the optical splitter. It is found that the power is -17 dBm, indicating that there

is abnormal attenuation on ODN lines.

Step 2

Check the optical fiber between the optical splitter and the ONU (the optical fiber is only 1 km

long). No optical connector is found, indicating that the attenuation on the optical fiber may be

caused by fiber splicing.

Step 3

Perform a test using a red pointer. It is found that severe transient interruption of optical signals

occurs on the splicing points. Open the splice box. Visible beads are found on the splicing points,

as shown in

Figure 5-26

.

Figure 5-26

Poor fiber splicing

EchoLife HG8010/HG8240B/HG8245T/HG8247T GPON

Terminal

Service Manual

5 Maintenance and Troubleshooting

Issue 01 (2011-10-18)

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Step 4

The system runs normally in the next week after re-splicing, and the ONU normally goes online.

----End

Suggestion and Conclusion

Check splicing quality after a fiber is spliced. Make sure that the splicing loss is smaller than

0.1 dB.

EchoLife HG8010/HG8240B/HG8245T/HG8247T GPON

Terminal

Service Manual

5 Maintenance and Troubleshooting

Issue 01 (2011-10-18)

Huawei Proprietary and Confidential

417

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