Huawei HG8245T Router Manual PDF (Setup & Configuration Guide)

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Possible Cause

Judgment Criterion

Troubleshooting Method

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

l

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.

l

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.

l

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.

l

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.

EchoLife HG8010/HG8240B/HG8245T/HG8247T GPON

Terminal

Service Manual

5 Maintenance and Troubleshooting

Issue 01 (2011-10-18)

Huawei Proprietary and Confidential

368

Page 377 / 429

Possible Cause

Judgment Criterion

Troubleshooting Method

The ODN is not properly

planned.

NOTE

l

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.

l

Protocols specify that

the receive optical

power of the OLT

should not exceed 15

dB. In addition, the

difference between the

maximum optical

power and the

minimum optical

power should not

exceed 15 dB.

The ODN does not meet the

requirements of the ODN link

plan or GPON Class B+.

l

Three-level splitting exists

in the ODN.

l

The network coverage of

the ODN exceeds 20 km by

far.

l

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.

l

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 backbone

optical fiber.

EchoLife HG8010/HG8240B/HG8245T/HG8247T GPON

Terminal

Service Manual

5 Maintenance and Troubleshooting

Issue 01 (2011-10-18)

Huawei Proprietary and Confidential

369

Page 378 / 429

Possible Cause

Judgment Criterion

Troubleshooting Method

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.

Step 3

Check for the possible causes on the ONU and troubleshoot the faults accordingly. If the ONU

still fails to be auto discovered by the OLT after that, proceed to

Step 4

.

Possible Cause

Judgment Criterion

Troubleshooting Method

The ONU is not powered

on.

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.

The ONU hardware is

faulty.

If either of the following two

situations occurs, the ONU

hardware is faulty.

l

The LEDs of the ONU are

off when the ONU is

powered on.

l

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.

EchoLife HG8010/HG8240B/HG8245T/HG8247T GPON

Terminal

Service Manual

5 Maintenance and Troubleshooting

Issue 01 (2011-10-18)

Huawei Proprietary and Confidential

370

Page 379 / 429

Possible Cause

Judgment Criterion

Troubleshooting Method

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:

l

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 (-1.5 dBm to +5

dBm).

l

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.

Step 4

Record the results of the preceding steps in the form for reporting a fault, fill in the form

completely, and then submit the form to Huawei for technical support.

Step 5

The fault is rectified.

----End

ONU Frequently Goes Online and Offline

ONUs connected to a GPON port frequently go online and offline and thus the OLT reports a

large number of ONU LOS alarms and relevant recovery alarms.

Location Method

NOTE

An ONU frequently goes online and offline because the OLT receives weak ONU signals. As a result,

packets exchanged between the OLT and the ONU are lost.

When an ONU frequently goes online and offline, locate the fault based on the following fault

symptoms and possible causes.

EchoLife HG8010/HG8240B/HG8245T/HG8247T GPON

Terminal

Service Manual

5 Maintenance and Troubleshooting

Issue 01 (2011-10-18)

Huawei Proprietary and Confidential

371

Page 380 / 429

Fault

Scope

Symptom

Possible Cause

OLT

All the ONUs connected to

a PON port on an OLT

frequently go online and

offline.

The PON port is faulty.

All the ONUs connected to

a board frequently go

online and offline.

The board or the slot is faulty.

ODN

NOTE

ODN

failures

are

generally

caused by

large

reflection

and

attenuatio

n caused

by

improper

optical

compone

nts,

design, or

constructi

on.

A single ONU or some

ONUs connected to an

OLT frequently go online

and offline.

l

The branch fiber is bent excessively.

l

The branch fiber connector is not clean.

l

Different types of branch fiber connectors are

interconnected.

l

The multi-mode optical fiber is used as the

branch fiber.

l

The ODN is not properly planned. For

example, the split ratio, network coverage and

attenuation difference are not planned within

the proper ranges.

l

The optical splitter is faulty or the connectors

on the optical splitter are not clean.

All the ONUs connected to

a PON port on an OLT

frequently go online and

offline.

l

The backbone fiber is bent excessively.

l

The backbone fiber connector is not clean.

l

Different types of backbone fiber connectors

are interconnected.

l

The multi-mode optical fiber is used as the

backbone fiber.

l

The optical splitter is faulty or the connectors

on the optical splitter are not clean.

ONU

A single ONU or some

ONUs connected to an

OLT frequently go online

and offline.

l

A rogue ONU (such as a continuous-mode

ONU) exists on the network and affects other

ONUs.

l

The ONU is restarted repeatedly.

CAUTION

To facilitate fault report, save the results of the following steps.

The parameters of the optical module in this topic comply with Class B+. Note that such

parameters are slightly different from the parameters in Class C.

EchoLife HG8010/HG8240B/HG8245T/HG8247T GPON

Terminal

Service Manual

5 Maintenance and Troubleshooting

Issue 01 (2011-10-18)

Huawei Proprietary and Confidential

372

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