ONU failure to go online – Problems with ONU (8)

Hi everybody!

This is the last segment about problems with connecting ONU. Before this post, I explained all problems with OLT and ODN. And now, I will detail explain all problems with ONU and how we can fix it.

In the next table, we can see all problems with ONU:

1. Problem with the hardware of the ONU

There are three main problems with the hardware of the ONU.

First, when we power on ONU, it doesn`t work – the indicators on the device don`t work (the power supply is ok).

Second The problem is with the optical module. We can see the indicator on the device for power supply (the LED for POWER is green), but the LED for PON is red. There are more two problems with the optical model – low Tx optical power and poor Rx sensitivity. When ONU has low Tx optical power, it can not connect to the OLT, optical power on the OLT isn`t enough for connecting. And, when ONU has a problem with Rx sensitivity, it can't detect correct optical power and it can't connect to the OLT.

The last problem with hardware is a problem with the power supply. It may happen that there is no electricity at the connection point of the device. Most often, the device's power adapter doesn`t work.

The first two problems are solved by replacing the device. The last problem is solved by changing the power supply in the house or by replacing the power adapter of the device.

2. Problem with pigtail or patch cord

It may happen that there are problems with optical power on the ONU. First, we have to check the optical power on the patch cord and ATB (access terminal box) (pigtail). For checking optical power, we use a PON power meter.

The first step is that we disconnect the patch cord and ONU, and measure optical power on the patch cord. If optical power is low or non-existent, we have to check the optical power on the pigtail. If the optical power is good, the problem is the patch cord. We must change the patch cord.

But if the optical power is still low or non-existent, the problem is probably in the ATB (pigtail, splice, optical adapter, bent fiber, dirty connector). To solve this problem, we can also use VFL. With this instrument, we can easily and quickly determine - bad splice, bent, or cracked fiber. After that, we can easily fix it.

Figure 1. ONT EG8247H5 

(https://e.huawei.com/en/products/enterprise-transmission-access/access/onu/echolife-eg8247h5)

3. Authentication conflicts

If an ONU is installed on the network, whose SN and password already exist, a conflict occurs. This ONU can't connect to the OLT.

The OLT will generate an alarm indicating this problem – 0x2e305015. We can fix this problem when we replace ONU.

4. Incorrect PON port

Sometimes it happens that the ONU connects to the wrong PON port. This means that the ONU cannot connect to the OLT.

Generally, the ONU cannot connect to that wrong port because that port is configured for ONUs that are at greater distances than the default distance between ONU and OLT (greater than 20km).

We can fix this problem, when we connect ONU on the correct PON port.

5. Rogue ONU

If there is a rogue ONU on the PON port to which we connect the new ONU, the rogue ONU may disable the connection. In general, rogue ONUs can transmit a signal constantly or randomly and thus bring all ONUs offline and prevent the connection of new ONUs.

The OLT will generate an alarm 0x2e314021 as soon as it detects the rogue ONU. When the OLT generates an alarm 0x2e314022, this indicates that ONU is a rogue ONU.

When we remove the rogue ONU, the situation is normal for further operation of all ONUs and connecting new ones.

Thank you!

For more information, please click:

ONU failure to go online – Problems with OLT (1)

ONU failure to go online – Problems with OLT (2)

ONU failure to go online – Problems with ODN (3)

ONU failure to go online – Problems with ODN (4)

ONU failure to go online – Problems with ODN (5)

ONU failure to go online – Problems with ODN (6)

ONU failure to go online – Problems with ODN (7)