Types and Causes of ONU Faults

- Aug 22, 2019-

Types and Causes of ONU Faults

1. ONU with slot drift

This fault usually results in slot drift of ONU upstream data transmission due to laser aging and other reasons. It may also be the number of downstream OLT bandwidth maps.


Errors are reported to cause ONU transmission slot errors. This kind of fault ONU is difficult to detect. OLT is usually required to monitor the upstream data of ONU in real time and determine whether it sends data in the slot allocated by OLT. For this kind of anomalously luminous ONU, because it mainly affects two adjacent ONUs, besides isolation, it can also increase the protection bandwidth between slots to mitigate its impact on other ONUs.

2. Long luminous ONU

This failure is due to the long time luminescence of the ONU laser, resulting in the whole PON port ONU can not communicate normally. If ONU has strong luminescence, the anomalous luminescence of ONU can be judged by testing the light power at the spectrometer when troubleshooting, but if ONU is weak luminescence, it will be difficult to judge, and the anomalous luminescence of ONU can not be measured at the spectrometer. Only through OLT intervention and specific detection algorithm can anomalous ONU be judged. Usually, the whole PON business will be affected, but due to its fault phenomenon has always existed, to a certain extent, it brings convenience to troubleshooting.

3. Intermittent luminescence

This kind of fault is the most difficult and irregular to judge. It is also the biggest fault of the current network which accounts for the abnormal luminescence of 0NU. Not only the anomalous luminescence of ONU can not be measured at the spectrometer, but also the PON ports need to be observed and monitored for a long time, which brings great challenges to network maintenance.

There are many faults in the network of anomalous light-emitting ONU. There is no perfect mechanism and process to solve the problem. Other operators also have no experience that can be used for reference. In the actual network operation. The author summarizes a set of process and experience in detecting anomalous luminescence ONU. It can effectively solve most of the existing network faults.

Causes of failure

1. Long-term luminescence problems: incorrectly connecting the photoelectric converter to branch optical fibers, the photoelectric converter long-term luminescence; ONU optical module turn off signal abnormal, the turn-off does not turn off, resulting in long-term ONU luminescence; ONU software crash, will also cause long-term ONU luminescence.

2. Coverage interference: For some reason (such as insufficient extinction ratio), individual ONUs emit light in unauthorized slots, which affects the normal business of other ONUs.

3. Overlapping interference problem: Different ONU optical module parameters are inconsistent, which results in partial overlap of upstream optical signals and affects each other's business.

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