The optical fiber connector is not clean. NOTE: An unclean optical fiber connector will cause excessive attenuation and abnormal reflection. | Test the backbone fiber and branch fiber by using the OTDR. It is found that the reflection and return loss are abnormal. Check the optical fiber connector on site by using the optical fiber endface detector. It is found that the optical fiber connector is not clean.
| Clean the optical fiber connector. |
The optical fiber is bent excessively. NOTE: Optical signals attenuate seriously on an optical fiber with an excessively small bending radius. | Test the backbone fiber and branch fiber by using the OTDR. It is found that abnormal return loss points exist on the optical fiber. Check the optical fiber on site. It is found that the optical fiber is bent excessively.
| Route and bundle the optical fiber in a proper manner. |
The optical fiber is not firmly connected or different types of optical fiber connectors are interconnected. NOTE: If the optical fiber is not firmly connected or different types of optical fiber connectors are interconnected, the attenuation and reflection will be excessively large. | Test the backbone fiber and branch fiber by using the OTDR. It is found that abnormal return loss points exist on the optical fiber. Check the optical fiber connectors on site. It is found that the optical fiber is not firmly connected or PC connector (blue) and APC connector (green) are interconnected.
| If the optical fiber is not firmly connected, reconnect the optical fiber firmly. If different types of optical fiber connectors are interconnected, replace the incompatible connector with a compatible one or replace relevant devices, such as the optical splitter.
NOTE: In the scenario of the CATV service, it is recommended that you use APC connectors (green) only. |
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. | Check the backbone fiber and branch fiber by using the OTDR. It is found that optical signals attenuate seriously. 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: 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. 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. 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. 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. |
The ODN is not properly planned. NOTE: 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. The differences between the OLT-received optical power from the two adjacent ONUs must be smaller than or equal to 15 dB.
| The ODN does not meet the requirements of the ODN link plan or GPON Class B+. Three-level splitting exists in the ODN. The network coverage of the ODN exceeds 20 km by far. 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. 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. | Check the backbone fiber by using the OTDR. It is found that a backbone fiber break occurs. Check the optical fiber on site. It is found that the optical fiber is broken or not connected.
| Reconnect the backbone optical fiber. |
A branch fiber break occurs. | Check the branch fiber by using the OTDR. It is found that a branch fiber break occurs. Check the optical fiber on site. It is found that the optical fiber is broken or not connected.
| Reconnect the branch optical fiber. |
