Hello, everyone!
Today I'm going to share with you when the split ratio is too large, causing frequent disconnection of ONUs
Symptom
Networking
The early system uses the first-level splitter with a splitting ratio of 1:8. Later, the customer adds a 1:16 splitter after the 1:8 splitter, and these 3 ONUs are hung on the 1:16 splitter the following.
During the start of an office, it was found that 3 of the ONUs frequently dropped.
Possible Causes
The optical power received by the ONU is greater than the overload optical power.
The optical power received by the ONU is less than the sensitivity value.
There is abnormal attenuation on the ODN line.
Steps
1. Measure the received optical power of the ONU and find that the received optical power of the three ONUs is near the sensitivity.
2. Analyze the total splitting ratio of this 3 ONUs as 1:(16×8)=1:128. The splitting ratio is too large, resulting in too much attenuation. As shown in Figure 1.
Figure 1 Split ratio is too large
3. After changing the 1:16 splitter to 1:4, the problem is solved.
4. The system runs for a week, and the ONU goes online stably.
Conclusions
When the ONU receiving power is close to the sensitivity, the ONU will experience bit errors and even drop the connection. It is recommended to reserve a margin of 3dBm during ODN planning.
Description
Optical path attenuation related specifications (the following are theoretical values, the specific values are related to the environment):
The optical attenuation from the GPON optical port of the ONT equipment should be between 15dB and 25dB.
The attenuation through 1km fiber is about 0.3dB.
After a splitter, the light attenuation is as follows :
1: 2 splitter: attenuation 3dB
1: 4 splitter: attenuation 6dB
1: 8 splitter: attenuation 9dB
1: 16 splitter: attenuation 12dB
1: 32 splitter: attenuation 15dB
1: 64 splitter: attenuation 18dB
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Thank you!
