Fault Description
Network topology: Optical split level: one level; split ratio: 1:32; connector: SC/APC connector. In an office, an ONU frequently goes online and offline.
Alarm Information
LOSi alarm and LOFi alarm
Possible Cause
l The ONU receive optical power is larger than the overload optical power.
l The ONU receive optical power is smaller than the sensitivity.
l There is abnormal attenuation on ODN lines.
Procedure
Step 1 Test the receive optical power on ONU optical ports. It is found that the receive optical power is -27 dBm. This indicates that there is abnormal attenuation on ODN lines.
Step 2 Perform a test on the optical splitter. It is found that the connector of the optical splitter is an SC/APC connector but that of the ONU fiber is an SC/PC connector. When an APC-endface fiber is connected to a PC-endface fiber, at least 3 dB attenuation will be generated, as shown inFigure 1.
Figure 1 Interconnection of PC and APC connectors
Step 3 Remove the SC/PC fiber (blue) and splice it to an SC/APC fiber (green). Test the ONU receive optical power again. It is found that the receive optical power becomes -23.5 dBm, which is within the normal range. This indicates that the mismatching fiber connector causes abnormal attenuation on ODN lines and consequently causes the ONU to go online and offline frequently.
Step 4 Such a fault does not recur in the next week.
—-End
Suggestion and Conclusion
It is recommended that you connect an SC/PC connector to an SC/PC connector (or an SC/APC connector to an SC/APC connector). The biggest difference between an SC/PC connector and an SC/APC connector lies in that the endface of an SC/PC connector is a plane but the endface of an SC/APC connector is a slop. If an SC/PC connector is connected to an SC/APC connector, at least 3 dB attenuation will be generated.
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