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F.A.Q.s
GPON Doctor reports uLOSb, why?
- GPON Doctor displays this message in the capture window when it expects an upstream burst according to downstream BWMaps (SSTART and SSTOP) and no optical signal is detected in the upstream direction. Please note that uLOSb and uLOFb are not messages exchanged by OLT and ONUs, but an indication generated by the GPON Doctor itself.
- The most common reason for this indication is that the addressed ONU is not connected in the same branch as the GPON Doctor. Other reasons for these notification is that the ONU is not working properly (it is not generating transmissions when indicated by the OLT) or that there are power issues.
- When GPON Doctor includes uLOSb indications in the capture window these are also reflected in the Errors Report as LOSB notifications. When 4 or more of these notifications happen consecutively for the same ONU this will be reported as an “ONU enters in LOSi” Warning.
There are a lot of CRC errors in the capture, why?
- Once transmission errors are discarded (both OLT and ONUs are operating “correctly”) and many CRC errors are still reported by GPON Doctor, the most common reason for these indications is that GPON Doctor is not working in the optimal optical operation range. Either the optical power is under the sensitivity limit or over the saturation point. Please, check the optical power before the capture to ensure GPON Doctor receives adequate optical power.
- Furthermore, some power meters obtain the average measure. In downstream, the value is reliable because the OLT sends a continuous optical signal, but in the upstream, the traffic is based on bursts. Therefore, the optical meters can provide a wrong or tricky measure.
GPON Doctor detects uLOFb, why?
- GPON Doctor displays this message in the capture window when it expects an upstream burst according to downstream BWMaps (SSTART and SSTOP) and although a valid optical signal is received, the delimiter cannot be found. Please note that uLOSb and uLOFb are not messages exchanged by OLT and ONUs, but an indication generated by the GPON Doctor itself.
- Possible reasons for this indication are that the ONU is not working properly (it is not generating transmissions when indicated by the OLT) or that there are power issues.
- When GPON Doctor includes uLOFb indications in the capture window these are also reflected in the Errors Report as LOFB notifications. When 4 or more of these notifications happen consecutively for the same ONU this will be reported as an “ONU enters in LOFi” Warning.
How to reduce the waiting time during the capture analysis
You can optimize GPON Doctor’s processing time by choosing the right capture configuration settings, the appropriate capture method and the right settings for the analysis tool.
How to capture for a long time
The amount of information that can be captured is limited by the memory available in the system. To run a capture for a long time you can limit what type of messages you want to capture. Also select either a Real Time capture or a Store and Display capture (not Full).
Does GPON Doctor detect DOWi?
This alarm is generated by the OLT when it receives an ONU transmission between 4 and 8 bits before or after the expected arrival time. Currently, GPON Doctor is not able to detect this condition with the required precision. On the other hand, GPON Doctor OLT Emulator generates DOWi alarm according to the Standard.