![VeEX MTTplus-420 Скачать руководство пользователя страница 37](http://html1.mh-extra.com/html/veex/mttplus-420/mttplus-420_user-manual_3827963037.webp)
Once the ONU registration is complete, the MTTplus-420 then uses the bandwidth allocation information contained in the downstream frames in
order to determine when the upstream burst from the ONU will occur and what data it will contain. Should the downstream frame become
corrupted at this point, the upstream frame reception will also therefore be affected.
If the OLT and an active ONU are connected to the MTTplus-420 before starting the test application,
the MTTplus-420 will not see the ONU activation and the above process will not be completed. In this
instance, LOF will be reported for the upstream side; no ONU ID or ONU S/N information on the
OPM results page will be displayed.
7.2 Histogram and OLT Loss History
Tap on 1490nm Histogram, 1310nm Histogram, and OLT Loss (Span Loss) Histogram tabs to Monitor Downstream and Upstream signals. Tap
on t he upper left and right arrows to scroll through the measurement period. The + and – keys zoom in/out of the time axis.
1490nm Histogram showing Downstream signals
OLT Loss Histogram showing Downstream and Upstream signals
MTTplus-420_User_Manual_RevC00
Page 37 of 75