But he said the only thing active on the return was the node itself.. I can't see anything in the return causing a problem with a digital carrier on the downstream.
What modulation are you using? 64 QAM? Have you checked the constellation , MER and BER at the output of the modulator, combiner, etc? Check everywhere in the headend until it hits the fiber TX. Make sure your Fiber TX is transmitting at proper levels, as a laser clipping issue is typically not picked up in MER readings. You can check this at the node on that downstream digital carrier, perhaps zooming in on one of the quadrants on your constellation display. If your dots are somewhat well defined , look for stray dots. If you have them, your downstream laser is more than likely clipping. Have someone at the headend back off on the TX level slowly until the clipping goes away..
We had a similiar experience a few months back when we migrated to 256 QAM and the digital carrier leaving the combiner read 5.5E - 5 ! Not as bad as your 10 to the 4, but we sure thought it was nasty! If all is good leaving your downstream TX's then have someone OTDR your fiber link with deadzone eliminators on each end to ensure the entire length including connectors, and if all's good start looking at your Node receivers, lid board, launch amp.. etc.. Test equipment leads ? ? lol never can tell.. HOPE THIS HELPS contact me if u need any further help.
Re: Bit Error Rate
Member #: 15503
Registered: 1996-2001
Posted:
26
Name:
Kevin
Occupation:
Equipment refurbishing
Location:
Louisiana
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