I have came in to several cable systems with this problem with poor C/N on the upstream and 75% of these C/N problems was the return optical reciever was turned up so loud that it raised the noise floor thus poor C/N the other 25% was improperly attenuation at the node / actives
B2
This is CABL.com posting #351383. Tiny Link: cabl.co/mbDzD