Hi,
My experience in working with several different ONTs and mini nodes (HG8247H, HG8247, EG8143A5, EG8247H5, HG8012) has shown that the optimal input optical power at 1550nm is in the range of +1 to - 4dBm. All values outside this range lead to degradation of RF parameters - MER and BER.
Output RF lever is from 65dBuV to max about 80dBuV.
Some devices have automatic regulation of the input optical level. But even if they do not, it is unlikely that the input optical power will change after the network is built. It is not like with HFC networks, so that the level changes under external influence.