For the FTTH network designing, the following data can be used to estimate the optical loss of ODN.
OLT optical transmitter Level: －4～2dbm(1490nm)；
OLT optical receiver Level: －28－8dbm(1310nm)；
ONU optical transmitter Level: －4.0～2.0dbm（1310nm）；
ONU optical receiver Level: －24.0～－8.0dbm（1490nm）；
The proposed ODN attenuation: 10～26db, (26dB usually used)；
G.652 Single-mode fiber attenuation: ≤0.34 dB/km（1310nm）；
Fiber splicing loss: 0.1db～0.3db；
Fiber connector insertion loss: ≤0.4db；
1：4 Splitter insertion attenuation: ≤7.1db；
1：8 Splitter insertion attenuation: ≤10db；
1：16 Splitter insertion attenuation: ≤13.8db；
1：32 Splitter insertion attenuation: ≤16.6db；
We usually estimate the loss of ODN at 1310nm window by using the worst value method.