you should remember that total allowed optical budget from the OLT to the ONT is 28dB. All FTTH design losses from OLT to ONT cannot be bigger than 26,5db (5% margin).In conventional PON based FTTH the minimum transmitter power and minimum receiver sensitivity is set as 0 and -34 dBm.

Alcatel-Lucent 7750
SERVICE ROUTER | RELEASE 13.0.R1
LAYER 2 SERVICES AND EVPN GUIDE: VLL, VPLS, PBB, AND EVPN

Alcatel-Lucent
Service Access Switch| Release 7.0 Rev.07
7 2 1 0 - S A S D , E , K O S
S e r v i c e s G u i d e