Now the simulation is working OK after i make the no of leading and trailing zero from script to normal values.
After that I add SOA at OLT side (before Optical Fiber on both the Downstream and Upstream). but the signal received at ONU side has degraded then before and signal received at OLT side has improved(when compared with the case of not using SOA).
I used Wideband Travelling Wave SOA on default settings. Im working in Optisystem Version7.