Choose WDM transmitter.. open its properties box set its channel to 80 then choose starting frequency and the channel spacing. Set the input power as well. in next tab set RZ or NRZ format and bit rate too . then u choose WDM Mux set its channels to 80 and in next tab individual u define te channel frequencies. the output of the this Mux is given to the transmission fiber. u may set its dispersion characteristics if needed
.. try this