Ok thanks for your reply M.Abouseif
Plz make some things more clear for me
1.delays may be used in either of two directions or compulsory for both the directions to add?
2.How we decide how much will be the value of delay to run the bidirectional simulation as i noticed that if “0 delay is set at both the delay unit in both direction” is used in a very simple bidirectional transmission system using bidirectional fiber then there is out put at both output ports of the fiber but if one delay is 0 while other is 1 then there will be output in one port while no output at other port???
Plz elaborate