As for as delay is concerned you have to introduce it for simulation purposes of bidirectional fibers.You have to introduce delay for the working of bidirectional fibers on optiwave by using delay element and sweep iteration and index value.
you should refer lesson 5 as the bidirectional topic is discussed in it thoroughly. i hope you will clear your doubts from his lesson.
Also attaching a link for bidirectional-optical-fiber in whcih delay aspect is discussed…..
with regards