Hi Priti,
Working with bidirectional fiber with the new OFDM modulator and demod block may not help in correct results because there is a bug in the BER testset tool, which calculates the BER.
Bidirectional design requires you to have number of iterations equal to the amount of bidirectional devices used in the design (for Eg: circulators, fiber etc). But the BER test set block does not work in the iteration mode.
Hope this helps