Thanks Alitsu ,for ur response .
I simulated the the SPD SAC OCDMA circuit and was able to achieve bit error rate of 10e-12,10e-13 and 10e-22.for user 1,2,3, resp.This seems to be different results as BER should be achieved near by for all user.
The power uptill the receiver demux is same for all three user the FBG i used are uniform,but FBG are giving power at refelective and transmittive end are differnt for the three user .i also tried tuning of the FBG by changing the reflectivity.
how icsn achieve approx same BER at all the three user.
Thanks and regards.