Irfan,
I had written a long response, but apparently it was not posted properly! I’ll post the main points here, but in that project you had been using the white light source, which is I think the correct way to do it.
The main issue is that the white light source was only generating noise bins and not a sampled signal. The proper way is to convert the noise bins, as done in our OptiSystem example in the \Metro and access systems\PON and CDMA systems\ folder.
The other problem is that the signal rate is pretty low when compared to the bandwidth of these SAC-OCDMA systems. Following the Nyquist sampling theorem you need at the sample rate to be at the very least twice the bandwidth of your signal. Your electrical signal is approximately 60 Ghz in bandwidth (in fact a bit more), so the sample rate should be at the very least 120 GHz. I would suggest a bit more. It seems like you have changed the project from the previous topic you made because here the Bit rate is 2.5 GHz.Previously the Bit rate was only about 30 MHz, so I calculated that you would need 8192 Samples per bit to correctly describe this large bandwidth signal. Attached is the previous project.
Some of the filters were also to low to pass the actual signal, so I modified them. I really suggest you try designing systems starting with a back to back configuration, that is no optical fiber and remove the noise generated from the photodetectors. The communication systems are complex and one should always try the simplest transmission scheme before moving on to an actual physical implementation.
Although there are still some details to iron out, the attached project is close to working. Hint: You might want to play with the power levels of the transmitter.
Damian