You’re welcome Gurpreet. On the receiver side, the signal first passes through the same FBGs as it has passed through on the transmitter side before being launched into the channel, and then through the photodetector. And the number of FBG equals the number of wavelengths of the number of weights used. So if W=3, then you should use three FBGs. I suggest that you take a look at optisystem SAC OCDMA sample.