Hello Hanan,
The Lasers’ wavelength and WDM MUX/DEMUX have to match. The BW is related to the user modulated signal bandwidth, which you need to consider in the MUX/DEMUX bandwidth.
Please refer to the examples on OCDMA in the Example library located at the following location.
C:UsersUSER NAMEDocumentsOptiSystem 18.0 SamplesMetro and access systemsPON and CDMA systems
Regards,
Ahmad