Hi gherbi mohamed,
The topic you are working on is a very interesting one and has been addressed in few researches from different points of view. In all the cases, the performance in BER and Q factor of the tow systems is the most important factor. As per your request, I am attaching two papers regarding comparison of SSB and SDB. First gives you an example of application of those techniques for OFDM-PONs (with BER and Q-factor performance). Second presents a comparison of their detection schemes.
Good luck!