Suppression of optical beat interference in WDM-SCMA networks using modulated optical combs

We proposed a new method to suppress the optical beat interference (OBI) in WDM/SCMA network. The proposed scheme uses the modulated optical combs. Since short optical pulse in time domain has broad linewidth in frequency domain, the generated OBI noise by beating of optical comb signals from several optical network unit (ONU)s spreads over wide frequency range. In addition, the chance of optical beating is low because optical pulse trains from different ONU have different pulse timing. We have demonstrated the proposed idea experimentally. In beating experiment, CNR was maintained over 20dBc despite of optical beating. In addition, optical comb modulation scheme showed 4dB enhancement of the power penalty in BER measurement compared with the generally used direct modulation case in presence of OBI noise.