Generalized model of optical single sideband generation using dual modulation of DML and EAM

The dual modulation of a directly modulated laser (DML) and an electro-absorption modulator (EAM) is known to be an effective way to generate an optical single sideband (SSB) signal in highly compact and cost-effective fashions. Two theoretical models were developed for this dual modulation scheme under the assumptions of negligible intensity modulation of DML and/or zero chirp of EAM. In this paper, we develop a generalized model of dual modulation scheme without those assumptions. We show theoretically that the previous models can be unified as special cases of our generalized model. We evaluate the validity of our model using numerical simulations and experiments. The results show that our model estimates the modulation conditions for optical SSB generation accurately over wide ranges of modulation frequency and EAM's chirp. We also show experimentally that we can achieve an optical sideband suppression ratio higher than 40 dB by using our generalized model. This is >25 dB higher than the ratios obtained from the previous models.