2. Principle of Operation
Fig. 1 shows the experimental configuration of the proposed scheme to generate UWB doublets by
means of an integrated SOA-MZI containing two 1-mm InGaAsP-InP SOAs with low polarization
sensitivity. The system is composed of a continuous wave signal source (labeled as cw1), the
mentioned interferometric structure, a pump source providing the input time-varying signal and a
photodetector. In principle, cross-gain modulation (XGM) and cross-phase modulation (XPM)
processes can be present in the SOAs. However, the linewidth enhancement factor of the SOAs is
large enough to neglect the XGM effect.