Characterization of Directly Modulated Self-Seeded Reflective Semiconductor Optical Amplifiers Utilized as Colorless Transmitters in WDM-PONs

The transmission performances of the wavelength-division-multiplexed passive optical networks based on directly modulated self-seeded reflective semiconductor optical amplifiers (RSOAs) are investigated and analyzed. The impacts of signal extinction ratio (ER), stable seeding power, pattern length dependency, bandwidth and shape factor of the wavelength multiplexer within the self-seeding cavity, and length of the self-seeding cavity on the transmission performance are investigated. The ER is optimized to bring the best receiver sensitivity when the loss of the self-seeding cavity is fixed. The optimal ER and the corresponding receiver sensitivity are improved with the stable seeding power which decreases with the loss of the self-seeding cavity. Compared to the Gaussian-shaped pass band, the wavelength multiplexer with a flat-top pass band brings better transmission performances and enables error-free transmission with a smaller pass band bandwidth. The transmission performance of the directly modulated self-seeded RSOA is robust against the phase perturbation induced by the micro change in the cavity length but is degraded remarkably when the cavity length is extended to several kilometers. Nevertheless, error-free transmission is achieved when the cavity length is extended to 4 km. The findings of this paper provide a better understanding of the mechanism of the directly modulated self-seeded RSOAs and also guidance on designing the WDM-PON systems using the self-seeded RSOAs.