Nonlinear phase-drift on 16-QAM optical signals due to semiconductor optical amplifier gain saturation were measured for two devices—a linear and a nonlinear one—considering the input optical power and the net optical gain. The signal when amplified by the nonlinear device is marred even for low Pin (−20 dBm), and for moderate input powers (−15 dBm) signal quality stays always above the forward error correction (FEC) limit (error vector magnitude = 16 % ). The nonlinear device as expected induced more degradation, being able to operate fairly just for small gain and input power; for moderate gain (12 dB), the amplified signals stay always above the FEC limit. The linear device showed fair operation even for moderate Pin = − 15 dBm, working under FEC limit for OSNR (at Rx) higher than 16.5 dB for 10 Gbaud, and higher than 20 dB for 25 Gbaud, with small penalties (<2 dB) in relation to the back-to-back configuration.
We propose an equivalent circuit modeling for a chip-on-carrier and for two encapsulated semiconductor optical amplifiers (SOAs). The models include main parasitic leaks and were used in reflection and transmission simulations, showing good agreement with experimental data. The model for each SOA is validated, comparing the simulated results with experimental data from SOAs operating as high-speed electro-optical switches, reaching rise times below 200 ps.
An all-optical scheme aimed at minimizing distortions induced by semiconductor optical amplifiers (SOAs) over modulated optical carriers is presented. The scheme employs an additional SOA properly biased to act as a saturated absorber, and thus counteract the distortions induced by the first amplifying device. The scheme here is demonstrated in silico, for 40 and 100 Gb/s (10 and 25 Gbaud, 16 QAM), with reasonable total gain (>20 dB) for symbol error rate below the forward error correction limit.