Performance degradations of multigigabit-per-second NRZ/RZlightwave systems due to gain saturation in traveling-wave semiconductoroptical amplifiers

A nonlinear model for a travelling-wave semiconductor optical amplifier has been used to determine eye closure degradations for 2.4 and 10 Gb/s NRZ/RZ lightwave systems due to gain saturation effects in the optical amplifier. At 10 Gb/s, with a carrier lifetime of 300 ps, the results indicate that the penalty is less than 1 dB for both NRZ and RZ systems provided that the ratio of the input power (P_in ) to the saturation output power (P_sat) is less than -17 dB. The NRZ system penalty is slightly larger than the RZ penalty when P_in/P_sat is larger than -17 dB. For example, with P_in/P_sat=-10 dB, the NRZ system penalty is about 2.8 dB versus 2 dB for the RZ system. The system penalty at 2.4 Gb/s is slightly less than that at 10 Gb/s. At P _in/P_sat=-10 dB, the NRZ system penalty is about 2.5 dB versus 1.5 dB for RZ