Performance degradations of multigigabit-per-second NRZ/RZ lightwave systems due to gain saturation in traveling-wave semiconductor optical 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/sub in/) to the saturation output power (P/sub sat/) is less than -17 dB. The NRZ system penalty is slightly larger than the RZ penalty when P/sub in//P/sub sat/ is larger than -17 dB. For example, with P/sub in//P/sub 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/sub in//P/sub sat/=-10 dB, the NRZ system penalty is about 2.5 dB versus 1.5 dB for RZ.>