Gain-saturation-induced self-phase modulation (SPM) leading to pulse distortion in a semiconductor optical amplifier (SOA) is overcome by shifting a tunable optical filter (TOF). A recovered or broadened pulse can be obtained after filtering the amplified pulse in the SOA even if the short pulse is only 2-3ps long. The input power dynamic range (IPDR) can be strongly increased by shifting the TOF and the direction of the shifted transparent wavelength is different for 10Gb/s return-to-zero (RZ) or nonreturn-to-zero (NRZ) signals. The transparent wavelength of the TOF should be shifted to a longer wavelength for RZ signals and to a shorter for NRZ signals. 80-Gb/s optical time division multiplexing (OTDM) signal amplification in the SOA is demonstrated for the first time. We also demonstrate that a large IPDR for the 80-Gb/s OTDM signal can be obtained by shifting the TOF.
Jianjun Yu and Palle Jeppesen, "Increasing Input Power Dynamic Range of SOA by Shifting the Transparent Wavelength of Tunable Optical Filter," J. Lightwave Technol. 19, 1316- (2001)