Suppression of cross-gain modulation in SOA using RZ-DPSK modulation format

Conventional ON-OFF keyed modulation format is susceptible to cross-gain modulation in saturated semiconductor optical amplifiers (SOAs) that leads to crosstalk penalty for dense wavelength-division-multiplexing (DWDM) input signals. Differential phase-shift keying of optical pulses has virtually no pulse-pattern effect and is robust to cross-gain modulation. We report experimental results that confirm reduction of crosstalk penalty in SOA with differential phase-shift-keyed DWDM input signals in comparison with ON-OFF keyed signals operating at 12.5 Gb/s with 25-GHz channel spacing.