DQPSK modulation has become particularly attractive in high-speed optical communications because of its resistance to fiber nonlinearities and its more efficient use of fiber bandwidth. Because of its wavelength conversion ability, SOA four wave mixing effect has attracted much attention. We experimentally study the FWM wavelength conversion of 40 Gbit/s (20 Gbaud) NRZ-DQPSK data. A bulk SOA with 21 dB gain and 10 dBm output saturation power is used. The Q factors of the input and wavelength converted signal are measured. Some signal regeneration properties are shown. A Q-factor improvement of maximum 1.7 dB is observed. The authors make an attempt at recreating the experiment with a prototype Quantum Dot SOA. FWM efficiency of a QD-SOA with 15 dB fiber-to-fiber gain and 3 dBm output saturation power is measured.