In this paper, several applications in all-optical signal processing based on a semiconductor optical amplifier (SOA) and variable delayed interferometers (DIs) have been experimentally demonstrated.Wavelength converter based on a nonlinear polarization switch (NPS) and a DI is proposed and presented for the wavelength conversion of nonreturn-to-zero (NRZ) signals. An alloptical nonreturn-to-zero to return-to-zero (NRZ-to-RZ) format converter with tunable duty cycles is achieved by the DI with variable delays. The 40 Gb/s reconfigurable optical OR/NOR gate in a single SOA, followed a tunable optical bandpass filter (OBF) and a DI, optical 2R regeneration using an SOA-DI are investigated. It is found that this combinative realization of filters has been endowed with great flexibility and quality for 40 Gb/s optical logic and 2R regeneration.