We demonstrated experimentally 40 Gbit/s all-optical format conversions between return-to-zero (RZ) and nonreturn-to-
zero (NRZ) using a fiber delay interferometer (FDI) and a single semiconductor optical amplifier (SOA). Firstly, 40 Gbit/s data format conversion from RZ to NRZ is realized using a FDI with temperature control and an optical bandpass filter (BPF). Then, 40 Gbit/s data format conversion from NRZ to RZ is implemented, using four-wave mixing (FWM)
effect of SOA, by injecting synchronously NRZ signal and clock pulses into a single SOA. Presented method has some distinct advantages including multi-channel parallel processing, easy integration, convenient tuning, good stability, and
so on, which has potential to be used in future optical networks that could combine wavelength division multiplexing
(WDM) and optical time domain multiplexing (OTDM) transmission techniques.