We report on the experimental and numerical investigations of an all-optical network interface from back-bone networks to local area networks based on semiconductor optical amplifiers (SOAs). All-optical signals at 40 Gbps with return-to-zero (RZ) format in backbone networks are demultiplexed to signals at 10 Gbps with nonreturn-to-zero (NRZ) format in local area networks. SOAs and optical band-pass filters are used in the optical interface. We study the waveform, optical spectrum, and bit error rate (BER) of the interface scheme based on the experimental and numerical simulation results. The interface technique can be used in variable length and bit-rate variable optical networks.