All-optical NAND gate using cross-gain modulation in semiconductor optical amplifiers

By using gain nonlinearity characteristics of a semiconductor optical amplifier, an all-optical NAND gate at 10 Gbit/s is demonstrated. The all-optical NAND gate operates in single mechanism, which is cross-gain modulation. In the NAND gate (AB+A), Boolean AB is obtained by using signal A as a probe beam and signal B as a pump beam in SOA-1. Also, Boolean A is obtained by using the clock signal as a probe beam and signal A as a pump beam in SOA-2. By adding the two outputs from SOA-1 and SOA-2, Boolean A+AB (logic NAND) can be acquired. The extinction ratio is about 6.1 dB.