All-optical or gate using cross gain modulation in semiconductor optical amplifier

In the near future, information processing capacity will increase up to several Tbit/s to satisfy various applications such as voice signals, vivid images, and motion pictures, etc. To transmit large-capacity information at high speed, all-optical signal processing is highly recommended. Recently, several all-optical OR logic gates were reported by using an ultrafast nonlinear interferometer (UNI), a Michelson interferometer (MI) [1], and a cross gain modulation (XGM) technique in the cascaded semiconductor optical amplifiers (SOAs) [2]. However, the reported speed of logic OR with the cascaded SOAs was limited by 2.5 Gbit/s because of relatively slow recovery time. In this paper, an all-optical OR logic gate has been for the first time proposed at 10 Gbit/s by using the XGM of single SOA. Figure 1 shows an experimental setup for the all-optical OR logic gate. The charateristics of all-optical logic OR are simulated by use of a commercially available VPI simulator. Fist of all, signal A as probe signal with 1100 pattern and signal B as pump signal with 0110 pattern are simultaneously passed through the SOA at 10 Gbit/s. Then, output signal is Boolean AB̄. Finally, signal B is divided by a 50:50 coupler and recombined by another coupler to generate Boolean AB̄ + B with 1110 pattern, which coincides with a truth table of OR logic gate. Figure 2 shows input and output signals for all-optical logic OR. In other words, probe signal A with 1100 pattern, pump signal B with 0110 pattern, Boolean AB̄, and output signal AB̄ + B with 1110 pattern are shown. In conclusion, all-optical OR logic operation is obtained at 10 Gbit/s by using single SOA.