Reduction of interchannel interference noise in a two-channel grating-based OCDMA system using a nonlinear optical loop mirror

We show that a nonlinear optical switch can be used to suppress the interch annel noise generated under multiuser operation within a coherent, direct-s equence optical code-division multiple-access (OCDMA) system. By incorporat ing a simple nonlinear optical loop mirror (NOLM) within the receiver, we d emonstrate a 3.6-dB power penalty reduction in a two-channel 1.25-Gb/s 64-c hip 160-Gchip/s grating-based direct-sequence OCDMA system. Even greater im provements in system performance were obtained at a data rate of 2.5 Gb/s, where the noise due to the overlap of adjacent decoded data bits also needs to be suppressed. In both instances, the system performance under two-chan nel operation with nonlinear filtering was shown to be comparable to that a chieved under single-channel operation using the conventional matched-filte r approach.