Using phase inversion to compensate fiber nonlinearity in Spectral-Amplitude Coding OCDMA network

Self-phase modulation (SPM) and cross-phase modulation (SPM) are leading nonlinear transmission penalty in Spectral-Amplitude Coding optical CDMA (SAC-OCDMA) systems. In nonlinear optical media, a phenomenon of the intensity dependence of the refractive index occurs through SPM or XPM, which leads to spectral broadening of optical pulses and therefore degrade system performance. A novel scheme for fiber nonlinearity compensation based on the principles of phase inversion compensation (PIC) is proposed to reduce the phase distortion. The phase of the data pulses is modulated in the middle of fiber spans. The magnitude of the phase modulation is proportional to the detected pulse intensity, and the sign is opposite to that of the nonlinear phase shift caused by SPM and XPM. Thus, the nonlinear phase noise induced in the first-half fiber is partially compensated for in the second-half fiber. Using an optimum value, we show by numerical simulations that a SAC-OCDMA format transmission in dispersion-managed system with such nonlinearities compensation can provide greater than 3 dB increase in launch power.