Compensation of nonlinear distortion through frequency shift free mid-span spectral inversion using counter-propagating dual pumped FWM in fiber

We propose and numerically verify a scheme of frequency-shift free mid-span spectral inversion for nonlinearity mitigation in standard single mode fiber. Spectral inversion is accomplished by optical phase conjugation, realized by counter-propagating dual pumped four-wave mixing in highly nonlinear fiber. The two pump frequencies are placed symmetrically around signal frequency to ensure that conjugate wave has the same frequency as that of signal wave. We examine the performance of mid-span spectral inversion under the effects of design parameters, nonlinear length and pump power. The bit-error rate is used to evaluate the performance of our system, carried out as a function of signal power to demonstrate near complete nonlinearity mitigation of 40 Gbps QPSK modulated data transmitted over 1000 km standard single mode fiber using our method of mid-span spectral inversion.