Normalized LMS filter for chromatic dispersion compensation in single polarization 40 Gbps CO-OFDM system in presence of timing and frequency offsets

We compare the performance of NLMS adaptive filter for chromatic dispersion compensation with pilot-tone based channel estimation technique for 40 Gbps CO-OFDM system in presence of timing and frequency offsets. Simulation results show that with NLMS adaptive filter, BER approaches that of back-to-back transmission. We study the effect of step size of NLMS filter on symbol error rate (SER) and obtain an optimum value of step size that minimizes SER. Results show that NLMS filter provides 2.82 dB gain in OSNR over pilot-tone based estimation for a normalized carrier frequency offset of 0.02 at BER of ≃ 10−3 over a fiber length of 560 km.