Polynomial Pulses for Mitigating Fiber Nonlinearity in Coherent Optical Fiber Communications

Root polynomial (RP) pulses are considered for mitigating fiber nonlinearity for 128 Gb/s dual-polarization 8-ary quadrature-amplitude-modulation dense wavelength division multiplexed (DWDM) systems. RP pulses exhibit a fast asymptotic decay rate, low peak-to-average power ratio, and narrow pulse width. Consequently, they are tolerant toward intrachannel nonlinearity, digital-to-analog converter quantization effects, and timing recovery errors. In a nine-channel DWDM transmission experiment with a 25 GHz channel spacing and null-to-null modulated optical signal bandwidth of 25 GHz, the RP pulse shape yields a maximum distance of 4800 km, which extends the transmission distance by 300 km (length of the recirculating loop) relative to the root raised cosine pulse shape.