High Resolution Characterization of the Spectral Broadening Due to Fiber Nonlinearities

Balanced heterodyne detection and a gated microwave spectrum analyzer are used to precisely measure the spectral broadening due to intra-channel fiber nonlinearities. Polarization resolved spectra for a 224 Gb/s dual polarization 16-ary quadrature amplitude modulation signal are quantified in terms of the spectral edge power, which serves as a useful metric for capturing the effects of both fiber nonlinearities and amplified spontaneous emission noise. It is shown that without and with perturbation-based pre-compensation for the signal distortion due to the Kerr effect, the launch powers that minimize the bit error ratio and spectral edge power coincide.