Mitigation of cross-modulation distortion in wideband analog photonic link based on digital post-processing

We experimentally demonstrate the compensation of cross modulation distortion (XMD) nonlinearity which exists in wide-band, multiple-carrier analog photonic link (APL) systems. Such nonlinearity is caused by out-of-band signals due to the inherent nonlinear transfer function of Mach-Zehnder modulator (MZM). Instead of precisely emulating the transfer function of the whole nonlinear system in the digital domain, we digitally multiply the distorted signals by a compensating signal which can be extracted through a digital low-pass filtering. As a result, the XMD will be well suppressed. Theory analysis shows that only the bias angle should be known by the algorithm. By low biasing the MZM, the experiment shows a well-suppressed XMD, where the fundamental sidebands to XMD sidebands ratio is improved by more than 19 dB.