Abstract

Signal impairments caused by the relative characteristic differences and crosstalk between electrical in-phase (I) lanes and quadrature (Q) lanes are some of the main obstacles to the development of 100-Gbaud-class high-symbol-rate transceivers. To address such IQ impairments, we propose a method for enabling fully frequency-resolved four-dimensional (4D) characterization of IQ impairments even in the presence of arbitrary crosstalk across four IQ lanes of polarization-multiplexed transceivers. We formulated a 4D signal-propagation model that takes into account inter-polarization IQ crosstalk and found how to separate the 4D IQ characteristics of the transmitter and receiver from the coefficients of a single-layer complex 8×2 multiple-input multiple-output adaptive equalizer on the basis of the model. We also introduce an application of the method for characterizing typical IQ impairments (e.g., IQ skew, IQ amplitude imbalance, phase deviation) from the filter coefficients. We numerically and experimentally tested our method with 96-Gbaud 16QAM signals and demonstrated its feasibility.

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