In-field Self-calibration Scheme Enabling Separation of Frequency Response/IQ Skew of Coherent Optical Transceivers

The in-field self-calibration scheme is proposed for coherent optical transceivers separating the frequency-response/IQ-skew characterization of Tx/Rx without extra optical equipment. Sub-ps timing correction (${\lt}0.2 \mathrm{ps}$) and frequency-response (${\lt}1 \mathrm{~dB},{\lt}0.25 \mathrm{rad}$) correction enable the 40/20 GBaud $16 / 64 \mathrm{QAM}$ signals transmissions.