Robust, wide-range, and precise transmitter IQ impairments monitoring scheme for coherent DSCM systems

• Linsheng Fan, Yucheng Jia, Muqi Liu, Jiexing Lin, Qun Zhang, siyu gong, Yongchao Jin, Pengxi Yang, chen cheng, and Yanfu Yang
• received 03/05/2024; accepted 04/30/2024; posted 04/30/2024; Doc. ID 523049
• Abstract: In this letter, we present a robust, wide-range, and precise monitoring scheme for transmitter impairments in coherent digital subcarrier multiplexing (DSCM) systems. The proposed scheme employs frequency-domain pilot tones to compensate for frequency offset, polarization aliasing, and carrier phase noise, thus isolating transmitter impairments from channel distortions. It then implements widely linear filter to compensate for transmitter impairments by equalizing symmetric subcarriers. Transmitter impairments monitoring are derived from the equalizer coefficients. By mitigating the interference from constant phase shifts in advance, wide-range and precise monitoring of transmitter impairments including IQ skew, IQ phase and gain imbalances is achieved. We experimentally validated our approach using a 48 GBaud, four-subcarrier, dual-polarization coherent DSCM system. The results confirm the method's capability for wide-range, robust, and precise transmitter impairments monitoring in coherent DSCM systems, maintaining performance even in presence of phase noise and rapid polarization variation.