Fan Linsheng, Jia Yuchen, Liu Muqi, Lin Jiexing, Zhang Qun, Gong Siyu, Jin Yongchao, Yang Pengxi, Cheng Chen, Yang Yanfu
Opt Lett. 2024 Jun 1;49(11):3022-3025. doi: 10.1364/OL.523049.
In this Letter, we present a robust, wide-range, and precise monitoring scheme for transmitter (Tx) impairments in coherent digital subcarrier multiplexing (DSCM) systems. The proposed scheme employs frequency-domain pilot tones (FPTs) to compensate for frequency offset (FO), polarization aliasing, and carrier phase noise, thus isolating Tx impairments from channel distortions. It then implements 4 × 4 real-valued MIMO to compensate for Tx impairments by equalizing symmetric subcarriers. Tx impairment monitoring is derived from the equalizer coefficients. By considering the phase shift caused by Tx impairments, a wide-range and precise monitoring of Tx 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 a wide-range, robust, and precise Tx impairment monitoring in coherent DSCM systems, maintaining performance even in the presence of ultra-fast polarization variation.
在本信函中，我们提出了一种用于相干数字子载波复用（DSCM）系统中发射机（Tx）损伤的强大、宽范围且精确的监测方案。所提出的方案采用频域导频音（FPT）来补偿频率偏移（FO）、极化混叠和载波相位噪声，从而将Tx损伤与信道失真隔离开来。然后，它实现4×4实值多输入多输出（MIMO），通过均衡对称子载波来补偿Tx损伤。Tx损伤监测是从均衡器系数得出的。通过考虑由Tx损伤引起的相移，实现了对包括IQ偏斜、IQ相位和增益不平衡在内的Tx损伤的宽范围且精确的监测。我们使用一个48 GBaud、四子载波、双极化相干DSCM系统对我们的方法进行了实验验证。结果证实了该方法在相干DSCM系统中进行宽范围、强大且精确的Tx损伤监测的能力，即使在存在超快极化变化的情况下也能保持性能。
