In a practical 4-λ coarse wavelength division multiplexing (CWDM) intensity modulation direct detection (IM/DD) system, different wavelength channels achieve different transmission performances due to 1) inter-channel component differences and 2) chromatic dispersion (CD) - chirp interaction. Large channel performance discrepancies could significantly degrade the average pre-forward error correction (pre-FEC) bit error rate (BER) performance of the system. To improve the system's robustness against channel performance discrepancies, we propose to employ a symbol-level wavelength-interleaver in conjunction with four-dimensional - 4-level pulse amplitude modulation - trellis coded modulation (4D-PAM4-TCM). We experimentally compare the performances of the proposed wavelength-interleaved 4D-PAM4-TCM system and a conventional 4D-PAM4-TCM system in a 4-λ × 100 Gb/s CWDM IM/DD link over 0-20 km. We observe that the wavelength-interleaved 4D-PAM4-TCM system outperforms the conventional 4D-PAM4-TCM system in terms of receiver sensitivity required at the KP4 FEC threshold when sizable channel performance discrepancies exist in such systems.

中文翻译：

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4 位×100 Gb/s CWDM 系统中的波长交错 4D-PAM4-TCM


在实际的 4 λ 粗波分复用 (CWDM) 强度调制直接检测 (IM/DD) 系统中，由于 1) 通道间分量差异和 2) 色散 (CD) - 线性调频，不同波长通道实现不同的传输性能相互作用。较大的信道性能差异可能会显着降低系统的平均预前向纠错 (pre-FEC) 误码率 (BER) 性能。为了提高系统针对信道性能差异的鲁棒性，我们建议将符号级波长交织器与四维 - 4 级脉冲幅度调制 - 网格编码调制 (4D-PAM4-TCM) 结合使用。我们通过实验比较了所提出的波长交错 4D-PAM4-TCM 系统和传统 4D-PAM4-TCM 系统在 0-20 km 的 4-λ × 100 Gb/s CWDM IM/DD 链路中的性能。我们观察到，当系统中存在相当大的信道性能差异时，波长交错 4D-PAM4-TCM 系统在 KP4 FEC 阈值所需的接收器灵敏度方面优于传统 4D-PAM4-TCM 系统。