As the capacity of the next-generation passive optical network (PON) is reaching 100 Gb/s and beyond, cost-effective transceivers have been widely discussed. In this work, we provide a comprehensive comparison of various simplified coherent and direct detection (DD) schemes operating at a ${100\; {\rm Gb/s/}}\lambda$100Gb/s/λ 4-ary pulse amplitude modulation signal through numerical simulation. According to the cost, the coherent receivers can be divided into three levels: intensity-only coherent receivers and phase-insensitive and phase-sensitive complex-value coherent receivers. The received power sensitivity at back-to-back, influence of laser frequency offset, local oscillator power, laser linewidth, analog-to-digital convertor resolution, fiber dispersion, and hardware complexity are investigated and analyzed for each transceiver structure. The results show the following: (1) Transmitter-side optical amplification is suggested for DD and intensity-only coherent receivers to meet the 29 dB power budget requirement, and these schemes have a large dispersion penalty. (2) Compared with ${3} \times {3}$3×3 coupler and ${2} \times {4}$2×4 hybrid-based coherent receivers, ${2} \times {2}$2×2 coupler and balanced-photodiode-based heterodyne detection exhibit similar performance with a simpler structure. (3) Both phase-insensitive and phase-sensitive complex-value coherent receivers have superior power budget and dispersion tolerance, and their application in PON would depend on the cost.

中文翻译：

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具有成本效益的100 Gb / s /λPON的相干和直接检测方案的比较研究

随着下一代无源光网络（PON）的容量达到100 Gb / s甚至更高，已广泛讨论了具有成本效益的收发器。在这项工作中，我们对以$ {100 \;运行的各种简化的相干和直接检测（DD）方案进行了全面比较。通过数值模拟{\ rm Gb / s /}} \ lambda $ 100Gb / s /λ4进制脉冲幅度调制信号。根据成本，相干接收机可以分为三个级别：仅强度的相干接收机以及对相位不敏感和对相位敏感的复值相干接收机。针对每个收发器结构，研究并分析了背对背的接收功率灵敏度，激光频率偏移，本地振荡器功率，激光线宽，模数转换器分辨率，光纤色散和硬件复杂性的影响。结果表明：（1）建议将DD和仅强度相干接收机的发射机侧光放大以满足29 dB的功率预算要求，并且这些方案具有较大的色散损失。（2）与$ {3} \ times {3} $ 3×3耦合器和$ {2} \ times {4} $ 2×4基于混合的相干接收机相比，$ {2} \ times {2} $ 2×2耦合器基于平衡光电二极管的外差检测具有相似的性能，但结构更简单。（3）相位不敏感和相位敏感的复数值相干接收机都具有出色的功率预算和色散容限，它们在PON中的应用取决于成本。并且这些方案具有较大的色散损失。（2）与$ {3} \ times {3} $ 3×3耦合器和$ {2} \ times {4} $ 2×4基于混合的相干接收机相比，$ {2} \ times {2} $ 2×2耦合器基于平衡光电二极管的外差检测具有相似的性能，但结构更简单。（3）相位不敏感和相位敏感的复数值相干接收机都具有出色的功率预算和色散容限，它们在PON中的应用取决于成本。并且这些方案具有较大的色散损失。（2）与$ {3} \ times {3} $ 3×3耦合器和$ {2} \ times {4} $ 2×4基于混合的相干接收机相比，$ {2} \ times {2} $ 2×2耦合器基于平衡光电二极管的外差检测具有相似的性能，但结构更简单。（3）相位不敏感和相位敏感的复值相干接收机都具有出色的功率预算和色散容限，它们在PON中的应用将取决于成本。