Through theoretical analysis and simulation, we investigate the system impact due to a sinusoidal jitter tone and the resultant local oscillator (LO) laser linewidth requirement in ultra-high baud rate and long distance coherent optical systems. We also carried out experiments in 64 Gbaud, dual-polarization (DP)-16 QAM systems to verify the theoretical analysis and simulation. We have also obtained a jitter interference tolerance mask to qualify LO lasers. A jitter tone with a frequency lower than ∼1 MHz has a higher tolerance since it generally causes constant frequency or phase shift, which can be tracked by a receiver DSP. For a jitter tone with a frequency higher than ∼1 MHz, the tolerance becomes much tighter since the tone will affect laser lineshape and induce equalizer-enhanced phase noise (EEPN). Consequently, a jitter tone in the higher frequency region could severely affect the system performance. Theoretical analysis and numerical result illustrate that EVM² due to the effect of laser linewidth and a sinusoidal jitter tone is proportional to the weighted sum of $[ \Delta \nu \times B_{s}\times \text{L}] $ and $[ \Delta f_{pp}\times B_{s}\times \text{L}] ^{2}$, where Δν is the laser linewidth, $B_{s}$ is the baud rate, $\Delta f_{pp}$ is the laser peak-to-peak frequency deviation due to a sinusoidal jitter tone, and L is the fiber transmission length. This result is applicable for all orders of QAM constellations. The implication to future 100 Gbaud and beyond systems is delineated.

中文翻译：

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本地振荡器频率抖动和激光线宽对超高波特率相干系统的影响

通过理论分析和仿真，我们研究了超高波特率和长距离相干光学系统中正弦抖动音调和由此产生的本地振荡器 (LO) 激光线宽要求对系统的影响。我们还在 64 Gbaud、双极化 (DP)-16 QAM 系统中进行了实验，以验证理论分析和仿真。我们还获得了一个抖动干扰容限掩模来鉴定 LO 激光器。频率低于 1 MHz 的抖动音具有更高的容限，因为它通常会导致恒定频率或相移，这可以由接收器 DSP 进行跟踪。对于频率高于 ~1 MHz 的抖动音，容限变得更小，因为该音会影响激光线形并引起均衡器增强相位噪声 (EEPN)。最后，较高频率区域的抖动音可能会严重影响系统性能。理论分析和数值结果表明 EVM²由于激光线宽的影响，正弦抖动色调正比于加权和$[ \Delta \nu \times B_{s}\times \text{L}] $ 和 $[ \Delta f_{pp}\times B_{s}\times \text{L}] ^{2}$，其中 Δν 是激光线宽， $B_{s}$ 是波特率， $\Delta f_{pp}$ 是由正弦抖动音引起的激光峰峰值频率偏差，和 升是光纤传输长度。这个结果适用于所有 QAM 星座的阶数。描绘了对未来 100 Gbaud 及更高系统的影响。