Abstract We present numerical and experimental study on the origin of fluctuations in the idler power in partially degenerate intermodal four wave mixing in a 1 km long few mode graded index fiber where both the fundamental and higher order modes are excited in both pump and signal wavelengths. Numerical simulation is carried out in the presence of different types of mode coupling processes and group delay fluctuations in order to independently predict the influence of these phenomena by considering the appropriate statistics of the corresponding processes. We propose a quasi-distributed model by choosing the locations of specific coupling events statistically, in correspondence to their correlation lengths. Idler conversion efficiency is experimentally evaluated for different detuning frequencies between the signal and pump through multiple trials, and it is found that even though distinct features of maxima and minima are retained, there are fluctuations in frequencies corresponding to maxima and minima. These experimental results are compared with those from numerical simulations in order to identify the origin of fluctuations.

中文翻译：

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线性耦合和群延迟涨落对少模光纤模间四波混频的影响

摘要 我们对 1 公里长的少模渐变折射率光纤中部分简并模间四波混频中闲散功率波动的起源进行了数值和实验研究，其中基模和高阶模在泵浦波长和信号波长都被激发。在存在不同类型的模式耦合过程和群延迟波动的情况下进行数值模拟，以便通过考虑相应过程的适当统计来独立预测这些现象的影响。我们通过统计选择特定耦合事件的位置，对应于它们的相关长度，提出了一个准分布式模型。通过多次试验对信号和泵之间的不同失谐频率进行了空转转换效率的实验评估，发现即使保留了极大值和极小值的明显特征，但对应于极大值和极小值的频率存在波动。将这些实验结果与数值模拟的结果进行比较，以确定波动的起源。