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基于耦合非线性薛定谔(NLS)方程组,利用分步傅里叶法(SSFM),研究了二阶色散长度与线性耦合系数的乘积LDκ、三阶色散长度与线性耦合系数的乘积L′Dκ以及模间色散(IMD)对双芯非线性光纤定向耦合器开关特性的影响。研究表明,在光纤正常色散区,当入射功率大于阈值功率时,从波导1到波导2有明显的能量转移,耦合器的开关性能差;而在光纤反常色散区,当LDκ<1时,非线性定向耦合器(NLDC)能够表现出良好的开关特性。且阈值功率随着LDκ的增大而减小。当|IMD|≤0.01,IMD对NLDC开关特性的影响可以忽略。当|IMD|=0.2,且LDκ的值较小时,在入射功率大于阈值功率的条件下,IMD对开关特性的影响不明显;而在入射功率小于阈值功率时,耦合器的开关特性下降。此外,三阶色散(TOD)效应对NLDC的影响通常可以忽略。
Based on the coupled NLS equations, the product of the second-order dispersion length and the linear coupling coefficient LDκ, the product of the third-order dispersion length and the linear coupling coefficient L’Dκ, Influence of Intermodulus Dispersion (IMD) on Switching Characteristics of Two - core Nonlinear Fiber Directional Coupler. The results show that when the incident power is greater than the threshold power, there is a significant energy transfer from the waveguide 1 to the waveguide 2, and the switching performance of the coupler is poor. In the anomalous dispersion region of the fiber, when LDK <1, Linear Directional Coupler (NLDC) can exhibit good switching characteristics. And the threshold power decreases with increasing LDK. When | IMD | ≤0.01, the influence of IMD on NLDC switching characteristics is negligible. When | IMD | = 0.2, and the value of LDK is small, the influence of IMD on the switching characteristics is not obvious when the incident power is greater than the threshold power. When the incident power is less than the threshold power, the switching characteristics of the coupler decrease. In addition, the effect of third-order dispersion (TOD) on NLDC can often be neglected.