This paper demonstrates the possibility to observe the modulational instability (MI) regions due to modified nonlinear saturability over and above other high-order nonlinearities for the triangular configuration of a three-core oppositely directed coupler. In this configuration, two channels are positive-refractive-index material, and one is a negative-index material. The governing equations are the modified coupled nonlinear Schrdinger equations, to which we add the higher-order nonlinearity terms and coupling terms. This equation is further modified with the saturable nonlinearity term. In the presence of several nonlinearities, we derive the dispersion relation for the optical coupler under consideration. We use a linear stability analysis to study the modulation stability characteristic gain in both the normal and anomalous group-velocity dispersion regimes. We have widely varied the parameter range of the physical system parameters to accommodate different possibilities. In the normal region, the saturable nonlinearity aids in increasing the bandwidth of the MI region, while in the anomalous regime, the bandwidth reduces. In the normal dispersion case, the simultaneous presence of all nonlinearities in the optical coupler does not provide a suitable scope for pulse propagation. On the other hand, in the anomalous regime, these nonlinearities favor for pulse propagation.

本文证明了观察调制不稳定性 (MI) 区域的可能性，这是由于三芯反向耦合器的三角形配置的三角形配置中的非线性饱和度高于其他高阶非线性。在这种配置中，两个通道是正折射率材料，一个是负折射率材料。控制方程是修正的耦合非线性薛定谔方程，我们在其中添加了高阶非线性项和耦合项。这个方程用可饱和非线性项进一步修改。在存在几个非线性的情况下，我们推导出所考虑的光耦合器的色散关系。我们使用线性稳定性分析来研究正常和异常群速度色散状态下的调制稳定性特征增益。我们广泛地改变了物理系统参数的参数范围以适应不同的可能性。在正常区域，可饱和非线性有助于增加 MI 区域的带宽，而在异常区域，带宽会减少。在正常色散情况下，光耦合器中所有非线性同时存在并不能为脉冲传播提供合适的范围。另一方面，在异常状态下，这些非线性有利于脉冲传播。可饱和非线性有助于增加 MI 区域的带宽，而在异常情况下，带宽会减少。在正常色散情况下，光耦合器中所有非线性同时存在并不能为脉冲传播提供合适的范围。另一方面，在异常状态下，这些非线性有利于脉冲传播。可饱和非线性有助于增加 MI 区域的带宽，而在异常情况下，带宽会减少。在正常色散情况下，光耦合器中所有非线性同时存在并不能为脉冲传播提供合适的范围。另一方面，在异常状态下，这些非线性有利于脉冲传播。