具有高阶耦合色散系数三芯光纤耦合器非线性光开关特性的研究

利用两种方法研究了高速光脉冲在具有交叉相位调制的等边三角形排列结构的非线性三芯光纤耦合器中传输和开关特性.首先利用变分原理得到三纤芯中传输转移系数随距离变化的方程，然后利用分裂步长傅里叶方法求得了光脉冲的数值解.变分法和数值模拟的结果表明：当一阶模间色散系数较小时，光脉冲仍能在三芯之间周期性耦合传输，并且表现出良好的开关特性，但是随着一阶模间色散系数的增大，脉冲耦合传输的周期性和陡峭的开关特性都遭到破坏，光脉冲在传输中发生分裂；二阶耦合色散系数和初始啁啾都能使光脉冲传输时的耦合长度变短、光脉冲在三纤芯之间 关键词： 三芯光纤耦合器 模间色散系数 耦合长度 开关阈值功率

Switching in three-core nonlinear fiber coupler with second order coupling dispersion coefficient

The propagation and switching of fundamental solitons in three-core fiber nonlinear directional coupler with three cores in an equilateral-triangle arrangement have been investigated with two methods. Firstly, by using variational method, we obtained the　equation of transmission coefficient with respect to distance. Secondly, we used the split-step Fourier method (SSFM) to solve the nonlinear Schrdinger equations. The results of both variational method and SSFM indicate that the energy of optical pulses transfer periodically between the three cores and have sharp switching characteristics when the first order intermodal dispersion coefficient is small. Otherwise, the periodicity of the coupling transmission characteristics of optical solitons in fiber coupler and the sharpness of switching are destroyed. The second order intermodal dispersion coefficient and initiative chirp reduce the coupling length, shorten the periods of the energy transfer of optical pulses between the three cores, and increase the threshold switching power. Though the cross phase modulation coefficient has weaker impact on transmission characteristics, it increases the threshold switching power of couplers.