五阶非线性下不同形状脉冲对的交叉相位调制

Cross-phase modulation of pulse pairs with different shapes in case of quintic nonlinearity

为了探讨光纤中五阶非线性下不同形状光脉冲对的交叉相位调制特性,从包含五阶非线性效应的扩展耦合非线性薛定谔方程组出发,导出了不同形状光脉冲对的非线性相移和频率啁啾公式。计算并比较了它们的相移、啁啾和功率频谱。结果表明,较强的负五阶非线性对相移、啁啾和频谱曲线中心附近的形状有较大的影响,而正五阶(较弱的负五阶)非线性则只使相移和啁啾量增大(减小),使频谱变宽(变窄)、谱峰变多(变少)。孤子对和高斯对的谱形相似,随五阶非线性系数的不同,能量最强的谱峰可能在中央附近也可能在最边缘处。各阶超高斯对的谱形也相似,但能量大部分集中在中央峰处。研究对光脉冲压缩、光开关器件和光纤通信系统性能的提高等有一定的意义。

The purpose of the paper is to study cross-phase modulation of pulse pairs with different shapes in optical fibers with quintic nonlinearity. Starting from the extended coupled nonlinear Schrodinger equations including quintic nonlinearity,the expressions for the nonlinear phase shifts and frequency chirps of different pulse pairs were derived, and the phase shifts, chirps and power spectra of pulse pairs with different shapes were simulated, compared and analyzed. The results show that, the powerful negative quintic nonlinearity can greatly influence the central regimes of the curve shapes of the phase shifts,chirps and spectra. While the positive quintic nonlinearity （weak negative quintic nonlinearity） can only increase （decrease） the phase shifts, chirps,the spectral width, and the number of spectral peaks. The soliton pairs are similar to Gaussian ones in terms of their spectral shapes. Depending on the quintic nonlinearity coefficients,the spectral peaks with the maximum energy may distribute in the vicinity of the center or near the edge. The super-Gaussian pairs are also similar to each other in terms of their spectral shapes. But the energy remains mainly on the central peak. To some degrees, this investigation may contribute to the pulse compression, optical switching devices and improving the performance of optical fiber communication systems, etc.