高阶色散和五阶非线性下的交叉相位调制不稳定性

Modulation Instability Induced by Cross-Phase Modulation in Case of High-Order Dispersion and Quintic Nonlinearity

在同时考虑到光纤的二至四阶色散和三、五阶非线性的情况下,研究了四阶色散、五阶非线性以及入纤功率对双光束交叉相位调制(XPM)不稳定性的综合影响。研究表明,在高阶色散下,正负五阶非线性的存在仍然分别对交叉相位调制不稳定性起加强和削弱的作用;三阶色散对不稳定性增益谱无影响;当四阶和二阶色散系数同号时,四阶色散的存在导致交叉相位调制不稳定性增益谱出现一个新的远离零点的第二谱区,且该谱区由两个始终相连的小谱区组成;第一谱区的谱峰与第二谱区中靠近零点的小谱区的谱峰相当;随着其中一束光的入射功率的增加,两大谱区从分离到靠近再到合二为一,从三个谱峰过渡到两个谱峰;正(负)色散区的第二谱区中靠近(远离)零点的小谱区的谱峰和谱宽很小。在其他色散区时,不稳定性增益谱则只有第一或第二谱区。

Taking into account the second- to the fourth-order dispersion and the quintic nonlinearity of an optical fiber, the synthetical effects of the fourth-order dispersion, the quintic nonlinearity and the input optical power on modulation instability induced by cross-phase modulation of two optical waves are investigated. The results show that, in case of high-order dispersion, the positive and negative quintic nonlinearity also intensifies and weakens the cross-phase modulation instability, respectively. The third-order dispersion does not influence the gain spectra of cross-phase modulation instability. When the fourth-order dispersion has the same sign as the second-order one, the existence of the fourth-order dispersion makes a new gain spectrum called the second one appear. And the second gain spectrum actually consists of two small spectra which are always linked togather. The first gain spectrum has nearly the same peak value as that of the small spectrum closing to the zero of the second gain spectrum. With the increase of the input optical power of one of the optical waves, from being separated from each other to drawing near, the two spectra merge into single one eventually, and the peak numbers of the gain spectra also become two from three. In the second gain spectrum, the peak value and the width of the small spectrum which is closing to （far away from） the zero are comparatively smaller in the normal （abnormal） dispersion region. In the other dispersion regions, there exists only the first or the second spectral region.