基于包含拉曼效应的三次-五次变系数非线性薛定谔方程的啁啾孤子解,研究了周期色散分布的饱和非均匀光纤系统中啁啾单孤子和双孤子的频谱演化特性。结果表明,在均匀光纤和非均匀光纤中,由于高阶效应仅与孤子的相位相关,因此高阶效应不会影响孤子时域中的波形,但会直接影响孤子的频谱。在均匀光纤中,孤子啁啾参数约化为零,高阶效应使无啁啾的单孤子频谱发生红移,且频谱的高频侧出现旁瓣;相对于单孤子,平行演化和相互碰撞的双孤子的频谱均会产生分裂,而高阶效应会加剧双孤子频谱的分裂。与均匀光纤中单孤子和双孤子的特性相比,在周期色散分布光纤中,啁啾参数周期性的变化导致单孤子的脉宽和频谱周期性地被压缩和展宽;而对于双孤子,在碰撞时其频谱出现极大展宽,啁啾使准平行传输和相互碰撞的双孤子在相互靠近时的频谱发生蓝移,而高阶效应使其频谱发生红移。研究结果对研究超快光通信系统中高功率信号的频谱特性具有重要的意义。

Based on the chirped soliton solutions of the nonlinear Schrödinger equation with cubic-quintic variable coefficients under Raman effect, the spectral evolution characteristics of chirped one-soliton and two-soliton in a saturable inhomogeneous fiber system with a periodic dispersion distribution are studied. The results show that in both homogeneous and inhomogeneous fibers, the high order effects do not affect the soliton waveforms in time domain, but directly influence their spectra, because they are only related to the phase of the solitons. In the homogeneous fiber, the chirp parameters of solitons are reduced to zero and the high-order effects make the spectrum of unchirped one-soliton redshift and the accompanied sidelobe appear at the side of high frequency. Compared with the one-soliton, the two-soliton with parallel transmission or colliding evolution shows splitting in its spectrum, and the high-order effects enhance the spectral splitting of two-soliton. Compared with the properties of one-soliton and two-soliton in a homogeneous fiber, the periodical change of chirp parameters in a periodic dispersion-distributed fiber causes that the pulse width and spectrum of one-soliton are periodically compressed and expanded. In contrast, as for the two-soliton, its spectrum is significantly broadened during collision and the chirp makes the spectrum of two-soliton blueshift for two-soliton with quasi-parallel transmission or colliding evolution, while the high-order effects make the spectrum redshift. The presented results are of great significance to study the spectral characteristics of high power signals in ultrafast optical communication systems.