通过数值计算,对色散平坦渐减光纤(DFDF)产生平坦超连续谱(SC)进行了研究。结果表明,该光纤中抽运脉冲峰值功率对超连续谱的形成有着重要的影响,超连续谱的产生存在阈值功率,抽运脉冲峰值功率由阈值逐步增大,超连续谱随之愈宽,平坦度愈好,但增大到一定值时,超连续谱的平坦度会开始劣化,综合考虑各因素找到了产生平坦超连续谱的最佳功率;四阶和五阶群速度色散(GVD)是该种光纤产生平坦超连续谱的决定因素,三阶及五阶以上群速度色散的作用可以忽略;进一步研究发现,超连续谱频谱展宽的机理主要来自脉冲的自相位调制效应,自变陡、受激拉曼散射等高阶非线性效应对平坦超连续谱的产生没有显著影响,在计算的时候完全可以忽略。

Supercontinuum generated in dispersion-flattened/decreasing fiber is simulated and analyzed in detail. It is found that the peak power of pump pulse is very important to supercontinuum generation from the fiber and there is a threshold power. With the increasing of the peak power of pump pulse, the spectral width becomes wider and the flatness of supercontinuum becomes better. But if the peak power of pump pulse is increased further, the flatness becomes bad. In the end, a optimal peak power for supercontinuum generation is found. It is also found that the fourth and fifth order group-velocity dispersions are crucial to flatly wideband supercontinuum generation from the fiber, dispersion of the third and the other higher than fifth order can be ignored. It is further found that the higher-order nonlinear effects such as stimulated Raman scattering and self-steepening are negligible in the case.