凹形色散分布光纤中超连续谱特性分析

比较了在不同色散分布的色散渐减光纤中超连续（SC）谱的产生。结果表明，当光纤的色散值关于中心波长对称、且随着传输距离增加，经由反常色散区过渡到正常色散区的、凹形色散分布的色散渐减光纤更有利于产生平坦、带宽的超连续谱。从频域的全场方程出发，模拟了脉冲在光纤中的传输情形，发现脉冲在凹形色散分布的光纤中传输时，不仅在反常色散区能更大程度被压缩，在正常色散区由于存在零色散波长点，还能更进一步展宽，从而得到更宽、更平坦的超连续谱。在谱强为-27dB时，谱宽可达到298nm，比相同情况下的凸形色散的光纤中超连续谱增宽97nm。结果显示，凹形色散分布的光纤比凸形色散分布的光纤在超连续谱的产生上有更明显的优势，可以得到更宽的超连续谱。

Supercontinuum Spectrum Generation in an Optical Fiber with a Concave Dispersion Profile

The supercontinuum(SC) spectra generated are compared in dispersion decreasing fibers(DDF) with different dispersion profile.Results show that DDF with concave dispersion profile is more beneficial to generate flat and broad SC spectra,when the dispersion profile of the fiber is symmetrical to central wavelength and decreases from anomalous dispersion region to normal with propagation distance.Optical pulses propagation in fibers has been studied by utilizing total field formation in the frequency field.It is found that optical pulse can be compressed more extensively in anomalous dispersion region,furthermore,optical spectra can be further broadened because there exits a zero-dispersion wavelength in normal dispersion region,leading to the generation of a flatter and broader SC spectra.The spectral bandwidth can reach 298 nm when relative spectral intensity is-27 dB,which is 97 nm broader than that in a convex dispersion profile fiber under the same situation.It is proved by numerical calculation that DDF with concave dispersion profile can generate broader spectrum than that in DDF with convex dispersion profile under the same conditions.