Studies on Wavelength Selective Filter and Light Source for Wavelength Division Multiplexing Utilizing the Third-Order Nonlinear Effect in Optical Fibers

1. 将两根单模光纤进行融合和拉长制成的光纤定向耦合器，在强激光的激励下，由于光学克尔效应，产生了强度相关的折射率，改变了耦合器的线性耦合特性。在一定波长的入射光下，可以观察到耦合器中耦合端口和通过端口的功率传输发生突变，并且发现随着入射光功率的增加，临界波长向更长的波长偏移。利用锁模钛蓝宝石激光器进行了实验验证，该激光器产生约50飞秒脉冲，波长为800-850nm，重复频率为80MHz。虽然理论计算与实验结果存在一定的差异，但在非线性定向光纤耦合器中证实了飞秒脉冲的全光开关。光纤中超连续谱（SC）的产生对于高凝聚波分（或频分）复用系统具有很大的吸引力，因为它可以在宽的频谱范围内提供短的光脉冲。本文对群速色散沿轴方向变化的色散平坦光纤的SC谱进行了计算机模拟。考虑到高阶色散效应（三阶、四阶和五阶色散效应）、高阶非线性效应（自陡增和受激拉曼散射（SRS）效应）和波长相关损失，我们得出结论：(i)色散衰减的光纤，群速度色散在两个零色散波长处为波长的凸，以及（ii）非线性效应增加的光纤(或等效的，对于入射脉冲（iii），高阶孤子的激发伴随着更高的光脉冲峰值功率，对于有效的SC产生是可取的。少

1. When a fiber directional coupler that is fabricated by fusing and elongating two single-mode fibers is excited with an intense laser light, an intensity dependent index of refraction is induced due to an optical Kerr effect and it modifies the linear coupling characteristics of the coupler. An abrupt change of power transmission at coupled and through ports in the coupler can be observed at a certain wavelength of incident light and it was found that the critical wavelength is shifted to a longer wavelength as the incident power increases. The experimental verification using a mode-locked Ti : sapphire laser that produces approximately 50 femtosecond pulses at wavelengths of 800-850nm with a repetition rate of 80MHz is followed by the theory. Although some discrepancies exist between theoretical calculations and experimental results, all-optical switching of the femtosecond pulses was confirmed in a nonlinear directional fiber coupler.2. The supercontinuum (SC) generation in optical … More fibers is attractive for high-condensed wavelength-division (or frequency-division) multiplexing system since it provides short optical pulses over a broad spectrum range. In this study, some computer simulations are carried out for the SC spectrum from adispersion-flattened fiber with group velocity dispersion varied along the axis. Taking into account of higher-order dispersion effects (the third, fourth, and fifth-order ones), higher-order nonlinear effects (self-steepening and stimulated Raman scattering (SRS) effects), and wavelength dependent losses, we concluded that ( i )a dispersion-decreasing fiber with group velocity dispersion being convex of the wavelength at two zero-dispersion wavelengths as well as ( ii )a fiber having an increasing nonlinear effect (or equivalently, decreasing effective core area) along the axis, and for an incident pulse (iii)the excitation of higher-order soliton that accompanies a higher peak power of optical pulses are desirable for efficient SC generation. Less