This tutorial presents a numerical analysis of continuous wave and ultrashort pulse evolution through a twisted single-mode optical fiber, modeled by the nonlinear Schrdinger equation. In this model, the polarization evolutions of the continuous wave and the pulse profile are studied by the changes in ellipticity and ellipse rotation, which are driven by the inherent linear birefringence of the optical fiber, the induced nonlinear birefringence due to the centrosymmetric response of the fiber and the induced circular birefringence due to a uniform twist applied along the fiber. In particular, the role of each birefringence effect is studied in detail. As a result, it is pointed out that a large uniform twist rate allows viewing the optical fiber as an isotropic waveguide that preserves ellipticity. On the other hand, a saturable absorber mechanism based on a linear polarizer and the ellipse rotation in a twisted fiber, which introduces a nonlinear transmission characteristic that is part of the principles of operation of the mode-locked fiber lasers, is analyzed in order to illustrate the applicability of this numerical study.

本教程介绍了通过扭曲的单模光纤对连续波和超短脉冲演化的数值分析，由非线性 Schrdinger 方程建模。在该模型中，通过椭圆度和椭圆旋转的变化来研究连续波和脉冲轮廓的偏振演变，这是由光纤固有的线性双折射驱动的，由光纤的中心对称响应引起的感应非线性双折射。纤维和由于沿纤维施加的均匀扭曲而引起的圆形双折射。特别是，详细研究了每个双折射效应的作用。结果指出，大的均匀扭曲率允许将光纤视为保持椭圆度的各向同性波导。另一方面，