根据光纤光学传输理论建立了偏芯光纤的理论计算模型, 通过菲涅耳公式推导出偏芯光纤倏逝波的表达式, 进而求出了倏逝波的穿透深度。运用 RSoft软件中的 BeamPROP模块对偏芯光纤进行光学结构建模, 仿真出偏芯光纤中的模场分布、倏逝波场以及基模有效折射率随纤芯偏移距离的变化趋势。仿真结果表明: 偏芯光纤的包层倏逝波散射随着纤芯与外界介质距离 δ增大而显著减小; 同时基模有效折射率随纤芯与外界介质距离 δ的增大而显著增大, 当 δ达到 8 μm时, 有效折射率趋于稳定。

The theoretical model of the eccentric core fiber is established according to the traditional optical transmission theory.Moreover, the expression of evanescent wave of eccentric core is deduced according to Fresnel equation so that the depth of penetration is solved.Through the structure modeling of eccentric core optical fiber completed by BeamPROP module, the variation trend of modal field distribution, evanescent wave, as well as fundamental mode effective index with the eccentric distance is obtained.The simulation result shows that the evanescent wave declines with the increase of δ.The fundamental mode effective index increases as δ dose, and it will be stabilized when δ equals 8 μm.