基于光束传播法的偏芯光纤传输特性研究

摘要

The propagation characteristics of eccentric core optical fiber are different from the conventional optical fiber. The numer⁃ical simulation method is analyzed and its advantages and disadvantages of the optical fiber′s propagation characteristics are com⁃pared then the Beam Propagation Method is adopted to study the propagation characteristics of eccentric core optical fiber. The the⁃oretical calculation model of eccentric core optical fiber is established and its mode field distribution characteristics are analyzed. The expression of evanescent wave of eccentric core optical fiber is deduced. It is shown that the evanescent wave can be used in optical sensing when the fiber core is close to the cladding. The BeamPROP module in the RSoft software is used to model the opti⁃cal fiber structure. Based on the beam propagation method the mode field characteristics and optical power characteristics of the ec⁃centric core optical fiber are simulated then the relationship between the effective refractive index of the base model as well as the birefringence index and the core shift distance.%偏芯光纤由于纤芯偏离中心轴线，其光纤传输特性与传统光纤不同。本文对常用的光纤传输特性数值模拟方法及其优缺点进行了分析比较，确定采用光束传播法对偏芯光纤的光传输特性进行研究。建立了偏芯光纤的理论计算模型，分析了偏芯光纤对应的模场分布特性。推导出偏芯光纤倏逝波的表达式，当纤芯距离包层外表面非常近或贴近外表面时，可利用倏逝波进行光学传感。运用 RSoft 软件中的 BeamPROP 模块对偏芯光纤进行了光学结构建模。基于光束传播法，对偏芯光纤中的模场特性及光功率特性进行了仿真分析，并得到了基模有效折射率和双折射与偏芯距离的变化关系。