光纤端面衍射场光束的特征参数

Characteristic beam parameters in diffracted field of fiber end face

光纤端面衍射场光束的特征参数由基于二阶矩和微分算子算法定义的近场模场半径、远场发散角角半径和基于二阶矩算法定义的光束传输因子综合描述.在傍轴近似条件下,推导出光束参数之间满足以光束传输因子为枢纽的简单关系式,给出光束传输因子大于1的结论.提出光纤端口衍射场的光束参数可直接由光纤模式场分布,或由可实际精确测量的远场衍射频谱分布精确计算,为精确测量和计算光纤特征参数提供了理论依据.最后推导出阶跃折射率光纤LP01模衍射场光束特征参数的解析函数表达式和光束特征参数的范围.

The mode field radii in the near field and the angular radii of the far field divergence defined by second moment and differential operator algorithm and the beam propagation factor defined by second moment algorithm were presented to describe the characteristic beam parameters in the diffracted field of the fiber end face comprehensively. In the condition of paraxial approximation, the simple relationship of the beam parameters hinged on the beam propagation factor were educed. The verdict that beam propagation should be more than 1 for fiber was presented. The beam parameters can be calculated accurately from the mode field distribution of the fiber, or from the diffraction frequency spectrum distribution in the far field, which is experimentally measurable exactly. The above principles and findings can serve as theoretical basis for measuring and computing the characteristic parameters of fiber. The analytic functions and scopes of the characteristic beam parameters in the diffracted field of LP01 mode step index fiber were deduced.