聚合物中空环芯光纤中OAM模式传输的几何容差特性研究

基于全矢量有限元法,研究了聚合物中空环芯光纤结构的椭圆、偏芯、直径不均匀等几何形变对光纤中轨道角动量模式性能的影响;此外,还研究了在保持轨道角动量模式稳定传输的条件下,光纤结构所能承受的最大形变.结果表明椭圆和偏芯会引起轨道角动量模式在传输过程中发生奇偶模间的模式走离,导致轨道角动量模式纯度降低,进而导致模式串扰增大;数值计算结果表明,当椭圆度或偏心度小于1%时,模式纯度大于99.02%,串扰小于-20.08dB.光纤的直径不均匀仅对光纤中所能支持的轨道角动量模式数量造成影响,纤芯半径越大,光纤中所能传输的轨道角动量模式越多;直径不均匀度在-3%~10%内的光纤均可支持原有的26个轨道角动量模式.

OAM Mode Transmission Characterization of Hollow Ring-core POF Related to Geometric Tolerance

The influences of the geometric deformation of the fiber such as ellipse,misalignment and diametrical nonuniformity on the performance of Orbital Angular Momentum(OAM)modes propagated in the Hollow Ring-core Polymer Optical Fiber(HRC-POF)are studied by full vector finite element method.In addition,the maximum deformation that the fiber can withstand under the condition that maintains the stable transmission of the OAM mode is also studied.The results show that the ellipse and misalignment will cause the mode walk-off upon propagation,leading to the decrease of the purity of synthesized OAM modes and the increase of the crosstalk.Numerical results show that the purity of synthesized OAM modes is more than 99.02%and the crosstalk is less than-20.08 dB when the ellipticity or misalignment is within 1.0%.The diametrical nonuniformity of the fiber will only affect the number of OAM modes supported in the HRC-POF.The larger the core radius is,the more OAM modes can be transmitted in the fiber.Besides,the original 26 OAM modes can be supported in HRC-POF when the diametrical nonuniformity is-3%to 10%.