单模螺旋光纤的本地场

LOCAL FIELD IN A SINGLE -MODE HELICAL FIBER

该文从波动方程出发，直接在本地坐标系（Ｓｅｒｒｅｔ－Ｆｒｅｎｅｔ框架）中求解单模阶跃型折射率分布的圆形芯弱导螺旋光纤，应用微扰分析法得到了基模场分布和传播常数的解析表达式。结果表明：（１）单模螺旋光纤的基模是右旋和左旋圆偏振模；（２）螺旋光纤基模间的传播常数之差为２τ。这两个理论结果和已知的实验结果一致。

Based on the wave equation,we directly analyse a single-mode helical fiberwith a circular cross section and step profile of the refractive index in the localcoordinate system. Withe the perturbation method,the analytical expressions ofthe fundamental mode field and the propagation constant are given,Two resultsare brought about:(1)the fundamental modes in a single-mode helical fiber areright-rotated and left-rotated circularly polarised modes.(2)the difference ofpropagation constants between the two modes iS 2τ.The theoretical results agreewith those of the known experimental measurements.