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从线性极化模的耦合模理论出发,分析了双叶应力区扭转光纤,即扭转保偏光纤,和四叶应力区扭转光纤。推导应力引起的在光纤芯区各向异性的介质张量表达式;利用该表达式得到线性极化模在有转角时的多叶应力区光纤中传输的耦合模方程;从而推得多叶应力区扭转光纤中的超本地模,由超本地模的相位常数来确定该光纤的双折射。在双叶、四叶应力区理想对称的条件下,前者可以得到较高的椭圆双折射,而后者则无任何双折射。同样的结论可推广到8叶或16叶的扭转光纤,都无任何双折射。
Based on the coupled-mode theory of linear polarization mode, the twisted fiber in the birefringent stress region, namely the twisted polarization maintaining fiber, and the twisted fiber in the four-leaf stress region are analyzed. The medium tensor expression of the anisotropy in the fiber core region is deduced by using this expression. The coupled mode equation of the linear polarization mode in the multi-leaf stress fiber with angle polarization is obtained by using this expression. The multi-leaf stress The zone inverts the local mode in the fiber and the birefringence of the fiber is determined by the phase constant of the super-local mode. Under the conditions of symmetrical bifurcated and four-leaf stress zones, the former can obtain higher elliptic birefringence, while the latter has no birefringence. The same conclusion can be extended to the 8-leaf or 16-leaf twisted fiber, without any birefringence.