圆芯边孔光纤的应力区和双折射

报道了圆芯边孔光纤(CSF)中应力分布和双折射的研究结果。用有限元法建立了求解圆芯边孔光纤横截面应力和双折射的计算模型,分析了圆芯边孔光纤横截面应力和应力双折射的分布形态,给出了详尽的物理解释。计算结果表明圆芯边孔光纤的横截面上出现应力分量的拉应力区和压应力区,应力区在纤芯附近对称分布,且不同应力区中应力双折射取向不同。应力分量和应力双折射在圆芯边孔光纤横截面上积分为零。圆芯边孔光纤的几何双折射随波长增加而增大,短波长处几何双折射为零,模式双折射等于应力双折射,随着波长增加,模式双折射逐渐偏离纤芯中心处应力双折射而靠近几何双折射,到长波长处模式双折射主要是几何双折射。对于不同材料组成和结构尺寸的圆芯边孔光纤,模式双折射的数值在10-5量级,随波长增加模式双折射先减小后增加。

Research on the Stress Zones and Birefringence of Circular-Core Side-Hole Fiber

The research results of stress distribution and birefringence of circular-core side-hole fiber(CSF)are reported.The finite element method is used to build a model,in which the stress distribution in cross-section of CSF and its birefringence is calculated.The distribution manner of stress and stress-induced birefringence on the cross-section are analyzed,at the same time,the clear explanation is given.Computed results show that tension-stress zones and compression-stress zones of stress components,which are symmetrically located near fiber core,appearing on the cross-section.It's also shown that stress-induced birefringence has different direction in different stress zones.The surface integral of stress components and stress-induced birefringence are equal to zero respectively.Geometrical birefringence of CSF will increase when the wavelength gets longer.At a shorter wavelength,such as 600 nm,Geometrical birefringence is equal to zero and mode birefringence is equal to stress-induced birefringence.When wavelength gets longer,mode birefringence will deviate from stress-induced birefringence at the center of fiber core and be close up to geometrical birefringence gradually.At a longer wavelength,such as 1550 nm,geometrical birefringence is the dominating component of mode birefringence.For CSFs with different materials and structural dimension,when wavelength gets longer,their mode birefringence will decrease little by little,and then increase gradually,with a value at level of 10-5.