应力双折射光纤的积分计算方法与优化设计

Integral Method of Stress Birefringence Calculation and Fiber Design Optimization

研究了任意形状应力区的光纤在纤芯中心处的应力场分布和双折射大小计算方法,并对领结光纤进行了优化设计。采用COMSOL Multiphysics软件中的固体力学模块,研究了相同应力区面积、不同形状的应力型光纤在纤芯中心处的应力场大小。结果表明,软件仿真值与运用微元应力积分公式计算得到的结果一致。因此对于任意形状应力区光纤在纤芯中心处的应力场分布与双折射可以直接运用解析公式求解。通过对相同应力区面积的不同类型光纤的应力微元分析,发现领结光纤在纤芯处的双折射并非最大,这与惯常认为的领结光纤双折射最大的结论相反。由此,对领结光纤重新进行了优化设计,得到了具有更大双折射的"月牙形"光纤。

The calculation method of stress field and birefringence at the fiber core center with any stress region shape is studied. The design of bow-tie fiber is optimized. With the help of solid mechanics module in COMSOL Multiphysics software, stress field distribution at fiber core center is studied when the stressinduced fiber has same stress area and different stress region shapes. The result shows that the numerical value acquired by integral method agrees with the value from software simulation. Therefore, the stress distribution and birefringence at fiber core center can be calculated by integral method directly even if the stress- induced fiber has any stress region shape. By means of stress element analysis based on integral method, it is found that the bow- tie fiber birefringence at fiber core is not the biggest compared with other type of stress- induced fiber if their stress area is the same. This is against the usual conclusion that the birefringence of bow- tie fiber is maximal. To get higher birefringence, bow- tie fiber is optimized again. As a result, a new fiber with＂lunar＂stress region is obtained.