Modeling of dispersion effects in elliptical care highly birefringent fibers

The results of modeling of spectral characteristics of modal birefringence and its sensitivity to temperature using different approaches for calculation the residual thermal stress are presented. The modeling was carried out using the modified perturbation approach first proposed by Kumar. The modification consists in introducing the first order correction term associated with stress induced changes of refractive index and makes it possible to model the fiber response to different physical parameters. The residual thermal stress distribution in the fiber cross section was calculated using two methods. First, we applied a widely known procedures proposed by Tsai et al. In this method the differences of Young's modulus and Poisson ratio between the core and cladding are neglected. We also calculated stress distribution using finite element method, in which the differences in material constants between the core and cladding were taken into account. Finally, the spectral characteristics of modal birefringence and its sensitivity to temperature were calculated for thermal stress distributions obtained with different methods. The comparison of calculated characteristics with experimental data shows that Tsai method is less accurate. For more accurate method of stress calculations. the differences between experimental and theoretical values was lower than 15% for modal birefringence and lower than 7% for sensitivity of modal birefringence to temperature.