Highly Birefringent Microstructured Fibers With Low Mode Asymmetry

Highly birefringent microstructured fibers (HB MSFs) with similar mode field sizes along the two orthogonal axes have been presented. The core of the HB MSF is surrounded by two or more concentric rings having identical circular air holes. The key feature of this setup is that the first ring contains one or two pairs of holes, which are more widely spaced than others, i.e., they have one or two wider bridges. The shape of the core may be circular or elliptical. The HB MSFs were characterized using the finite element method. Simulation results show that HB MSFs with a certain relationship between the width of the wider bridges and the core ellipticity may have high birefringence (more than 2.7 × 10^-3) and equal mode sizes along the two orthogonal axes. We have fabricated and investigated several such fibers, that have birefringence up to 2.9 × 10^-3 and almost equal measured mode field sizes along the two orthogonal axes.