Highly birefringent microstructured fibers with low mode field asymmetry

In this paper we continue numerical and experimental investigations of highly birefringent microstructured fibers (HiBi MSFs) proposed earlier. These HiBi MSFs have an elliptical or circular core surrounded by two or more concentric rings of holes of constant diameter d. The holes in the first ring around the core have equal spacing Λ between the centers, except one or two pairs of holes with increased spacing Λ1. For convenience, we use the following code name characterizing the new HiBi MSF structure: MNKLec, where M is the number of holes in the first ring; N is the number of gaps in the first ring; K is the number of additional holes, which cover the gaps; L is the number of holes in the second ring; e means that the core is elliptical (c, circular); c means that the holes are circular (e, elliptical). To characterize the HiBi MSF shape, we use parameter δ defined as the deviation of the angle between adjacent holes in the first ring from its maximum value.