In contrast with conventional optical fibers, photonic crystal fibers (PCF) present a diversity of new

and improved features, which provide several new applications such as nonlinear fiber optics, fiber

lasers, supercontinuum generation, and fiber sensors. In many applications of all-optical signal

processing, optical fibers with both high birefringence and high nonlinearity are desired, because

many nonlinear effects in optical fiber are polarization-sensitive, and maintaining the state of

polarization (SOP) is essential for good performance. In particular, with enhanced nonlinearity, both

the footprint and power-consumption of optical device can be reduced. By carefully arranging the air

holes of PCF, high birefringence in excess of 103 can be readily achieved