Birefringence Properties of Side-Hole Optical Fibers

An analysis of birefringence properties of side-hole optical fibers has been presented in this work by using a finite element method. The birefringence caused by the thermal stress due to the different thermal expansion coefficients of core and cladding and also the geometrical birefringence are simultaneously considered. The validity of the calculations are checked for circular fibers with circular or elliptical core by comparing with the existing results. The influences of core ellipticity, air-hole radius and position, as well as the thermal expansion coefficient of core and cladding materials are discussed. The change of refractive index in x and y polarized light due to photo-elastic effect is also calculated. The birefringence increases with the core ellipticity as the stress in and around the core gets higher with the increase in the core ellipticity and pitch length.