Polarization properties of photonic bandgap birefringent holey fiber

We studied polarization properties of the photonic bandgap holey fiber, in which birefringence is induced by residual ellipticity of the hollow core. Using specially developed interferometric method, we measured dependence of phase and group modal birefringence upon wavelength within guidance band. Our results show that the phase birefringence (B) is of the order of 10–5 , depends parabolically upon wavelength, and reaches minimum value at the center of the bandgap. Due high chromatic dispersion of B, the absolute value of the group modal birefringence (|G|) is one order of magnitude higher than B at the boundaries of the bandgap and crosses zero value at the center of the bandgap. We also determined the susceptibility of the phase and group modal birefringence to strain and hydrostatic pressure in the whole analyzed spectral range.