Confinement losses in air-guiding photonic bandgap fibers

The wavelength dependence and the structural dependence of confinement losses in air-guiding photonic bandgap fibers (PBGFs) are, for the first time, investigated by using a full-vector finite element method. It is confirmed from computed results that one of the main causes of transmission losses in air-guiding PBGFs is the confinement loss and that, even if using large air holes of diameter to pitch ratio of 0.9, at least twenty rings of air hole arrays are required in the cladding region to reduce the confinement loss to a level of 0.01 dB/km.