Advances in photonic bandgap fiber functionality

In order to take advantage of the many intriguing optical properties of photonic bandgap fibers, there are some technological challenges that have to be addressed. Among other things this includes transmission loss and the fibers ability to maintain field polarization. The work presented in this thesis addresses these two fundamental properties in both hollow core photonic crystal fibers and solid photonic bandgap fibers. Transmission loss in hollow core photonic crystal fibers is dominated by light scattering at the silica surfaces inside the fiber. In the current work it has been experimentally demonstrated that the minimum loss wavelength is located in the spectral region around 2000 nm, where the transmission loss in these fibers is significantly lower than in conventional solid silica fibers. Additionally it has been shown that transmission loss can be lowered roughly 40% by implementing six antiresonant feature on the core wall to expel the light field from the silica surfaces. Form induced birefringence can be introduced by making the fiber cross section 2-fold symmetric. This was achieved by implementing only four antiresonant features on the core wall. A low loss fiber with a transmission loss of 16 dB/km and a polarization cross talk