A novel selective-filling technology of photonic crystal fibers (PCFs) employing a simple selective-blocking process using UV gel is demonstrated in this thesis. In this study the liquid-filled PCFs with the filling in inside three layers and whole four layers represent the insertion loss of gel 7.5dB and the photonic band gap (PBG) guiding effect at wavelength 1100nm~1300nm, having potential to be tunable optical filters by filling the liquid crystal. The liquid-filled PCFs without the filling of the most inside 1ayer represent low insertion loss of gel 2dB and the total index reflection (TIR) guiding effect, having potential to be low loss tunable fiber gratings by filling the liquid crystal. The liquid-filled PCFs with the filling in middle a layer represent the elliptical far field pattern and effect of birefringence at wavelength 1600nm.