Design and analysis of a single mode bend insensitive equiangular spiral photonic crystal fiber with large effective area

Abstract

The theories and properties of the conventional hexagonal lattice Photonic Crystal Fiber (PCF) are well established and their worth in different applications in fiber optics is also well accepted. On the other hand, the newly introduced equiangular spiral PCF is yet to be investigated thoroughly. In this thesis, the optical mode of the PCF structure is determined by using full vectorial finite element method (FEM) based software ‘COMSOL Multiphysics’ and different properties of ES-PCF are calculated therefrom. Different useful designs like dispersion compensating ES-PCF, highly birefringent ESPCF, bend insensitive single mode ES-PCF with large effective area have been obtained. To be specific, an ES-PCF is designed having flat negative dispersion profile with average dispersion around −396 ps/nm-km and dispersion variation of only 10.4 ps/nm-km for residual dispersion compensation of the fiber optic communication link over the wavelength range 1350 nm to 1675 nm. Also, a similar design has been developed that exhibits a very high birefringence of 0.0278 as well as flat negative dispersion profile. Next, liquid crystal infiltration in some air holes in the core is exploited to achieve a completely single polarization dispersion compensating fiber having average dispersion −259 ps/nm-km with dispersion variation of only 4.58 ps/nmkm over the same wavelength range. Moreover, a new circular lattice air hole PCF (CPCF) has been proposed for both WDM transmission and fiber to the home application. The C-PCF exhibits single modedness along with very low bending loss for the fundamental mode and effective area as high as 260 μm2 for WDM application which is higher than the previously reported values in the literatures. Apart from the above works, a modified bend loss formula for step index fibers has been developed and verified in this thesis. Also, this modified formula applies well, though in a limited range for PCFs, in predicting bending loss. The works in this thesis is believed to be a gateway for the future research on ES-PCF and PCFs with irregular lattice structures.