We design various silicon nanowire embedded photonic crystal fibers (SN-PCFs) with different core geometries, namely, circular, rectangular and elliptical using finite element method. Further, we study the optical properties such as group velocity dispersion (GVD), third order dispersion (TOD) of x and y-polarized modes and effective nonlinearity for a wavelength range from 0.8 to 1.6 mu m. The proposed structure exhibits almost flat GVD (0.8 to 1.2 mu m wavelength), zero GVD (approximate to 1.31 mu m) and small TOD (0.00069 ps(3)/m) at 1.1 mu m wavelength and high nonlinearity (2916 W-1 m(-1)) at 0.8 mu m wavelength for a 300 nm core diameter of circular core SN-PCF. Besides, we have been able to demonstrate the supercontinuum for the different core geometries at 1.3 mu m wavelength with a less input power of 25 W for the input pulse of 20 fs. The numerical simulation results reveal that the proposed circular core SN-PCF could generate the supercontinuum of wider bandwidth (900 nm) compared to that from rest of the geometries. This enhanced bandwidth turns out to be a boon for optical coherence tomography (OCT) system.