We design a photonic silicon nanowire embedded microstructured optical fiber which is a special class of waveguide whose core diameter is of subwavelength or nanometer size with the air holes in the cladding. We study the optical waveguiding properties, namely, waveguide dispersions, fractional power and effective nonlinearity by varying the core diameter. The results reveal that the air-clad silicon subwavelength nanowire exhibits several interesting properties such as tight-confinement, a large normal dispersion (82,385 ps²/km) for 300 nm core diameter and a large anomalous dispersion (−6817.3 ps²/km) for 500 nm core diameter at 1.95 μm wavelength. The structure offers two zero dispersions, one at 1.26 μm wavelength for a core diameter of 300 nm and another at 1.83 μm wavelength for 400 nm core diameter. Besides, it provides a large nonlinearity (5672.7 W⁻¹ m⁻¹) at 0.450 μm wavelength for 300 nm core diameter. These enhanced optical properties might be suitable for various nonlinear applications.