We study the role of sub-micron defect in the characteristics of fiber for potential nonlinear applications. Out of several geometries of fiber designs, we recognize that fiber with minimum positive dispersion along with a large nonlinearity is a potential candidate for continuum generation. Using the theory of soliton fission, we demonstrate the role of soliton self-frequency shift in the spectral broadening and an octave-spanning continuum in 1 m of defective core PCF is reported. © 2019 The Author(s).