A robust design for a photonic crystal fiber (PCF) based on pure silica with small normal dispersion and high nonlinear coefficient for its dual concentric core structure is presented. This design is suitable for flat broadband supercontinuum (SC) generation in the 1.55-μm region. The numerical results show that the nonlinear coefficient of the proposed eight-ring PCF is 33.8 W?1.km?1 at 1550 nm. Ultraflat dispersion with a value between -1.65 and -0.335 ps/(nm.km) is obtained ranging from 1375 to 1625 nm. The 3-dB bandwidth of the SC is 125 nm (1496–1621 nm), with a fiber length of 80 m and a corresponding input peak power of 43.8 W. The amplitude noise is considered to be related to SC generation. For practical fabrication, the influence of the random imperfections of airhole diameters on dispersion and nonlinearity is discussed to verify the robustness of our design.