We present a numerical investigation of the generation of an ultra-broadband optical similariton spectrum in a photonic crystal fiber (PCF) with a carbon disulfide core through Raman amplification. The proposed PCF has an extremely high nonlinear coefficient of 4519 W −1 km −1 at a telecommunication wavelength of 1550 nm and exhibits near-zero ultraflattened normal dispersion of −1.5ðps∕nm∕kmÞ as well as low confinement loss of about 10 −9 dB∕m at 1550 nm. The numerical study was conducted using full vectorial finite-element method with a circular perfectly matched layer as a boundary condition. The similariton generated in the proposed PCF has an ultrabroadband and flat spectrum centered at 1550 nm, which spans from 1383 to 1719 nm via 14 mW input peak power and over a fiber length of only 83 cm. This continuum spectrum covers both C and L bands and can be divided into several narrow bands centered at the wavelengths of the wavelength division multiplexing channels.