The present invention relates to a single module transmitting optic fiber with large capacity and low slope of chromatic dispersion. The fiber includes a core and a coating, characterized in that the core has 3-5 core layers with different distributions of refraction index, the coating has 4-6 coating sub-layers. The general slope of chromatic dispersion of the optic fibers at 1550 nm is less than 0.060 ps/nm2.km, the wavelength with zero chromatic dispersion is less than 1420 nm, the effective area is between 55-65 micron m2, the chromatic dispersion in the range of 1530-1565 nm is between 5.0-12.0 ps/nm2.km. The present invention has the advantages of low slope chromatic dispersion, moderate amount of chromatic dispersion, low attenuation, and excellent bend resistance properties.