Abstract: An optical fiber for compensating chromatic dispersion of a positive chromatic dispersion optical fiber has at a wavelength of 1 550 nm a chromatic dispersion less than −40 ps/(nm.km), a ratio between the chromatic dispersion and the chromatic dispersion slope in the range from 50 nm to 230 nm, an effective area greater than or equal to 12 &mgr;m2 and curvature losses less than or equal to 0.05 dB. It is used for in-line compensation of cumulative chromatic dispersion in a positive chromatic dispersion line fiber. A fiber optic transmission system is also disclosed using a fiber of this kind to compensate the cumulative chromatic dispersion in the line fiber.