Disclosed is a chromatic dispersion compensating optical fiber comprising a central core, an intermediate cladding having a width (r.sub.2-r.sub.1) of 2.0 microns or greater, and a depressed inner cladding having a refractive index difference Dn.sub.3 with the external optical cladding of -3.0.times.10.sup.-3 or lower. At a wavelength of 1550 nm, the optical fiber exhibits a positive chromatic dispersion of 21 ps/(nmkm) or higher and a ratio of mode radius to intermediate cladding radius of (W.sub.02/r.sub.2) of 0.7 or less. The present optical fiber has a good figure of merit value and limited bending and microbending losses. The optical fiber can be rolled up in a housing of reduced size in a chromatic dispersion compensating optical module having limited insertion losses and reduced polarization mode dispersion.