A dispersion-shifted optical fiber (NZDSF) includes a central core (r1, Dn1), an inner cladding having at least three zones with a first intermediate cladding zone (r2, Dn2), a second ring zone (r3, Dn3) and a third buried trench zone (Wtr, Dnt). The buried trench zone has an index difference (Dnt) with the optical cladding between −5·10−3 and −15·10−3 and has a width (Wtr) between 2.5 μm and 5.5 μm. The present optical fiber, at a wavelength of 1550 nm, has reduced Rayleigh scattering losses of less than 0.164 dB/km, with limited bending losses.