An optical cable for telecommunications having an optical core and a plurality of protecting and reinforcing elements or avers placed around the optical core. The optical core has a central reinforcing element, a polymer layer, a plurality of optical fibers incorporated in the polymer layer and a thin sheath which covers the polymer layer. The optical fibers have an alternating spin about their own axes with a maximum value of at least 4 twists per meter, and a core having a mean ellipticity in the range of 0.25 to 0.55, in such a way that the effects of birefringence of the fibers caused by the cabling process are significantly reduced.