A telecommunication optical fiber cable and in particular a reduced diameter optical cable with improved installation features for use in the end part of an access telecommunication network. The optical fiber cable has a number of optical fibers; at least a core tube containing the optical fibers; a jacket surrounding the core tube; and at least one strength rod spaced from the central axis, the cable having a twisting stiffness G*J.sub.p, wherein G is the elastic shear modulus; and J.sub.p is the polar moment of inertia of a cable section, wherein the twisting stiffness G*J.sub.p is lower than or equal to 0.10 Nm.sup.2, preferably lower than or equal to 0.05 Nm.sup.2, and more preferably lower than or equal to 0.02 Nm.sup.2. The cable is profitably installable by a blown method.