A fiber optic cable can comprise small spheres or balls disposed in the cable's interstitial spaces, for example between the cable's optical fibers and a surrounding buffer tube. The spheres can comprise foam rubber, closed-cell or open-cell porous polymer, or some other soft material. Typical diameters for the spheres can be in a range of 1 to 2.5 millimeters. A soft composition of the spheres can cushion the optical fibers and physically impede water ingress into the cable. Additional fiber protection can arise from the ability of the loose spheres to rotate individually, in a ball-bearing effect. Thus, sphere-to-sphere motion can absorb physical stresses associated with bending, twisting, bumping, and stretching the cable during installation, thereby shielding the fibers from damage.