High fiber density ribbon cable

An optical fiber cable comprising:

• a plurality of stranded core subunits, each core subunit comprising a flexible sheath and a plurality of ribbons arranged in a ribbon group, wherein each ribbon of the plurality of ribbons comprises a plurality of optical fibers such that 50-70% of the cross-sectional area inside the sheath is occupied by the optical fibers;
• and
• a jacket surrounding the plurality of stranded core subunits;
• wherein the plurality of ribbons is arranged into a medial group of ribbons positioned between a first lateral group of ribbons and a second lateral group of ribbons;
• wherein each ribbon of the medial group of ribbons comprises a first number of optical fibers and each ribbon of the first lateral group of ribbons and of the second lateral group of ribbons comprises a second number of optical fibers, the first number being twice the second number;
• and
• wherein the plurality of ribbons comprises at least one first step location where the first lateral group of ribbons transitions to the medial group of ribbons and at least one second step location where the medial group of ribbons transitions to the second lateral group of ribbons and wherein the flexible sheath comprises concave bridging portions at each of the at least one first step location and the at least one second step location.