A fiber optic ribbon having a plurality of optical fibers held together by a matrix material is disclosed. The matrix material has a first end with a first shape and a second end with a second shape, where the first shape is different than the second shape. In one embodiment, the first end has a concave end portion and the second end has a convex end portion. The fiber optic ribbon is advantageous as a subunit of a larger ribbon since the first end of a first subunit can interlock with a second end of a second subunit, thereby providing a robust structure. Moreover, the distance between optical fibers of adjacent subunits is reduced so the fiber optic ribbon may allow mass fusion splicing of same using standard splice chucks.