US Patent 7116872 Optical fiber tape core

In an optical fiber ribbon 1 according to the present invention, four optical fibers 10, 20, 30 and 40 are arranged in parallel to each other in a plane, a part of the periphery of these four optical fibers is covered with a ribbon matrix 51, but no rest thereof is covered with the ribbon matrix. First areas covered with the ribbon matrix 51 and second areas uncovered with the ribbon matrix alternate with each other along the longitudinal direction thereof. Alternatively, the optical fiber ribbon 1 is covered with the ribbon matrix over its entire length. In the glass section of each optical fibers, the mode field diameter defined by the definition of Petermann-I at a wavelength of 1.55 μm is 8 μm or less, and the cable cutoff wavelength is 1.26 μm or less.