The present invention introduces a concept of “smart” ribbons, which use functionally tensioned optical fibers during the manufacture of
fiber optic ribbons to create
fiber ribbons with controlled geometrical configuration, optimized
strain distribution and reduced attenuation. The ribbons may have flat or bowed cross section and be straight along the length or curved in its plane, or twisted unidirectionally, or periodically. These shapes and
residual stress-strain state are induced and controlled by using tension functions instead of traditional constant-value tension per
fiber during the ribbon manufacture. Further, the present invention reduces
signal loss and / or attenuation in ribbon fibers caused by an increase in the strain variation from
tensile strain to compressive strain along the length of the individual fibers when ribbons are manufactured, stacked, stranded around a strength member or twisted and bent during cable installation. In a first embodiment of the present invention, either a symmetric or non-symmetric
load distribution is applied across the fibers being placed or drawn into a ribbon structure to eliminate or control residual twist in a completed fiber ribbon. Additionally, in the present invention, the
load distribution on the fibers of a ribbon can be varied (e.g. periodically changed) along the length of the ribbon to provide a ribbon with the required
design characteristics for any particular application. In a second embodiment of the invention, a fiber optic ribbon is made up of a plurality of sub-unit ribbons arranged in substantially the same plane. Each sub-unit ribbon includes a plurality of optical fibers coated by sub-unit matrices.