An assembly for fabricating an optical fiber ribbon from optical fibers that extend in a longitudinal direction includes a spacing device. The spacing device is operative to vary the spacing between the optical fibers in the lateral direction. The spacing device can be a rotatable cylinder having diverging external grooves that respectively receive the optical fibers. A bonding device applies bonding material to the optical fibers to form an optical fiber ribbon, after the spacing between the optical fibers has been varied by the spacing device. In accordance with a method of manufacturing an optical fiber ribbon, optical fibers that extend in a longitudinal are advanced along travel paths defined by the grooves of the spacing guide. The travel paths diverge from one another in a lateral direction that is generally perpendicular to the longitudinal direction so that as the optical fibers are advanced the optical fibers become further spaced apart from one another in the lateral direction. The increased spacing between the optical fibers is maintained by bonding the optical fibers together.