Lighting units include a light source, a light-diffusing optical fiber assembly, and a support substrate. The light-diffusing optical fiber assembly includes a plurality of light-diffusing optical fibers that are arranged in a bundled portion surrounded by a jacket and a splayed portion free from the jacket. The plurality of light-diffusing optical fibers in the splayed portion scatter light optically coupled into the plurality of light-diffusing optical fibers from the light source. The plurality of light-diffusing optical fibers within the splayed portion are structurally coupled to the support substrate.