Lighting units and light fixtures incorporating lighting units having light-diffusing optical fiber are disclosed. Lighting units include a light source, at least one light-diffusing optical fiber optically coupled to the light source, and a support plate. The at least one light-diffusing optical fiber scatters light that is optically coupled into the at least one light-diffusing optical fiber from the light source. The support plate has a retention groove to which a portion of the at least one light-diffusing optical fiber is coupled. The support plate also includes a perimeter. A groove length of the retention groove is greater than the perimeter of the support plate.