The invention relates to an optical guide made from transparent or translucent material extending along a main direction and including a rounded, tubular guide portion formed with a rounded, tubular dioptric interface, the tubular guide portion being suitable for guiding light along the main direction through successive reflections off the dioptric interface with a rib adjacent to the guide portion that is suitable for allowing light to exit the tubular guide portion. The rib exhibits a variable shape along the main direction so as to modify the amount of light that exits along the main direction. The invention also relates to a lighting module that includes the optical guide and a lighting device that includes the lighting module.