A rear exterior lamp for a vehicle including an optical fiber (61) for providing an optical fiber light output, an optical coupler (50) responsive to the optical fiber light output for providing an optical coupler light output, and a light panel (11, 13, 15, 100) responsive to the optical coupler light output for providing an exterior lamp output. The optical coupler more particularly includes a transparent substrate having an input side (53) for receiving the optical fiber light output, an output surface (51), and a plurality of internally reflecting surfaces (55a) opposite the output surface for internally reflecting light that enters the input surface toward the output surface.