Disclosed are optical couplers (10) and optical coupling systems for coupling a source of non-coherent light to a light distribution harness, wherein the couplers are polygonal in cross section to increase light mixing. The couplers have inlet (12) and outlet (14) arms and an intermediate bend region (16A) configured to achieve compactness and minimal light loss through the bend region. In one embodiment, the bend region is an integral part of the coupler, with the inlet arm having a different cross-sectional dimension (12A) from the outlet arm (14A) in such manner that substantially all light (30) directed from the inlet portion (12) to the bend portion (16A) reaches (31,32) the outlet arm portion (14), and light rays parallel to the inlet axis are reflected in the bend portion to be directed substantially parallel to the outlet axis. In a second embodiment, the bend region comprises a prism having a pair of parallel spaced surfaces, and inlet, outlet, and third surfaces that are non-parallel to the spaced surfaces. The inlet arm projects from the inlet surface, and the outlet arm projects from the outlet surface. One of the inlet and outlet surfaces forms a first interface with a first material having an index of refraction different from that of the prism, so that light rays within the prism totally internally reflect from the first interface.